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KARINA REJANE GROCH
Biologia Populacional e Ecologia Comportamental da Baleia Franca
Austral, Eubalaena australis (Desmoulins, 1822), CETACEA,
MYSTICETI, no litoral sul do Brasil.
Tese submetida ao Programa de Pós-Graduação em
Biologia Animal, Instituto de Biociências,
Universidade Federal do Rio Grande do Sul, como
requisito parcial à obtenção do título de Doutor em
Biologia Animal.
Orientador: Profa. Dra. Marta Elena Fabián
PORTO ALEGRE
2005
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AGRADECIMENTOS
Em especial agradeço à minha mãe Neiva pela minha existência, pela amizade,
incentivo, coragem e exemplo de dedicação. Pelo carinho e compreensão ao longo de todos
esses anos.
Ao meu pai pelo apoio e incentivo, ainda que da sua maneira conservadora!
Ao meu amado Janir, pela persistência, por mais uma vez ter tido a paciência
de suportar minha ausência, e a compreensão de tolerar minha distância mesmo quando
presente. Obrigado, ainda, por acreditar nos meus ideais, e me acompanhar nessa caminhada.
A José Truda Palazzo Jr. por sua irreverência, persistência, paciência,
determinação e dedicação à conservação da natureza e, principalmente, pelo crédito e
confiança.
Ao Hemerson Adair Silveira por ter “segurado as pontas” nos bastidores dos
últimos anos.
Ao Dr. Paulo André de Carvalho Flores pela amizade e ensinamentos ao longo
dos vários passos dessa caminhada.
À Vicky Rowntree pela amizade, incentivo, paciência e orientação valiosos e
indispensáveis à realização desse trabalho.
Aos diversos voluntários que participaram de coleta de dados ao longo desses
anos.
Em especial à Petrobras, Petróleo Brasileiro SA., pelo patrocínio vital à
realização e continuação deste trabalho.
À Fundação Brasileira para a Conservação da Natureza (FBCN), Fundação o
Boticário de Proteção à Natureza e Fundação McArthur, Fundo Mundial para a Vida Silvestre
(WWF), Fundo Mundial para o Bem-Estar Animal (IFAW), Companhia Têxtil Schlöesser,
Fundação Bárbara Delano, Mormaii, New Millenium Promoções e Eventos, Issaig Táxi
Aéreo, Pousada do Surf, Pousada Pinheira, Silvestre Praia Hotel.
À Comissão de Aperfeiçoamento de Pessoal (CAPES – Ministério da
Educação) e ao Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq –
Ministério da Ciência e Tecnologia) pelas bolsas de Doutorado e de Estágio no Exterior
(Bolsa Sanduíche - PDEE).
A todas as pessoas que direta ou indiretamente contribuíram para o sucesso de
cada temporada de campo, e para a realização deste trabalho.
SUMÁRIO
CAPÍTULO 1
INTRODUÇÃO ................................................................................................................................................... 12
1. CLASSIFICAÇÃO............................................................................................................................................. 12
2. CARACTERÍSTICAS GERAIS DO GÊNERO EUBALAENA ..................................................................................... 12
3. DISTRIBUIÇÃO E USO DE HABITAT ................................................................................................................ 14
4. ORGANIZAÇÃO SOCIAL E ASPECTOS COMPORTAMENTAIS............................................................................. 18
5. CONSERVAÇÃO.............................................................................................................................................. 19
6. TURISMO DE OBSERVAÇÃO DE BALEIAS (“WHALEWATCHING”) ....................................................................21
7. EUBALAENA AUSTRALIS NO BRASIL ................................................................................................................. 22
OBJETIVOS........................................................................................................................................................27
CAPÍTULO 2
RIGHT WHALES (EUBALAENA AUSTRALIS) OFF SOUTHERN BRAZIL: ANNUAL AND
SEASONAL PATTERNS OF OCCURRENCE, SITE FIDELITY AND GROUP STRUCTURE.............. 29
ABSTRACT ..................................................................................................................................................... 30
INTRODUCTION............................................................................................................................................31
MATERIALS AND METHODS......................................................................................................................32
Distribution .................................................................................................................................................... 34
Inter-annual distribution................................................................................................................................34
Seasonal distribution...................................................................................................................................... 35
Coastal movements and approximate residence period ................................................................................. 35
Site fidelity...................................................................................................................................................... 36
RESULTS......................................................................................................................................................... 36
Population structure....................................................................................................................................... 36
Inter-annual distribution................................................................................................................................37
Seasonal distribution...................................................................................................................................... 39
Coastal movements and approximate residence period ................................................................................. 40
Site fidelity...................................................................................................................................................... 42
DISCUSSION................................................................................................................................................... 43
AKNOWLEDGEMENTS ................................................................................................................................ 48
REFERENCES.................................................................................................................................................49
LIST OF TABLES............................................................................................................................................ 54
LIST OF FIGURES ..........................................................................................................................................55
CAPÍTULO 3
RECENT RAPID INCREASES IN THE BRAZILIAN RIGHT WHALE POPULATION......................... 73
ABSTRACT......................................................................................................................................................... 74
RESUMO ............................................................................................................................................................74
INTRODUCTION.................................................................................................................................................. 75
MATERIALS AND METHODS............................................................................................................................... 76
RESULTS............................................................................................................................................................ 78
DISCUSSION....................................................................................................................................................... 79
ACKNOWLEDGMENTS ........................................................................................................................................81
REFERENCES...................................................................................................................................................... 81
LIST OF TABLES................................................................................................................................................. 86
LIST OF FIGURES ............................................................................................................................................... 86
CAPÍTULO 4
PRELIMINARY ESTIMATE FOR THE BRAZILIAN RIGHT WHALE POPULATION........................ 93
ABSTRACT......................................................................................................................................................... 94
INTRODUCTION.................................................................................................................................................. 94
MATERIALS AND METHODS............................................................................................................................... 95
RESULTS............................................................................................................................................................ 97
DISCUSSION....................................................................................................................................................... 98
ACKNOWLEDGMENTS ........................................................................................................................................99
REFERENCES.................................................................................................................................................... 100
LIST OF TABLES AND FIGURES......................................................................................................................... 104
CAPÍTULO 5
MONITORING RESPONSES OF SOUTHERN RIGHT WHALES TO WHALEWATCHING
ACTIVITIES IN THE SOUTHERN BRAZILIAN COAST AND ITS IMPLICATIONS FOR
CONSERVATION ............................................................................................................................................ 109
ABSTRACT ................................................................................................................................................... 110
INTRODUCTION..........................................................................................................................................111
METHODS..................................................................................................................................................... 113
Study area..................................................................................................................................................... 113
Surveys ......................................................................................................................................................... 113
Theodolite tracking data collection.............................................................................................................. 114
Focal observations....................................................................................................................................... 115
Whalewatching............................................................................................................................................. 115
Focal observations during non-whalewatching days...................................................................................117
Individual Identification............................................................................................................................... 117
Data Analysis ............................................................................................................................................... 117
RESULTS....................................................................................................................................................... 118
Theodolite tracking ......................................................................................................................................119
Focal observations in non-whalewatching days .......................................................................................... 121
Identified individuals.................................................................................................................................... 122
Whalewatching monitoring without theodolite............................................................................................. 123
DISCUSSION................................................................................................................................................. 123
CONCLUDING REMARKS AND RECOMMENDATIONS ....................................................................... 127
ACKNOWLEDGEMENTS ......................................................................................................................... 129
REFERENCES CITED................................................................................................................................... 129
LIST OF TABLES.......................................................................................................................................... 136
LIST OF FIGURES ........................................................................................................................................138
CONSIDERAÇÕES FINAIS............................................................................................................................ 154
REFERÊNCIAS BIBLIOGRÁFICAS ............................................................................................................ 159
RESUMO
As baleias francas austrais (Eubalaena australis) eram historicamente
distribuídas do Nordeste ao Sul do Brasil, mas a intensa caça comercial realizada até 1973
quase levou-as à extinção. De 1986 a 2003 foram realizados sobrevôos ao longo da costa sul
do Brasil principalmente para fotoidentificação individual da população remanescente de
baleias francas. Um total de 481 baleias (223 grupos) foi avistado em 16 sobrevôos durante o
pico de abundância de baleias. Os grupos consistiram principalmente de dois indivíduos
(67,3%, n=150), mas grupos de até oito baleias foram avistados. Foram registradas 149
avistagens de pares de fêmea com filhote, e 183 de indivíduos não-acompanhados de filhotes.
As baleias estavam concentradas entre os ‘bins’ (unidades de 12 minutos de latitude) J
(Garopaba) e N (Araranguá), com pico de avistagem em L (Laguna). A distribuição dos pares
de fêmea e filhote e dos indivíduos não-acompanhados está um pouco sobreposta, mas uma
principal área de concentração foi identificada, especialmente para as fêmeas com filhotes, o
que coincide com a área de agregação previamente reconhecida no Brasil.
Em 2002 e 2003, anos em que foram realizados sobrevôos mensais, as baleias
chegaram na região em Julho/Agosto, atingindo pico em Setembro, e declinando em
Outubro/Novembro. Padrões de reavistagem intra-anual foram obtidos a partir de 39 baleias
reavistadas. A maioria das reavistagens foi de fêmeas com filhotes, reavistadas pelo menos
uma vez em dois sobrevôos consecutivos.
Até 2003, o Catálogo Brasileiro de Fotoidentificação das Baleias Francas tem
315 baleias identificadas individualmente, das quais 31 foram reavistadas em outros anos (23
fêmeas, 3 filhotes de um ano e 5 baleias de sexo e idade desconhecidos). Nenhuma
reavistagem ocorreu antes de 1994 e 71% (n=24) foram registradas em 2003. Das 120 fêmeas
identificadas no Brasil, 19,2% (n=23) têm mostrado algum nível de fidelidade de área. O
intervalo modal observado entre nascimentos foi de três anos, consistente com o sucesso
reprodutivo.
De 1997 a 2003, o número de fêmeas reprodutivas na área Central sobrevoada
aumentou a uma taxa de 29,8% por ano (95% CL 15,7, 44,0) e de 1987 a 2003 14% por ano
(95% CL 7,1, 20,9). Ambas as taxas são significativamente diferentes de zero (t=4,133,
p<0,009 e t=4,06, p<0,004, respectivamente), e mais altas que as taxas observadas para as
baleias francas em outras áreas de concentração reprodutiva no Atlântico Sul. A abundância
das baleias francas na costa sul do Brasil foi estimada em no máximo 555 indivíduos,
utilizando-se a Taxa Anual Reprodutiva (de uma população estável). Este número reflete o
aumento observado na população em anos recentes, porém devido à estimativa não ter
incorporado parâmetros como mortalidade e/ou emigração e imigração, deve ser utilizado
com cautela, e considerado somente uma estimativa preliminar.
As interações entre as baleias francas e as embarcações de turismo foram
estudadas em 2002, utilizando-se um teodolito. Foram realizadas 65,5 horas de observações
antes, durante e depois dos encontros entre fêmeas com filhotes e embarcações, durante 25
cruzeiros de “whalewatching” em cinco enseadas diferentes. A média da velocidade de
natação das baleias antes, durante e depois dos encontros com embarcações variou de acordo
com a enseada e a fase de aproximação, (t=4,133, p<0,009 e t=4,06, p<0,004,
respectivamente). Não foi encontrada nenhuma alteração significativa nas velocidades médias
de natação nestas três fases (p>0,05), porém houve variação significativa durante alguns
intervalos de tempo. As probabilidades previstas das baleias nadarem em direção aos barcos
em função do tempo foram significativamente próximas aos valores esperados na Gamboa e
Ibiraquera (p>0,05) porém variaram significativamente durante alguns intervalos em
Garopaba, Silveira e Rosa. As baleias reagiram tanto a distâncias curtas e longas das
embarcações, e as reações variaram de acordo com as enseadas. Apesar da dificuldade de
avaliar impactos a longo prazo, nenhuma evidência clara sobre distúrbios a esta população
foram observados durante este estudo, sugerindo que as embarcações de “whalewatching” que
operam segundo as legislações Brasileiras não alteram o comportamento das mesmas.
Se o número de baleias francas continuar a aumentar, pode-se esperar que as
baleias francas reocupem sua área de distribuição histórica ao longo de cerca de 2400km de
costa, aumentando a possibilidade de conflitos entre as baleias francas e atividades humanas.
O uso de técnicas de rastreamento com teodolito, se realizadas em conjunto com as usadas
para o monitoramento a longo prazo dos indivíduos e seus padrões de uso de habitat poderão
permitir aos cientistas uma melhor possibilidade de manejo das atividades de
“whalewatching” de modo a assegurar a conservação apropriada da espécie alvo e a
sustentabilidade da indústria deste turismo a longo prazo.
ABSTRACT
Southern right whales (Eubalaena australis) in Brazil were historically
distributed from northeastern to southern coast, but intensive commercial whaling held until
1973 almost extirpated whales from the region. From 1986 through 2003 aerial surveys were
conducted off southern Brazil primarily for photo-identification of the remnant population. A
total of 481 whales (223 groups) were sighted in 16 surveys during peak whale abundance.
Groups consisted mostly of two whales (67.3%, n=150) and groups of up to eight whales
were sighted. From the total, 149 sightings were of females with calves and 183 were
unaccompanied whales. Whales concentrated between bins (unit with 12 minutes latitude
long) J (Garopaba) and N (Araranguá), with a peak in L (Laguna). Distribution of females
with calves and unaccompanied whales is somewhat overlapped, but a major concentration
area was identified, especially for mother/calf pairs, which coincides with a previously
recognized aggregation area off Brazil.
In 2002 and 2003, when monthly surveys were conducted, whales arrived in
July/August, reaching peak in September, and declining in October/November. Intra-annual
resighting patterns were obtained from 39 non-calf whales. The majority of resightings were
of females with calves, resighted at least once in two consecutive surveys.
As of 2003 the Brazilian Right Whale Catalogue has 315 different individual
whales of which 31 were resighted in other years (23 females, 3 yearlings and 5 whales of
unknown age/sex). No resightings occurred before 1994 and 71% (n=24) were recorded in
2003. From 120 females identified in Brazil, 19.2% (n=23) have shown some level of site
fidelity. The modal observed interval between calving events is 3 years, consistent with
successful reproduction.
From 1997 to 2003 the number of reproductive females in the Central Survey
Area off Brazil increased at a rate of 29.8% per year (95% CL 15.7, 44.0) and at 14% per year
(95% CL 7.1, 20.9) from 1987 to 2003. Both rates are significantly different from zero
(t=4.133, p<0.009 and t=4.06, p<0.004, respectively) and higher than the rates observed for
right whales in other wintering grounds in the South Atlantic.
The abundance of right whales off southern Brazil was estimated to be
possibly as high as 555 whales, using the Gross Annual Reproductive Rate (GARR) of a
stable population. This number reflects the increase observed in the population in the recent
years, but because this estimate does not incorporate parameters like mortality and/or
emigration and immigration, it should be treated with caution and as a preliminary rough
estimate only.
Interactions between southern right whales and whalewatching boats were
studied in 2002 using a surveyor theodolite. It were recorded 65.5 hours of observations
before, during and after encounters between mother/calf pairs and boats during 25
whalewatching cruises in five different bays. Mean swimming speed varied by bay and
approaching phase, (t=4.133, p<0.009 and t=4.06, p<0.004, respectively). No significant
differences were found in mean swimming speeds of whales tracked before, during and after
encounters with boats (p>0.05). The predicted probabilities of whales heading towards the
boats as a function of time were significantly near the expected values in Gamboa and
Ibiraquera (p>0.05) but varied significantly during certain time intervals (p<0.001) in
Garopaba, Silveira and Rosa. Whales reacted at both long and short distances from boats and
the reactions varied with bays. Although long-term impacts are difficult to assess, no clear
evidence of immediate disturbance to this right whale population was observed during the
study, suggesting that the whalewatching boats operation under Brazilian regulations did not
disrupt their behavior.
If the number of whales continues to increase they will probably expand their
distribution throughout their historical 2,400 km range and come into increasing conflict with
human activities. The use of the theodolite techniques, if taken together with those used for
long-term monitoring of individual whales and their pattern of habitat use may enable
scientists to provide the best possible management advice for whalewatching in order to
ensure the proper conservation of target species and the sustainability of this industry on a
long-term basis.
CAPÍTULO 1
INTRODUÇÃO
1. Classificação
As baleias francas Eubalaena sp. pertencem à Ordem Cetacea, Subordem
Mysticeti. Junto com as baleias “bowhead” (Balaena mysticetus Linnaeus, 1758) compõe a
família Balaenidae (Cummings, 1985). Duas espécies do gênero Eubalaena são reconhecidas:
E. glacialis (Muller, 1776), a baleia franca boreal, com duas populações que habitam o
Atlântico e Pacífico Norte, e E. australis (Desmoulins, 1822), a baleia franca austral, com
várias populações que habitam o Hemisfério Sul (Rice, 1998; IWC, 2001). Recentes estudos
baseados na análise de DNA mitocondrial indicam, porém, uma forte evidência genômica
para a existência de uma terceira espécie, Eubalaena japonica, com uma população que habita
o Pacífico Norte (Rosenbaum et al. 2000; Gaines et al., 2005).
As populações do Hemisfério Norte e Sul aparentemente apresentam
distribuição descontínua através do Equador e são geograficamente isoladas devido a
diferenças temporais no comportamento reprodutivo (Cummings, 1985). Possuem pequena
diferenciação morfológica e fisiológica, como segue: diferenças no esqueleto (Omura apud
Rosenbaum et al., 2000, p.1794) variação no comprimento do corpo (Best, 1987), diferenças
de freqüência no aparecimento das calosidades (Best, 1970; Kraus et al., 1986), associação
diferenciada de parasitas (Scarff, 1986), diferenças nas manchas dorsais e ventrais (Payne et
al. 1983; Payne, 1986; Schaeff & Hamilton, 1999; Schaeff et al., 1999) e níveis contrastantes
de variabilidade genética baseado na análise de DNA mitocondrial (Schaeff et al., 1991;
Schaeff et al., 1997; Rosenbaum et al., 2000). As análises filogenéticas realizadas por
Rosenbaum et al. (2000) mostraram, ainda, que as E. glacialis do Pacífico Norte são distintas
das E. glacialis do Atlântico Norte, e mais proximamente relacionadas às E. australis do que
às E. glacialis do Pacífico Norte .
2. Características Gerais do Gênero Eubalaena
As baleias francas podem ser facilmente distinguidas dos outros grandes
cetáceos por várias características. A principal delas é a ausência da nadadeira dorsal,
característica exclusiva dentre as baleias que habitam o Hemisfério Sul, e ausência de pregas
ventrais características dos balenopterídeos. Possuem os orifícios respiratórios bastante
13
separados, originando um vapor característico em forma de “V” durante a respiração
(Cummings, 1985).
Uma característica única do gênero são as calosidades de pele características
na região da cabeça, ao redor do orifício respiratório e da boca (Payne et. al., 1983). Essas
calosidades são espessamentos da epiderme infestados por colônias de crustáceos anfípodos
da família Cyamidae (piolhos-de-baleia, Cyamus sp.), responsáveis pela coloração branca ou
amarelada (Payne et. al., 1983; Rowntree, 1993, 1996). A distribuição das calosidades nas
baleias francas segue um padrão geral, mas o formato, tamanho e número de calosidades
variam entre os indivíduos e em geral são assimétricos num mesmo indivíduo (Payne et al.,
1983). Esta distribuição se estabelece logo nos primeiros meses de vida dos filhotes,
permanecendo constante ao longo do tempo e permitindo a identificação individual (Payne et
al., 1983). Apesar da sutil diferença, os machos possuem calosidades em maior quantidade e
tamanho que as fêmeas (Payne & Dorsey, 1993). Acredita-se que as calosidades sejam
utilizadas para o reconhecimento entre os indivíduos e, baseado na maior quantidade de
marcas e arranhões temporários existentes no dorso dos machos em relação às fêmeas, sugere-
se que as calosidades funcionem como instrumento para agressão intraespecífica (Payne &
Dorsey, 1993).
A coloração do corpo das baleias francas pode variar do preto ao acinzentado,
com manchas brancas no ventre e no mento (Payne et al., 1983; Cummings, 1985). Alguns
indivíduos de baleias francas austrais podem apresentar manchas brancas ou acinzentadas no
dorso, que também podem ser usadas para fotoidentificação. Cerca de 10% da população de
baleias francas que freqüenta as áreas de concentração reprodutiva na Argentina e África do
Sul apresentam estas manchas (Schaeff et al., 1999). Uma análise genética mostrou que
indivíduos que apresentam manchas acinzentadas, ou a combinação destas com manchas
brancas são invariavelmente fêmeas, e indivíduos com manchas brancas apresentam
proporção sexual de 1:1. Estas manchas podem ocorrer em todo o corpo, resultando em
indivíduos parcialmente albinos. O indivíduo parcialmente albino possui a maior parte do
corpo branca com pequenas pintas pretas quando filhote, mas escurece nos primeiros anos de
vida adquirindo aparência marrom ou acinzentada (Payne et al., 1983; Best, 1990a; Schaeff et
al., 1999). Através de uma análise genética mostrou-se que esses indivíduos são
invariavelmente machos (Schaeff et al. 1999). As nadadeiras peitorais são curtas e largas,
com formato de trapézio, e a cauda larga e pontuda. A cabeça é robusta (cerca de 1/3 do
comprimento total do corpo) com rostro estreito, mandíbulas bastante arqueadas e numerosos
pelos na região da mandíbula e maxila (Cummings, 1985).
14
As fêmeas adultas são maiores que os machos, atingindo até 18 m de
comprimento e pesando de 50 a 56 toneladas (Cummings, 1985; Evans, 1987). Os filhotes
nascem em média com 6 metros de comprimento (Best, 1994) pesando 4-5 toneladas
(Whitehead & Payne, 1981).
A maturidade sexual é atingida em torno dos 6 anos (Payne, 1986) e a idade da
primeira gestação ocorre em torno dos 9 anos (Payne, 1986; Payne et al. 1990; Knowlton et
al., 1994; Cooke et al., 2001; Hamilton et al., 1998). O período de gestação é de 11-12 meses
(Payne, 1986; Best, 1994; Burnell & Bryden, 1997) e as fêmeas têm, em média, um filhote a
cada 3 anos (Payne, 1986; Bannister, 1990; Best, 1990a; Payne et al. 1990; Hamilton &
Mayo, 1990; Burnell, 2001; Cooke et al., 2001; Hamilton et al. 1998). O desmame parece
ocorrer após o primeiro ano de idade (Thomas & Taber, 1984; Hamilton et al., 1995; Burnell,
2001; Hamilton et al., 1998). A expectativa de vida reprodutiva da fêmea é de
aproximadamente 30 anos, sendo que uma fêmea pode produzir até nove filhotes e viver pelo
menos 65 anos (Hamilton et al., 1998). A taxa de mortalidade estimada está em torno de 1-3%
para os adultos, porém esta estimativa é considerada abaixo do que é geralmente proposto
para os misticetos (Payne et al. 1990; Knowlton et al., 1994; Cooke et al., 2001; Best &
Kishino, 1998).
3. Distribuição e Uso de Habitat
As baleias francas passam o verão nos pólos onde se alimentam, e migram para
águas tropicais mais quentes durante o inverno para acasalamento e procriação (Cummings,
1985). Apesar da maioria dos autores considerarem este padrão de migração como regra geral
para os misticetos, evidências diretas só foram obtidas recentemente, através de reavistagens
de indivíduos fotoidentificados em áreas de reprodução e alimentação (Best et al., 1993;
Bannister et al., 1997; Bannister et al., 1999; Moore et al., 1999).
Existem quatro estoques
1
reprodutivos principais de baleias francas austrais
reconhecidos no Hemisfério Sul, definidos com base na existência de diferentes áreas de
concentração reprodutiva. Porém em função da ausência de barreiras geográficas entre estas
áreas de concentração, e dos hábitos migratórios dos cetáceos, a definição de estoques
1
O termo “estoque” se refere a uma "unidade estabelecida para fins de manejo populacional" (Wells, et al.
1999).
15
genéticos, essencial à conservação da diversidade genética, representa um desafio (Hoelzel,
1994). Além disso, a escassez de muitas informações biológicas sobre as populações de
cetáceos tem colocado em discussão a validade dos diferentes estoques para a efetiva
conservação e manejo dos cetáceos (IWC, 1986, 2001; Donovan, 1991).
Com relação às baleias francas que frequentam o Brasil e a Argentina, segundo
Ott (2000), embora algumas diferenças genéticas tenham sido observadas em nível
mitocondrial, estas populações não se enquadram nas classificações tradicionais, como a
proposta por Waples (1991) e Moritz (1994) como distintas Unidades Evolutivamente
Significativas, nem nas definições de Unidades de Manejo apresentadas por Moritz (1994),
devido à alta homogeneidade genética detectada em nível nuclear, ao elevado número de
haplótipos compartilhados, e à alta proporção de deslocamentos individuais entre as duas
regiões.
Para Camus e Lima (2002), a definição de uma população é um problema
fundamental para a compreensão da dinâmica ecológica, e tem grandes implicações em
questões como manejo e conservação. Segundo os critérios apresentados por Berryman
(2002), os grupos de baleias francas que freqüentam, por exemplo, Brasil e Argentina, seriam
populações locais que fariam parte de uma metapopulação. Ainda segundo Berryman (2002),
a dinâmica das populações locais será fortemente influenciada pela dispersão e imigração,
enquanto que a da metapopulação somente será influenciada pela difusão rara e/ou aleatória
entre populações vizinhas.
Para fins desta tese, o termo população será aplicado referindo-se a
concentrações reprodutivas, quando necessário, porém sem a pretensão de uma definição
conclusiva, haja visto principalmente a carência, até o presente, de informações conclusivas
referentes às áreas de alimentação utilizadas pelas baleias francas que freqüentam a América
do Sul.
Os estoques
reprodutivos principais de baleias francas austrais reconhecidos no
Hemisfério Sul estão localizados na África do Sul, Austrália, América do Sul e região sub-
Antártica da Nova Zelândia, com pequenas populações locais associadas a eles (IWC, 1986;
Klinowska, 1991; IWC, 2001). Na Austrália, concentrações reprodutivas de baleias francas
são encontradas principalmente a oeste e sul (abaixo dos 32ºS) desde a região do Cabo
Leewin até a Grande Baía da Austrália, a leste da Baia Israelite, durante os meses de junho a
outubro, com pico de avistagens em agosto e setembro (Bannister, 1990; Burnell & Bryden,
1997; Bannister, 2001). Na África do Sul, as maiores concentrações ocorrem também abaixo
dos 32ºS, entre a Baía de Walker e de Plettenburg, de junho e outubro, com pico de avistagens
16
em setembro e início outubro (Best, 1990b). Na região sub-Antártica da Nova Zelândia, a
principal área de concentração reprodutiva conhecida está nas Ilhas Auckland, de junho a
outubro, com pico de avistagens em Julho-Agosto, com alguns indivíduos avistados nas
proximidades das Ilhas Campbell (Patenaude et al. 1998; Barrett, 2000; Patenaude & Baker,
2001). Na América do Sul a principal concentração reprodutiva ocorre nas águas costeiras da
Península Valdés, Argentina (Payne, 1986; Payne et al. 1990), com uma pequena área de
concentração encontrada no sul do Brasil (IWC, 2001) com indivíduos provavelmente
relacionados à população da Argentina (Best et al., 1993; Ott, 2000). As avistagens na
Península Valdés ocorrem de junho a dezembro, com pico e entre o final de setembro e início
de outubro (Payne, 1986). Outra pequena concentração reprodutiva é encontrada na região de
Tristão da Cunha e Ilhas Gough, onde evidências demonstram uma possível relação com
Argentina ou África do Sul (Best et al., 1993).
As áreas de alimentação dos misticetos estão associadas a áreas de alta
produtividade primária, onde há grandes concentrações de zooplâncton (Laws, 1985; Evans,
1987; Moses & Finn, 1997; Clapham, 1999). Áreas de alimentação conhecidas no Hemisfério
Sul são as regiões próximas à Convergência Antártica (Goodall & Galeazzi, 1986) e no
entorno das Ilhas Geórgias do Sul (Moore et al., 1999).
