Developmental evidence for foraging traditions in wild bottlenose dolphins

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.