Elsevier

Animal Behaviour

Volume 78, Issue 3, September 2009, Pages 715-721
Animal Behaviour

Developmental evidence for foraging traditions in wild bottlenose dolphins

https://doi.org/10.1016/j.anbehav.2009.05.037Get rights and content

Patterns of social learning in bottlenose dolphins (Tursiops spp.) may help explain behavioural variants and selection pressures favouring cultural evolution, but evidence for social transmission derived from field observations is controversial. The dolphins of Shark Bay, Australia are known for diverse, individually specific foraging behaviours, including tool use with marine sponges. We examined the relative contributions of habitat, maternal foraging and foraging behaviours of associates to the use of seven foraging tactics by bottlenose dolphin calves (Tursiops sp.). Three tactics were predicted by maternal foraging, one was predicted by water depth, one was weakly predicted by several factors, and two tactics were not predicted by any variable. Our findings provide support for the social learning of foraging behaviours in wild dolphins, illustrate the diverse pathways of foraging development, and offer insight into conditions that are likely to favour reliance on social information The evidence for vertical social learning (mother-to-offspring) indicates the dominance of a ‘do what mother does’ strategy, rather than copying the foraging behaviour of associates. However, since not all foraging behaviours were predicted by whether a calf's mother used them, dolphins may only use social information in some contexts, perhaps for more difficult tactics. This study provides unprecedented support for socially learned foraging tactics in wild dolphins by simultaneously addressing multiple factors during behavioural development, and thus illustrates the benefits of using multivariable techniques on ontogenetic data to identify social learning in wild animals.

Section snippets

Methods

Shark Bay, Western Australia (25°47′S, 113°43′E) is a shallow sea grass ecosystem, featuring a mosaic of sea grass banks and sand flats (<4 m), embayment plains (4–13 m) and deeper channels (>6 m). The wild bottlenose dolphins of Shark Bay have been the focus of a longitudinal research project based at Monkey Mia since 1984 (Connor et al. 2000). Individual dolphins were identified by their natural dorsal fin shapes and markings using a photographic identification catalogue. Sexes were determined

Results

Table 2 shows, for each tactic, explanatory variables retained in multiple regression models following backward elimination model selection. Tests of model fit (penalized likelihood ratio test) and the odds ratio estimates and corresponding penalized likelihood ratio tests for each explanatory variable are also provided. The odds ratio can be interpreted as a measure of effect size and represents the increase in odds of a particular outcome with each unit increase in the explanatory variable

Discussion

Although social learning is thought to contribute to foraging development in wild dolphins, this is the first study that provides evidence for social learning while statistically accounting for additional factors. Despite independent correlations between foraging, sex and habitat use evident in previous studies, we identified strong, robust patterns that remained even after incorporating multiple factors into a single model. Thus, our findings illustrate that invoking ecological or social

Acknowledgments

B.L.S designed the study, collected and analysed data and conceived of and wrote the paper. J.M. contributed data and logistical support, helped with the study design and wrote the paper. Sincere thanks to K. Laland, J. Kendal, R. Kendal, A. Wirsing, L. Douglass and R. Barr for helpful discussions and/or comments on previous versions of the manuscript, our colleagues of the Shark Bay Dolphin Research Project for contributing to the long-term database, many invaluable field assistants, and David

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