Nas áreas de reprodução a distribuição das baleias francas é freqüentemente
relacionada a águas calmas e rasas. Evans (1987) sugere a manutenção de determinadas áreas
de reprodução simplesmente por tradição, como um reflexo da história evolutiva dos
misticetos, e menciona a preferência por regiões com águas calmas bem como regiões que
ofereçam proteção contra predadores como orcas (Orcinus orca Linnaeus, 1758) e tubarões.
Na Península Valdés, Argentina, o ataque de uma orca a duas baleias francas fez com que
estas se movessem de uma região com 30 m de profundidade para uma área com 7-11 metros
(Cummings et al., 1972). Clapham (1999) relata haver uma maior freqüência de baleias
francas em águas rasas com fundo relativamente plano, e com temperaturas entre 10
o
e 14
o
C,
na única área de concentração reprodutiva conhecida para as baleias francas do Atlântico
Norte. Entretando, o autor não deixa clara a existência de uma relação entre estes fatores e a
preferência por esta área, mas menciona a predominância de águas calmas na região como
provável fator determinante. Pares de mãe-filhote parecem ter preferência por águas rasas
para evitar interações de alto custo energético com grupos sociais de baleias francas (Lockyer
1981; Corkeron & Connor, 1999; Thomas & Taber, 1984).
Estudos de fotoidentificação a longo prazo realizados em várias áreas de
concentração das baleias francas no Hemisfério Sul demonstram haver uma certa fidelidade às
17
áreas de reprodução. As fêmeas grávidas tendem a retornar à mesma região a cada 3 anos, em
geral no mesmo local ou em áreas adjacentes ao local do primeiro ano de avistagem, para
concepção de um novo filhote (Payne, 1986; Bannister, 1990, 2001; Best, 1990b, 2000; Payne
et al., 1990; Burnell. 2001). Já os adultos não acompanhados por filhotes são reavistados a
intervalos variados podendo ser avistados em anos subsequentes, seguindo o mesmo padrão
de fidelidade por área. Payne (1986), Bannister (1990), Best (1990b, 2000) e Burnell &
Bryden (1997) mencionam haver preferência por determinadas áreas de agregação dentro das
áreas de concentração reprodutiva, bem como uma separação entre áreas de concentração de
fêmeas com filhotes e grupos de acasalamento, porém sem associação direta com nenhum tipo
de fator ambiental. Na área de concentração reprodutiva da África do Sul, Elwen & Best
(2004) sugerem a preferência por áreas que oferecem proteção contra a ondulação em mar
aberto e ventos sazonais, bem como áreas de fundo sedimentar e pouca declividade. Em geral,
as baleias francas são encontradas próximas da costa. Adultos não acompanhados de filhotes
permanecem mais afastados da região das ondas (em locais com profundidades de até 60-80
m) e fêmeas com filhotes são avistadas logo após a arrebentação das ondas ou a distâncias de
até 1000 m da costa, em profundidades menores que 20m e mais freqüentemente em torno de
10m (Payne, 1986; Thomas, 1986; Best, 1990b; Patenaude & Baker, 2001).
Não se sabe ao certo se os acasalamentos observados em determinada região
resultam nos filhotes observados no ano seguinte (Payne, 1986). Porém, a concepção ocorre
na mesma região onde as fêmeas são avistadas com seus filhotes (Payne, 1986; Best, 1990b;
Burnell & Bryden, 1997). As fêmeas grávidas se aproximam da costa alguns dias antes do
nascimento dos filhotes, e permanecem com os recém-nascidos em torno de 11 semanas na
mesma área de concentração; o tempo de permanência observado para adultos sem filhotes
varia bastante e, pelo menos em algumas regiões, permanecem próximos à costa durante
menos tempo que fêmeas com filhotes (em torno de seis semanas) (Bannister, 1990; Burnell
& Bryden, 1997). Fêmeas com filhotes apresentam menos movimentação ao longo da costa
do que outros indivíduos (Bannister, 1990; Best, 1990b, 2000; Burnell & Bryden, 1997;
Rowntree et al., 2001). A estação reprodutiva dura em torno de cinco meses (Payne, 1986;
Bannister, 1990; Best, 1994; Burnell & Bryden, 1997), ao término do qual os pares de fêmeas
com filhote iniciam a migração para as áreas de alimentação (Taber & Thomas, 1982; Thomas
& Taber, 1984).
18
4. Organização Social e Aspectos Comportamentais
As baleias francas são animais pouco gregários tanto em áreas de alimentação,
quanto em áreas de reprodução (Payne, 1986; Bannister, 1990; Best 1990b; Patenaude &
Baker, 2001; Best et al. 2003). Animais solitários ou grupos de dois indivíduos são os mais
freqüentemente observados, podendo vários grupos estarem distribuídos em pequenas áreas
de agregação (Payne, 1986; Bannister, 1990; Best, 1990b; Palazzo & Flores, 1996; Simões-
Lopes et al., 1992; Palazzo et al., 1999; Groch, 2000; Patenaude & Baker, 2001). Grupos de
baleias francas podem ser compostos por indivíduos solitários, pares de mãe e filhote ou
grupos de adultos (Payne, 1986; Cassini & Vila, 1990). Interações sociais entre grupos e/ou
indivíduos são observados, podendo ocorrer durante horas, principalmente em se tratando de
grupos de acasalamento (Payne, 1986; Patenaude & Baker, 2001). Raramente são observadas
interações entre pares de mãe e filhote, mesmo estando próximos uns dos outros (Thomas,
1986).
Vários níveis de interações inter-específicas são relatadas entre baleias francas
e aves, bem como com outros mamíferos marinhos. Dentre as aves o caso mais extremo já
relatado é o que ocorre com os gaivotões, Larus dominicanus (Lichtenstein, 1823), na
Península Valdés, Argentina (Cummings, 1972; Thomas, 1988; Verheyden, 1993; Rowntree
et al., 1998). Os gaivotões têm o hábito de se alimentar de pedaços de pele descamada e da
gordura do dorso das baleias francas. O molestamento provocado por este comportamento
aumentou cinco vezes em 1995, em relação ao primeiro estudo realizado por Thomas (1988)
na Península Valdés. Diversos episódios foram observados recentemente no litoral de Santa
Catarina, Brasil (Groch, 2001b, dados não-publicados) Os ataques dos gaivotões podem
alterar o comportamento calmo e tranqüilo que pode ser vital para as baleias francas em fase
de lactação (Thomas, 1988), podendo comprometer o desenvolvimento dos filhotes e
provocar o abandono de determinadas áreas de reprodução (Rowntree et al 1998; Rowntree et
al., 2001).
No que diz respeito a mamíferos marinhos já foram observadas interações com
leões-marinhos (Phocarctos hookeri Gray, 1844) (Stewart and Todd, 2001), baleias jubarte
(Megaptera novaeangliae Borowski, 1781) (Goodall & Galeazzi, 1986; Cremer, 1996; Engel
et al., 1997), golfinhos nariz-de-garrafa (Tursiops truncatus Montagu, 1821) (Ellis, 1980 in
Goodall & Galeazzi, 1986; Flores, pers. comm.) e golfinhos Dusky (Lagenorhynchus
obscurus Gray, 1828) (Ellis, 1980 in Goodall & Galeazzi, 1986).
19
Os comportamentos mais freqüentemente observados em grupos de baleias
francas em áreas de reprodução são: 1) natação (deslocamento aparente e em velocidade
constante); 2) descanso (sem movimento aparente, com a parte dorsal da cabeça e corpo
acima da água); 3) atividade sexual (grupos com presença de machos e fêmeas, e observação
de macho com pênis estendido); 3) atividade social (grupos com presença somente de adultos,
possivelmente machos e fêmeas, em geral em intensa atividade); e 4) brincadeiras (diversas
atividades realizadas entre fêmeas e filhotes). Atividades individuais observadas incluem:
exposição caudal, batida da nadadeira caudal, exposição peitoral, batida de nadadeira peitoral,
exposição da cabeça, salto, exposição ventral (Cummings, 1972, 1974; Clark, 1983; Thomas
& Taber, 1984; Payne, 1986; Cassini & Vila, 1990).
Experimentos realizados por Clark & Clark (1980), demonstraram que as
baleias francas reconhecem os sons produzidos por indivíduos da mesma espécie e
diferenciam estes de outros sons do ambiente. Clark (1983) correlaciona algumas atividades
comportamentais exibidas pelas baleias francas e seu contexto social com o tipo de som
produzido pelos grupos observados. Oito padrões sonoros são descritos e, embora não se saiba
ao certo sua função comunicativa, sabe-se que os diferentes padrões estão relacionados a
diferentes níveis de interação entre os indivíduos e entre estes e seu habitat (Clark, 1983).
5. Conservação
As populações de baleias francas foram alvo da explotação comercial no
mundo inteiro até o início do século passado. Estima-se que a população original no
Hemisfério Sul, antes das atividades de caça, era em torno de 90.000 indivíduos (Richards,
1998) e atualmente esteja entre 7000 a 8000 indivíduos (IWC, 2001). A proteção
internacional teve início em 1935, mas mesmo após esta data, atividades de explotação ilegais
tiveram continuidade em diversas regiões (Palazzo & Carter, 1983; Klinowska, 1991;
Tormosov et al., 1998). Segundo Best (1988) a maioria das populações de baleias francas no
Hemisfério Sul foram reduzidas a níveis extremamente baixos até metade da década de 30, e
aparentemente não demonstraram recuperação até cerca de 40 anos atrás. A única exceção é a
população que freqüenta Tristão da Cunha. Esta população teria escapado da atenção dos
baleeiros no final do século XIX e início do século XX, período de maior atividade de caça
comercial, demonstrando sinais de recuperação há cerca de 60 anos atrás.
20
A baleia franca glacial, Eubalaena glacialis, está listada como “ameaçada”
segundo a classificação da União Internacional para Conservação da Natureza e dos Recursos
Naturais (IUCN) (Klinowska, 1991). É considerada a espécie mais ameaçada de extinção
dentre os grandes cetáceos e não tem demonstrado sinais de recuperação desde o término das
atividades de caça (Caswell et al., 1999). Atualmente, a população de baleias francas que vive
no Atlântico Norte Ocidental está reduzida a cerca de 300 indivíduos, e a taxa de crescimento
populacional estimada em 1994 é de 0,97% ao ano, 0,02 % menor do que a estimada em 1980
(Caswell et al., 1999). A população do Atlântico Norte Oriental é considerada extinta
(Schaeff et al., 1997; Caswell et al., 1999). Não se sabe ao certo quantos indivíduos existem
na população do Pacífico Norte, mas dados sugerem que esta população esteja na mesma
situação que a do Atlântico Norte (IWC, 2001).
No Hemisfério Sul, a proteção contra a caça em áreas de reprodução parece
estar surtindo efeito na recuperação populacional da baleia franca austral, Eubalaena
australis. Na Argentina, onde a população total estimada em 1997 foi de 2500 indivíduos e na
África do Sul, onde a população estimada estava em torno de 3000 indivíduos, acredita-se que
a taxa de crescimento populacional seja de 7,8 % ao ano (IWC, 2001).
Na região das Ilhas Geórgias do Sul, área de alimentação das baleias francas
no Hemisfério Sul, a espécie mais avistada em um levantamento de dados feito por Moore, et
al. (1999) desde 1979 foi Eubalaena australis (n=68). A partir da reavistagem entre
indivíduos fotoidentifcados nesta região e em outras áreas do Atlântico Sul (e.g. Argentina e
África do Sul) e da similaridade genética entre estas populações, Moore et al. (1999) sugerem
a mesma taxa de crescimento populacional estimada para estas áreas de concentração para a
população das Geórgias do Sul.
Apesar das populações do Hemisfério Sul apresentarem sinais de recuperação,
ainda são consideradas vulneráveis. Vários fatores de ameaça à recuperação tanto das
populações do Hemisfério Sul quanto do Hemisfério Norte são indicados, como: condição
nutricional dos indivíduos, poluição química, emalhamento em equipamentos de pesca,
interações com embarcações (e.g. colisões com navios e distúrbios sonoros) e perda e
degradação de habitat (IWC, 2001; Clapham (ed.), 1999; Clapham et al., 1999).
Clapham (ed.) (1999) e Clapham et al. (1999) sugerem que dentre os vários
fatores que potencialmente afetam os misticetos, emalhamento em equipamentos de pesca e
colisões com navios são os mais significantes a nível populacional. Segundo Caswell et al.
(1999), a única chance da população de baleias francas glaciais que vivem no Atlântico Norte
21
se tornar viável é reduzir o risco de mortalidade causado por estes dois fatores. Estes autores
estimam, ainda, que, sob as condições atuais, esta população estará extinta em 191 anos.
6. Turismo de observação de baleias (“Whalewatching”)
O turismo de observação de baleias, “whalewatching”, é uma das atividades
turísticas que mais cresce no mundo inteiro. Este uso não letal dos cetáceos pode trazer
benefícios econômicos a comunidades locais, incluindo as que realizavam caça comercial,
propiciar pesquisa científica, desenvolver campanhas educacionais e a conservação do
ambiente marinho e dos próprios animais (IFAW, Tethys and Europe Conservation 1995;
IFAW, 1997, IFAW, 1999, IWC, 2001).
As atividades de “whalewatching”, se não conduzidas de acordo com normas
apropriadas podem causar vários impactos às baleias. Estes impactos não são necessariamente
negativos, e podem ser neutros, positivos ou não conhecidos (Watkins, 1986; IFAW, Tethys
and Europe Conservation, 1995). Vários parâmetros podem ser usados para se avaliar os
impactos das atividades de “whalewatching” sobre os cetáceos. Parâmetros comportamentais,
fisiológicos e acústicos podem ser medidos a curto prazo, e produtividade, condição física dos
indivíduos, distribuição, habituação e tolerância como efeito a longo prazo. As reações das
baleias a atividades humanas tais como “whalewatching” variam de acordo com a espécie e
ao longo do tempo. As baleias francas podem reagir de várias maneiras de acordo com o tipo
de aproximação da embarcação. Aproximações bruscas e ofensivas podem resultar em
respostas negativas das baleias, enquanto aproximações mais cautelosas podem resultar na
aproximação à embarcação (Cummings, et al., 1972; Payne, et al., 1983; Findlay, 1998; IWC,
2001; Rivarola et al., 2001).
Estudos dos impactos antropogênicos sobre os cetáceos têm sido
desenvolvidos em diversos lugares no mundo todo. Enquanto a maioria tem relatado
alterações significantes no comportamento dos cetáceos, tem sido mencionado, quase sem
exceção, que o significado biológico a longo prazo destas alterações não está claro (Richter et
al., 2000). Ademais, o pouco que se sabe provém de observações relativas a determinadas
espécies em algumas regiões, e geralmente as informações obtidas não podem ser diretamente
comparadas com outras espécies ou outros lugares (Richter et al., 2000). Tendo em vista o
crescimento e expansão das atividades de “whalewatching” em nível mundial, torna-se cada
vez mais necessário o desenvolvimento planejado e controlado das atividades de
22
“whalewatching”, bem como estudos sobre seu impacto a longo prazo nos cetáceos (IFAW,
Tethys and Europe Conservation, 1995).
7. Eubalaena australis no Brasil
O litoral sul do Brasil representa uma importante área de concentração
reprodutiva das baleias francas austrais, Eubalaena australis, durante os meses de maio a
dezembro (com maior freqüência de agosto a outubro), principalmente ao longo da costa de
Santa Catarina (~ 26º00’ - 28º25’ S) (Lodi & Bergallo, 1984; Câmara & Palazzo, 1986;
Simões-Lopes et al. 1992; Palazzo & Flores, 1996, 1998).
Desde o século XVII tem-se registro de atividades de caça à baleia franca no
litoral do Brasil, desde a Bahia até Santa Catarina. A partir de meados daquele século,
estações baleeiras chamadas “Armações” começaram a ser instaladas em diversos pontos do
litoral de Santa Catarina. A baleia franca era considerada a “baleia certa” para caçar por sua
docilidade e vulnerabilidade, lentidão e espessa camada de gordura. Por isso, era o principal
alvo das atenções dos baleeiros que utilizavam a sua espessa camada de gordura para a
extração de óleo empregado na iluminação, lubrificação e fabricação de argamassa para
construções, bem como as barbatanas para a fabricação de espartilhos (Ellis, 1969).
Não se sabe ao certo quantas baleias francas foram mortas no Brasil durante o
período de caça, mas estima-se que centenas delas possam ter sido dizimadas. Na costa
brasileira a espécie era abundante com uma distribuição desde a divisa com o Uruguai até a
baía de Todos os Santos, Bahia (Ellis, 1969). O último registro de caça da baleia franca no
litoral do Brasil data de 1973 na cidade de Imbituba, SC (Palazzo & Carter, 1983). Após esta
data, a população parecia ter sido eliminada na região, e a maioria das informações sobre a
presença destes animais se tratava de casos isolados, muitas vezes não confirmados, ou
provenientes de animais encalhados (Castello & Pinedo, 1979; Câmara & Palazzo, 1986; Lodi
et al. 1996). Somente a partir da década de 80 foram reavistados no litoral sul-sudeste do país
os primeiros indivíduos após o término das atividades de caça (Lodi & Bergallo, 1984;
Câmara & Palazzo, 1986; Ximenez et al. 1987; Simões-Lopes & Ximenez, 1993; Lodi et al.,
1996). Apesar das baleias francas estarem protegidas internacionalmente desde 1935, a
proibição oficial da caça comercial de cetáceos no Brasil ocorreu somente em 1987 (Lei
Federal Nº. 7643, de 18 de dezembro de 1987). Desde 1989 a baleia franca encontra-se citada
23
na Lista Oficial Brasileira das Espécies Ameaçadas de Extinção (Portaria IBAMA Nº. 1522,
de 19 de dezembro de 1989).
Desde 1981 este grupo de baleias francas vem sendo monitorado pelo Projeto
Baleia Franca - International Wildlife Coalition/Brasil. Através de avistagens a partir de terra
e censos aéreos, foi possível estabelecer uma área principal de concentração destes animais
em Santa Catarina entre o Cabo de Santa Marta, Laguna (28º36’ S, 48º49’ W) e Florianópolis
(27º25’ S, 48º30’ W) (Simões-Lopes et al., 1992; Palazzo & Flores, 1998a). Esta região
caracteriza-se por possuir a costa bastante recortada, com inúmeras enseadas e pequenas
baías, oferecendo às baleias francas alguma proteção contra os fortes ventos característicos
dos meses de inverno (Palazzo & Flores, 1998a). Nesta área, a maioria das avistagens consiste
de pares de mãe/filhote, que são observados por vários dias nas mesmas enseadas próximos à
arrebentação, ou ao longo de alguns quilômetros durante semanas, movendo-se lentamente de
uma enseada para outra (Simões-Lopes et al., 1992; Palazzo & Flores, 1996, 1998a; Palazzo
et al., 1999; Groch, 2000). A observação de indivíduos solitários e ausência de filhotes nos
primeiros meses (maio a julho) da “estação reprodutiva”, e uma maior freqüência de
avistagem de fêmeas com filhotes a partir de agosto, com registros de neonatos, é evidência
de que os nascimentos ocorram nesta região (Simões-Lopes et al. 1992; Palazzo & Flores,
1998a). Grupos de acasalamento têm sido observados com mais freqüência no litoral norte do
Rio Grande do Sul (29º19’ S, 49º43’ W a 31º15’ S, 50º54’ W) (Simões-Lopes et al., 1992;
Moreno et al., 1996), o qual caracteriza-se por uma longa praia de mar aberto. Recentemente,
porém, grupos sociais e/ou de acasalamento tem sido observados ao longo de todo o litoral
centro-sul de Santa Catarina (Palazzo & Flores, 1998a; Flores et al., 2000; Groch, 2001a; obs.
pessoais). Conforme Palazzo & Flores (1998a), parece haver áreas definidas separadas para
grupos de acasalamento e grupos de mãe-filhote, mas somente estudos a longo prazo poderão
assegurar esta hipótese. Palazzo et al. (1999) relatam a reavistagem de um par de fêmea e
filhote a um intervalo de três anos no litoral de Santa Catarina, sugerindo para esta área de
concentração reprodutiva o mesmo padrão de fidelidade observado em outras áreas no
hemisfério sul (Payne, 1986; Bannister, 1990; Best, 1990b; Payne et al., 1990).
Em função da importância do litoral catarinense para a espécie, a baleia franca
foi declarada, em 1995, Monumento Natural do Estado de Santa Catarina pelo Decreto
Estadual Nº. 171, de 06 de junho de 1995. Mais recentemente, em 2000, a principal área de
concentração reprodutiva da espécie recebeu proteção especial, através da "Área de Proteção
Ambiental (APA) da Baleia Franca", criada pelo Decreto de 14 de Setembro de 2000. A APA
24
da Baleia Franca possui 156.100 hectares e abrange desde o Sul da Ilha de Santa Catarina até
o Balneário de Rincão.
O número de avistagens de baleias francas no litoral Sul do Brasil (Câmara &
Palazzo, 1986; Secchi, E.R. 1994; Lodi et al. 1996; Moreno et al., 1996; Palazzo & Flores,
1998a), bem como em algumas regiões do Sudeste (Lodi et al. 1996; Santos et al., 2001) e
Nordeste (Lodi et al. 1996; Engel et al., 1997; Baracho et al., 2002) vem aumentando a cada
ano, e acredita-se que a espécie esteja recuperando sua distribuição original no Atlântico Sul
Ocidental. Porém, em sua maioria, são observações casuais e pontuais, muitas delas
provenientes de encalhes (Greig et al., 2001). Apesar do histórico de intensa caça comercial,
estudos moleculares revelaram que a variabilidade genética das populações no Atlântico Sul
Ocidental é relativamente elevada (Ott, 2002), o que sem dúvida está contribuindo para o
crescimento populacional.
Em anos recentes tem se registrado o aparecimento cada vez mais freqüente de
baleias francas na costa do Uruguai (García et al., 1996; García & Sabah, 1998; García,
2000). Uma rede de avistagens foi montada desde 1995, para obter dados sistemáticos ao
longo dos anos. Não se sabe ainda até que ponto esta região é apenas uma rota migratória dos
indivíduos que vem para o Brasil, ou uma área de concentração reprodutiva, porém a maior
parte dos grupos avistados são grupos de acasalamento (García, 2000), e possivelmente este
indivíduos façam parte do estoque de baleias francas que freqüenta Santa Catarina
(IWC/Brasil, 1999). Em função do padrão de ocorrência da espécie no Atlantico Sul
Ocidental e da possível relação entre os grupos que ali frequentam, a baleia franca foi
declarada Patrimônio Natural do Mercosul, e denominada "Ballena Mercosureña" na XV
Reunião Plenária da Comissão Parlamentar Conjunta do Mercosul, a 5 de Julho de 2000, em
Santa Fé, Argentina.
Observações sistemáticas sobre os padrões de ocupação sazonal, composição
dos grupos e comportamento das baleias francas no litoral centro-sul de Santa Catarina são
realizadas em desde 1998 (Groch, 2000, 2001a, 2002, 2005). A maioria das avistagens
consiste de pares de mãe-filhote, mas grupos com até sete indivíduos foram avistados em
algumas áreas. As avistagens dos grupos sem filhotes ocorreram nas mesmas enseadas que os
pares de mãe-filhote, observando-se diversas vezes interações entre os grupos, e
comportamento de acasalamento (Groch, 2001a; 2002; 2005; dados não publicados). Um
aumento na freqüência dos grupos sem filhotes pode ser percebido, assim como um aumento
no número total de avistagens ao longo destes anos. Esse aumento no número de avistagens
pode ser um reflexo do aparente aumento populacional ou pode ser meramente casual, e
25
somente a continuação deste estudo a longo prazo e de forma sistemática, e a intensificação
dos estudos de fotoidentificação poderão verificar tais fatos.
Apesar das baleias francas estarem protegida através de legislação federal, a
recente implantação das atividades de turismo de observação de baleias, "whalewatching",
desde 1999 (Groch, 2001a; Mourão, 2000), em Santa Catarina, pode representar uma
potencial ameaça, se não conduzida de acordo com as normas apropriadas. As embarcações
para operarem na região devem estar cadastradas junto a APA da Baleia Franca, e as
atividades devem ser conduzidas de acordo com as normas federais de aproximação aos
cetáceos (Portaria IBAMA No. 117, de 26 de dezembro de 1996). Um estudo preliminar
realizado em 2000 (Groch, 2001a) mostrou que a reação das baleias durante os encontros com
a embarcação foi de "desinteresse" em 52% dos encontros observados, "positiva" em 36% e
"negativa" em 12%. Em 87,9% dos grupos aproximados, estes eram compostos por pares de
mãe-filhote, sendo o restante grupos sem a presença de filhotes. O aumento de 150% na
procura por este serviço registrado em 2000 em relação ao ano anterior (Mourão, 2000), a
conseqüente perspectiva de aumento no número de embarcações e o grande potencial para o
desenvolvimento desta atividade no litoral de Santa Catarina (IWC/Brasil, 1999), tornam a
caracterização dos padrões de uso de hábitat e do comportamento das baleias francas com e
sem a presença de embarcações, um instrumento valioso para o manejo adequado desta
atividade (IFAW, Tethys and Europe Conservation, 1995, IWC/Brasil, 1999).
Dentre as linhas de pesquisa fundamentais a serem desenvolvidas no sentido de
se obter melhores informações sobre a as baleias francas em Santa Catarina, recomendadas
pelo "Plano de Ação para a Conservação da Baleia Franca, Eubalaena australis, em Santa
Catarina" (IWC/Brasil, 1999), Plano de Ação para os Mamíferos Marinhos do Brasil
(IBAMA, 2001) e conforme enfatizado na “Reunião Especial do Comitê Científico da
Comissão Internacional da Caça a Baleia - CIB para avaliação do status mundial das baleias
francas” realizada em Cape Town, África do Sul, de 16 a 25 de março de 1998 (IWC, 2001;
Palazzo & Flores, 1998b), destacam-se:
a) a continuidade dos vôos regulares de censagem e fotoidentificação das
baleias;
b) o aprofundamento e a sistematização de estudos comportamentais
referentes, em especial, aos pares mãe-filhote, visando definir padrões de uso do habitat e a
monitorar reações advindas de ações antrópicas.
26
Com vistas a assegurar a proteção e garantir a recuperação populacional da
espécie na sua área de concentração reprodutiva no sul do Brasil torna-se necessário a
realização dos estudos recomendados, bem como a continuação e intensificação do
monitoramento da espécie durante a sua ocorrência não só no Brasil como também nas outras
áreas de ocorrência no Atlantico Sul Ocidental.
27
OBJETIVOS
Considerando-se as lacunas existentes no que diz respeito à biologia das
baleias francas, Eubalaena australis, no sul do Brasil, e às atividades de pesquisa
recomendadas, a presente tese tem os seguintes objetivos em relação as baleias francas
austrais:
1) Objetivo Geral:
a) Analisar a biologia e dinâmica populacional das baleias francas no Sul do
Brasil.
2) Objetivos Específicos:
a) Verificar a distribuição espacial das baleias farncas austrais identificadas
individualmente no litoral centro-sul de Santa Catarina e Norte do Rio Grande do Sul;
b) Analisar e determinar os padrões de ocupação sazonal dos indivíduos
fotoidentificados;
c) Estimar o tamanho e o crescimento do grupo de baleias francas que
freqüenta o litoral sul do Brasil;
d) Verificar a taxa de retorno dos indivíduos fotoidentificados e o intervalo
reprodutivo das fêmeas;
e) Verificar o comportamento dos grupos-alvo das operações de
“whalewatching”.
CAPÍTULO 2
RIGHT WHALES (EUBALAENA AUSTRALIS) OFF SOUTHERN BRAZIL: ANNUAL
AND SEASONAL PATTERNS OF OCCURRENCE, SITE FIDELITY AND GROUP
STRUCTURE.
Karina R.Groch
1,2
, José T. Palazzo Jr.
2
., Paulo A.C. Flores
3
, Marta E. Fabian
1
Contact e-mail: [email protected]
1
PPG Bio Animal, UFRGS, Av. Bento Gonçalves 9500, Prédio 43435 Sala 101, Porto Alegre,
RS, 91501-970, Brazil.
