Within-population behavioural variation can greatly affect the ecology of a species and the outcome of evolutionary processes. This study aimed to determine how variable sperm whale social and vocal behaviour is between both individuals and their social units. The population of whales off Dominica is small and isolated from communities in neighbouring waters. Female and immature whales live together in social units containing about 7 animals. I analysed their social relationships and their ‘coda’ communication signals using an unparalleled dataset of social and vocal interactions at the level of the individual. Within units, calves were significant nodes in their social unit’s network, and thus I provide quantitative support for the hypothesis that communal calf care acts as the primary evolutionary driver for group formation in this species. Social relationships within and between units were diverse, while the spatial spread of individuals within units and their travel speeds were similar among all of the units. I identified long-term patterns of association between units consistent over decadal time scales. Social units had characteristic vocal repertoires, but all were dominated by the ‘1+1+3’ and ‘5R’ coda types. Differences between units resulted from some units using specific 4-click coda types. Units and individuals used different accents on their ‘5R’ codas, but the ‘1+1+3’ coda was stereotyped across all individuals and units studied. The repertoires of different units were as similar as units within vocal clans in the Pacific. My results support the hypothesis that the ‘5R’ coda may function in individual identification. The stability of the ‘1+1+3’ coda may be the result of selection for a marker of clan membership. Individual repertoires differed consistently across years; and contrary to an existing hypothesis, new mothers did not vary their repertoire to be more distinct after giving birth. However, calves did use a class-specific ‘3+1’ coda. In summary, sperm whale social and vocal behaviour vary between individuals and among units. Variation in the social and vocal behaviour of female sperm whales results from a trade-off between individuality and conformity within units and clans.

Dissertação(mestrado) - Universidade Federal do Rio Grande, Programa de Pós–Graduação em Oceanografia Biológica, Instituto de Oceanografia, 2013 / Submitted by Cristiane Gomides (cristiane_gomides@hotmail.com) on 2013-12-16T11:59:50Z No. of bitstreams: 1 rodrigo.pdf: 2838178 bytes, checksum: 0ed5e3967d18f3075d7e2c1c3f615170 (MD5) / Approved for entry into archive by Sabrina Andrade (sabrinabeatriz@ibest.com.br) on 2013-12-18T18:12:23Z (GMT) No. of bitstreams: 1 rodrigo.pdf: 2838178 bytes, checksum: 0ed5e3967d18f3075d7e2c1c3f615170 (MD5) / Made available in DSpace on 2013-12-18T18:12:23Z (GMT). No. of bitstreams: 1 rodrigo.pdf: 2838178 bytes, checksum: 0ed5e3967d18f3075d7e2c1c3f615170 (MD5) Previous issue date: 2013 / Investigamos a estrutura social e padrões espaciais de uso da área por uma população de golfinhos, Tursiops truncatus, que habitam o estuário da Lagoa dos Patos e águas costeiras adjacentes, no sul do Brasil. Nós estimamos o índice de associação a partir de 102 indivíduos regularmente observados em 243 saídas de foto-identificação realizadas entre agosto de 2005 e outubro de 2012. As análises sociais e de rede, com a divisão proposta pela modularidade, indicou que esta população de botos é composta por três unidades sociais principais. Embora exista certa sobreposição espacial, houve distinção entre as zonas preferenciais de cada unidade. Uma das unidades esta fortemente associada com o estuário da Lagoa dos Patos, enquanto as outras duas ocuparam, respectivamente, as áreas marinhas adjacentes norte e sul. Dentro das unidades, as associações entre os indivíduos foram predominantemente de curta duração (dinâmica de fissão-fusão), embora tenham sido identificadas algumas associações de longa duração. Embora tenham ocorrido interações entre as unidades sociais, as associações foram rápidas e ocorreram apenas entre alguns indivíduos. A segregação destes indivíduos é motivada, pelo menos em parte, pelos padrões de associação entre os indivíduos e sua fidelidade a áreas específicas. Recomenda-se que as unidades sociais sejam a base para modelar a viabilidade e dinâmica intrapopulacional, bem como para investigação de padrões de fluxo gênico dentro e entre unidades sociais. / We investigated the social structure and spatial patterns of area usage by a population of bottlenose dolphins, Tursiops truncatus, inhabiting the Patos Lagoon estuary and adjacent coastal waters, in southern Brazil. We estimated the association index from 102 individuals regularly sighted in 243 photo-identification surveys carried out between August 2005 and October 2012. Social and network analyses, with the division proposed by modularity, indicated that this bottlenose dolphin population consists of three social units. Although some spatial overlap exists, preferred areas of each unit were distinct. One of the units was strongly associated with the Patos Lagoon estuary while the other two occupied, respectively, the southern and northern adjacent marine coasts. Within unit associations among individuals were predominantly of short duration (fission-fusion dynamics), though a few long-lasting bonds were detected. Although interactions between social units occurred, the associations were brief and occurred only among a few individuals. The segregation of these individuals is motivated, at least in part, by the bonding patterns among individuals and their fidelity to specific areas. It is recommended that the social units be the framework for modeling the intrapopulation dynamic and viability as well as for investigating patterns of gene flow within and between social units.

Bottlenose dolphins exhibit fission-fusion social systems in which group size and composition change fluidly throughout the day. Societies are typically sexually segregated, and the quality and patterning of individual relationships in this social species shape the social structure of a population. Female dolphins usually have a large network of associates with whom they form recurring moderate bonds, while male associations are highly variable due to their mating strategies. Males employ one of two strategies; males may be solitary, and encounter and herd females individually, while others may form strong bonds with one to two other males and cooperatively herd individual females in the shape of a first-order alliance. Second-order alliances are more uncommon and have only been observed in Shark Bay, Australia, and more recently within the St. Johns River (SJR), Jacksonville, Florida. Given the inter-population variation in male mating strategies, greater documentation of social structure in neighboring populations along the Atlantic coast is needed. Therefore, chapter one documents the social structure of the Indian River Lagoon (IRL) estuarine system where dolphins have experienced recurrent cetacean morbillivirus (CeMV) epizootics. Although environmental disturbances can affect both social and mating systems, IRL dolphin sociality does not seem to be affected by the 2008 CeMV mass mortality event. Additionally, males only form first-order alliances within this population. Because multi-level alliances are unique to the SJR in this region, chapter two analyzes the stability and function of SJR alliances. Both first- and second-order alliances exhibited variation in stability, while alliance association appears dependent on female presence. Thus, SJR alliances likely function within a reproductive context. Together, this work provides insight into the social and mating systems of bottlenose dolphins, as well as the function of multi-level alliances at a relatively new study site.

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