Can environmental heterogeneity explain individual foraging variation in wild bottlenose dolphins (Tursiops sp.)?
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Because behavioral variation within and among populations may result from ecological, social, genetic and phenotypic differences, identifying the mechanism(s) responsible is challenging. Observational studies typically examine social learning by excluding ecological and genetic factors, but this approach is insufficient for many complex behaviors associated with substantial environmental variation. Indian Ocean bottlenose dolphins (Tursiops sp.) in Shark Bay, Western Australia show individual differences in foraging tactics, including possible tool use with marine sponges and social learning may be responsible for this diversity. However, the contributions of ecological factors to the development of these foraging tactics were not previously investigated. Here, we determined the relationship between ecological variables and foraging tactics and assessed whether differences in habitat use could explain individual differences in foraging tactics. We monitored 14 survey zones to identify how foraging tactics were spatially distributed and matched behavioral data to the ecological variables within each zone. Three of four foraging tactics were significantly correlated with ecological characteristics such as seagrass biomass, water depth, presence of marine sponges and season. Further, individual differences in habitat use were associated with some tactics. However, several tactics overlapped spatially and previous findings suggest demographic and social factors also contribute to the individual variation in this population. This study illustrates the importance of environmental heterogeneity in shaping foraging diversity and shows that investigating social learning by ruling out alternative mechanisms may often be too simplistic, highlighting the need for methods incorporating the relative contributions of multiple factors.
KeywordsForaging Bottlenose dolphins Ecological variation Social learning
We thank our colleagues from the Shark Bay Dolphin Research Project for their contributions to the long-term database, the Western Australia Department of Conservation and Land Management for providing logistical support and the Western Australia Department for Planning and Infrastructure for providing tidal data. The Monkey Mia Dolphin Resort and Magellan also contributed generous support during data collection. We thank L. Douglass for valuable statistical advice and R. Barr, L. Dill and anonymous reviewers for helpful suggestions. Special thanks to A. Hough, R. Lam, R. Abernethy, V. Alla, L. Barre, F. Bretos, S. Buchannan, J. Burghardt, M. Davis, H. Finn, C. Genrich, P. Greene, K. Harper, J. Laski, K. Martin, J. McLash, R. McPhie, B. Stalvie, and K. Wirsing for assistance with data collection and to J. Watson-Capps for providing the bathymetry map for the study area. Funding was provided by the Dolphins of Monkey Mia Research Foundation, the Eppley Foundation for Research (JM), Florida International University (MRH), Georgetown University (BLS, JM), the Helen V. Brach Foundation (JM), Honda Motors (BLS, JM), the Lerner-Gray Award (American Museum of Natural History) (MRH), Magellan (BLS, JM), Mercury Marine (AJW, MRH), Monkey Mia Wildsights (AJW), the National Geographic Society Expeditions Council grants (EC0151-03, EC26-98) (AJW, MRH), the National Science Foundation Graduate Research Fellowship (BLS, MRH), the National Science Foundation grant 9753044 (JM), NSERC Canada grant A6869 (L.M. Dill, AJW, MRH), the PADI Foundation (AJW, MRH) and the Shane Award (Society for Marine Mammalogy) (MRH). This research was conducted under permits from the Western Australia Department of Conservation and Land Management and the Georgetown University Animal Care and Use Committee.
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