2
International Wildlife Coalition/Brazil, Caixa Postal 201, Imbituba, SC, 88780-000, Brazil.
3
Dolphin Reasearch and Conservation Institute, Caixa Postal 5087, Florianópolis, SC, 88040-
970, Brazil.
Keywords: southern right whales, habitat use, coastal movements, southern Brazil, wintering
ground, aerial surveys.
(*) ESTE ARTIGO SERÁ SUBMETIDO À PUBLICAÇÃO NO JOURNAL OF CETACEAN RESEARCH
AND
MANAGEMENT.
30
ABSTRACT
Southern right whales (Eubalaena australis) in Brazil were historically distributed from
northeastern to southern coast, but intensive commercial whaling held until 1973 almost
extirpated them from the region. From 1986 through 2003 we conducted aerial surveys off
southern Brazil primarily for photo-identification of the remnant population. A total of 481
whales (223 groups) were sighted in 16 surveys during peak whale abundance. Groups
consisted mostly of two whales (67.3%, n=150) and groups of up to 8 whales were sighted.
From the total, 149 sightings were of mother/calf pairs and 183 were unaccompanied whales.
Because unequal survey coverage and irregularity throughout the period, we compared
cumulative density of whales/bin (unit with 12 minutes latitude long) between blocks of years
with similar survey coverage and approximate date of flight to verify tendencies on
distribution. Whales concentrated between bins J (Garopaba) and N (Araranguá), with a peak
in L (Laguna). Distribution of mother/calf pairs and unaccompanied whales where apparently
different, though not supported statistically (Mann-Whitney: U=71.5, z=0.301, p=0.763,
n
1
=11, n
2
=14). Within-season distribution was described after monthly surveys conducted
between July and November in 2002 and 2003. Whales arrived in July/August, reaching peak
in September, and declining in October/November. The identification of 39 non-calf whales
provided information on intra-annual resighting patterns. Thirty-one whales were resighted
inter-annually at least once (sighting interval: 1-10 years). There where 71% of resightings in
2003 (none before 1994), and 93.5% (n=29) of whales were resighted at least once. From 120
females identified in Brazil, 19.2% (n=23) have shown some level of site fidelity. 82.6%
(n=19) of these females were in calving years. From the 149 identified unaccompanied
whales, 3.4% (n=8) have been resighted, at a one-year modal interval. The distribution of
right whales along the southern Brazilian coast was not uniform, indicating specific areas as
important wintering habitat for this recovering species. Survey effort varied, but patterns of
distribution are identified. Distribution of mother/calf pairs and unaccompanied whales is
somewhat overlapped, but a major concentration area was identified, especially for
mother/calf pairs, which coincides with a previously recognized aggregation area off
Brazilian coast.
31
INTRODUCTION
Southern right whales (Eubalaena australis) migrate to coastal waters of continents and
oceanic islands during the austral winter/spring time seeking for shallow and protected areas
to give birth, nurse their calves and apparently mate (Payne 1986; Best 1988; Bannister 1990;
Best 1990, 2000; Burnell and Bryden 1997; Patenaude and Baker 2001). These areas are the
preferred habitat of females with calves, mainly because they enable energy conservation by
the calves (Lockyer 1981; Thomas and Taber 1984; Corkeron and Connor 1999). According
to Thomas (1987), shallow waters and gently sloping beaches are preferred for being areas
free from underwater obstacles where whales can drift freely following the tides.
Additionally, it has been suggested that shallow waters offer protection against killer whales
(Thomas and Taber 1984; Thomas 1987; Corkeron and Connor 1999).
The right whales that frequent the southern Brazilian coast were severely depleted by
commercial whaling in the 19
th
and early 20
th
centuries. Although protected from hunting by
international agreements since 1935, illegal catches on the right whales’ pelagic summer
grounds in the mid 20
th
century were recently reported (Tormosov et al. 1998). Historically,
right whales in Brazil were distributed from the northeastern to southern coast, but were also
subject to intensive commercial whaling until 1973. By that time the whale population
appeared to be extirpated from the region (Palazzo Jr. and Carter 1983). It was only in the
early 1980s that whales were 'rediscovered' in this region, and have been studied since then
(Câmara and Palazzo 1984).
Groups of right whales have been sighted from May to December especially along the
southern Brazilian coast (Lodi and Bergallo 1984; Câmara and Palazzo 1986; Palazzo and
Flores, 1996, 1998; Simões-Lopes et al. 1992; International Wildlife Coalition/Brazil 1999)
with peak abundance from August to October (Simões-Lopes et al. 1992; Palazzo and Flores
1996; Groch 2000, 2001).
Aerial surveys for the individual identification of southern right whales using their
callosity patterns (Payne et.al .1983) have been conducted since 1986 along the southern
Brazilian coast when the whales are on their wintering ground. The first years of the surveys
combined with incidental sightings and shore-based counts have shown a main aggregation
area along the waters of Santa Catarina State particularly the central-southern coast from
Santa Catarina Island (27º25’S, 48º30’W) to Santa Marta Cape, Laguna (28º36’S, 48º48’W)
(Simões-Lopes et al. 1992; Palazzo and Flores 1996, 1998; International Wildlife
Coalition/Brazil 1999). An increase in the number of right whales off Brazil has been
32
observed and the population is estimated to be increasing at a rate of 14% per year (Groch et
al. in press) The authors have also reported on a higher rate of 29% of increase during the
latest years of their study (1997-2003).
Sightings from aerial surveys have been used to describe distribution, movements and
coastal residence periods in many wintering areas (Payne 1986; Bannister 1990; Best 1990,
2000; Burnell and Bryden 1997; Rowntree et al. 2001). Right whales can be flexible in many
aspects of their habitat use (Rowntree et al. 2001). Patterns of use may change over time but a
preference by certain aggregation areas is reported as well as the segregation of concentration
areas between females with calves and mating groups (Payne 1986; Bannister 1990; Best
1990, 2000; Burnell and Bryden 1997; Rowntree et al. 2001). In addition, females with calves
have shown longer coastal residence periods than adults unaccompanied by calves (Bannister
1990; Burnell and Bryden 1997) and present less movement along the coast (Bannister 1990;
Best 1990; Rowntree et al. 2001).
In this paper we describe inter-annual and seasonal patterns of distribution of right whales
sighted along the Southern Brazilian coast during aerial surveys for individual identification,
as well as movements and site fidelity of individually identified whales.
MATERIALS AND METHODS
From 1986 through 2003 we conducted aerial surveys off southern Brazil with the main
purpose of photographing whales for individual identification. We have also recorded the
distribution, number and group composition of all right whales seen. Surveys were conducted
on an irregular basis from 1986 to 1994 (1986, 1987, 1988, 1992, 1993 and 1994) and
annually from 1997 to 2003, preferable during the time of peak whale abundance (Table 1).
The surveys from 1986 to 1997 were made using fixed wing aircrafts and from 1998 to 2003
we have used a helicopter. No sightings were recorded in 1986.
The extent of the coastline surveyed each year varied but a standard 120km region of the
coast between Santa Catarina Island and Santa Marta Cape, Laguna, was always included
(Figure 1). In some flights we extended the surveyed area to include 400km of coastline
(between bins A to T shown in figure 1, through different combinations of successive bins).
Techniques and personnel were kept as constant as possible but varied according to the
aircraft. The flight crew consisted of the pilot and one to three observers, depending on the
33
aircraft. One observer acted as the annotator and recorded whale number, group composition,
location, behavior and photographic information for each whale or group of whales spotted.
The surveys were flown generally at an altitude of 1000 ft (300m), at a mean ground
speed of 90 knots (167km/h) and at ~500m from the coastline. Surveys were conducted
preferable during days with optimal conditions, i.e. low surface winds, sea states (<3 Beaufort
Sea Scale) and adequate lighting. Searching was conducted in the zone from beyond the
breaking waves to not more than 1500m from the coastline. Whenever a whale or group of
whales was spotted they were approached at a minimum height of 300ft (100m) for
determination of the number of whales, group composition, and location. Locations of whales
during the surveys made until 1997 were recorded relative to buildings and distinct
geographic features along the coast, and from 1998 on using a Global Positioning
System.When using the airplane each whale or group of whales was circled for taking the
photographs; while the helicopter enabled us to hover above the group. When using a GPS,
the position of the whales was recorded at this moment.
Whales accompanied by calves were assumed to be females and were classified as
females with calves. Calves are all young-of-the-year whales with 1/3 to 1/2 of their mother’s
length. One-year-old whales identified in the previous year are called yearlings and immature
whales of unknown age were classified based on relative length and morphology of the head
and referred to as ‘subadults’. Adult whales not accompanied by calves will be here referred
as unaccompanied whales. This category contains mostly whales of unknown sex but also
previously identified and thus known females in non-calving years as well as animals of
unknown age (excluding subadults). For all analysis subadults and yearlings were included in
the unaccompanied whales category because of the low sample size. Whales were considered
to be in a group when two or more whales were seen within close proximity of one another (at
least approximately 15m or one adult whale length). Animals more then one whale length
apart were also considered a group if their behavior appeared to be coordinated (Clark, 1983).
We followed the methodology described by Payne et al. (1983) for taking and analyzing
photographs. The analysis of the photographs was aided by the automated Right Whale
Photo-identification Software developed by Hiby and Lovell (2001). All whales identified
were included in a catalogue created at the beginning of the study.
34
Distribution
Since the coastline runs primarily in northeast-southeast direction and the flight path was
made along the coast, we divided the survey area into bins of 12 minutes of latitude long
(Figure 1). The total survey area resulted in 20 bins with the length of the coastline varying
from 23 to 56km (31.2±7.8km). Because positions recorded without GPS (1987 to 1997) are
not geographically precise, the processing of data into this scale also contributed on
minimizing bias for the study of overall coastwise distribution. In 9 flights (1986-1988, 1992-
1994, 2001-2003) we have surveyed bins G to S and in 1993 we have extended the flight to
bin T (Table 1). Bins A to F were surveyed in October 2000 and August 2003, and bins E and
F in September 1988 but no whales were sighted.
The distribution of whales is described in terms of density of whales sighted per bin and
an overall distribution pattern is given for the entire period, using flights conducted during the
peak of whale abundance in the region (Table 1). All data presented here are considered
minimum counting of whales sighted because whales that were underwater were not seen
when we were passing above them.
Inter-annual distribution
Because the unequal survey coverage as well as the irregularity throughout the period, we
divided the data series in order to see whether there was any tendency on the distribution
throughout the years of the study. The first set was grouped according to the survey coverage
and consist of the following three periods: 1987 through 1994 (hereafter referred to as 1987-
94), 1997-2000 and 2001-2003. The second set was grouped according to the approximate
date of flight: 1987, 1992-1994 (27 August to 1
st
September) (hereafter referred to as Block
A); 1988, 1997, 1998, 2002 (23-27 September) (hereafter referred to as Block B) and 1999,
2001, 2003 (10-14 September) (hereafter referred to as Block C). The survey of the year 2000
was made in 8 October and because we considered it somewhat skewed of the dataset in terms
of the date of the survey, it was not included in this analysis. The timing of the flights
included in each block differed between 4 and 7 days. We have also divided the survey area
into five distinct sub-regions according to physical characteristics of the coastline (Fig. 1) to
see whether there was any evidence of habitat segregation. The resulting sub-regions also
reflect the different survey effort over the years (see Table 1). For this reason two of them
comprise different number of bins. Sub-regions ‘SC1’ and ‘SC2’ group six and two
35
successive bins, respectively, and have different number of bins in relation to sub-regions
‘SC3’, ‘SC4’ and ‘RS1’, each with four successive bins (Figure 1). Sub-regions ‘SC4’ and
‘RS1’ are similar in their physical features, separated only by a few coastal cliffs, but were
divided in order to comprise the same number of bins of sub-region ‘SC3’ for comparison
purposes. Sighting data were processed using a GIS software package (ArcView 3.2a,
Environmental Systems Research Institute, Inc., ESRI).
We used Mann Whitney and Kruskall-Wallis Tests to compare the density of whales in
each set of years, and the Qui-square contingency test to examine tendency in whale
distribution by sub-region.
Within-season distribution
To describe the within-season distribution of whales sighted along the study area we used
data from 2002 and 2003. In these years we conducted four surveys each year covering the
same stretch of the cost (bins G to S). Monthly surveys were made from July to November in
2002 (with the except of October) and from August to November in 2003. The Kruskall-
Wallis Test was used to compare the density of whales between months in each year.
Coastal movements and approximate residence period
Resightings of individual whales during monthly surveys conducted in 2002 and 2003
provided information on within-season movements and period of stay in the region. Females
with calves sighted during shore and boat-based observations in the study area have been
reported to stay at least 20-25 days in the same bay (Groch 2000; Groch et al. 2003) and as
long as 69 days moving between different bays (Palazzo et al. 1999; Groch et al. 2003). For
this reason movements that occurred within a wintering season were considered to have been
made in coastal waters, with the assumption that movements took place along the coast and
that between these sightings whales remain within the aggregation area. Because these
assumptions can potentially overestimate whales’ true period of stay, data provided in this
paper are considered to be approximate residence period. In addition, whales could have been
in the area before the survey was conducted and hence this data could also have been
underestimated. The approximate residence period was based on minimum distance traveled
between sightings in different days, and was measured on a 1:280.000 nautical chart.
Unaccompanied whales are known to spend less time than females with calves in wintering
36
grounds (Burnell and Bryden 1997) but no previous information on residence period is
available for the study area. For this reason, the same assumptions as for females with calves
were considered for unaccompanied whales, and so the information provided here should be
treated more carefully when used for comparison purposes.
In September 2002 the survey was made during two consecutive days with flights
covering two adjacent areas. Some whales were sighted in both flights but included only once
in the above analysis. We used sightings of these whales to provide information on swimming
speed and daily movements, combining the time and position of sightings in both flights.
Site fidelity
The Brazilian Right Whale Catalogue has 315 different individual whales (120 females,
149 whales of unknown sex/age and 46 calves identified in their calf year) (Groch et al. in
press). Ten percent (n=31) of the whales have been resighted providing information on site
fidelity. In addition to the main surveys conducted during the time of peak whale abundance,
and the monthly surveys conducted in 2002 and 2003, we have also included for this analysis
whales identified during 13 surveys made in non-regular basis between July and October in
1988 (August, n=1), 1997 (September, n=3), 1998 (September, n=4), 1999 (July-October,
n=3) and 2000 (October, n=2). These surveys covered mainly the standard survey area
(120km of coast) and will be hereafter referred as non-main flights. Data considered for this
analysis comes from the first sighting of each individual in a year.
Southern right whales, specially females with calves, are considered to exhibit levels of
site fidelity for wintering areas (Bannister 1990; Best 1990, 2000; Burnell and Bryden 1997;
Rowntree et al. 2001). We used individual identified whales resighted at least once during
aerial surveys in different years to verify the degree of fidelity in the study area. An individual
was considered to display some level of fidelity when it was sighted at least twice, each in
different year, in a particular region.
RESULTS
Population structure
37
Between 1987 and 2003, 481 whales were sighted in 16 aerial surveys conducted during
the time of peak whale abundance along the Southern Brazilian Coast (Table 2). The majority
of sightings were of groups with two whales (67.3%, n=150) and groups of up to four whales
were the most commonly sighted. The maximum number of whales sighted in a group during
the surveys was eight (0.9%, n=2). From the total number of whales, 149 were females, 149
were calves, and 183 unaccompanied whales, distributed in 223 groups. Most of the groups
(58.3%, n=130) consisted of single pairs of females with calves and 35.9% (n=80) were
sightings of 1 to 8 unaccompanied whales. Single females with calves were seen accompanied
by non-calf whales in 11 occasions and in one occasion two pairs of females with calves were
sighted associated with four unaccompanied whales. Unaccompanied whales were most
commonly seen as single individuals (16.6%, n=37), thought groups of two individuals were
also very frequent (12.1%, n=27). Three subadults and two yearlings were sighted and
included in the category of unaccompanied whales. The subadults were sighted each in groups
of up to four whales (one in a group with a female with calf) and the yearlings in groups of
two and six unaccompanied whales.
Inter-annual distribution
The density of whales sighted per bin in the surveys conducted during the time of peak
whale abundance in the entire study period is given in Figure 2. Whales concentrated between
bins J (Garopaba) and N (Araranguá) with a peak of sightings in bin L (Laguna) and it is
coincident with the previously identified aggregation area. This area is also coincident with
the standard surveyed area, and the concentration of sightings could have been biased by the
higher survey effort in relation to the total area. A region with lower density occurred between
O and S with a peak in Q and R. Females with calves followed the same overall pattern of
distribution but there were no sightings in bins G, H and T. The distribution of
unaccompanied whales extended further south and along a wider area, from bin L to bin R,
with a peak in the outmost bins. A high density was also observed in bin J, though half the
peak in the main density area. A lower density occurred between G and I, K and S-T.
Although the distribution of mother/calf pairs and unaccompanied whales was apparently
different, this was not supported statistically (Mann-Whitney: U =71.5, z =0.301, p =0.763,
n
1
=11, n
2
=14), maybe because of the low sample size.
a) Distribution by survey coverage
38
The distribution of whales grouped according to the survey coverage over the years is
shown in Figure 3. In 1987-1994 bins G to S were surveyed, with an extension to bin T in
1993. Whales were concentrated along bins J to N and P to R, and the cumulative density of
whales per bin peaked in bins J and L. A region with lower cumulative density of whales
occurred between bins G and I, and S-T. There were no sightings in bin O. The period 1997-
2000 had the most variable survey coverage, varying between bins G and N, thus the resulting
pattern of distribution could have been biased towards higher densities in bins with greater
survey effort. The distribution of whales was concentrated in bins J to L with a peak in J and
L. Bins I and M to O had lower cumulative densities with a peak in bin N. In 2001-2003 bins
G to T were surveyed but no sightings were recorded in bins G, H and T. The whales were
concentrated between bins J to M with a peak in bin L, and a lower concentration occurred in
bin I and from bin N to S.
As expected after the overall distribution of whales during the entire study period, a
region of major concentration in the three blocks of years was observed between bins J and N,
and secondly in bins Q and R. When comparing the cumulative density of whales per bin
between 1987-1994 and 2001-2003, which had similar survey coverage, the distribution of all
whales sighted was significantly different (Mann-Whitney: U =19, z =3.0417, p = 0.0024, n
1
= 13, n
2
= 11). The distribution was not significantly different when comparing only
unaccompanied whales (Mann-Whitney: U =32, z = 1.8463, p = 0.0649, n
1
= 12, n
2
= 10),
but no significant difference was observed in the distribution of females with calves (Mann-
Whitney: U =27.5, z =1.6714, p = 0.0946, n
1
= 9, n
2
= 11). The low number of sightings in
bin T could have been biased in 1987-1994 because this bin was surveyed in only one out of
five years. However, bin T was flown in all surveys from 2001 to 2003 and no sightings were
recorded as well.
b) Distribution by approximate date of flight
The resulting distribution of whales from the combination of the aerial surveys by
approximate date of flight is shown in Figure 4. During the surveys combined in block A,
whales were concentrated from bins J to N and bins Q-R. In block B the whales were
concentrated mostly between bins J and N while in block C three major areas of concentration
are observed, in bins I-J, L-M and O-R. The distribution of whales in block A was
significantly different from blocks B and C (Kruskall-Wallis: n =3, H = 6.246, p =0.044;
p(AxB)= 0.0317 p(AxC)= 0.0423; p(BxC)= 0.8659), but blocks B and C were not
significantly different from each other. However, when comparing the distribution by
39
category of whales no significant differences were found (females with calves: Kruskall-
Wallis: n =3, H =5.1771, p =0.0751; unaccompanied whales: Kruskall-Wallis: n =3, H
=0.2001, p =0.9048).
c) Distribution by sub-region
The distribution of whales along four sub-regions in the study area is given in Table 3.
Sub-region ‘SC1’ corresponds to bins A to F and, as mentioned above, had no sightings over
the entire period.
Females with calves showed the same pattern of distribution over the years. The sightings
were concentrated in sub-region ‘SC3’ in all blocks of years, followed by ‘SC4’ and ‘RS1’.
No sightings were recorded in sub-region ‘SC2’ in 1987-1994 and 2001-2003. For
unaccompanied whales in 1987-1994, the higher number of sightings was recorded in sub-
region ‘RS1’ followed by ‘SC3’, ‘SC4’ and ‘SC2’. In 1997-2000 and 2001-2003 the higher
number of sightings was recorded in sub-region ‘SC4’, followed by ‘SC3’. In 2001-2003 a
lower number of sightings was recorded in sub-region ‘RS1’ and no sightings were recorded
in ‘SC2’. It’s important to note that in 1997-2000 only sub-regions ‘SC3’ and half of ‘SC4’
were surveyed. The number of whales sighted in sub-regions ‘SC3’ to ‘RS1’ was significantly
different between 1987-1994 and 2001-2003 for both unaccompanied whales (Chi-square:
χ
2
= 5.783; df = 2; p = 0.0555) and females with calves (Chi-square:
χ
2
= 0.704; df = 2; p =
0,7034), although for unaccompanied whales the level of significance was low. The 1997-
2000 period was not compared because of low sample size and variable survey coverage.
Within-season distribution
Sightings in 2002 and 2003 indicate that whales began arriving in the study area in
July/August, reaching a peak of occurrence in September, and declining in October/November
(Fig. 5). This pattern is also apparent both to females with calves and unaccompanied whales
when treated separated. Within-season distribution of whales sighted per bin in 2002 and
2003 is shown in Figures 6 and 7.
In 2002, 210 whales were sighted (including double sightings), being 61.9% (n=130)
females with calves and 38.1% (n=80) unaccompanied whales. From the total, 58.6% (n=123)
of whales were sighted in September, 29% (n=61) in August, 11.4% (n=24) in July and 1%
(n=2) in November. There was no aerial survey during October. Because November had only
one sighting, a female with calf, it was not included in the statistical analysis. The distribution
40
of females with calves was not continuous along the survey area, but significantly uniform
through the months (Kruskal-Wallis: n=3, H=4.9379, p=0.0847), concentrated in the
northernmost bins, between H and N (Fig. 6). A few isolated sightings occurred in bins R (in
August) and S (in September). The distribution of unaccompanied whales was continuous in
July, but not continuous in August and September, and varied through the months. In July and
August whales where concentrated along the southernmost bins, from M to T, but in
September there was two major concentration areas, one along the northernmost bins, from I
to N, and the other in bins R and S. The distribution of unaccompanied whales was
significantly similar between July and August, but differed significantly in September
(Kruskal-Wallis: n=3, H = 8.2342, p =0.0163; p (jul x aug) = 0.5506; p (jul x sep) = 0.0079; p
(aug x sep) = 0.0319).
In 2003, 191 whales were sighted (including double sightings), being 55.5% (n=106)
females with calves and 44.5 (n=85) unaccompanied whales. From the total, 59.2% (n=113)
of whales were sighted in September, 23% (n=44) in October and 17.8% (n=34) in August.
There was no aerial survey in July, and no sightings were recorded in November. The
distribution of females with calves was significantly uniform over the months (Kruskal-
Wallis: n=3, H=1.643 p=0.4398), but not continuous in September and October, and
somewhat skewed to the south when compared to 2002. A concentration area is observed
between bins K and O with a few sightings between bins P and T. The distribution of
unaccompanied whales was not continuous over the months and whales were concentrated
from bins O to R in August, and I to M in October. In September, a major concentration area
occurred from bins O to R, but the peak of sightings occurred in bin L. Although the
distribution in October was apparently different from August and September, this was not
supported statistically (Kruskal-Wallis: n=3, H=3.8114, p=0.1487).
Coastal movements and approximate residence period
Sighting frequencies of whales identified during monthly surveys in 2002 and 2003 were
analyzed and data on monthly resighting patterns of non-calf whales are presented in Tables 4
and 5. A total of 37 whales were resighted, 20 in 2002 and 17 in 2003 (Table 5). In 2002,
most of the resightings occurred in September (85.7%, n=18) and in 2003 in October (66.7%,
n=12) (Table 4). Patterns of resighting were not repeated between 2002 and 2003, but there
was no flight in October 2002 and July 2003 to enable a direct comparison between all
months.
41
The majority of resightings both in 2002 and 2003 were of females with calves, resighted
at least once in two consecutive monthly surveys. From the total number of whales identified
in 2002 (n=145), 13.8% (n=20) were resighted at least once in different surveys, of which
85% (n=17) are females with calves and 15% (n=3) unaccompanied whales. In 2003, 12.3%
(n=17) of the whales identified (n=138) were resighted at least once, of which 94.1% (n=16)
are females with calves and 5.9% (n=1) unaccompanied whales. Most of the resightings were
in two consecutive months either in 2002 (80%, n=16) or 2003 (94.1%, n=16) (Table 5).
Considering that during this period the whales remained in the area, these whales spent
between 25 and 37 days in the region. Two females with calves were sighted in three
consecutive months, one in 2002 and another in 2003, and may have spent 62 and 64 days in
the region. In 2002 three females with calves were sighted in two interrupted months (i.e.,
July – September). One of these females with calves was sighted in September and November
but there was no survey in October, so the approximate residence period was not speculated.
The sample size was not large enough to test for significant differences in the resighting rates
among the females with calves and unaccompanied whales.
Table 6 shows data on the within-season movements of the non-calf whales resighted in
2002 and 2003. Females with calves resighted in 2002 displayed more northbound
movements (61.1%, n=11) between sightings in relation to southbound movements (38.9%,
n=7), which were displayed mostly between August and September. Unaccompanied whales
displayed more southbound (66.7%, n=2) than northbound (33.3%, n=1) movements and all
resightings were between August and September. In 2003 females with calves displayed
similar rates both southbound and northbound (52.9% and 47.1% respectively) and the only
unaccompanied whale resighted displayed a southbound movement. Similar proportions of
southbound and northbound movements were displayed in the three possible monthly
combinations of resighting patterns in 2003 (see Table 6).
The spatial distribution of the within-season movements of females with calves resighted
in 2002 and 2003 is shown in Figures 8 and 9. The position of whales when first sighted, in
terms of bins of latitude, was plotted according to the direction of movement in relation to the
position of the resighting (Figure 8). Data from 2002 and 2003 were grouped because of the
small sample size. There appears to be a tendency for whales first sighted in the northernmost
bins being resighted in a southernmost bin as well as the opposite movement, and these
patterns were significantly similar (Mann-Whitney: U =16.5, z=1.0222, p=0.3067, n
1
=n
2
=7).
Whether whales movement from the first sighting was constantly northbound or southbound
42
is not known and because data presented here comes from punctual observations it is not
intended to be exhaustive. In Figure 9 the position of whales when first sighted was plotted by
bin, according to the month of first sighting. Monthly distribution followed the overall pattern
of movements (shown in Figure 8) and no obvious tendency was observed between months.
The number of unaccompanied whales resighted was too small to detect any tendency or
pattern of spatial distribution.
Eleven non-calf whales were sighted in the two complementary flights in the 23 and 24 of
September 2002, most of which being females with calves and only one unaccompanied
whale. The mean minimum distance traveled between sightings by females with calves was
6.5 ± 6.2km during 16.8±0.3h at a mean swimming speed of 0.4 ± 0.4km/h. The
unaccompanied whale traveled a minimum of 11km at 0.7km/h. All but one sighting and
resighting were in bin K, the exception being a female with calf sighted in bin L and resighted
in bin K, indicating that at least some whales demonstrate fidelity to some particular bin over
a short period of time.
Site fidelity
Data from the 31 whales identified and resighted between 1987 and 2003 are shown in
Table 7. There were no resightings before 1994 and 71% of the resightings occurred in 2003.
The time period between sightings varied from one to 10 years. With the exception of two
females resighted in two and three different years, all other whales were resighted only once.
Five whales (16.1%) included in this analysis were first sighted only in non-main flights but
resighted in main flights, and another four whales (12.9%) were resighted only in non-main
flights.
