Spatiotemporal use predicts social partitioning of bottlenose dolphins with strong home range overlap

© 2018 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.Ranging behaviour and temporal patterns of individuals are known to be fundamental sources of variation in social networks. Spatiotemporal dynamics can both provide and inhibit opportunities for individuals to associate, and should therefore be considered in social analysis. This study investigated the social structure of a Lahille's bottlenose dolphin (Tursiops truncatus gephyreus) population, which shows different spatiotemporal patterns of use and gregariousness between individuals. For this, we constructed an initial social network using association indices corrected for gregariousness and then uncovered affiliations from this social network using generalized affiliation indices. The association‐based social network strongly supported that this dolphin population consists of four social units highly correlated to spatiotemporal use patterns. Excluding the effects of gregariousness and spatiotemporal patterns, the affiliation‐based social network suggested an additional two social units. Although the affiliation‐based social units shared a large part of their core areas, space and/or time use by individuals of the different units were generally distinct. Four of the units were strongly associated with both estuarine and shallow coastal areas, while the other two units were restricted to shallow coastal waters to the south (SC) and north of the estuary (NC), respectively. Interactions between individuals of different social units also occurred, but dolphins from the NC were relatively more isolated and mainly connected to SC dolphins. From a conservation management perspective, it is recommended that information about the dolphin social units should be incorporated in modeling intrapopulation dynamics and viability, as well as for investigating patterns of gene flow among them

Genetic divergence between two phenotypically distinct bottlenose dolphin ecotypes suggests separate evolutionary trajectories

Due to their worldwide distribution and occupancy of different types of environments, bottlenose dolphins display considerable morphological variation. Despite limited understanding about the taxonomic identity of such forms and connectivity among them at global scale, coastal (or inshore) and offshore (or oceanic) ecotypes have been widely recognized in several ocean regions. In the Southwest Atlantic Ocean (SWA), however, there are scarce records of bottlenose dolphins differing in external morphology according to habitat preferences that resemble the coastal‐offshore pattern observed elsewhere. The main aim of this study was to analyze the genetic variability, and test for population structure between coastal (n = 127) and offshore (n = 45) bottlenose dolphins sampled in the SWA to assess whether their external morphological distinction is consistent with genetic differentiation. We used a combination of mtDNA control region sequences and microsatellite genotypes to infer population structure and levels of genetic diversity. Our results from both molecular marker types were congruent and revealed strong levels of structuring (microsatellites FST = 0.385, p < .001; mtDNA FST = 0.183, p < .001; ΦST = 0.385, p < .001) and much lower genetic diversity in the coastal than the offshore ecotype, supporting patterns found in previous studies elsewhere. Despite the opportunity for gene flow in potential “contact zones”, we found minimal current and historical connectivity between ecotypes, suggesting they are following discrete evolutionary trajectories. Based on our molecular findings, which seem to be consistent with morphological differentiations recently described for bottlenose dolphins in our study area, we recommend recognizing the offshore bottlenose dolphin ecotype as an additional Evolutionarily Significant Unit (ESU) in the SWA. Implications of these results for the conservation of bottlenose dolphins in SWA are also discussed

Estrutura social do boto Tursiops truncatus (CETACEA: DELPHINIDAE), no estuário da Lagoa dos Patos e águas costeiras adjacentes, sul do Brasil

Dissertação(mestrado) - Universidade Federal do Rio Grande, Programa de Pós–Graduação em Oceanografia Biológica, Instituto de Oceanografia, 2013Investigamos 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

Long-term and gender-related variation in the feeding ecology of common bottlenose dolphins inhabiting a subtropical estuary and the adjacent marine coast in the western South Atlantic

<p>We combined stomach content analysis and stable isotopes to investigate long-term changes in the feeding ecology of common bottlenose dolphins (<i>Tursiops truncatus</i>) from the Patos Lagoon estuary and adjacent marine coast, southern Brazil, during the past 35 years. Stomach contents of bottlenose dolphins collected between 2002 and 2012 (Period II) were compared to those previously described for this population (1977–1980, Period I), and <i>δ</i>¹³C and <i>δ</i>¹⁵N values in tooth dentine from specimens collected between 1977 and 2012 were used to assess temporal changes in contribution of the main prey to the diet of dolphins over time. Additionally, these data were used to verify the magnitude of trophic overlap between males and females from Period II. Bottlenose dolphins consumed a wide variety of prey. Demersal and demersal–pelagic teleost fish predominated. These results show that bottlenose dolphins from the Patos Lagoon estuary are opportunistic feeders and confirm the plasticity of the species, which preys upon the most available prey. Differences in diet were found between seasons and periods. Stable isotopes and stomach contents detected a significant long-term change in the proportions of their main prey. The contribution of <i>Micropogonias furnieri</i> and <i>Menticirrhus</i> sp. decreased after 1990 while a significant increase in the importance of <i>Trichiurus lepturus</i> was observed. Males consumed a significantly higher proportion of <i>T. lepturus</i> while <i>Mugil liza</i> was the main prey for females. These changes might be due to fishing-related changes in fish abundance.</p

Genetic divergence between two phenotypically distinct bottlenose dolphin ecotypes suggests separate evolutionary trajectories

Due to their worldwide distribution and occupancy of different types of environments, bottlenose dolphins display considerable morphological variation. Despite limited understanding about the taxonomic identity of such forms and connectivity among them at global scale, coastal (or inshore) and offshore (or oceanic) ecotypes have been widely recognized in several ocean regions. In the Southwest Atlantic Ocean (SWA), however, there are scarce records of bottlenose dolphins differing in external morphology according to habitat preferences that resemble the coastal-offshore pattern observed elsewhere. The main aim of this study was to analyze the genetic variability, and test for population structure between coastal (n = 127) and offshore (n = 45) bottlenose dolphins sampled in the SWA to assess whether their external morphological distinction is consistent with genetic differentiation. We used a combination of mtDNA control region sequences and microsatellite genotypes to infer population structure and levels of genetic diversity. Our results from both molecular marker types were congruent and revealed strong levels of structuring (microsatellites FST = 0.385, p < .001; mtDNA FST = 0.183, p < .001; ΦST = 0.385, p < .001) and much lower genetic diversity in the coastal than the offshore ecotype, supporting patterns found in previous studies elsewhere. Despite the opportunity for gene flow in potential “contact zones”, we found minimal current and historical connectivity between ecotypes, suggesting they are following discrete evolutionary trajectories. Based on our molecular findings, which seem to be consistent with morphological differentiations recently described for bottlenose dolphins in our study area, we recommend recognizing the offshore bottlenose dolphin ecotype as an additional Evolutionarily Significant Unit (ESU) in the SWA. Implications of these results for the conservation of bottlenose dolphins in SWA are also discussed.Organization for the Conservation of South American Aquatic Mammals-YAQU PACHA e.V., the Brazilian Long Term Ecological Program (PELD-National Council for Research and Technological Development/CNPq), Chevron Brasil Upstream Frade Ltda, BG Group, Brasil, Instituto Aqualie.http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)2045-7758am2018Mammal Research Institut