Seventeen whales (48.4%) were resighted in the same sub-region of the first sighting
(‘SC3’ or ‘SC4’), 10 (32.3%) in adjacent sub-regions (‘SC3’ and ‘SC4’) and 6 (19.4%)
between ‘RS1’ and ‘SC3’. The number of bins traversed between sightings was obviously
lower between the same or adjacent sub-regions than in non-adjacent ones. Most of the
resighted whales were females (74.2%, n=23), which were predominantly resighted in the
same sub-region of first sighting (‘SC3’). ‘SC3’ was the preferred sub-region either for first or
subsequent sightings for most of the whales (96.8% were sighted at least once in ‘SC3’).
From the total number of females individually identified in Southern Brazil (n=120),
19.2% (n=23) have shown some level of site fidelity by returning to this wintering ground.
43
From the total number of females resighted, 82.6% (n=19) were sighted with newborn calves
(and thus were in calving years) in both first and the subsequent year of sighting. Of the 18
females first sighted in sub-region ‘SC3’, 83.3% (n=15) were in their calving year and 38.7%
(n=11) were resighted in the same sub-region in another calving year. From the four females
sighted only once with calves, two were sighted with their calves in sub-region ‘SC3’, one
when first sighted and the other when resighted. The females resighted in two and three
different years were in their calving year during all sightings and were sighted mostly in sub-
region ‘SC3’ (the last resighting of both females was in ‘SC4’). Both females have traversed 1
to 3 bins between resightings.
Only 3.4% (n=8) of the total unaccompanied whales identified (n=149) have been
resighted, mostly in the sub-region adjacent to the first sighting (‘SC3’ and ‘SC4’). The modal
interval between sightings for unaccompanied whales was one year. It’s worth noting that
three of these whales were yearlings (6.5% of the total unaccompanied whales identified),
returning to their region of birth, one to five bins far from the bin where first sighted. The
three yearlings were first identified accompanied by their mothers in September 2002, and
resighted in 2003 without their mothers, one in August and the other two in September. Their
mothers were not sighted in 2003, indicating that by the time of the sighting the yearlings
were already weaned.
When resightings did not occurred in the same sub-region of first sighting, females have
dispersed equally either northwards or southwards. Dispersal of unaccompanied whales was
mostly towards a southernmost region. There was a tendency for unaccompanied whales
(87.5%) to return to the same or adjacent sub-region slightly more frequently than females
(78.3%). The pattern of resighting of females and unaccompanied whales did not varied
significantly (Mann-Whitney: U =4.5, z=1.3472, p=0.1779, n
1
=5, n
2
=4).
DISCUSSION
The distribution of southern right whales within the study area was not uniform,
indicating that some specific areas are important wintering habitats for this recovering
species. Whales were sighted mostly in pairs of females with calves, characterizing the area as
an important nursery area, as previously mentioned (Simões-Lopes et al. 1992; Palazzo and
Flores 1996, 1998; International Wildlife Coalition/Brazil 1999). Right whale associations of
44
many individuals are not common in breeding areas (Payne 1986; Bannister 1990; Best 1990;
Patenaude and Baker 2001; Best et al. 2003), excepting the temporary associations of groups
engaged in social or sexual activity (Donnelly 1967; Payne et al., 1983; Best et al. 2003).
Survey effort varied among years, but patterns of right whale distribution can be
identified. The distribution of females with calves and unaccompanied whales is overlapped
to some extent, but a major concentration area can be identified, especially for females with
calves, in the northernmost bins. This area is coincident with the previously recognized
aggregation area in the region (Simões-Lopes et al. 1992; Palazzo and Flores 1996, 1998;
International Wildlife Coalition/Brazil 1999). A smaller concentration area occurs in the
southernmost bins. This pattern is also observed when data is grouped by blocks of years with
similar survey coverage and also by approximate date.
When grouped by sub-regions with distinct geographic features, two major adjacent areas
of concentration can be identified. The first, SC3, is characterized by small bays in all
extension, and had mostly sightings of females with calves. The second, SC4, is a straight
coastline and had mostly sightings of unaccompanied whales. The relatively small proportion
of females with calves in the southernmost region of this study indicates a geographic
segregation is occurring, as previously mentioned (Palazzo and Flores 1998; International
Wildlife Coalition/Brazil 1999). Geographic segregation of different group categories has also
been observed in Argentina (Payne 1986) and South Africa (Best 1981; Best 1990, 2000). In
these areas different bays or stretches of coastline are used for nursing and mating. Because
we could not sex the unaccompanied whales, it is not possible to assert that the SC4 region is
a mating area but the behavior of some of the groups without calves indicates that this may be
the case.
Regions of concentrations have also been identified for other wintering areas (e.g.
Argentina (Payne, 1986), South Africa (Best 1990; 2000) and Australia (Bannister 1990)). In
these areas, some stretches of the coast are more favored than others and have higher number
of whales. Elwen and Best (2004) suggested that environmental factors play an important rule
on the distribution of right whales in South Africa. According to these authors, whales
concentrate in areas that provide reasonable protection from open ocean swell and seasonal
winds, as well as areas with sedimentary floors and gentle slopes. In a study using data from
shore-based observations, Groch (2000) found no evidence on the influence of wind on the
distribution of right whales in their main concentration area off southern Brazil, but did not
tested the other factors found by Elwen and Best (2004) to have influence.
45
Best (2000) and Rowntree et al. (2001) reported shifts in distribution of right whale
along South African and Península Valdés coasts, respectively. In South Africa, the preferred
areas along the coastline have not changed over 30 years of study (Best, 2000). However, the
number of right whales has changed, increasing in some areas and decreasing in others,
shifting the median number of whales in some areas 40-46 min to the west. According to Best
(2000) one explanation for this shift could be the females’ previous experience in the choice
of the nursery area. Though no changes in distribution were observed in southern Brazil
during the study period, females’ previous experience may also influence the choice of
females with calves for the some specific wintering region off southern Brazil. On the other
hand, right whales in Peninsula Valdés, have shifted their distribution in recent years,
abandoning the Outer Coast in favor of the northern and southern bays of the Peninsula
(Rowntree et al. 2001). One possible explanation for this shift was major changes in bottom
topography due to storms. Inside the bays, whales were also observed moving from the center
of a whalewatching industry to areas with intense development of human activities and high
incidence of gull harassment. The authors attributed such movements more to individual
preference and social cohesion than disturb caused by whalewatching boats.
Despite no aerial survey was made in July 2003, a few sightings in this month were
reported in the standard survey area during systematic land based observations (bins I to L)
(Groch, unpublished), indicating that whales begun arriving at this time of the year, as in
2002. From July on the population builds up reaching a peak in September and declines in
October/November, following the overall pattern of occurrence of the other wintering grounds
in the Southern Hemisphere (e.g. Peninsula Valdés, Argentina (Payne 1986), South Africa
(Best and Scott 1993) and Australia (Bannister 1986)).
The greater number of females with calves in relation to unaccompanied whales resighted
both in 2002 and 2003 reflects the tendency of females with calves to stay longer in Southern
Brazil than unaccompanied whales, a pattern also observed in other wintering grounds (Payne
1986; Bannister 1990; Burnell and Bryden 1997; Best 2000; Rowntree et al. 2001). Given the
time between the surveys, female right whales may spend ~30 days or more in the region, a
residence period also observed during shore and boat-based observations (Palazzo et al. 1999;
Groch 2000; Groch et al. 2003). According to Taber and Thomas (1982) the main reason for
this period of stay of females with calves in wintering areas is the need of newborn calves to
pass through specific developmental stages during the first months of life. During this period,
calves have to acquire motor ability, some level of competency in swimming, ability to
46
protect themselves and to identify and remain with their mothers. The time of departure is
probably given by compensation between the semi-starved mother and the pre-migratory
stage in behavior (Taber and Thomas 1982; Thomas and Taber 1984). At this time calves are
prepared for the relatively rapidly depart for their summer feeding grounds (Taber and
Thomas 1982; Thomas and Taber 1984), which results in a rapid decline in the number of
whales sighted at the end of the season, as observed between October and November in
southern Brazil.
Females with calves present less movements along the coast in wintering areas than
unaccompanied whales (Bannister 1990; Best 1990, 2000; Burnell and Bryden 1997;
Rowntree et al. 2001), but little is known on the movement patterns of unaccompanied
whales. They can be males looking for receptive females, pregnant females in their
conception year (especially those sighted early in the season) or subadults. Burnell and
Bryden (1997) reported sightings of unaccompanied whales at widely separated aggregation
areas and great variations in residence period. To these authors, the variation in distribution
does not necessarily represent less residence period in the area but could be simply less site
fidelity to particular areas than the pattern shown by calving females. Additionally, Burnell
(2001) reported that the residency of non-accompanied whales is often interrupted by periods
away from the wintering ground. Subadults and yearlings in Peninsula Valdés, Argentina,
have presented similar resighting patterns as females in calf years, indicating the importance
of that region for this class of whales (Rowntree et al. 2001). From the five whales classified
in this category, two of them (yearlings) were resighted, representing 5% of the total number
of whales resighted, indicating that the waters in southern Brazil are not being used as
frequently as Peninsula Valdés by young whales. Whether whales born in southern Brazil are
going to Peninsula Valdés in the following wintering season or to other wintering ground is
not known.
The mean swimming speed of 0.4±0.4km/h of the females with calves resighted during
the two complimentary flights is lower than the mean swimming speeds of 0.9 to 2.78km/h of
females with calves tracked by theodolite from shore during the monitoring of boat-based
whalewatching activities in the study area (Groch et al. 2003). One explanation for this
discrepancy is the implicit assumption that the whales traveled in a straight line between the
two sightings. In South Africa, Best (1990) reported very similar average speeds (0.8 to 2.89
km/h) of females with calves resighted within a one day period during aerial surveys, but
higher average speeds (0.4 to 3.62 km/h) from shore based observations. However, data from
47
shore-based observations in South Africa are presumably of undisturbed whales, differently
from data from aerial surveys, where whales could have potentially been disturbed by the
aircraft. Females with calves tracked in Peninsula Valdés averaged 2.3 km/h in presumably
undisturbed conditions (Colombo et al. 1990). In Brazil, data from shore-based observations
were collected before, during and after whales were approached by whalewatching boats
(Groch et al. 2003). The mean swimming speeds of 0.9 to 2.78km/h are of females tracked
before being approached by boats and thus are also presumably from undisturbed whales.
Notwithstanding, comparable values for the aerial survey data are the ones recorded during
approaches. In this phase the mean swimming speeds of the whales ranged from 1.10 to
2.71km/h, which are also much higher that the value obtained during the aerial surveys.
Burnell (2001) recorded average speeds of 1.1 to 3.66 km/h for unaccompanied whales,
values higher that the recorded for this category of whales in Brazil, but only one
unaccompanied whale was resighted during these complimentary flights and no data from
shore-based observations is available. Swimming speeds of unaccompanied whales tracked in
Peninsula Valdés averaged 1.7 to 3km/h (Colombo et al. 1990). The low speed values
recorded for right whales in this work reinforces that in southern Brazil at least some right
whales demonstrate fidelity to some particular area over one day or more periods of time,
even after being potentially disturbed during aerial surveys.
It is apparent that the southernmost regions are mostly used as transiting area. In 2002,
most of the resighted females with calves were first sighted in southernmost regions and
resighted in northernmost regions. In addition, these movements occurred between July and
September, when whales appear to be arriving in the region. This pattern, however, was not so
evident for whales resighted in 2003. On the other hand, a slightly greater number of females
with calves were first sighted in a northernmost region in September, and were next sighted in
a southernmost region (in October), indicating the possible use of the southernmost region
also by transiting whales at the end of the wintering season.
Despite the relatively small number of whales resighted in Brazil, these whales displayed
some level of fidelity, especially to the main concentration area, where the characteristics of
the coastline fit the preferred wintering habitat for this species. It was only recently that
known right whales begun to return in southern Brazil, thus presenting low levels of annual
return (Groch et al. 2005). Females with calves from southern Brazil have been calving once
every three years (Groch et al. 2005). Although rarely seen in the intervening years, this
calving interval undoubtedly had influenced the rate of resightings of this category of whales.
48
Given that most of the resightings were of females, this pattern can be viewed only as relative
measures and do not represent the actual return frequencies of the different category of
whales. Because the survey effort was constant towards photographing all categories, the
differences in the resighting rates of females with calves and unaccompanied whales should
reflect real differences in their residence period or the behavior of females with calves, which
usually spend more time at surface, being more likely to be sighted than unaccompanied
whales.
In South Africa, Best (2000) concluded that fidelity to the actual stretch of the coast was
not too strong, because only 52.9% of the females had their first calf in the same or adjacent
areas where first photographed, and 60.9% of the multigravid females. In Argentina, 52% of
the females exhibited fidelity to the same region of concentration with successive calves.
Burnell (2001) considered that some level of fidelity was displayed by females returning at
least once to the study area and at most in as many years at other regions. Because of the low
individual resighting rate presented by most of the whales in Brazil, we did not attempt to
evaluate the degree of fidelity.
It is not clear which factors determine the presence and distribution of right whales in
Southern Brazil. Resightings of right whales photographed off southern Brazil in Peninsula
Valdés (Best et al. 1993; Groch unpublished) indicates some the degree of flexibility in the
habitat use. It is likely that specific areas may have greater importance to mother/calf pairs
than to unaccompanied whales, but a better understanding of this characteristic will only be
possible with a longer time series of data. This flexibility and the extension of movement
shown by females with calves in some wintering areas are encouraging signs of the increase
in the population and the expansion to historic areas. Data presented here are initial and
further research is needed in a long-term basis for a comprehensive monitoring of this
recovering population.
AKNOWLEDGEMENTS
We are indebted to a number of people involved with data collection during the aerial
surveys. Funding from PETROBRAS Brazilian Oil Company has been vital for the
continuation of this work. Funding from Brazilian Conservation Fundation (FBCN), World
Wildlife Fund, International Schloesser Textil Company, The Barbara Delano Foundation,
49
Mormaii, New Millenium Promoções e Eventos also supported this work in past years.
Comissão de Aperfeiçoamento de Pessoal (CAPES – Ministry of Education) and Conselho
Nacional de Desenvolvimento Científico e Tecnológico (CNPq – Ministry of Science and
Technology) for the Ph.D. scholarship to the first author (2001-2005). Thanks to Dr. Rafael
Sperb and his Lab (Environmental Engineering of UNIVALI) for initial assistance with the
GIS software.
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52
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53
Thomas, P.O. 1987. Social behavior, habitat use, and interspecific interactions of southern
right whales (Eubalaena australis) mother-calf pairs. Ph.D dissertation, University of
California, Santa Cruz, CA. vi + 133pp.
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171.
LIST OF TABLES
Table 1 - Summary of aerial surveys from 1987 to 2003 used to describe the inter-annual
distribution of right whales along the Southern Brazilian coast (letters correspond to bins
of 12 minutes of latitude long). .......................................................................................56
Table 2 – Number of whales sighted during aerial surveys conducted from 1987 to 2003,
along the Southern Brazilian coast, by group category (percentage of total number of
groups shown in parenthesis). (UW = unaccompanied whales; FC = females with
calves)..............................................................................................................................56
Table 3 - Number of right whales seen during aerial surveys along the Southern Brazilian
coast, by sub-regions and blocks of years with similar survey coverage, from 1987 to
2003 (percentage of whales seen by sub-region in each block of years is given in
parenthesis)......................................................................................................................57
Table 4 – Number of right whales resighted during monthly aerial surveys along the Southern
Brazilian coast in 2002 and 2003. ...................................................................................57
Table 5 – Summary data on non-calf whales identified and resighted during monthly aerial
surveys along the Southern Brazilian coast in 2002 and 2003 (percentage of resightings
shown in parenthesis). .....................................................................................................58
Table 6 – Movements of non-calf whales resighted during monthly aerial surveys along the
Southern Brazilian coast in 2002 and 2003 (percentage of movements shown in
parenthesis)......................................................................................................................59
Table 7 – Between year resighting patterns of whales identified during aerial surveys along
the Southern Brazilian coast between 1987 and 2003.....................................................61
LIST OF FIGURES
Figure 1 – Map of the study area. A, South America; B, Santa Catarina State, Brazil; C,
South of Santa Catarina State. Triangles indicate observation sites (letters correspond to
bins of 12 minutes of latitude long).................................................................................62
Figure 2 – Cumulative density of right whales sighted per latitudinal bin during aerial surveys
conducted from 1987 to 2003, along the Southern Brazilian coast (data series is not
continuous – see text for details) (letters correspond to bins of 12 minutes of latitude
long).................................................................................................................................63
Figure 3 – Cumulative density of right whales sighted per latitudinal bin during aerial surveys
conducted from 1987 to 2003 along the Southern Brazilian coast, by blocks of years with
similar survey coverage (survey effort was concentrated in bins I to O in 1997-2000 –
see text for details) (letters correspond to bins of 12 minutes of latitude long). .............64
Figure 4 – Cumulative density of right whales sighted per latitudinal bin during aerial surveys
conducted from 1987 to 2003 along the Southern Brazilian coast, grouped by
approximate date of flight (letters correspond to bins of 12 minutes of latitude long)...65
Figure 5 – Number of right whales sighted during monthly aerial surveys along the Southern
Brazilian coast, between July and November in 2002 and 2003 (letters correspond to bins
of 12 minutes of latitude long). .......................................................................................66
Figure 6 – Density of right whales sighted per bin during monthly aerial surveys along the
Southern Brazilian coast, from July to September 2002 (letters correspond to bins of 12
minutes of latitude long)..................................................................................................67
Figure 7 – Density of right whales sighted per bin during monthly aerial surveys along the
Southern Brazilian coast, from August to October 2003 (letters correspond to bins of 12
minutes of latitude long)..................................................................................................68
Figure 8 - Position of the first sighting of whales resighted during monthly surveys along the
Southern Brazilian coast in 2002 and 2003, according to the direction of movement
between sightings (letters correspond to bins of 12 minutes of latitude long)................69
Figure 9 – Distribution of whales by bin of latitude and direction of movement according to
the month of first sighting during monthly surveys along the Southern Brazilian coast in
2002 and 2003 (letters correspond to bins of 12 minutes of latitude long).....................70
56
Table 1 - Summary of aerial surveys from 1987 to 2003 used to describe the inter-annual
distribution of right whales along the Southern Brazilian coast (letters correspond to bins of
12 minutes of latitude long).
Year
Flight
considered for
this analysis
Aircraft
Bins
surveyed
No. whales
sighted /
survey
Unaccomp.
whales
Females
with
calves
1987
1-Sep Piper PA-22 singlemotor G - S 33 21 6
1988
28+29 Sep (*) Cessna 170 singlemotor E - S 16 4 6
1992
30+31 Aug (*) Cessna 182 singlemotor G - T 16 12 2
1993
27-Aug Cessna 182 singlemotor G - S 28 20 4
1994
1-Sep Cessna 182 singlemotor G - S 27 7 10
1997
27-Sep Citabria Singlemotor I - N 20 8 6
1998
23-Sep Enstrom helicopter I - O 24 0 12
1999
10-Sep Enstrom helicopter I - P 20 0 10
2000
8-Oct Squirrel helicopter G - N 24 2 11
2001
13+14 Sep (*) Jet Ranger helicopter G - S 44 0 22
2002
23+24 Sep (*) Jet Ranger helicopter G - S 128 46 41
2003
12-Sep Jet Ranger helicopter G - S 112 60 26
(*) Two complementary flights covering adjacent areas.
Table 2 – Number of whales sighted during aerial surveys conducted from 1987 to 2003,
along the Southern Brazilian coast, by group category (percentage of total number of
groups shown in parenthesis). (UW = unaccompanied whales; FC = females with
calves).
Frequency of sightings by group category
(higher frequencies highlighted in bold)
Group
Category
No. of
whales
1 2 3 4 5 6 7 8
No. of
groups
No. of
whales
Mean no.
of whales
by group
UW
37
(16.6)
27
(12.1)
9
(4.0)
4
(1.8)
2
(0.9)
2
(0.9)
0
1
(0.4)
82
(36.8)
164
(34.1)
2 ± 1
FC
-
123
(55.2)
-
7
(3.1)
- 0 - 0
130
(58.3)
274
(57.0)
2 ± 0
FC+UW
Frequency
- -
6
(2.7)
3
(1.3)
1
(0.4)
0 0
1
(0.4)
11
(4.9)
43
(8.9)
4 ± 2
Total
37
(16.6)
150
(67.3)
15
(6.7)
14
6.3)
3
(1.3)
2
(0.9)
0
(0)
2
0.9)
223 481
2 ± 1
57
Table 3 - Number of right whales seen during aerial surveys along the Southern Brazilian
coast, by sub-regions and blocks of years with similar survey coverage, from 1987 to
2003 (percentage of whales seen by sub-region in each block of years is given in
parenthesis).
Females with calves Unaccompanied whales TOTAL
1987-
1994
1997-2000 2001-2003 Total 1987-1994 1997-2000 2001-2003 Total
SC2 (*)
0 0 0 0
4
(5.9)
0 0
4
(2.2)
4
(1.2)
SC3
18
(66.7)
23
(59.0)
48
(57.8)
89
(59.7)
22
(32.4)
2
(22.2)
34
(32.1)
58
(31.7)
147
(44.3)
SC4
(**)
7
(25.9)
16
(41.0)
26
(31.3)
49
(32.9)
19
(27.9)
7
(77.8)
49
(46.2)
75
(41.0)
124
(37.3)
RS1 (*)
2
(7.4)
-
9
(10.8)
11
(7.4)
23
(33.8)
-
23
(21.7)
46
(25.1)
57
(17.2)
Total 27 39 83 149 68 9 106 183 332
(*) Apart from SC2 in 2000, these regions were not surveyed in 1997-2000.
(**) Only half of this sub-region (2 bins) was surveyed in 1997-2000.
58
Table 4 – Summary data on non-calf whales identified and resighted during monthly aerial
surveys along the Southern Brazilian coast in 2002 and 2003 (percentage of resightings
shown in parenthesis).
2002
Month of flight
Days
between
flights
No. of
females
with
calves
resighted
No. of
unaccompanied
whales resighted
Total
July – Aug
25
1 (5.9) 0 1 (5.0)
Aug – Sep
36-37(*)
12 (70.6) 3 (100) 15 (75.0)
July – Aug – Sep
-
1 (5.9) 0 1 (5.0)
July – Sep
61-62(*)
2 (11.8) 0 2 (10.0)
Sep – Nov
46
1 (5.9) 0 1 (5.0)
Total no. of non-calf whales resighted
- 17 (85.0) 3 (15.0) 20
Total no. of non-calf whales identified
- 65 80 145
% Resightings in relation to total
identified
- 11.7 % 2.1 % 13.8%
2003
Month of flight
Days
between
flights
No. of
females
with
calves
resighted
No. of
unaccompanied
whales resighted
Total
Aug – Sep
31
5 (31.3) 0 5 (29.4)
Sep – Oct
33
10 (62.5) 1 (100) 11 (64.7)
Aug – Sep – Oct
-
1 (6.3) 0 1 (5.9)
Total no. of non-calf whales resighted
- 16 (94.1) 1 (5.9) 17
Total no. of non-calf whales
identified
- 53 85 138
% Resightings in relation to total
identified
- 11.6 % 0.7 % 12.3%
(*) The survey of September 2002 was completed after two complementary flights covering
adjacent areas, which resulted in two values for the interval between sightings.
59
Table 5– Number of resightings of right whales during monthly aerial surveys along the
Southern Brazilian coast in 2002 and 2003.
2002
Females with calves Unaccompanied whales TOTAL
Month of
survey
No. of
resighti
ngs
%
Resightin
gs/ month
% Resi
g
htin
g
in relation to
total whales
identified
No. of
resighting
s
%
Resightings/
month
%
Resi
g
htin
g
s in
relation to
total whales
identified
N
Distributio
n of
Resightings
/ month
(%)
Aug
2 11.1 1.4 0 0,0 0.0
2 9,5
Sep
15 85.7 10.3 3 100.0 2.1
18 85,7
Nov
1 5.6 0.6 0 0.0 0.0
1 4,8
TOTAL 21
-
12.4 3
-
2.1
21 -
2003
Females with calves Unaccompanied whales TOTAL
Month of
survey
No. of
resighti
ngs
%
Resightin
gs/ month
% Resi
g
htin
g
in relation to
total whales
identified
No. of
resighting
s
%
Resightings/
month
%
Resi
g
htin
g
s in
relation to
total whales
identified
N
Distributio
n of
Resightings
/ month
(%)
Sep
6 35.3 4.3 0 0 0
6 33.3
Oct
11 66.7 8.0 1 100.0 0.7
12 66.7
TOTAL 17
-
12.3 1 - 0.7
18 -
60
Table 6 – Movements of non-calf whales resighted during monthly aerial surveys along the
Southern Brazilian coast in 2002 and 2003 (percentage of movements shown in
parenthesis).
2002
Females with calves Unaccompanied whales
Month
of flight
Days
between
flights
No. of
Southbou
nd
movement
s
No. of
Northbou
nd
movement
s
Mean
minimum
distance
traveled
(km)
Mean
minimu
m bins
traverse
d
No. of
Southbou
nd
movement
s
No. of
Northbou
nd
movement
s
Mean
minimum
distance
traveled
(km)
Mean
minimu
m bins
traverse
d
Jul –
Aug
25 1 (5.6) 0 76.0 3 - - - -
Aug –
Sep
36-37(*) 4 (22.2) 8 (44.4)
49.5 ±
46.7
1.8 ± 1.6 2 (66.7) 1 (33.3) 84.0 ± 27.7 3 ± 1
Jul –
Aug –
Sep
- 1 (5.6) 1 (5.6) 29.5 ± 4.9 1.5 ± 0.7 - - - -
Jul –
Sep
61-62(*) 0 2 (11.1)
97.0 ±
84.8
4 ± 4.2 - - - -
Sep –
Nov
46 1 (5.6) 0 193.0 6 - - - -
TOTAL - 7 (38.9) 11 (61.1) - 2 (66.7) 1 (33.3) -
-
2003
Females with calves
Unaccompanied whales
Month
of flight
Days
between
flights
No. of
Southbou
nd
movement
s
No. of
Northbou
nd
movement
s
Mean
minimum
distance
traveled
(km)
Mean
minimu
m bins
traverse
d
No. of
Southbou
nd
movement
s
No. of
Northbou
nd
movement
s
Mean
minimum
distance
traveled
(km)
Mean
minimu
m bins
traverse
d
Aug –
Sep
31 2 (11.8) 3 (17.6)
58.8 ±
59.8
1.4 ± 1.9
- - -
Sep –
Oct
33 6 (35.3) 4 (23.5)
61.9 ±
46.6
2.1 ± 1.4
1 (100) 0 102.0 4.0
Aug –
Sep –
Oct
- 1 (5.9) 1 (5.9)
106± 19.8 4.5 ± 0.7
- - -
TOTAL - 9 (52.9) 8 (47.1) - 1 (100) 0 -
-
(*) The survey of September 2002 was completed after two complementary flights covering adjacent
areas, which resulted in two values for the interval between sightings.
61
Table 7 – Between year resighting patterns of whales identified during aerial surveys along
the Southern Brazilian coast between 1987 and 2003.
Females Unaccompanied whales
Sub-region of
first and
second
sighting
Total
no. of
whales
resighte
d (%)
N
(% from
total no.
of
resightin
gs)
Mean no.
of years
between
sightings
No. of
bins
traversed
Females in
calving years in
both sightings
(% from females
resi
g
hted in each
combination of
sub-region)
N
(% from
total no. o
f
resighting
s)
Mean
no. of
years
between
sighting
s
No. of
bins
traversed
SC3 → SC3
14
(45.2)
12 (38.7)
3.3 ± 1.2 1.5 ± 1.5
11 (91.7) 2 (6.5) (*)
1.0 ± 0.0 1.5 ± 0.7
SC3 → SC4
7 (22.6) 3 (9.7) 2.7 ± 1.5 1.3 ± 1.2 1 (33.3) 4 (12.9) (*)
2.25 ±
2.5 3 ± 1.4
SC3 → RS1
4 (12.9) 3 (9.7)
3.0 ± 1.0 6.7 ± 2.5
3 (100.0) 1 (3.2) 1 7
SC4 → SC3
3 (9.7) 3 (9.7)
4.0 ± 1.7 1.7 ± 2.1
3 (100.0) 0 - -
SC4 → SC4
1 (3.2) 0 - - - 1 (3.2) 1 1
RS1 → SC3
2 (6.5) 2 (6.5)
8.0 ± 2.8 4.0 ± 1.4
1 (50.0) 0 - -
Total 31 23 (74.2) -
-
19 (82.6) 8 (25.8) - -
(*) 50% of these whales are yearlings.
62
Figure 1 – Map of the study area. A, South America; B, Santa Catarina State, Brazil; C,
South of Santa Catarina State (letters correspond to bins of 12 minutes of latitude long).
63
Figure 2 – Density of right whales sighted per latitudinal bin during aerial surveys conducted
from 1987 to 2003, along the Southern Brazilian coast (data series is not continuous –
see text for details) (letters correspond to bins of 12 minutes of latitude long).
64
Figure 3 – Cumulative density of right whales sighted per latitudinal bin during aerial surveys
conducted from 1987 to 2003 along the Southern Brazilian coast, by blocks of years with
similar survey coverage (survey effort was concentrated in bins I to O in 1997-2000 –
see text for details) (letters correspond to bins of 12 minutes of latitude long).
65
Figure 4 – Cumulative density of right whales sighted per latitudinal bin during aerial surveys
conducted from 1987 to 2003 along the Southern Brazilian coast, grouped by
approximate date of flight (letters correspond to bins of 12 minutes of latitude long).
66
Figure 5 – Number of right whales sighted during monthly aerial surveys along the Southern
Brazilian coast, between July and November in 2002 and 2003.
67
Figure 6 – Density of right whales sighted per bin during monthly aerial surveys along the
Southern Brazilian coast, from July to September 2002 (letters correspond to bins of 12
minutes of latitude long).
68
Figure 7 – Density of right whales sighted per bin during monthly aerial surveys along the
Southern Brazilian coast, from August to October 2003 (letters correspond to bins of 12
minutes of latitude long).
69
Figure 8 - Position of the first sighting of whales resighted during monthly surveys along the
Southern Brazilian coast in 2002 and 2003, according to the direction of movement
between sightings (letters correspond to bins of 12 minutes of latitude long).
70
Figure 9 – Distribution of whales by bin of latitude and direction of movement according to
the month of first sighting during monthly surveys along the Southern Brazilian coast in
2002 and 2003 (letters correspond to bins of 12 minutes of latitude long).
CAPÍTULO 3
RECENT RAPID INCREASES IN THE BRAZILIAN RIGHT WHALE
POPULATION
Karina R.Groch
1,2
, José T. Palazzo Jr.
2
., Paulo A.C. Flores
2
, Fred R. Adler
3
, Marta E.
Fabian
1
Contact e-mail: [email protected]
1
PPG Biologia Animal, UFRGS, Av. Bento Gonçalves 9500, Prédio 43435 Sala 101,
Porto Alegre, RS, 91501-970, Brazil.
2
International Wildlife Coalition/Brazil, Caixa Postal 201, Imbituba, SC, 88780-000,
Brazil.
3
University of Utah, Department of Biology and Department of Mathematics, 257
South 1400 East, Salt Lake City, UT 84112, USA.
Keywords: southern right whales, population increase, Southern Brazil, wintering
ground, Eubalaena, calving interval
*ESTE ARTIGO FOI APRESENTADO AO COMITÊ CIENTÍFICO DA 56A. REUNIÃO DA COMISSÃO
INTERNACIONAL DA BALEIA (INTERNATIONAL WHALING COMMISSION AND ASSOCIATED
MEETINGS), 2004, SORRENTO, ITALIA, E ESTÁ NO PRELO DO THE LATIN AMERICAN JOURNAL OF
AQUATIC MAMMALS.
74
Abstract
Right whales that gather on a wintering ground off southern Brazil have been
aerial surveyed and photographically identified since 1987. As of 2003 the Brazilian
Right Whale Catalogue has 315 different individual whales of which 31 were
resighted in other years (23 females, 3 yearlings and 5 whales of unknown age/sex).
No resightings occurred before 1994 and 71% (n=24) were recorded in 2003. The
modal observed interval between calving events is 3 years, consistent with successful
reproduction. From 1997 to 2003 the number of reproductive females in the Central
Survey Area off Brazil increased at a rate of 29.8% per year (95% CL 15.7, 44.0) and
at 14% per year (95% CL 7.1, 20.9) from 1987 to 2003. These rates are significantly
different from zero (t=4.133, p<0.009 and t=4.06, p<0.004, respectively) and the
increase from 1997 to 2003 is higher than the rates observed for right whales in other
wintering grounds in the South Atlantic. The right whales on the Brazilian wintering
ground are not just transients. Ten percent of the whales have been resighted. If the
number of whales continues to increase they will probably expand their distribution
throughout their historical 2,400 km range and come into increasing conflict with
human activities.
Resumo
As baleias francas que freqüentam a área de concentração reprodutiva de
inverno no sul do Brasil têm sido monitoradas através de levantamentos aéreos e
fotoidentificadas desde 1987. Até 2003, o catálogo brasileiro de identificação das
baleias francas conta com 315 baleias identificadas individualmente, das quais 31
foram reavistadas em outros anos (23 fêmeas, 3 baleias de um ano de idade e 5 baleias
de sexo/idade indeterminados). Nenhuma reavistagem foi registrada antes de 1994 e
71% (n=24) foram registradas em 2003. O intervalo modal observado entre o
nascimento dos filhotes foi três anos, o que é consistente com o sucesso reprodutivo.
De 1997 a 2003, o número de fêmeas registradas com filhotes na Área Central
sobrevoada no sul do Brasil aumentou a uma taxa de 29,8% ao ano (95% CL 15,7 -
44,0), e de 14% ao ano (95% CL 7,1 - 20,9) de 1987 a 2003. Estas taxas são
significativamente diferentes de zero (t=4,133, p<0,009 e t=4,06, p<0,004,
respectivamente) e o aumento de 1997 a 2003 é maior que as taxas observadas para as
75
baleias francas nas outras áreas de concentração reprodutiva de inverno no Oceano
Atlântico Sul. As baleias francas na área de concentração reprodutiva de inverno no
sul do Brasil não são apenas transientes. Dez por cento das baleias têm sido
reavistadas. Se o número continuar a aumentar, pode-se esperar que as baleias francas
reocupem sua área de distribuição histórica ao longo de cerca de 2400km de costa,
aumentando a possibilidade de conflitos entre as baleias francas e atividades humanas.
Introduction
Southern right whales (Eubalaena australis) were severely depleted by
commercial whaling from the 18
th
through the early 20
th
centuries. Tormosov et al.
(1998) describe unreported Soviet catches of right whales on their pelagic summer
grounds in the mid 20
th
century despite international protection since 1935. In
addition, right whales were also subject to intensive commercial whaling along the
southern Brazilian coast until 1973, when the whale population appeared to be
extirpated from the region (Palazzo and Carter, 1983). In the early 1980s, whales were
'rediscovered' in this region and have been studied there since 1981 (Câmara and
Palazzo, 1986).
From May to December groups of right whales use the shallow, protected waters
of southern Brazil as a wintering ground
2
(Lodi et al., 1996; Câmara and Palazzo,
1986; Palazzo and Flores, 1998; Simões-Lopes et al., 1992; International Wildlife
Coalition/Brazil, 1999). Their main aggregation area occurs off Santa Catarina State
particularly the central-southern coast from Ilha de Santa Catarina (27º25’S,
48º30’W) to Cabo de Santa Marta, Laguna (28º36’S, 48º48’W)
1
(Figure 1) (Simões-
Lopes et al., 1992; Palazzo and Flores, 1998; International Wildlife Coalition/Brazil,
1999). The time of peak abundance is from August to October
1
(Simões-Lopes et al.,
1992; Groch, 2000; Groch et al., 2003).
The whales have been surveyed along the southern coast of Brazil since 1987.
During aerial surveys, the presence and location of individual whales is documented
by photographing the individually distinctive pattern of callosities on each whale’s
head and marking its location on a map (Payne et al., 1983). The growth rate and
2
Palazzo Jr., J.T. and Flores, P.A.C. (1996) Progress report on the southern right whale Eubalana
australis off Santa Catarina, Southern Brazil: 1995. Page 27 in Abstracts, VII Reunión de Trabajo de
Especialistas en Mamíferos Acuáticos de América del Sur/ Primero Congreso de la Sociedad
Latinoamericana de Especialistas en Mamíferos Acuáticos, 22-25 Octubre, Viña del Mar, Chile.
76
other demographic parameters of right whale populations in southern hemisphere
have been estimated from the number of whales photo-identified each year during
aerial surveys off their wintering grounds (e.g. Bannister, 1990; Best et al., 2001;
Cooke et al., 2001). The annual growth rates of these right whale populations range
between 7 to 8% per year (IWC, 2001). In this paper we address two questions about
the right whales off southern Brazil: 1) what is their rate of increase and 2) do they
show inter-annual fidelity to this region?
Materials and Methods
From 1987 through 2003 we conducted aerial surveys of right whales off Brazil
in which we photo-identified individuals and marked their locations on a map.
Surveys were conducted on an irregular basis from 1987 to 1994 (1987, 1988, 1992,
1993 and 1994) and annually from 1997 to 2003, during the time of peak whale
abundance. Photographs taken from all aerial surveys have been used to create a
catalogue of right whales identified off southern Brazil.
The extent of the coastline surveyed each year varied (Table 1) but one 120 Km
region of the coast was included in every survey (south of Ilha de Santa Catarina
(27º53’S, 48º34’W) to Cabo de Santa Marta, Laguna (28.36S, 48.48W)) (Figure 1),
and is hereafter called the Central Area. In some flights we surveyed 400Km of
coastline, a region we called the Total Area. The results for the Central and Total
Areas were compared to look for evidence of habitat segregation (Best, 1990; Payne,
1986).
Surveys were conducted from a single-engine aircraft from 1987 to 1997 and
from a helicopter from 1998 to 2003. Despite the higher cost/hour, the helicopter has
proved to be a better platform because of its safety, maneuverability and more
panoramic view of the whales. Surveys were conducted at an altitude of 1000ft
(~300m), a speed of 90kt (167km/h) and ~500m off the shoreline. Attempts were
made to conduct surveys during days with optimal conditions, i.e. low wind, low sea
states (<3 Beaufort Sea Scale) and adequate lighting.
One to three observers were in the aircraft in addition to the pilot. With more than
one observer, the principal observer sat beside the pilot and looked continuously out
77
of the front of the aircraft and recorded whale number, group composition, location,
behavior and photographic information. The second observer sat behind the pilot,
watched for whales on the pilot’s side of the aircraft, took photographs and observed
whale behavior and group composition. The third observer sat next to the
photographer, watched for whales on the other side of the aircraft and assisted the
photographer.
Whenever a whale or group of whales was spotted they were approached at a
minimum height of 328ft (100m) and the number of whales was counted. The
helicopter hovered over the group and as the callosity patterns of individuals became
visible, they were photographed. From the airplane, the whales were circled until all
animals were photographed. An approach was halted if it appeared to change the
whales’ behavior, even if it resulted in not photographing all of the counted whales.
We followed the methodology described by Payne et al. (1983) for taking and
analyzing photographs. The analysis of the photographs was aided by the automated
Right Whale Photo-identification Software developed by Hiby and Lovell (2001). A
catalogue was created at the beginning of the study and each new year of aerial survey
photographs were compared to the existing catalogue to look for matches. If a whale
was not found in the catalogue, it was given a new number and added to the
catalogue. Whales accompanied by calves were assumed to be females. Individuals
were called calves if they were between 1/3 to just over 1/2 of their mother’s length.
To describe the increase in the number of whales off Brazil we assumed a
constant survey effort over time and a constant growth rate and used a linear
regression of the natural log of the number of identified females with calves in each
year seen in the Central Area. We used females with calves because of their greater
sightability, longer residency times, tendency to spend long periods of time at the
surface, and distribution close to shore in shallow water (Payne, 1986, Best, 1990;
Cooke et al., 2001). Only data from the Central area was used to look for population
trends because this area was covered in all aerial surveys.
78
Results
The Brazilian Right Whale Catalogue has 315 different individual whales
including 120 females, 149 whales of unknown sex/age and 46 calves identified in
their calf year. Thirty-one whales (10%) have been resighted including 23 females, 3
yearlings (photographed in 2002 as newborns), and 5 whales of unknown age/sex.
There were no resightings before 1994 and 71% (n=24) were recorded in 2003. The
intervals between resightings varied from one to 16 years. One female was resighted
in three different years with newborn calves and another was resighted in two
different years with newborns. All the other whales were resighted only once.
The modal calving interval for whales resighted in Total Area was 3 years (Figure
2). The distribution of calving intervals does not necessarily imply the true calving
interval because it is likely that not all calvings were observed and the time series is
too short for longer calving intervals to yet become apparent. In addition, resightings
of females photographed in Brazil that were also photographed in other years with
calves on the wintering ground off Peninsula Valdes, Argentina (Best et al., 1993)
indicate that some females are using different calving grounds in different years.
Table 2 shows the number of whales identified (calves excluded) during single
surveys at the time of peak whale abundance from 1987 to 2003 in both the Total and
Central Areas.
We made two estimates for the increase in numbers of whales seen off Brazil.
One includes all survey years from 1987 to 2003 and the other includes only the later
years (1997-2003) when the effort and timing of the surveys were more consistent.
Both estimates are presented here because we are unsure which estimate is most
representative of the observed changes in population size. The variability of the low
numbers of whales identified in the early years of the study and a possible sudden
immigration of whales later in the study contribute to this uncertainty. We think the
estimate for 1997-2003 is more realistic because the effort during this time period was
more consistent and there were surveys in every year at the time of peak whale
abundance in the Central Area. However, by including the earlier years we have a
longer time series that resulted in lower confidence intervals for the increase rate.
79
Figure 3 shows the linear regression of the of the natural log number of females
with calves identified each year from 1997 through 2003 and for the whole period
(1987-2003) in the Central Area. If these counts are considered reliable indices of
growth rate, the number of calving females off Brazil increased at a rate of 29.8% per
year (95% CL 15.7, 44.0) for 1997-2003 and 14% per year (95% CL 7.1, 20.9) for
1987-2003. Both of estimates are significantly different from zero (t = 4.133, p <
0.009 and t = 4.06, p < 0.004). Non-calving whales appear to be increasing at rates of
34.4% for 1997-2003 and 10.2% per year for the whole period but the increases were
not significant at the 95% level (t = 1.721, p < 0.1240 and t = 1.761, p < 0.1390). The
estimated growth rate for calving females from 1997-2003 is higher than the 10.4%
rate of increase of identified females with calves calculated by Whitehead et al.
(1986) using a similar methodology for the right whales off Peninsula Valdes,
Argentina. However, the lower 95% confidence interval for the longer period includes
the 10.4% rate calculated by Whitehead et al. (1986) as well as several of the increase
rate values estimated for Argentina. Whitehead et al. (1986) calculated a rate of 6.8%
for the growth of the entire population but later analysis of the Peninsula Valdes
population using different models estimated growth rates from 6.8 to 7.6% (Payne et
al., 1990; Cooke et al., 2001; and Cooke et al., 2003). These later models cannot yet
be applied to the Brazilian whales due to insufficient data.
Discussion
The right whales on the Brazilian wintering ground are not just transients. Ten
percent of the whales have been resighted. Most females with calves that were
resighted had three-year calving intervals, consistent with successful reproduction.
Even those females with two, four and five year calving interval (indicative of failed
pregnancies) (Knowlton et al., 1994) returned to Brazil for their subsequent calvings.
The number of right whales off Brazil appears to have increased at a rate of
29.8% per year in the last seven years of the study and at a lower rate of 14% per year
over the entire period. It is unlikely that the rapid increase could have been the result
of the productivity of whales seen off Brazil earlier in the study, given the probable
age of first reproduction of approximately 8 or 9 years (Best et al., 2001; Cooke et al.,
2001). Plausible rates of increase have been calculated for humpback whales and it is
80
suggested that growth rates greater than 12.6% are unlikely to be biologically realistic
(Brandão et al. 2000; Clapham et al. 2001). Both of the point estimates calculated for
southern right whales in our study lie outside the range of biological plausibility for a
natural rate of increase for southern right whales (Best et al., 2001), although the
lower 95% confidence interval for the lower estimate does overlap with estimates of
the maximum intrinsic rate of increase. Thus at least the higher rate of increase must
include some other element, such as immigration, distributional shift or increasing
survey effort. The increase is not limited to females with calves but also occurs in the
number of whales without calves, though their rates of increase are not significant. A
possible explanation for the increase is immigration from other wintering grounds
such as Peninsula Valdes, Argentina, where the whale numbers have been increasing
from 6.8 to 7.6% for the past 32 years (Whitehead et al., 1986; Payne et al., 1990;
Cooke et al., 2001; Cooke et al., 2003). In addition, the whales in Argentina are being
severely harassed by kelp gulls (Thomas, 1988; Rowntree et al., 1998), suggesting
that the harassment might contribute to immigration to Brazil. Resightings in Brazil of
whales previously photographed off Argentina supports this hypothesis (Best et al.,
1993), as well observations of whales with kelp gulls attack marks (Groch et al.,
unpublished). An ongoing comparison of catalogues from these two wintering
grounds will help define the extent of the overlap, as well as the direction of
movement between these wintering areas.
If the numbers of right whales off Brazil continue to increase, we can expect the
whales to expand their range as they have off Argentina and South Africa (Best, 1990;
Rowntree et al., 2001). Whaling records indicate that right whales were found from
Bahia to Santa Catarina State (Ellis, 1969), along some 2,400km of coastline. Much
of this area is now developed which will increase the potential of conflicts between
right whales and human activities as the whales reoccupy or expand their range. In
fact, the number of right whale sightings has been increasing along the southeastern
Brazilian coast along with the number of reported strandings (Lodi et al., 1996;
Santos et al., 2001). Because the population appears to be growing, it will likely
undergo a rapid change in distribution. Our estimates of the size and growth rate of
the right whale population using the Brazilian wintering ground will become more
accurate as we extend the time series of the data. To ensure the recovery of this right
81
whale population off the coast of Brazil, it is vitally important to continue and expand
comprehensive annual monitoring of this population.
Acknowledgments
We are indebted to a number of people involved with data collection during the
aerial surveys, especially to Maria do Carmo Both for her invaluable and dedicated
work during the early years of this study. The Brazilian Conservation Foundation
(FBCN), World Wildlife Fund, Schloesser Textil Company, The Barbara Delano
Foundation, Mormaii, New Millennium Promoções e Eventos and PETROBRAS
Brazilian Oil Company have provided invaluable support for this study. Thanks to
Comissão de Aperfeiçoamento de Pessoal (CAPES – Ministry of Education) and
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq – Ministry
of Science and Technology, Proc. 142247/2003-0) for the Ph.D. scholarship to the
first author (2001-2005). P.A.C. Flores was partially supported by a PhD. scholarship
from Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq Proc.
146609/1999-9). Special thanks to Vicky Rowntree for the invaluable insights and
advice; Jon Seger for careful reading of the manuscript; and Lex Hiby, Phil Lovell
and International Fund for Animal Welfare for developing the right whale computer
identification system which made this work possible. We would like to express our
gratitude to P. Best and an anonymous reviewer for constructive comments on the
manuscript.
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whale, Eubalaena australis. Ethology 79: 89-103.
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Brownell, R. L. (1998) Soviet catches of southern right whales Eubalaena
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List of Tables
Table 1 - Summary of aerial surveys from 1987 to 2003 used to document the
increase of right whales on the Brazilian wintering ground. ............................................87
Table 2 - Number of whales individually identified and sighted during aerial surveys
from 1987 to 2003, off Southern Brazil, divided into Total Area and Central
Area...................................................................................................................................88
List of Figures
Figure 1 – Map of the study area showing the boundaries of Total Area and the
Central Area, which were surveyed for photo-identification of southern right
whales on their wintering ground off Southern Brazil from 1987 to 2003.......................89
Figure 2 – Distribution of observed calving intervals of female right whales identified
in Total Area off southern Brazil......................................................................................90
Figure 3 – Linear fit of the log number of identified females with calves
photographed during aerial surveys off Brazil (data from Central Area only).................91
87
Table 1 - Summary of aerial surveys from 1987 to 2003 used to document the
increase of right whales on the Brazilian wintering ground.
Year
No. of
flights
Flight
considered
for this
analysis
Aircraft
Total
length of
coastline
(Km)
Effective
flying
Time (h)
Number
of
observer
s
Maximum No.
whales sighted
/ survey in
Total Area
No. of whales
sighted in the
Central Area
1987
2 1-Sep Piper PA-22 singlemotor 400 7.8 2 33 9
1988
2 28+29 Sep* Cessna 170 singlemotor 400 9 2 16 2
1992
2 30+31 Aug*
Cessna 182 singlemotor
400 4.5 2 16 5
1993
1 27-Aug
Cessna 182 singlemotor
400 NA 2 28 16
1994
1 1-Sep
Cessna 182 singlemotor
400 5.3 1 27 12
1997
4 27-Sep Citabria Singlemotor 400 2 1 20 20
1998
5 23-Sep Enstrom helicopter 150 3.5 2 24 16
1999
4 10-Sep Enstrom helicopter 150 3.2 2 20 16
2000
3 8-Oct Squirrel helicopter 300 4 2 24 24
2001
4 13+14 Sep* Jet Ranger helicopter 250 5.3 3 44 30
2002
4 23+24 Sep* Jet Ranger helicopter 400 8.0 3 128 84
2003
4 12-Sep Jet Ranger helicopter 400 6.5 3 112 49
*Two complimentary flights covering adjacent areas.
NA = precise location and time information not available.
88
Table 2 - Number of whales individually identified and sighted during aerial surveys
from 1987 to 2003, off Southern Brazil, divided into Total Area and Central
Area.
Whales sighted but not identified
TOTAL AREA CENTRAL AREA
RESIGHTINGS
IN TOTAL AREA
TOTAL AREA CENTRAL AREA
Year
Adults
without
calves
Females
with
calves
Adults
without
calves
Females
with
calves
Adults
without
calves
Females
with
calves
Adults
without
calves
Females
with
calves
Adults
without
calves
Females
with
calves
1987
4 5 1 4 0 0 17 1 0 0
1988
3 3 0 1 0 0 1 3 0 0
1992
7 0 4 0 0 0 5 2 1 0
1993
8 0 NA 0 0 0 12 4 NA NA
1994
7 4 4 4 1 0 0 6 0 0
1997
6 5 6 3 1 1 2 1 2 3
1998
0 9 0 6 0 1 0 3 0 2
1999
0 10 0 7 0 0 0 0 0 1
2000
1 11 2 11 0 2 1 0 0 0
2001
0 18 0 11 0 2 0 4 0 4
2002
39 37 15 31 0 2 7 4 3 2
2003
45 26 17 15 10 14 15 0 2 0
NA = available data are incomplete.
89
Figure 1 – Map of the study area showing the boundaries of Total Area and the
Central Area, which were surveyed for photo-identification of southern right
whales on their wintering ground off Southern Brazil from 1987 to 2003.
Total Area
Central
Area
48
o
W
26
o
S
32
o
S
52
o
W km
Santa Catarina
State
Santa Catarina Is.
Cabo de
Santa Mart
a
90
0
2
4
6
8
10
12
14
16
23 456
Observed calving interval (years)
Frequency
Figure 2 – Distribution of observed calving intervals of female right whales identified
in Total Area off southern Brazil.
91
Figure 3 – Linear fit of the log number of identified females with calves
photographed during aerial surveys off Brazil (data from Central Area only).
Y (1987-2003)= 0.2985x - 594.7404
Y (1997-2003) = 0.1399x - 277.5268
92
CAPÍTULO 4
PRELIMINARY ESTIMATE FOR RIGHT WHALES OFF BRAZIL
Karina R.Groch
1,2
, José T. Palazzo Jr.
2
., Paulo A.C. Flores
2
, Fred R. Adler
3
, Marta E.
Fabian
1
Contact e-mail: [email protected]
1
PPG Biologia Animal, UFRGS, Av. Bento Gonçalves 9500, Prédio 43435 Sala 101,
Porto Alegre, RS, 91501-970, Brazil.
2
International Wildlife Coalition/Brazil, Caixa Postal 201, Imbituba, SC, 88780-000,
Brazil.
3
University of Utah, Department of Biology and Department of Mathematics, 257
South 1400 East, Salt Lake City, UT 84112, USA.
Keywords: population estimate, southern right whales, Brazil, wintering area
* ESTE ARTIGO SERÁ SUBMETIDO À PUBLICAÇÃO NO THE LATIN AMERICAN
JOURNAL OF AQUATIC MAMMALS
.
94
Abstract
Photographic identifications of the individually distinctive pattern of callosities
on the head’s of right whale’s (Eubalaena australis) were used to estimate the size of
the population of right whales that winters off southern Brazil, using the Gross
Annual Reproductive Rate (GARR) of a stable population. The abundance of right
whales off southern Brazil was estimated to be possibly as high as 555 whales. This
number is more realistic than the previous estimate of 137 animals, because it reflects
the increase observed in the population in recent years. However, because this
estimate does not incorporate parameters like mortality and/or emigration and
immigration, they should be treated with caution and as a preliminary rough estimate
only.
Keywords: southern right whales, population estimate, Southern Brazil, wintering
ground, Eubalaena australis
Introduction
Photographic identifications of the individually distinctive pattern of callosities
on the head’s of right whale’s (Eubalaena australis) have been used to estimate
demographic parameters of right whale populations worldwide (e.g. Kraus et al. 1986;
Caswell et al., 1999; Payne et al. 1990; Bannister, 1990; Best et al., 2001; Cooke et
al., 2001).
The right whales have been studied along the coast of Brazil since 1981, when
whales were 'rediscovered' in the region after being severely depleted by four
centuries of commercial whaling (Palazzo and Carter, 1983; Câmara and Palazzo,
1986; Tormosov et al. 1998). Aerial surveys have been conducted along the southern
coast of Brazil since 1987 for the purpose of documenting the presence and location
of individual right whales through photography (Simões-Lopes et al., 1992; Palazzo
and Flores, 1998; International Wildlife Coalition/Brazil, 1999). The recovery of right
whales wintering in this area was apparently slow in the first years but a recently
rapid increase in numbers has been observed (Groch et al., 2005). The number of
calving females off Brazil is increasing at a rate of 29.8% per year for 1997-2003 and
95
14% per year for 1987-2003. Both these estimates are higher than the estimated
growth rates for calving females and the entire population of right whales off
Peninsula Valdes, Argentina (Whitehead et al., 1986; Payne et al., 1990; Cooke et al.,
2001; and Cooke et al., 2003) and are not a biologically plausible natural rate of
increase for southern right whales (Best et al., 2001). Resightings in Brazil of females
previously photographed off Argentina indicate that at least some individuals use
more than one wintering area (Best et al., 1993). Groch et al. (in press) proposed that
the increase estimated for right whales off Brazil could result from immigration, a
distributional shift and/or increasing survey effort.
Estimates of the total population size of all known breeding stock areas in the
Southern Hemisphere, including the Brazilian right whale stock, totalled 7,571 whales
in 1997 (IWC, 2001). The Brazilian stock by 1995 was estimated to have 137
different right whales, using the Gross Annual Reproductive Rate (GARR) of a stable
population (IWC, 2001). This estimate was based on 25 mature females sighted
between 1993, 1994 e 1997. As of 2003 the Brazilian Right Whale Catalogue has 315
different individual whales including 130 females, of which 23 were seen in two or
more years, providing a modal calving interval of 3 years (Groch et al., in press). In
this paper we present an update of the estimate of the Brazilian right whales
population.
Materials and Methods
From 1987 through 2003 we conducted aerial surveys of right whales off Brazil
in which we photo-identified individuals and marked their locations on a map.
Surveys were conducted on an irregular basis from 1987 to 1994 (1987, 1988, 1992,
1993 and 1994) and annually from 1997 to 2003. Flights were conducted in the time
of peak whale abundance, from August to October (Simões-Lopes et al., 1992; Groch,
2000, Groch et al., 2003). The years 1992 and 1993 were not included in these
estimates because available data is incomplete.
The extent of the coastline surveyed each year varied (Table 1) but one 120Km
region of the coast was included in every survey (south of Ilha de Santa Catarina
(27º53’S, 48º34’W) to Cabo de Santa Marta, Laguna (28.36S, 48.48W)) (Figure 1).
This is the main aggregation area of the whales in southern Brazil (Simões-Lopes et
al., 1992; Palazzo and Flores, 1998; International Wildlife Coalition/Brazil, 1999), as
96
well as the main aggregation for mother/calf pairs, and is hereafter called the Central
Area. In some flights we surveyed 400Km of coastline, a region called in this study
the Total Area. Photographs taken from all aerial surveys have been used to create a
catalogue of right whales identified off southern Brazil. Detailed description of the
surveys and the analysis of the photographs are given by Groch et al. (2005).
To estimate the number of right whales off Brazil it was used two slightly
different versions of the Gross Annual Reproductive Rate (GARR) technique (IWC,
1986; IWC, 2001). These estimates were based on females with calves because of
their greater sightability, longer residency times, tendency to spend long periods of
time at the surface, and distribution close to shore in shallow water (Payne, 1986;
Best, 1990b; Cooke et al., 2001). Separate estimates were derived for the Central
Area and the Total Area because of unequal survey coverage over the years and for
this reason estimates for the Total Area were derived only for years with complete
coverage of the area.
Method I – GARR derived from an idealized right-whale life history
The modal age of first reproduction for female southern right whales is 9 years
(Best et al., 2001; Cooke et al., 2001) and the modal observed calving interval is 3
years (Payne et al., 1990; Best, 1990b; Best et al., 2001; Cooke et al., 2001; Groch et
al., in press). Therefore, in Method 1 we simply assume that:
(1) each adult female has a calf every three years;
(2) juveniles mature at age 9;
(3) there is no mortality; and
(4) the sex ratio is 50:50.
Then the population can be represented as the sum of the numbers in various
age/sex classes as follows:
N = C
0
+ J
1
+ J
2
+ J
3
+ J
4
+ J
5
+ J
6
+ J
7
+ J
8
+ F
I
+ F
II
+ F
III
+ M
I
+ M
II
+ M
III
,
where N is the total population size, C
0
is the number of calves produced this year by
adult females of cohort I (F
I
), the J
i
are juveniles of age i, and the males are arbitrarily
divided into three groups corresponding to the three female cohorts I, II and III.
Our assumptions imply that C
0
= F
I
. In fact, all of the terms on the right hand side
would be equal to C
0
if the population were not growing, and they do not differ
greatly from each other even when the population is growing, as it must be doing on
97
the assumption of no mortality. Thus, given our idealized right-whale life history we
have that
N ≈ 15 C
0
and we can therefore estimate the population size N as 15 times the number of calves
produced in a year. A more realistic multiplier would probably be lower than 15
owing to juvenile mortality and population growth, but calving intervals longer than
three years will offset these effects to some extent by making the number of calves an
underestimate of one-third the number of adult females. Consistent with this
expectation, the GARR method described by IWC (2001) uses a multiplier slightly
less than 15, as explained below.
Method II – GARR as applied by IWC (2001)
This variation on the method uses an empirically based estimate of the ratio of
juveniles to adults. As explained in IWC (2001), the population in a given year can
be represented as the number of calving females multiplied by:
(1) three to account for the 3-year calving interval (i.e., seeing only 1/3 of the
females);
(2) two to account for males (again assuming a 50:50 sex ratio); and
(3) 2.4 to account for an estimated 1.4:1 ratio of juveniles to adults.
Multiplying these together gives 14.4 (3 x 2 x 2.4 = 14.4) and we therefore
estimate the population size N as 14.4 times the number of calving females of a given
year. IWC (2001) notes that the ratio of juveniles and calves to adults is relatively
high, as a consequence of the relatively high population growth rate. But our
derivation, above, shows that this high ratio of juveniles to adults can just as well be
viewed as resulting from a low mortality rate; in Method I, the ratio of calves and
juveniles to adults is 9:6, which is 1.5:1.
Results
Table 2 gives the estimated population sizes for each surveyed year between 1987
and 2003 using GARR Methods I and II in the Central and Total Area. The estimates
of the total population size ranged between 15 and 465 for the Central Area, and 45
and 555 for the Total Area.
98
Discussion
The abundance of right whales off southern Brazil was estimated to be possibly as
high as 555 whales. This number is more realistic than the previous estimate of 137
animals, because it reflects the increase in the population in the recent years (Groch et
al., 2005). However, these numbers are not likely to be as good an estimation of the
population size as mark recapture or maximum likelihood models because they do not
incorporate parameters like mortality and/or emigration and immigration.
Mark-recapture methods have been used to estimate population sizes and other
demographic parameters of many cetacean species (Hammond, 1986; Hammond, et
al., 1990), including southern right whales (Whitehead et al., 1986; Bannister 1990,
2001; Best, 1990a, 1990b; Payne et al., 1990; Best et al., 2001; Cooke and Glinka,
1999; Cooke et al., 2001, 2003). However, conventional models are not suitable for
this species, because of the periodic nature of the calving process (Payne et al., 1990;
Cooke et al., 2001). Breeding females calve at intervals of 2-5 years, (modal interval
being 3 years), and tend to return to breeding areas more frequently in calving years
(Bannister 1990, 2001; Best, 1990a, 1990b; Payne et al., 1990; Cooke et al., 2001,
2003; Best et al., 2001, 2005). For this reason, the assumptions of independence of
sightings probabilities from year to year or of the probability of sighting a whale
being independent of whether or not it has a calf, required for most mark recapture
models are not fulfilled (Barlow and Clapham, 1997). In light of this, Payne et al.
(1990) developed their own mark-recapture model updated by Cooke et al. (2001),
taking into account the calving sequences occurring in the population and maximizing
the likelihood of the observed data. This model of the female breeding population has
been used to estimate demographic parameters of southern right whales in Argentina
(Payne et al., 1990; Cooke et al., 2001) and also in South Africa (Best et al., 2001,
2005). These studies have shown that precise information of demographic parameters
can only be obtained from data collected over a long enough period.
Precise information on the total number of right whales wintering off Brazil as
well as other demographic parameters cannot be obtained yet due to relatively short
time series of data. Moreover, resightings of females photographed in Brazil that were
also photographed in other years with calves on the wintering ground off Peninsula
Valdés, Argentina (Best et al., 1993; Groch, unpublished data) indicate that some
99
females are using different calving grounds in different years. In fact, Groch et al.
(2005) suggested that one of the reasons for the rapid increase in the population
estimated for right whales off Brazil could be immigration. Cooke et al. (2001)
pointed out on the sensitiveness of their model to immigration or emigration in light
of the possible interchange between Brazil and Argentina. These authors noted that if
emigration is occurring, it is not reflected in the demographic parameters and
concluded that their analysis provides no evidence that significant immigration has
occurred in the right whale population off Argentina. Since their model makes no
assumptions about the extent of immigrations, it cannot be applied to right whales off
Brazil, even provided enough time series of data.
Groch et al. (2005) also pointed that distributional shift and/or increasing survey
effort may have also influenced their estimated rate of increase for right whales off
Brazil. In addition, right whales have been observed along the northeast coast of
Brazil (Engel et al. 1997) and the southeastern coast (Lodi et al., 1996; Santos et al.,
2001), and this estimate was based on aerial surveys made along the southern coast of
Brazil.
Nevertheless, we believe that the estimates presented here do provide a minimum
estimate of the number of whales in the population that have been seen yearly off the
coast of southern Brazil. Because the whales appear to be using waters off Argentina
as well as Brazil, a combined estimation of right whales sighted in both areas as well
as the inclusion of other parameters that may be affecting the population size is
recommended, and should provide a more realistic estimate for the size of right whale
population off eastern South America.
Acknowledgments
We are indebted to a number of people involved with data collection during the
aerial surveys, especially to Maria do Carmo Both for her invaluable and dedicated
work during the early years of this study. PETROBRAS Brazilian Oil Company has
provided invaluable support for the continuity of this study. The Brazilian
Conservation Foundation (FBCN), World Wildlife Fund, Schloesser Textil Company,
The Barbara Delano Foundation, Mormaii, New Millennium Promoções e Eventos
have also provided support for this study in previous years. Thanks to Comissão de
Aperfeiçoamento de Pessoal (CAPES – Ministry of Education) and Conselho
100
Nacional de Desenvolvimento Científico e Tecnológico (CNPq – Ministry of Science
and Technology, Proc. 142247/2003-0) for the Ph.D. scholarship to the first author
(2001-2005). P.A.C. Flores was partially supported by a PhD. scholarship from
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq Proc.
146609/1999-9). Special thanks to Vicky Rowntree for the invaluable insights and
advice and Lex Hiby, Phil Lovell and International Fund for Animal Welfare for
developing the right whale computer identification system, which made this work
possible.
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List of Tables and Figures
Table 1 - Summary of aerial surveys from 1987 to 2003 used to document the increase of
right whales on the Brazilian wintering ground. ................................................................. 105
Table 2 - Number of whales individually identified during aerial surveys from 1987 to 2003,
off Southern Brazil, divided into Total Area and Central Area and the estimated number
of whales in the population.................................................................................................. 106
Figure 1 – Map of the study area showing the boundaries of Total Area and the Central Area,
which were surveyed for photo-identification of southern right whales on their wintering
ground off Southern Brazil from 1987 to 2003................................................................... 107
105
Table 1 - Summary of aerial surveys from 1987 to 2003 used to document the increase of
right whales on the Brazilian wintering ground.
Year
No. of
flights
Flight
considered
for this
analysis
Aircraft
Total
length of
coastline
(Km)
Effective
flying
Time (h)
Number
of
observers
Maximum No.
whales si
g
hted
/ survey in
Total Area
No. of whales
sighted in the
Central Area
1987
2 1-Sep
Piper PA-22
singlemotor
400
7.8
2 33 9
1988
2 28+29 Sep*
Cessna 170
singlemotor 400
9
2 16 2
1992
2 30+31 Aug*
Cessna 182
singlemotor
400
4.5
2 16 5
1993
1 27-Aug
Cessna 182
singlemotor
400
NA
2 28 16
1994
1 1-Sep
Cessna 182
singlemotor 400
5.3
1 27 12
1997
4 27-Sep Citabria Singlemotor 400 2 1 20 20
1998
5 23-Sep Enstrom helicopter 150 3.5 2 24 16
1999
4 10-Sep Enstrom helicopter 150 3.2 2 20 16
2000
3 8-Oct Squirrel helicopter 300 4 2 24 24
2001
4 13+14 Sep* Jet Ranger helicopter 250 5.3 3 44 30
2002
4 23+24 Sep* Jet Ranger helicopter 400 8.0 3 128 84
2003
4 12-Sep Jet Ranger helicopter 400 6.5 3 112 49
*Two complementary flights covering adjacent areas.
NA = precise location and time information not available.
106
Table 2 - Number of whales individually identified during aerial surveys from 1987 to 2003,
off Southern Brazil, divided into Total Area and Central Area and the estimated number
of whales in the population.
TOTAL AREA CENTRAL AREA
Year
Females with
calves
GARR
Method I
GARR
Method II
Females with
calves
GARR
Method I
GARR
Method II
1987
5 75 72 4 60 57,6
1988
3 45 43,2 1 15 14,4
1994
4 60 57,6 4 60 57,6
1997
5 75 72 3 45 43,2
1998
- - - 6 90 86,4
1999
- - - 7 105 100,8
2000
- - - 11 165 158,4
2001
- - - 11 165 158,4
2002
37 555 532,8 31 465 446,4
2003
26 390 374,4 15 225 216
NA = available data are incomplete.
107
Figure 1 – Map of the study area showing the boundaries of Total Area and the Central Area,
which were surveyed for photo-identification of southern right whales on their wintering
ground off Southern Brazil from 1987 to 2003.
Total Area
Central
Area
48
o
W
26
o
S
32
o
S
52
o
W km
Santa Catarina
State
Santa Catarina Is.
Cabo de Santa
Marta
CAPÍTULO 5
MONITORING RESPONSES OF SOUTHERN RIGHT WHALES TO
WHALEWATCHING ACTIVITIES IN THE SOUTHERN BRAZILIAN COAST AND
ITS IMPLICATIONS FOR CONSERVATION
Karina R. Groch
1,2
, José T. Palazzo Jr.
2
and Marta E. Fabián
1
Contact e-mail: [email protected]
1
PPG Bio Animal, UFRGS, Av. Bento Gonçalves 9500, Prédio 43435 Sala 101, Porto Alegre,
RS, 91501-970, Brazil.
2
International Wildlife Coalition/Brazil, Caixa Postal 201, Imbituba, SC, 88780-000, Brazil.
Keywords: southern right whale; whalewatching; survey-shore-based; behavior; habitat use;
breeding ground; management
* ESTE ARTIGO FOI APRESENTADO AO COMITÊ CIENTÍFICO DA 55A. REUNIÃO DA COMISSÃO INTERNACIONAL
DA
BALEIA (INTERNATIONAL WHALING COMMISSION AND ASSOCIATED MEETINGS), 2003, BERLIM,
ALEMANHA. E SERÁ SUBMETIDO À PUBLICAÇÃO NO JOURNAL OF CETACEAN RESEARCH AND MANAGEMENT.
110
ABSTRACT
Boat based whalewatching of Southern right whales (Eubalaena australis) has been
conducted in the species´ wintering ground off Santa Catarina State, Southern Brazil since
1999. Whalewatching boats operate under guidelines of restriction in accordance with
national legislation. Interactions between southern right whales and whalewatching boats
were studied in 2002 using a surveyor theodolite. It was recorded 65.5 hours of encounters
between mother/calf pairs and boats, during 25 whalewatching cruises in five different bays.
Swimming speed, linearity and reorientation rates were examined before, during and after
encounters to assess the potential impact of whalewatching activities to this population. Mean
swimming speed varied by bay and approaching phase, from 0.9 to 2.78km/h. No significant
differences were found in mean swimming speeds of whales tracked before, during and after
encounters with boats in all bays (p>0.05). The separate analysis of each bay also showed no
significant differences. The values of linearity obtained were similar in all observation sites.
The whales did not maintain constant direction during the observation period (mean values
<0.5) but were mostly travelling at low reorientation rates (mean rates <32 degrees/min). The
predicted probabilities of whales heading towards the boats as a function of time were
calculated, and analyzed using logistic regression. Predicted probabilities were significantly
near the expected values in Gamboa and Ibiraquera (p>0.05). In Garopaba, Silveira and Rosa
the predicted probabilities varied significantly during certain time intervals (p<0.001). We
observed that whales reacted at both long and short distances from boats and the reactions
varied with bays. Data from whales´ movements in no-whalewatching days were also
obtained and compared with the whalewatching days. No significant differences were
observed between the datasets (p>0.05). Although long-term impacts are difficult to assess,
no clear evidence of immediate disturbance to this right whale population was observed
during the study, suggesting that the whalewatching boats operation under Brazilian
regulations did not disrupt the behavior of right whales on this wintering ground off Southern
Brazil. While data presented here comes from the observation of a small whalewatching
industry, the economic interest is likely to result in the growth of whalewatching activities.
The use of the techniques described in this paper, if taken together with those used for long-
term monitoring of individual whales and their pattern of habitat use, may enable scientists to
provide the best possible management advice for whalewatching in order to ensure the proper
conservation of target species and the sustainability of this industry on a long-term basis.
111
INTRODUCTION
Whalewatching is one of the most rapidly growing and economically attractive tourist
activities worldwide and provides for the “sustainable use” of cetacean populations (IFAW et
al., 1997). If properly managed, it can bring benefit to local economies, scientific research,
educational purposes, public awareness, recreational activities and, ultimately, the whales
themselves (IFAW, Tethys and Europe Conservation, 1995).
Southern right whales, Eubalaena australis, approach the Southern Brazilian coast during
the winter and spring to use the shallow and protected waters to give birth, nurse their calves
and apparently mate (Palazzo and Flores, 1996, 1998; Simões-Lopes et al., 1992;
International Wildlife Coalition/Brazil, 1999). This right whale population was severely
depleted by commercial whaling until 1973, when the whale population seemed to be
extirpated from the Southern Brazilian coast (Palazzo and Carter, 1983). Since the early
1980s, when whales were 'rediscovered' in this region, the population has been monitored by
the Brazilian Right Whale Project (Projeto Baleia Franca - IWC/Brasil). The whales
concentrate along the Southern coast of Santa Catarina State, from Cabo de Santa Marta,
Laguna (28º36’S, 48º49’W) to Santa Catarina Island (27º25’S, 48º30’W) (Simões-Lopes et
al., 1992; Palazzo and Flores, 1996, 1998; International Wildlife Coalition/Brazil, 1999).
Most groups sighted in this region are mother-calf pairs with a few sightings of single adults
and mating groups (Simões-Lopes et al., 1992; Palazzo and Flores, 1996, 1998; International
Wildlife Coalition/Brazil, 1999; Groch, 2000.).
The resighting of some females along the Southern Brazilian coast (Palazzo et al., 1999;
Groch, ongoing research) indicates that at least some females return regularly to this nursing
area and present the same three year return and calving interval reported for other Southern
Hemisphere calving grounds (Payne, 1986; Bannister, 1990; Best, 1990; Payne et al., 1990).
Resighting of calving females in Santa Catarina waters that were previously photoidentified
on the wintering area off Península Valdés, Argentina, (Best et al., 1993 and Groch et al.,
ongoing research) indicates some degree of relationship between these right whale
populations. A systematic land-based research program has been conducted in Santa Catarina
waters since 1998, which has provided information on the whales’ preferences on habitat use
and behavior (Groch, 2000; Groch, 2001a). Since 1998, sighting frequencies have increased
in all group categories and the whales have expanded their distribution. This may reflect the
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recovery of the southern right whale population stocks (IWC, 2001). Estimates of right whale
abundance off Brazilian coast are currently under analysis.
Whalewatching activities in the Southern coast of Santa Catarina State begun in 1999.
Boats operate under restrictions to national legislation. Shore based whalewatching is
conducted by tourism agents, local fishermen, residents and tourists. Surface behavioral
responses of right whales to the whalewatching activities have been monitored since 2000
(Groch, 2001, 2002), to ensure the conservation and management of the right whale
population along the coast of Santa Catarina State. Preliminary results suggested that most
right whales groups are approachable by whalewatching boats and make no apparent changes
in their behavior. However, the results cannot be extrapolated since observations were made
from only one type of whalewatching boat. Considering the increasing interest in
whalewatching, it is likely that the number of boats operating in the region will increase in the
coming years. On September 14, 2000, this wintering ground in the western South Atlantic
was designated a Right Whale Environmental Protection Area, to ensure the conservation and
protection of this southern right whale population and its habitat. Long-term studies on habitat
use and behavior of right whales in this region are needed to ensure the appropriated
management of this right whale population and the adequate development of whalewatching
in the protected area.
Surveyor’s theodolites have been used since the 1970s to study a variety of marine
mammals around the world (e.g. Würsig et al. 1991; Acevedo, 1991; Kruse, 1991; Smith,
1993; Frankel and Clark, 1998; Bejder, 1999; Suryan and Hervey, 1999; Heckel, et al. 2001;
Harzen, 2002; Johnston, 2002; Williams et al. 2002; Jahoda et al. 2003). The theodolite
tracking technique has been proved to be a powerful tool to observe the animals from distance
and in an non-invasive manner. Successive readings of the angles and time can be used to
calculate relatively precise data on their positions, movement patterns and travel speed
(Würsig et al., 1991).
Here we present results of a study on right whale responses to whalewatching boats using
theodolite tracking in the Right Whale Environmental Protection Area off the coast of Santa
Catarina State, southern Brazil. The objective was to describe short-term (immediate)
responses of right whales to encounters with whalewatching boats and provide reference data
for future comparisons regarding whales’ behavior and movements in relation to boats in the
study area.
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METHODS
Study area
The study area comprises 70 km of coast on the Right Whale Environmental Protection
Area off the coast of Santa Catarina State (27º52’S, 48º34’W and 28º28’S, 48º46’W) (Fig. 1),
Southern Brazil. The coast is characterized by a series of small bays, created by the
morphology of the Brazilian coastal Mountain Ridge. The bays range in size from 1.5 to 14
km in length, and most of them have coastal cliffs in at least some section of the bay and
sandy beaches. Some bays are composed of extensive regions of high sand dunes.
Surveys
Observations were carried out from July to November (winter/spring time) 2002, the
months of main whales presence in the region (Simões-Lopes et al., 1992; Palazzo and Flores,
1998). Twelve observation land-based sites were chosen along the study area (Fig. 1). The
sites are 16 to 92m above sea level, depending on the bay. Daily surveys were made
simultaneously at sites with the help of eight volunteers, who remained with the project
throughout the season. The surveys were conducted on two shifts (7-10 am and 1-4pm) and
provided general information on the presence and distribution of the whales along the study
area. This enabled the theodolite tracking effort to be directed to places where whale sightings
were recorded.
Data recorded during surveys included: date, time of the observation, number of groups
sighted, group composition (mother/calf pairs, adults without calves, juveniles), position of
sighting (registered on detailed nautical charts in relation to buildings and distinct geographic
features along the coast). The term “group” refers to one or more whales seen within close
proximity of one another (at least approximately 15m or one adult whale length). Animals
more then one whale length apart were also considered a group if their behavior appeared to
be coordinated (Clark, 1983). The decision for when a group had split up was made when
members were more than 3-4 adult whale lengths apart for more than 10 min. For statistical
purposes, a group was considered as a unit (e.g. if a change was detected in a single
individual, such change was attributed to the group). Environmental data including wind
speed and direction, cloud cover, visibility and Beaufort Sea state were also recorded.
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Observations sessions were excluded from the analysis when the Beaufort Sea state was >4.
Cloud cover and visibility are factors that can influence the sighting conditions thus were
evaluated for the data collection. Visibility was scaled from 1 (poor) to 5 (perfectly visible
horizon). Observations were not carried when the visibility was 1 or 2, combined with high
cloud cover rates.
Theodolite tracking data collection
Observations on the movements and behavior of whales were conducted in days with and
without whalewatching cruises. Whales were tracked using a surveyor’s digital electronic
theodolite (ALKON DE with a 30X telescope and precision of ±10” arc). Theodolite is a
surveying instrument capable of measuring angles to a target with great accuracy. The
horizontal angle is given in relation to a ‘zero’ reference point and the vertical angle relative
to the gravity. If the altitude and position of the theodolite as well as the position of the
reference point are known, one can retrieve, together with the angles, the position of the target
in (x,y) coordinates. The accuracy of the readings is inherent to the precision of the theodolite,
proportional to the instrument’s elevation and inversely proportional to the distance of the
animal. The detailed technique is described by Würsig et al. (1991). In order to minimize
errors in the readings, the height and position of the observation sites was calculated by a
professional surveyor using a Geodetic GPS receptor (Topcon Legacy-H GD with precision
of 5mm±5ppm). As most research techniques, theodolite tracking has some limitations: the
use of the theodolite is limited to a minimum height from the sea level. The farther the
animals are from the coast, the higher the theodolite station must be for reasonable precision
and accuracy. In general terms, animals up to 5km away from shore must be tracked from a
vantage point at least 20 m above the surface of the water (see Würsig et al., 1991 for height-
related errors).
Three observers were normally present at the observation site. One person operated the
theodolite. A second observer provided the theodolite operator information on the position
and behavior of the groups aided by Pentax 12 x 50 mm binoculars and a Bushnell 22-45 x 60
mm spotting scope, depending on the range of the individuals. A third observer recorded
behavior data for each theodolite reading on a standardized datasheet for posterior input in the
computer.
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Focal observations
Survey protocol (Altmann, 1974) was used to search, count and identify groups of whales
present in each bay at the beginning of each observation session. Continuous following of
focal groups (Altmann, 1974) was used to record the following data: time and duration of
sighting, whales behavior and movement patterns (swimming speed and orientation). The
following behavioral states of the whales were recorded: swimming, resting, play, other
activity (Table 1) (see Thomas and Taber, 1984; Clark, 1983; Thomas, 1986; Cassini and
Vila, 1990; Groch, 2000). Behavioral states were recorded each time we recorded a fix on the
theodolite and the time spent in each category was calculated. Because right whales
mother/calf pairs in winter/spring areas prefer shallow waters (Payne, 1986; Best, 1990) and
spend most of their time resting or swimming at or just bellow the surface (Clark and Clark,
1980; Thomas and Taber, 1984), they are more easily visible and likely to be observed most
of the time. Therefore we were able to record every time they changed their orientation,
displayed a surface-active behavior or at least get positions on them once every five minutes.
Since mothers and calves can have different rates of behavior (Thomas and Taber, 1984) and
calves are difficult to follow we recorded the behavior on mother/calf pairs in terms of
mother’s behavior. During whale/boat encounters, when more than one group was present in
the bay, we attempted to record the position of all groups at least every 10 minutes.
Behavioral states of these groups were recorded using instantaneous sampling (Altmann,
1974).
Whalewatching
Whalewatching boats operating in the region were tracked in cooperation with the
whalewatching operators, through the communication with the boat operator or the tour
guides present in the boat. The whalewatching operators notified us when they took tourists
on whalewatching cruises in the study area, which allowed us to monitor the whales’
responses to boats. On these occasions the team moved to the site where the boat was
supposed to go (pre-selected bay according to whales presence in that day) and recorded the
behavior of the right whales groups before, during and after the encounter with boat, as well
as the boat speed and movements. The before-approach phase consisted of any period before
the first boat approach; the during-approach phase consisted by the time when the boat was
stopped (with the engine in neutral or turned off) close to the target group; the after-approach
phase begun when the boat left the group after the last approach. When more than one attempt
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to approach the target group was made, the total during-approach phase was the time between
the beginning of the first and the end of the last approach made by the boat.
For each whale/boat encounter, the following data were recorded: time and duration of the
encounter (total during-approach phase), whales behavior and movement patterns, and kind of
boats approaches to whales (Table 2).
Because cetaceans are known to detect and react to acoustic stimuli at great distances (Au
and Perryman, 1982; Richardson et.al., 1995), and sound propagation varies according to the
physical characteristics of a given bay (Richardson et.al., 1995), whalewatching boats were
tracked as they entered the bays. Every group of whales within a bay was considered to be in
a potentially disturbed condition. Boats were recorded less frequently than the focal groups,
and were assumed to travel at a constant speed between fixes. Every time it was noticed that
the boat was turning on and off the engine to change its position or reapproach the group, its
position was recorded. When more than one boat approached the same whale group at the
same time an attempt of monitoring both boats was made.
Whalewatching activities were monitored from July 28 to October 28, 2002. The boats
were 29-ft. inflatable boats with fiberglass hull and capacity for 20 passengers each. Whales
were still present in November, but no whalewatching cruises were conducted during this
period. Whalewatching cruises occurred according to whales frequency and distribution,
weather conditions and tourist demand. Since the whalewatching season coincide with stormy
winter weather, poor weather conditions limited the number of days boats could operate.
During the ‘2002 whalewatching season’ 53 cruises were conducted by the operators, of
which 35 (66%) were tracked. Approaches made by boats other than the two authorized ones
were monitored on two occasions. One was an opportunistic approach (a small non-
commercial whalewatching boat) driven by local residents. The other was a fisherman
carrying tourists and probably conducting a ‘commercial whalewatching cruise’.
Ten whalewatching cruises could not be monitored with the theodolite. During the
observations of these cruises we recorded: time and duration of the encounter (total during-
approach phase), whales behavior, kind of boats approaches to whales (Table 2) and whale
reactions to boat operation (approach “A”, no reaction "U" or move away "N", as described in
Table 3).
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Focal observations during non-whalewatching days
Observations on the behavior and movement patterns of whales when no whalewatching
cruises were made (non-whalewatching days) were conducted as a control. The observations
focused on individual identified whales and whales present in the same bays where
whalewatching cruises were conducted. We tried to follow whales that could have been
previously approached by boats, following the same sampling methods for observations on
whalewatching days. The theodolite tracks were collected and analyzed using the same
methodology as the data from whalewatching days. The observations were made in Silveira
and Ibiraquera (Fig.1).
Individual Identification
Individual right whales can be recognized by the callosity patterns on their heads and
other distinct body marks through aerial photography (Payne et. al., 1983). The use of
photographs and a standard drawing sheet, permitted to follow some of the individuals
targeted by boat operators.
Data Analysis
Theodolite tracking data was analyzed using the software Pythagoras (Gailey and Ortega-
Ortiz, 2000, 2002). This software provided detailed information on movements and spatial
patterns of whales through the calculation of the leg speed (swimming speed between two
sequential fixes, hereafter referred as swimming speed), linearity (deviation of a trackline
from a straight line) and reorientation rates (magnitude of bearing changes along a trackline).
Whales responses to whalewatching boats were measured through the analysis of their
movements before, during and after the encounters with boats. The non-parametric Kruskall-
Wallis (ANOVA by ranks) and Mann-Whitney U tests (Siegel, 1975) were used to compare
the mean swimming speed values of each sighting between each phase of the encounters. It is
not known if the behavior and movements of whales can be influenced by the physical
features of a given bay. For this reason we have also analyzed mean swimming speeds of
whales tracked in each phase of encounters with boats in each bay. Mean swimming speed
data from Praia do Rosa and Silveira were combined for statistical purposes due to limited
sample sizes. In addition, we compared mean swimming speed values between
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whalewatching and non-whalewatching days. The results were considered significant at the
5% level. Linearity and reorientation data permitted to trace a profile on the orientation of the
movements of the right whales. Linearity values close to one indicate whales traveling in a
straight trackline; values close to zero indicate that whales were constantly changing
direction. The analysis were made using BioEstat 2.0.
Pythagoras allowed us to estimate distance and bearing between tracks, according to the
scheme developed by Bejder et al. (1999) (Fig. 2), which enabled us to correlate the
movements and orientation of the whales in relation to approaching boats (Gailey and Ortega-
Ortiz, 2000, 2002). The program quantifies the “approaches” and “avoidances” displayed by
whales towards a boat in terms of a whale’s angle to a boat (Fig. 2). The data were analyzed
using logistic regression to predict the probability of the occurrence of an “orientation” as a
function of the time of the encounter (Hosmer and Lemeshow, 1989). In the analysis of
whale/boat distances and orientation the data was interpolated into 1-min intervals. A 600 sec
critical time-interval (CTI) was used which means that fixes with time intervals longer than
600 seconds were excluded. Interpolation was necessary because it was impossible to
determine the position of two targets at a time with only one theodolite (for details on the
calculations see Gailey and Ortega-Ortiz, 2000, 2002).
RESULTS
A total of 111.9 hours of observation (including time before, during and after the
encounters of the whales with whalewatching boats) were conducted on 27 days (hereafter
referred as ‘whalewatching day’), with a mean of 4.1 hours of observation/day. A mean of 6.5
whales were present in the bays during whalewatching days (N=175 whales). Of these 89.1%
(n=156) where mother/calf pairs and 10.9% (n=19) were unaccompanied whales.
Whalewatching cruises occurred at a rate of 1.4 per day and were conducted between 10AM
and 1PM. On two occasions two whalewatching boats approached the whales at the same
time. When more than one whalewatching cruise was conducted in the same day, they were
mostly carried in the same bay. The boats approached the same group or went to different
groups. The target and number of approaches were based on the whales’ first reaction to boat
approach and weather conditions (wave height and wind speed). If the whales showed no
reaction or moved away, the boat operator attempted to approach it again or moved to another
group. The number of whalewatching cruises per month and whales approached are presented
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in Table 4. Most of the cruises were conducted in October, probably due to comparatively
better weather conditions.
Most of the monitored whalewatching cruises occurred in Garopaba (28.6%, n=10) and
Ibiraquera (28.6%, n=10), followed by Gamboa (14.3%, n=5), Silveira (14.3%, n=5), Praia do
Rosa (11.4%, n=4) and Ferrugem (2.9%, n=1) (Table 5). Since Ibiraquera had the most whale
sightings during the season, it was expected to have most of the whalewatching cruises. The
fact that Garobapa is the point of embarkation of the whalewatching cruises, so it is not
surprising that such a high proportion of the cruises occurred there.
Theodolite tracking
During the monitored whalewatching cruises, boat operators followed national legislation
guidelines. Boats stopped (with the engine in neutral or turned off) at a distance of over 100m
from the whales. They mainly stopped in the path of whales and were allowed to drift onto the
whale(s) (approach classified as ‘stationary’).
Whale/boat distance varied between less than 10m up to 4242m, depending on the bay
where the encounter was tracked. The maximum and minimum distances between whales and
boats measured in each bay are given in Table 6.
Between July to October 2002, we collected 2931 fixes (vertical and horizontal angular
readings) of whales and boats over 65,5 hours period. Eighty-three percent (n=2431) were of
mother/calf pairs and 17% (n=500) were of boats. No lone adults or groups of adults without
calf were sighted during these observations. Tables 7 and 8 show data of the theodolite
tracking sessions for each observation site. Table 9 shows mean swimming speed of whales in
each bay in days with whalewatching cruises before, during and after encounters with boats.
No significant differences were found in mean swimming speeds of whales tracked
before, during and after encounters with boats in all bays (Kruskall-Wallis: n = 107, H =
2.1656, p = 0,3387). The separate analysis of each bay also showed no significant differences
in Gamboa (Kruskall-Wallis: n = 54, H= 2.6386, p = 0.2673), Garopaba (Kruskall-Wallis: n =
21, H = 1.1771, p = 0.5551) and Ibiraquera (Kruskall-Wallis: n = 54, H = 2.1539, p =
0.3406), as well as the combined mean swimming speeds of whales tracked in Praia do Rosa
and Silveira between the during and after phases (Mann-Whitney: U = 8, z =0.4899, p =
0.6242, n
1
= 4, n
2
= 5).
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Table 10 shows data on linearity and reorientation rates of whales tracked during
whalewatching-days for each bay. The values of linearity obtained for the mother/calf pairs
were similar in all observation sites. The whales did not maintain constant direction during the
observation period. What was observed were mother/calf pairs moving in parallel to the
coastline, traveling back and forth within a bay, wandering (not necessarily in a constant
straight line). However, whales were mostly traveling at low reorientation rates (mean rates
<32 degrees/min).
Figure 3 shows the predicted probability of mother/calf pairs heading toward the boats
during the whale/boat encounters for each bay. If whale movement relative to the approaching
whalewatching boats was random, it would be expected that the proportion of each orientation
would be the same, at a rate of 0.25 (see Fig. 2). Predicted probabilities of whales heading
towards the boats were significantly near the expected values in Gamboa (Chi-square: χ
2
=1.216, p=0.2701) and Ibiraquera (Chi-square: χ
2
=1.268, p=0.26), the later showing a slight
decrease from the beginning to the end of the whale/boat encounter. In Garopaba, Silveira and
Rosa the predicted probabilities varied significantly during certain time intervals (p<0.001).
Values higher than the expected were observed in Garopaba during the first 25 minutes,
having lower probabilities until the end of the encounters. In Silveira predicted probabilities
were lower than the expected during the total time of the encounter but increased towards the
end, approaching expected values at the >45-50 min interval. In Praia do Rosa the predicted
probabilities of heading towards boats were higher than the expected during the first 15
minutes of the encounter, but decreased during the next 25 minutes. Figure 4 shows the mean
distances between whales and whalewatching boats during encounters as well as the observed
probabilities of the whales heading towards boats. Whales showed similar mean probabilities
of heading towards the boat at shorter (<=300m) and greater (>300m) distances (Table 11).
Total time the whales spent in different behavioral states is shown in Table 12 and Figure
5. Mother/calf pairs spent most of their time traveling in Garopaba (76.6%), Rosa (68.2%),
Ibiraquera (89.2%) and Silveira (74.8%). In Garopaba and Ibiraquera mother/calf pairs played
for less than 10% of the time and in Silveira for less than 5% of the time. Mother/calf pairs
rested for about 20% of the time in Garopaba and Silveira and 1% of the time in Ibiraquera,
and where never seen resting in Praia do Rosa. In Gamboa, whales spent almost half of the
time traveling, around 30% of the time playing and 20% of the time resting.
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Focal observations in non-whalewatching days
A total of 25.6 hours of focal observations were conducted on 13 days in which there were
no whalewatching cruises, in October and November. During that time we followed whales
for a mean of 1.9 hours of observation/day and tracked 51 groups of mother/calf pairs.
Theodolite tracking data are present in Tables 13 and 14.
Swimming speed, linearity, and reorientation rates for whales tracked in the two bays are
shown in Table 15. On non-whalewatching days, mother/calf pairs traveled at a mean of 0.98
km/h in Silveira and 1.32 km/h in Ibiraquera. The linearity value for the mother/calf pairs in
Silveira shows that whales did not traveled in a constant direction during the sampling period,
which is reinforced by the reorientation rate. Mother/calf pairs tracked in Ibiraquera showed a
more directional movement with lower reorientation rate.
In the comparison of swimming speed data from non-whalewatching days to observations
taken before, during and after whalewatching cruises in Ibiraquera, no significant differences
were observed (Kruskall-Wallis: n = 87, H=4.64, p=0.2). Mean swimming speed values in
Silveira were lower during non-whalewatching days than during and after whalewatching
cruises but the sample was too small for meaningful statistical treatment. The linearity values
and reorientation rates obtained on non-whalewatching days also showed no difference to
values recorded on whalewatching days.
Total time spent in a behavioral state for whales tracked in Ibiraquera and Silveira is
shown in Table 16. Mother/calf pairs spent 83.33% of their time traveling during non-
whalewatching days in Ibiraquera and 16.67% playing. There was no significant difference in
time spent traveling (Mann-Whitney: U = 28, z = 1.0662, p = 0.2863, n
1
= 8, n
2
=10) and
playing (Mann-Whitney: U = 23.5, z = 1.4661, p = 0.1426, n
1
= 8, n
2
=10) between
whalewatching and non-whalewatching days. Mother/calf pairs spent no time resting in non-
whalewatching days. In Silveira, mother/calf pairs spent the same amount of the time
traveling (46.17%) and resting (41.63%) and 12.21% of their time playing (Table 15).
Although the sample was too small for meaningful statistical treatment, these proportions
were different than observed in Silveira on whalewatching days, when the tracked mother/calf
pair spent most of their time traveling (74.8%) (see Table 11). It’s worth noting that during
two days of observations in Silveira on non-whalewatching days one mother/calf pair could
be identified (through identification of the mother, named Tno.01 - sighting history in Table
16). This pair was tracked in many occasions over more than two months during this field
season in different bays, and displayed a variety of proportions in behavioral states during this
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period. This mother/calf pair was not in Silveira on whalewatching days so they are not
included in these observations.
Identified individuals
Whales were photographed from shore, boat and during aerial surveys. Analysis of the
photographs showed that some individuals moved between bays during the season. On
whalewatching days, three females with calves were identified and resighted on more than
one day, always accompanied by their calves. The whales were individually identified during
aerial surveys and also resighted on non-whalewatching days. The resightings allowed us to
follow their movements through the field season as well as compare their behaviors on days
with and without whalewatching cruises. The sighting history for each pair is showed in Table
17 and the values for movements are in Table 18. The female “Tno.01” had a series of
propeller scars on the posterior part of her back, which helped in identifying the pair
throughout the season. The scars were healed and probably acquired some time before her
arrival in the study area.
The mean swimming speed of the mother/calf pair Tno. 01 was 2.6 times higher during
whalewatching days than in non-whalewatching days. However, no significant differences
between the mean values were found (Kruskall-Wallis: n = 15, H = 5.7025, p = 0.127)
throughout the period they were observed, probably due to low sample size during non-
whalewatching days. This pair spent most of their time (78.3%) traveling during
whalewatching days and little time playing (13.9%) and resting (7.8%). In non-
whalewatching days they spent half of their time traveling (58.5%), 7.6% of their time playing
and 33.9% resting. The pair Tno. 03 also presented higher mean swimming speed values
during whalewatching days than in non-whalewatching days (1.9 times), with no significant
differences (Kruskall-Wallis: n =10, H = 0.9056, p =0.3413). They spent 83.7% of their time
traveling in whalewatching days, 14.5% playing and 1.8% resting. In non-whalewatching
days the proportions of time spent traveling (86.6%) and playing (13.4%) were similar to
whalewatching days but they spent no time resting in non-whalewatching days. Tno 01 and 03
traveled at higher linearity rates in whalewatching days than in non- whalewatching days. The
reorientation rates of the pair Tno 01 were lower in whalewatching days than in non-
whalewatching days. The pair Tno. 03 had higher reorientation rates in whalewatching days
then in non-whalewatching days. The pair Tno. 02 was tracked during only one
whalewatching day so statistical comparison with non-whalewatching days was not possible.
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Their swimming speeds and linearity values were similar during the observations but they
reoriented their swimming direction at a slightly higher rate in non-whalewatching days than
in whalewatching days (Table 18). This pair spent most of their time traveling (86.2%)
during the whalewatching day they were tracked, 13.8% of their time playing and no time
resting. During non-whalewatching days the pair also spent most of their time traveling
(82.7%), 17.3% of the time playing and no time resting.
Whalewatching monitoring without theodolite
During the instances when no theodolite was used to monitor whale/boat interactions, a
total of 32.3 hours of observation were made (28.9% from the total time of whalewatching
monitoring). All but two of the cruises were carried by the two authorized whalewatching
boats. The others were opportunistic whalewatching cruises taken by a small inflatable boat
and a fisherman boat. Twenty approaches to whales were made by the whalewatching boats.
Fifty-five percent (n=11) were directed toward nine mother/calf pairs and 45% (n=9) were
directed toward five groups of adults. In 90% (n=18) of the approaches, whales showed “no
reaction” to the approaching boat (the stimuli were apparently ignored and the whales
continued their activities uninterrupted). During these occasions, whales were not necessarily
unaware of the presence of the boat, but their behaviors were not changed by it. In 10% (n=2)
of the approaches, whales appeared to have approached and interacted with the boat for a
brief period, appearing to be curious. These whales moved from the immediate area before
resuming their former activities. Whales that approached boats included mother/calf pairs.
During the two opportunistic whalewatching cruises, the whales showed “no reaction” during
the approach.
DISCUSSION
The focal observations of the behavior of right whales in relation to boat approaches
conducted during the 2002 right whale season showed that most of the whales appeared to
have ignored the presence of the boats and didn’t change their behavior. We observed no clear
evidence of immediate disturbance of right whales, suggesting that whalewatching can be
continued in the study area if conducted in agreement to the national legislation.
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Minor changes in behavior were observed in few occasions when whales were seen to
swim towards the boats but later, after a period of apparent interest, they moved away and
resumed their former activities. Whales were never seen leaving a bay after being approached
by a whalewatching boat. Whales didn’t appear to react to the boat approaches even when
more than one approach was made to the same group. According to Watkins (1986) whales
can have some degree of negative reactions to first approaches but ignore a vessel after three
or four passes, showing habituation to relatively non-disturbing stimuli. The author also
mentioned that northern right whales (Eubalaena glacialis) moved slowly but consistently
away from passing ships and dived quickly when disturbed. In Argentina, some southern right
whales were reported to allow close boat approaches when the boat moved slowly and some
whales even approached stationary boats (Cummings et al., 1972; Payne et al., 1983).
Colombo et al. (1990) described faster mean swimming speeds of whales not accompanied by
calves in areas with whalewatching boats when compared with areas not subjected to boats,
but no differences were observed in mother/calf pairs. However, in a recent study Rivarola et
al. (2001) described changes in swimming speed and headings as avoidance reactions of
southern right whales to whalewatching boats. The authors mentioned that the behavior of the
whales was affected by high impact boat maneuvers like direct approach, encircling or
chasing, thought the whales response was not consistent. Whales were observed to move
away from boats only when the three types of maneuvers occurred during the same
whalewatching trip.
Changes in swimming speed as a reaction to disturbance were also reported by studies in
different cetacean species (Richardson et al., 1985; Baker and Herman, 1989; Green and
Green, 1990; Richardson et al., 1990; Kruse, 1991; Heckel et al. 2001; Jahoda et al., 2003).
Richardson et al. (1985) noted strong and consistent increases in swimming speeds of
bowhead whales (Balaena mysticetus) in response to approaching boats. Humpback whales
(Megaptera novaeangliae) in Hawaiian waters altered swimming direction as boats
approached and decreased swimming speeds after boats departed (Green and Green, 1990).
When approached by whalewatching boats in their wintering area in Ecuador, humpbacks
were recorded to increase swimming speeds and adopted a more direct path after the
encounter (Scheidat, et al. 2004). Killer whales (Orcinus orca) in Johnstone strait responded
to approaching boats by increasing their swimming velocities and by tending to swim toward
open water (Kruse, 1991). Heckel et al. (2001) detected changes in swimming speeds of gray
whales (Eschrichtius robustus) in the presence of boats during migration along the Mexican
125
coast. Jahoda et al. (2003) report on travel at increased velocity and reduction of time spent at
the surface as avoidance behavior performed by Mediterranean fin whale (Balaenoptera
physalus) after a disturbance by boat.
Effects of anthropogenic disturbance may range from temporary changes in behavior
(Gauthier and Sears, 1999) to possible interference with feeding (Richardson et al., 1990;
Johnson, S.R. 2002; Jahoda et al. 2003), reproduction (Miller et al., 2000; Weller et al., 2002)
or migration (Heckle et al., 2001). Despite the differences in the mean swimming speeds of
right whales observed in the present study were not statistically significant, it is broadly
accepted that changes in swimming speed is a common cetacean response to boat disturbance.
The lack of statistical significance can be a result of small sample size or the differences
observed were casual. Notwithstanding, Watkins (1986) found that right whales are less easily
disturbed than other species of whales like minkes (Balaenoptera acutorostrata), fin and
humpbacks, and showed over the years apparently the same variety of responses with little
changes.
The predicted probabilities observed at Gamboa and Ibiraquera infers that the movements
of mother/calf pairs relative to whalewatching boats were probably random throughout the
encounter. A decreasing probability was observed from the beginning to the end of the
encounter in Garopaba and Praia do Rosa, and an increase in Silveira. The decrease implies
that mother/calf pairs were more attracted to and approached boats during the first minutes of
an encounter and less attracted during the next intervals, when whales could be showing
avoidance or moving randomly with respect to the boat. In Silveira the whales were less
attracted to boats during the first minutes of an encounter and more attracted to the end of the
encounter. Its worth noting that higher values for the predicted probabilities were observed in
Praia do Rosa in relation to Garopaba. These two bays are of very different size and
orientation to the open sea. Praia do Rosa is smaller than Garopaba, which results in a shorter
distance between the whales and boats at the beginning of an encounter. It is possible that the
mother/calf pairs could be reacting in a different way at that place as a result of having
different perception on the acoustic stimuli.
Right whales may appear not to react to boat approaches for many reasons but sometimes
they simply appear indifferent to the presence of a boat. We observed that whales were
approaching boats at either shorter or greater distances. Sometimes boats maintained great
distances from the whales, not only as a precautionary conduct due to the limits on the
distance of approach imposed by the national legislation but due to adverse weather
126
conditions (high waves and strong winds) which could hurl the boat towards whales direction
or the breaking waves.
As mentioned by Bejder et al. (1999), measuring distances are an ambiguous analysis
because you can get the same distance measure from a boat leaving or approaching a group of
whales. In their study the authors observed no clear relationship between the distance of the
boats and the orientation of the Hector’s dolphins (Cephalorhynchus hectori). We observed
that whales reacted at both long and short distances from boats and the reactions varied with
bays. For example, Silveira and Rosa are very similar in size and the mother/calf pairs showed
opposite swimming orientations in relation to the whalewatching boats at similar distances.
Boat speed may also influence the perception of boat approaches and whales reactions
may have been to boat speed. Whalewatching boats typically entered the bays at about 4.96
km/h (SD=2.62 km/h), slowed down when approaching the whales, and then put the engine in
idle or turned it off when getting close to 100m from the whales. This type of approach makes
the sound level diminish as the boat approaches the whales and probably reduces the potential
for disturbance during boat approaches. According to Richardson et al., 1995, many reactions
to ships or boats are presumably reactions to noise but responsiveness may vary widely
between and within-species, according to physical and biological factors, which must be
considered in determining the radius of responsiveness and zone of noise influence
(Richardson et al., 1995). Underwater sound appears to be the primarily stimuli of reaction by
whales (Watkins, 1986; Novacek et al., 2004). However, there is limited information on noise
produced by small boats typically used in coastal waters (Richardson et al., 1995), as well as
on the frequency range of hearing and sensitivity of baleen whales (Ketten, 1994; National
Research Council, 2004).
Avoidance responses to oncoming vessels have also been noted in many species of small
odontocets including spotted (Stenella attenuata), spinner (S. longirostris) and striped (S.
coeruleoalba) dolphins (Au and Perryman, 1982), arctic beluga whales (Delphinapterus
leucas) (Richardson, 1995), harbour porpoises (Phocoena phocoena) (Evans et al. 1994),
bottlenose dolphins (Tursiops truncatus) (Janik and Thompson, 1996; Williams et al., 2002;
Hastie (2003); Constantine et al., 2004; Goodwin and Cotton, 2004), Hector’s dolphins
(Bejder et al. 1999) and sperm whales (Magalhães et al. 2002). Despite these studies have
indicated boat-avoidance behavior of cetaceans to approaching boats, only few of them
reported clear patterns of short-term reactions. Moreover, whether the stimuli were caused by
127
the physical presence of the boat, the underwater noise generated or the interaction between
both agents is not known.
The time mother/calf pairs spend on the nursery ground is of great importance for calf
growth and development (Taber and Thomas, 1982). During this period, females probably do
not feed and channel most of their energy into nursing and taking care of their calves and as a
consequence appear to show low levels of activity. In fact, despite traveling during most of
the time we observed mother/calf pairs, their average swimming speed was less than 2 km/h
(see Table 9). It is known that right whales are very slow swimmers. They can average 2kt
(~4km/h) and rarely exceed 5 kt (~9km/h) (Slijper, 1979; Cummings et al. 1972), but can
travel at speeds of 16 km/h when frightened (Slijper, 1979) and an average of 5-11km/h
during migration (Lockyer, 1981). Satellite-monitored northern right whales in feeding areas
have been reported to travel at average speeds of 3.5 km/h (Mate et al. 1997). Swimming
speeds of right whales tracked with theodolite on their wintering ground at Peninsula Valdes
averaged 2-3km/h (Colombo et al., 1990) and off South Africa 1.67±0.85km/h (Best, 2000).
Additionally, mother/calf pairs on nursery grounds generally presents less movements along
the coast than other individuals (Bannister, 1990; Best, 1990). The theodolite data presents
here actual speeds of mother/calf pairs on the wintering ground and can be used for future
comparisons of whale movements in this and other areas.
CONCLUDING REMARKS AND RECOMMENDATIONS
Marine mammals are target of a growing ecotourism industry worldwide and the
whalewatching activities are exposing these animals to potential disturbance at an ever-
increasing rate. In some places the numbers of recreational vessels approaching whales and
dolphins is cause for serious concern. The whale and dolphinwatching industry has
considerable economic and educational potential, creating concern about its impacts on
cetacean populations. But techniques exist that can be used to assess impacts on a short and
long-term basis, with different efficacies and from different platforms (IFAW, Tethys
Research Institute and Europe Conservation, 1995).
Studies of anthropogenic impacts on cetaceans have been developed in many places all
over the world. Most of them found some significant change in cetacean behavior, but almost
all stated without exception that the long-term, biological meaning of these changes is not
128
clear (Richter et al., 2000).
While data presented here comes mainly from the observation of a small whalewatching
industry operating under the guidelines of national legislation, the growing economic interest
increases the potential for the growth of uncontrolled activities if whalewatching is not
permanently monitored and not properly managed. A general increase in the interest is
apparent in the region not only by tourists but also by local residents to conduct boat and
shore based whalewatching.
Some aspects of both whalewatching operation and the protection of this right whale
population must be considered with respect to the monitoring and management of
whalewatching in the study area:
1) whalewatching has been operational for only four years and is carried out within
restrictions imposed by national legislation, in a controlled way;
2) the geography of the study area provides many advantageous observation sites for
studying the whales and their encounters with boats;
3) whalewatching is carried out near to shore and whales are distributed just outside the
breaking waves region;
4) the current national legislation can be improved if specific studies are conducted for
each cetacean species;
5) right whales appear to be recovering after many decades of commercial whaling (Groch
et al., 2004), along with the rest of the as the South Atlantic “stock”, which is estimated to be
increasing annually at about 8% (IWC, 2001);
6) short-term studies cannot document long-term effects on marine mammals, hence long-
term monitoring is vital for this right whale population and a valuable tool for the
development of appropriate management of whales in this area.
Information derived from theodolite tracking studies can be coupled to other types of
studies in order to provide a more complete dataset for the management of whalewatching and
the development of whale conservation strategies. For instance, while theodolite itself cannot
detect habitat use changes over time, long-term photo-ID studies can document changes in the
whale distribution which, when analyzed in conjunction with theodolite data and other field
studies, may help clarify the actual impact of whale watching on whale populations. It is to be
noted that, from a management perspective, whalewatching needs to be part of a more
129
comprehensive assessment of all possible disturbances (e.g. fishing, ship traffic) within the
right whale wintering ground. Therefore, the systematic gathering of more comprehensive
records of other human activities are strongly advisable, so that researchers and managers can
adequately assess the conservation status and propose management measures for targeted
populations.
The year 2002 was the third year of monitoring of the whalewatching operations in the
study area. Further research to access potential impacts of the whalewatching operations on
the right whale population in a long-term basis in the region is advisable, as well as the
continuing development of educational programs for tourists and local residents.
ACKNOWLEDGEMENTS
We would like to thank the community of Itapirubá for accommodation during field
activities, IWC-Brasil Scientific Director Paulo A.C. Flores for the incentive and supervision,
the volunteers Audrey Amorim, Ana Paula Ruthes, Clara I. Berron, Dayse de Mello, Felipe
Ruzzarin, Marcel Ferrari, Mariana and Schana Vieiro for the help with data acquisition and
friendship, the International Wildlife Coalition for support and help with equipment
acquisition. Special thanks to Vicky Rowntree for the invaluable insights and careful reading
of the manuscript. Many thanks to PETROBRAS Brazilian Oil Company, Fundação O
Boticário de Proteção a Natureza and McArthur Foundation, and the International Fund for
Animal Welfare, for its invaluable support to this work. The first author was partially
supported by a scholarship grant from Comissão de Aperfeiçoamento de Pessoal (CAPES –
Ministry of Education) (2001-2003) and Conselho Nacional de Desenvolvimento Científico e
Tecnológico (2004-2005) (Ministry of Science and Technology, CNPq - Proc. 142247/2003-
0).
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LIST OF TABLES
Table 1 - Description of behavioral states recorded during focal observations of whales...139
Table 2 - Types of boat approaches during whalewatching encounters with whales (adapted
from Findlay, 1998).................................................................................................139
Table 3 - Reactions of whales to boat approaches during whalewatching encounters (adapted
from Watkins, 1986)................................................................................................139
Table 4 - Number of whalewatching cruises, number and group composition of right whales
encountered by month during the monitoring of the whalewatching activities off the
central-southern coast of Santa Catarina State, Southern Brazil, from July to October,
2002. ........................................................................................................................140
Table 5 - Distribution of the whalewatching cruises monitored from July to October 2002,
according to the site, number and group composition of the right whales sighted off the
central-southern coast of Santa Catarina State, Southern Brazil.............................140
Table 6 - Distances measured during encounters between right whales and whalewatching
boats monitored from July to October 2002, in the central-southern coast of Santa
Catarina State, Southern Brazil. ............................................................................1141
Table 7 - Total theodolite tracking data obtained during the monitoring of right whales on
whalewatching days, by observation site, in the central-southern coast of Santa Catarina
State, Southern Brazil, from July to October 2002. ................................................141
Table 8 - Mean rates of theodolite tracking data obtained while monitoring right whales on
whalewatching days, by observation site, in the central-southern coast of Santa Catarina
State, Southern Brazil, from July to October 2002. ................................................142
Table 9 - Mean values for swimming speed of right whales mother/calf pairs tracked in each
bay before, during and after encounters with whalewatching boats in the central-southern
coast of Santa Catarina State, Southern Brazil, from July to October 2002. ..........143
Table 10 - Mean values for linearity and reorientation rates of right whales mother/calf pairs
tracked in each bay during whalewatching days, in the central-southern coast of Santa
Catarina State, Southern Brazil, from July to October 2002...................................144
Table 11 - Mean probability of mother/calf pairs heading towards whalewatching boats at
shorter and greater distances during whale/boat encounters tracked in each bay during
whalewatching days, in the central-southern coast of Santa Catarina State, Southern
Brazil, from July to October 2002...........................................................................144
137
Table 12 - Behavioral states of mother/calf pairs tracked on days that included whalewatching
encounters in the central-southern coast of Santa Catarina State, Southern Brazil, from
July to October 2002. ..............................................................................................145
Table 13 - Theodolite data colleted on non-whalewatching days, by observation site, in the
central-southern coast of Santa Catarina State, Southern Brazil, from October to
November 2002: ......................................................................................................145
Table 14 - Mean rates of theodolite tracking data obtained while following mother/calf pairs
on non-whalewatching days, by observation site, in the central-southern coast of Santa
Catarina State, Southern Brazil, from October to November 2002:........................146
Table 15 - Mean values for swimming speed, linearity and reorientation rates of right whales
mother/calf pairs tracked in each bay during non-whalewatching days, in the central-
southern coast of Santa Catarina State, Southern Brazil, from October to November
2002:........................................................................................................................147
Table 16 - Behavioral states of mother/calf pairs tracked in no-whalewatching days in
Silveira and Ibiraquera, during the monitoring of whalewatching activities in the central-
southern coast of Santa Catarina State, Southern Brazil, from October to November
2002. ........................................................................................................................147
Table 17 - Sighting history of individually identified mother/calf pairs tracked while
monitoring right whales on whalewatching and non-whalewatching days in the central-
southern coast of Santa Catarina State, Southern Brazil, from August to October 2002.
.................................................................................................................................148
Table 18 - Mean swimming speed, linearity and reorientation rates of individually identified
mother/calf pairs tracked while monitoring right whales on whalewatching and non-
whalewatching days in the central-southern coast of Santa Catarina State, Southern
Brazil, from August to October 2002......................................................................149
LIST OF FIGURES
Figure 1 – Map of the study area. A, South America; B, Santa Catarina State, Brazil; C,
South of Santa Catarina State. Triangles indicate observation sites........................150
Figure 3 – Probability of mother/calf pairs traveling towards the whalewatching boats as a
function of the time of the encounter during the monitoring of whalewatching activities
in the central-southern coast of Santa Catarina State, Southern Brazil, from July to
October 2002. ..........................................................................................................152
Figure 2 - Classification of whale/boat orientation (according to Bejder et al., 1999).Erro!
Indicador não definido.
Figure 4 – Mean distances between mother/calf pairs and boats observed during the
monitoring of whalewatching activities in the central-southern coast of Santa Catarina
State, Southern Brazil, from July to October 2002. ................................................153
Figure 5 - Behavioral states of mother/calf pairs tracked in whalewatching days during the
monitoring of whalewatching activities in the central-southern coast of Santa Catarina
State, Southern Brazil, from July to October 2002. ................................................154
139
Table 1 - Description of behavioral states recorded during focal observations of whales.
Behavioral State Description
Travelling Directional forward movement in constant speed, that resulted in a change of location.
Resting
Individuals remain motionless without any evidence of physical exertion, in general
with the dorsal surface of the head and body above the water.
Play Activities between mother and calf not directly related to any of the above categories.
Other activity Activity not directly related to any of the above categories.
Table 2 - Types of boat approaches during whalewatching encounters with whales (adapted
from Findlay, 1998).
Type Of Approach Description
SA (Side on approach)
Slow speed approach (no-wake speed) from the left or right side of the whale(s).
HA (Head on approach)
Slow speed approach (no-wake speed) towards the head of the whale(s).
TA (Tail on approach)
Slow speed approach (no-wake speed) from behind the whale(s).
OA (Obtrusive approach)
Higher speed approach (with wake produced), with direction and speed changes
and circling of whale(s).
S (Stationary)
Boat stopped (with the engine in neutral or turned off) at a distance of over 100
m from the whales in the path of whales and were allowed to drift onto the
whale(s).
Table 3 - Reactions of whales to boat approaches during whalewatching encounters (adapted
from Watkins, 1986).
Whale Reaction Description
A (approach)
Whales showed apparent curiosity and appeared to provide some reward. Whales'
previous activities were suspended and they permitted close approaches or they
approached and interacted with the boat. After a period of such interest, whales often
moved away from the immediate area before resuming their former activities.
U (no reaction)
The stimuli were apparently ignored and the whales continued their activities
uninterrupted. Whales are not necessarily unaware of the presence of the boat, but their
behaviors were not interrupted by it.
N (move away)
Sudden changes in behavior (include: persistent movements away from the boat, turn
sharply away or dive quickly).
140
Table 4 - Number of whalewatching cruises, number and group composition of right whales
encountered by month during the monitoring of the whalewatching activities off the
central-southern coast of Santa Catarina State, Southern Brazil, from July to October,
2002.
Month
No. Cruises
monitored (%)
No. mother/calf
pairs sighted*
(%)
No. Adults
without calves
sighted* (%)
No. whales sighted*
(%)
July
3 (8.6) 0 (0.0) 7 (4.3) 7 (4.3)
August
7 (20.0) 14 (8.6) 3 (1.9) 31 (19.1)
September
9 (25.7) 18 (11.1) 0 (0.0) 36 (22.2)
October
16 (45.7) 44 (27.2) 0 (0.0) 88 (54.3)
TOTAL
35 76 (46.9) 10 (6.2) 162
* Includes possible double-counting.
Table 5 - Distribution of the whalewatching cruises monitored from July to October 2002,
according to the site, number and group composition of the right whales sighted off the
central-southern coast of Santa Catarina State, Southern Brazil.
Site of the cruises
No. WW Cruises
monitored (%)
No. mother/calf
pairs sighted*
(%)
No. Adults
without calves
sighted* (%)
Total No. of whales
sighted* (%)
Gamboa
5 (14.3) 11 (6.8) 0 (0.0) 22 (13.6)
Garopaba
10 (28.6) 14 (8.6) 7 (4.3) 35 (21.6)
Ibiraquera
10 (28.6) 28 (17.3) 0 (0.0) 56 (34.6)
Praia do Rosa
4 (11.4) 13 (8.0) 0 (0.0) 26 (16.0)
Silveira
5 (14.3) 8 (4.9) 3 (1.9) 19 (11.7)
Ferrugem
1 (2.9) 2 (1.2) 0 (0.0) 4 (2.5)
TOTAL
35 76 (46.9) 10 (6.2) 162
* Includes possible double-counting.
141
Table 6 - Distances measured during encounters between right whales and whalewatching
boats monitored from July to October 2002, in the central-southern coast of Santa
Catarina State, Southern Brazil.
Observation site Maximum distances (m) Minimum distances (m)
Gamboa
1316.6 14.9
Garopaba
4242.1 6.1
Silveira
1167.3 63.1
Praia do Rosa
1710.8 27.5
Ibiraquera
3201.0 6.7
Table 7 - Total theodolite tracking data obtained during the monitoring of right whales in
whalewatching days, by observation site, in the central-southern coast of Santa Catarina
State, Southern Brazil, from July to October 2002.
TOTAL TRACK
Duration
(hh:mm:ss)
#Fix Points
No. of whales
tracked*
Gamboa
13:36:45 768 11
Garopaba
10:38:11 445 15
Silveira
6:19:23 371 6
Praia do Rosa
2:48:15 133 4
Ibiraquera
32:08:44 1214 65
TOTAL 65:31:18 2931 101
*Includes possible double counting of individual whales tracked.
142
Table 8 - Mean rates of theodolite tracking data obtained while monitoring right whales on
whalewatching days, by observation site, in the central-southern coast of Santa Catarina
State, Southern Brazil, from July to October 2002.
Mother/calf pairs Whale/boat encounter*
TOTAL TRACK
Duration
(h:mm:ss)
Fix points / min
Duration
(h:mm:ss)
Fix points / min
a) Gamboa
Mean
2:34:24 0.36 0:55:31 0.32
SD
1:45:08 0.20 0:17:22 0.07
Maximum
5:40:28 --- 1:22:10 ---
Minimum
0:29:30 --- 0:38:21 ---
Total no. of fix points 678 --- 90 ---
b) Garopaba
Mean
1:11:26 0.23 1:09:17 0.38
SD
0:39:14 0.17 0:12:41 0.1
Maximum
3:10:41 --- 1:25:11 ---
Minimum
0:32:44 --- 0:56:54 ---
Total no. of fix points 288 --- 157 ---
c) Silveira
Mean
1:49:28 0.52 0:40:18 0.34
SD
1:01:37 0.21 0:13:12 0.05
Maximum
2:43:18 --- 0:51:30 ---
Minimum
0:08:00 --- 0:21:23 ---
Total no. of fix points 316 --- 55 ---
d) Praia do Rosa
Mean
1:02:09 0.63 0:48:37 0.29
SD
0:31:54 0.68 0:14:40 0.07
Maximum
1:30:11 --- 0:59:00 ---
Minimum
0:34:06 --- 0:38:15 ---
Total no. of fix points 106 --- 27 ---
Mother/calf pairs Whale/boat encounter* Other boats**
e) Ibiraquera
Duration
(h:mm:ss)
Fix points /
min
Duration
(h:mm:ss)
Fix points /
min
Duration
(h:mm:ss)
Fix
points /
min
Mean
1:34:13 0.20 0:46:40 0.31 0:18:12 0.58
SD
1:13:05 0.15 0:16:36 0.08 0:13:17 0.53
Maximum
4:33:37 --- 1:06:45 --- 0:29:11 ---
Minimum
0:02:26 --- 0:14:20 --- 0:03:26 ---
Total no. of fix points 1043 --- 161 --- 10 ---
* Encounter with authorized whalewatching boats.
** Encounter with other than the authorized whalewatching boats.
143
Table 9 - Mean values for swimming speed of right whales mother/calf pairs tracked in each
bay before, during and after encounters with whalewatching boats in the central-southern
coast of Santa Catarina State, Southern Brazil, from July to October 2002.
Distance
Between
Fixes (m)
Swimming
Speed
(km/h)
Time of
Observation
(h:mm:ss)
Time Dec
(min)
No. of
phase(s)**
a) Gamboa
Before
Mean 0.05 0.90 0:44:45 44.75 3
SD 0.05 0.94 0:28:01 28.02 ---
During
Mean 0.03 1.39 0:42:48 42.80 11
SD 0.05 1.65 0:21:01 21.02 ---
After
Mean 0.03 1.55 0:34:20 34.33 8
SD 0.04 2.10 0:24:17 24.28 ---
b) Garopaba
Before
Mean 0.08 1.67 0:18:21 18.35 5
SD 0.08 1.78 0:07:47 7.78 ---
During
Mean 0,12 2,71 0:30:22 30,37 12
SD 0,15 2,77 0:20:53 20,88 ---
After
Mean 0.06 2.46 1:02:34 62.57 4
SD 0.07 1.89 0:58:57 58.95 ---
c) Ibiraquera
Before
Mean 0.08 1.51 0:37:43 37.72 12
SD 0.08 1.59 0:12:59 12.98 ---
During
Mean 0.10 1.85 0:26:54 25.17 29
SD 0.11 1.52 0:14:57 15.93 ---
After
Mean 0.09 1.51 0:48:49 48.82 13
SD 0.08 1.30 0:24:23 24.38 ---
d) Rosa
Before
Mean 0.06 2.78 0:34:57 34.95 1
SD 0.07 3.34 0:00:00 0.00 ---
During
Mean 0.04 1.99 0:39:38 39.63 3
SD 0.05 2.37 0:17:29 17.48 ---
After
Mean 0.07 1.08 0:30:56 30.93 2
SD 0.04 0.88 0:01:07 1.12 ---
e) Silveira
Before*
Mean --- --- --- --- ---
SD --- --- --- --- ---
During
Mean 0.03 1.10 0:44:46 44.77 2
SD 0.03 0.66 0:02:43 2.72 ---
After
Mean 0.04 1.80 0:26:22 26.37 2
SD 0.03 1.74 0:18:34 18.57 ---
* There was no data collected during this phase.
**Before (B), during (D) and after (A) the encounter with whalewatching boats.
144
Table 10 - Mean values for linearity and reorientation rates of right whales mother/calf pairs
tracked in each bay during whalewatching days, in the central-southern coast of Santa
Catarina State, Southern Brazil, from July to October 2002.
Linearity Reorientation Rate
(degrees/min)
Observation Site Mean SD Mean SD
Gamboa
0.36
0.35
23.57 8.08
Garopaba
0.38 0.22 15.94 8.03
Silveira 0.17 ---
23.74 ---
Rosa 0.34 0.19
31.63
20.97
Ibiraquera 0.49 0.27
13.42
13.20
Table 11 - Mean probability of mother/calf pairs heading towards whalewatching boats at
shorter and greater distances during whale/boat encounters tracked in each bay during
whalewatching days, in the central-southern coast of Santa Catarina State, Southern
Brazil, from July to October 2002.
Prob. at distance
≤ 300m
Prob. at distance
>300m
Mean SD Mean SD
Garopaba
0,16 0,07 0,21 0,06
Gamboa
0,24 0,01 0,24 0,01
Ribanceira
0,18 0,01 0,20 0,01
Rosa
0,18 0,22 0,17 0,16
Silveira
0,06 0,03 0,11 0,08
145
Table 12 - Behavioral states of mother/calf pairs tracked on days that included whalewatching
encounters in the central-southern coast of Santa Catarina State, Southern Brazil, from
July to October 2002.
Gamboa Garopaba Rosa Ibiraquera Silveira*
Mean time
spent (%)
SD
Mean time
spent (%)
SD
Mean time
spent (%)
SD
Mean time
spent (%)
SD
Total time
spent (%) SD
Travel
47.92 22.75 76.60 25.70 68.18 19.28 89.20 5.28 74.8 -
Play
31.58 20.74 5.48 7.27 31.82 19.28 9.74 4.87 3.5 -
Rest
20.50 34.63 17.91 25.91 0.00 0.00 1.06 1.77 21.7 -
*SD values for Silveira are not provided because only one mother/calf pair was included in this analysis.
Table 13 - Theodolite data colleted on non-whalewatching days, by observation site, in the
central-southern coast of Santa Catarina State, Southern Brazil, from October to
November 2002:
TOTAL TRACK
Duration
(hh:mm:ss)
#Fix Points
No. of mother/calf
pairs tracked*
Days of
observation
Silveira
6:24:21 271 8 3
Ibiraquera
19:10:03 614 43 10
TOTAL 25:34:24 885 51 13
*Includes possible double counting.
146
Table 14 - Mean rates of theodolite tracking data obtained while following mother/calf pairs
on non-whalewatching days, by observation site, in the central-southern coast of Santa
Catarina State, Southern Brazil, from October to November 2002:
Mother/calf pairs
TOTAL TRACK
Duration
(h:mm:ss)
Fix points/min
a) Silveira
Mean
2:05:03 0.45
SD
1:17:22 0.14
Maximum
3:21:43
---
Minimum
0:43:17
---
Total no. of fix points 258
---
b) Ibiraquera
Mean
1:09:14 0.24
SD
0:46:39 0.29
Maximum
3:22:42
---
Minimum
0:01:49
---
Total no. of fix points 529
---
147
Table 15 - Mean values for swimming speed, linearity and reorientation rates of right whales
mother/calf pairs tracked in each bay during non-whalewatching days, in the central-
southern coast of Santa Catarina State, Southern Brazil, from October to November
2002:
Swimming Speed Linearity Reorientation Rate
(degrees/min)
Observation Site Mean SD Mean SD Mean SD
Silveira
0.98 0.87 0.17 0.12 28.58 10.38
Ibiraquera
1.32 1.33 0.57 0.31 10.50 11.31
Table 16 - Behavioral states of mother/calf pairs tracked in no-whalewatching days in
Silveira and Ibiraquera, during the monitoring of whalewatching activities in the central-
southern coast of Santa Catarina State, Southern Brazil, from October to November
2002.
Silveira Ibiraquera
Mean time
spent (%)
SD
Mean time
spent (%)
SD
Travel
46.17 32.48 83.33 11.00
Play
12.21 17.33 16.67 11.00
Rest
41.63 41.23 0.00 0.00
148
Table 17 - Sighting history of individually identified mother/calf pairs tracked while
monitoring right whales on whalewatching and non-whalewatching days in the central-
southern coast of Santa Catarina State, Southern Brazil, from August to October 2002.
No. of follows
Total Time of tracking
(hours)
Mother/
calf pair
Date of
first
sighting
Date of
last
sighting
Observation
sites in which
the pair was
sighted
whalewatch
. days
non-
whalewatch
days
whalewatch.
days
non-
whalewatc
h days
Period
between
first and
last sighting
(days)
Tno. 01*
18/08/02 26/10/02 Gamboa
Garopaba
Silveira
Ibiraquera
01
03
-
04
-
-
02
02
17.5 4.1 69
Tno. 02*
24/09/02 28/10/02 Ibiraquera
Praia da Vila
01
03
01
2.2 3.2 33
Tno. 03*
14/10/02 28/10/02 Ibiraquera 03 05 10.7 6.9 25
* Mother/calf pairs identified during aerial surveys.
149
Table 18 - Mean swimming speed, linearity and reorientation rates of individually identified
mother/calf pairs tracked while monitoring right whales on whalewatching and non-
whalewatching days in the central-southern coast of Santa Catarina State, Southern
Brazil, from August to October 2002.
Mother/calf
pair
Mean swimming speed Linearity Reorientation Rate
Whalewatching
days
Non-
whalewatching
days
Whalewatching
days
Non-
whalewatching
days
Whalewatching
days
Non-
whalewatching
days
Tno. 01*
2.21±0.72 0.85±0.2 0.44±0.34 0.21±0.13 14.42±9.65 22.46±5.66
Tno. 02*
0.85±0.19 0.77±0.31
0.61
0.53±0.57
6.49
9.26±6.26
Tno. 03*
1.70±1.05 0.89±0.55 0.55 ± 0.13 0.39 ± 0.39 15.50 ± 6.14 7.78±3.56
* Mother/calf pairs identified during aerial surveys.
150
Figure 1 – Map of the study area. A, South America; B, Santa Catarina State, Brazil; C,
South of Santa Catarina State. Triangles indicate observation sites.
151
Figure 2 - Classification of whale/boat orientation (according to Bejder et al., 1999).
152
Figure 3 – Probability of mother/calf pairs traveling towards the whalewatching boats as a
function of the time of the encounter during the monitoring of whalewatching activities
in the central-southern coast of Santa Catarina State, Southern Brazil, from July to
October 2002.
153
Figure 4 – Mean distances between mother/calf pairs and boats observed during the
monitoring of whalewatching activities in the central-southern coast of Santa Catarina
State, Southern Brazil, from July to October 2002.
154
Figure 5 - Behavioral states of mother/calf pairs tracked in whalewatching days during the
monitoring of whalewatching activities in the central-southern coast of Santa Catarina
State, Southern Brazil, from July to October 2002.
CONSIDERAÇÕES FINAIS
O litoral centro-sul de Santa Catarina e o norte do Rio Grande do Sul é uma
importante área de concentração durante os meses de inverno e primavera para as baleias
francas austrais, Eubalaena australis, que consistem no período reprodutivo desta espécie. A
distribuição nesta região, no entanto, não é uniforme indicando a ocorrência de algumas
áreas específicas de maior relevância. A maioria das avistagens registradas durante os
sobrevôos consistiram de pares de fêmeas com filhotes, caracterizando esta área como um
importante berçário, confirmando estudos anteriores (Simões-Lopes et al. 1992; Palazzo and
Flores 1996, 1998; International Wildlife Coalition/Brazil 1999). Apesar de grupos de até
oito indivíduos terem sido avistados, associações de diversos indivíduos em áreas de
reprodução não são comuns (Payne 1986; Bannister 1990; Best 1990; Patenaude and Baker
2001; Best et al. 2003), excetuando-se associações temporárias de grupos envolvidos em
atividades social ou sexual (Donnelly 1967; Payne et al. 1983; Best et al. 2003).
Apesar do esforço amostral variado ao longo dos anos, alguns padrões de
distribuição podem ser identificados. A distribuição das fêmeas com filhotes e dos adultos
não-acompanhados está sobreposta até certo ponto, mas uma área principal de concentração
pode ser identificada especialmente no que se refere às fêmeas com filhotes, nos
‘bins’(unidades de 12 minutos de latitude) localizados mais ao norte. Essa área coincide com
a área de concentração previamente reconhecida em estudos anteriores (Simões-Lopes et al.
1992; Palazzo and Flores 1996, 1998; International Wildlife Coalition/Brazil 1999).
Duas grandes áreas de concentração com distintas características geográficas
foram identificadas. Nestas áreas, há ocorrência distinta de pares de fêmeas com filhotes e
indivíduos não-acompanhados, indicando a existência de uma segregação geográfica mais ao
norte dos pares de fêmeas com filhotes, conforme observado em estudos anteriores (Palazzo
and Flores 1998; International Wildlife Coalition/Brazil 1999). Durante este estudo não foi
156
possível, porém, definir a região de maior ocorrência de indivíduos não-acompanhados como
área de acasalamento, devido aos indivíduos não terem sido sexados. Porém o
comportamento observado de alguns grupos indica essa possibilidade.
A freqüência de avistagens ao longo dos meses de inverno e primavera indica
que as baleias francas começam a chegar na área de estudo em julho, aumentando em
número e atingindo um pico em setembro, e declinando rapidamente em outubro e
novembro. Fêmeas com filhotes tendem a permanecer períodos mais longos em áreas de
reprodução no inverno do que os indivíduos não-acompanhados (Payne 1986; Bannister
1990; Burnell and Bryden 1997; Best 2000; Rowntree et al. 2001), podendo permanecer na
área de estudo em torno de 30 dias ou mais, coincidindo com informações anteriores
(Palazzo et al. 1999; Groch 2000; Groch et al. 2003). As fêmeas com filhotes apresentam
menos movimentos ao longo da costa do que indivíduos não-acompanhados enquanto que
estes parecem apresentar um menor grau de fidelidade de área. Ao contrário do que ocorre
em outras áreas de concentração reprodutiva como a Peninsula Valdés, na Argentina
(Rowntree et al. 2001), o litoral sul do Brasil não parece ser tão importante para indivíduos
subadultos e filhotes de um ano.
Os baixos valores de velocidade de natação observados para os indivíduos
avistados em dois dias consecutivos, quando comparados com observações a partir de terra,
bem como valores obtidos em outras áreas, indicam que pelo menos alguns indivíduos
demonstram fidelidade a algumas áreas em particular, ainda que por curtos períodos de
tempo, mesmo que potencialmente perturbados, por exemplo, durante os sobrevôos.
Aparentemente a região mais ao sul da distribuição observada é utilizada como
área de trânsito para a região mais ao norte no início da temporada, e mais ao sul final.
Apesar do pequeno número de baleias reavistadas interanualmente no Brasil, estas
demonstraram algum nível de fidelidade, especialmente à principal área de concentração,
onde as características da costa condizem com o habitat preferido desta espécie no inverno e
primavera.
O índice de reavistagem interanual das baleias francas identificadas no sul do
Brasil demonstra que as mesmas não são de ocorrência esporádica, e principalmente as
fêmeas retornam à região para o nascimento e cuidados com os filhotes. O intervalo modal
entre filhotes é de três anos, o que é consistente com o sucesso reprodutivo da espécie.
O numero de baleias francas que freqüenta o sul do Brasil parece estar
crescendo no Brasil a uma taxa de 14% ao ano, quando considerado todo o período de
157
estudo, e de 29,8% nos últimos sete anos de estudo (Groch et.al. 2005). Ambas as taxas estão
acima dos níveis considerados biologicamente realísticos de crescimento natural para a
espécie até o presente momento (Best et al., 2001). É pouco provável que este crescimento
seja resultado da taxa reprodutiva das baleias avistadas no Brasil nos primeiros anos de
estudo, devido à provável idade da primeira reprodução de 8 a 9 anos (Best et al., 2001;
Cooke et al., 2001) Possivelmente esse crescimento se deva à imigração de outras áreas de
concentração reprodutiva como a Argentina, visto a existência de indivíduos reavistados em
ambas a áreas em anos diferentes (Best et al., 1993).
O número estimado de baleias francas que freqüenta o sul do Brasil pode ser
de até 555 baleias. Este número pode ser considerado mais realista do que a estimativa
realizada em 1997, pois reflete o aumento populacional observado recentemente, porém deve
ser tratado com cautela, pois não incorpora parâmetros como mortalidade e imigração.
Se o número de baleias francas continuar a aumentar, pode-se esperar que as
baleias francas reocupem sua área de distribuição histórica ao longo de cerca de 2400km de
costa, aumentando a possibilidade de conflitos entre as baleias francas e atividades humanas.
As observações focais do comportamento das baleias francas em relação às
aproximações de embarcações de turismo em 2002 mostraram que algumas baleias
aparentam ignorar a presença das embarcações e não alteram o seu comportamento. Não
foram observadas evidências claras de distúrbio imediato às baleais francas, sugerindo que as
atividades de ‘whalewatching’ podem continuar na área de estudo se conduzidas segundo a
legislação brasileira. Pequenas alterações no comportamento foram observadas em algumas
ocasiões em que as baleias foram observadas nadando em direção às embarcações, mas após
um período de interesse, as baleias se afastaram e restabeleceram suas atividades prévias. As
baleais francas podem não reagir às aproximações de embarcações por várias razões,
podendo às vezes simplesmente estar indiferentes à presença de uma embarcação. Esse
comportamento pode ser resultante de vários aspectos, inclusive da propagação de som nas
enseadas resultante da entrada das embarcações nas mesmas. Porém não se sabe se o
estímulo para determinado comportamento deve-se à presença da embarcação ou ao som
gerado embaixo d’água, ou à combinação dos dois agentes.
Apesar do considerável potencial econômico e educativo das atividades de
“whalewatching”, há grande preocupação sobre os possíveis impactos desta atividade nas
populações de cetáceos. Existem diversas técnicas de avaliação destes impactos a curto e a
longo prazo, em diferentes níveis de eficácia e a partir de diferentes plataformas de pesquisa
158
(IFAW, Tethys Research Institute and Europe Conservation, 1995). Apesar disso, a maioria
dos estudos de impacto realizados até hoje, que demonstraram alterações comportamentais,
não deixam claro o significado biológico de efeitos a longo prazo nas populações estudadas
(Richter et al., 2000). Dada a importância e o potencial crescimento do turismo de
observação de baleias, principalmente em Santa Catarina, torna-se imprescindível a
continuidade de estudos a longo prazo visando documentar possíveis efeitos da atividades
embarcadas sobre as baleias francas, para o apropriado manejo da espécie na área de estudo.
Não se sabe ao certo quais os fatores que determinam a presença e distribuição
das baleais francas no sul do Brasil, porém reavistagens na Peninsula Valdés de indivíduos
fotografados no Brasil (Best et al. 1993; Groch, dados não publicados) indicam algum grau
de flexibilidade no uso de habitat por esta população. É provável que algumas áreas tenham
maior importância para os pares de fêmeas com filhotes que para os indivíduos não-
acompanhados, porém somente estudos a longo prazo permitirão um melhor entendimento
dessa característica. A flexibilidade e a extensão dos movimentos demonstrados pelas fêmeas
com filhotes em algumas áreas de concentração reprodutiva no inverno são sinais
encorajadores do crescimento da população e da expansão para áreas históricas de
distribuição.
Informações derivadas de rastreamento utilizando-se teodolitos se combinadas
com outras técnicas como estudos de longo prazo de foto-identificação individual podem
ajudar a esclarecer, de uma perspectiva de manejo, as necessidades envolvendo as atividades
como a de ‘whalewatching’ que possam fazer parte de uma avaliação mais compreensiva dos
possíveis distúrbios, como por exemplo pesca e tráfego de embarcações, na principal área de
concentração reprodutiva da espécie no Brasil. Portanto, a coleta sistemática de informações
mais aprofundadas sobre outras atividades humanas relacionadas às baleias francas deve ser
feita de forma intensiva de modo que pesquisadores e administradores possam avaliar
adequadamente o estado de conservação da espécie e propor medidas de manejo para as
populações alvo.
159
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