Kinship as a basis for alliance formation between male bottlenose dolphins, Tursiops truncatus, in the Bahamas

Alliances between reproductive males have been described in both cetacean and terrestrial mammal societies, and kin selection theory has often been invoked to explain these stable male coalitions. However, recent studies of bottlenose dolphins, Tursiops aduncus, in Australia suggest that mechanisms other than kinship are fundamental in the formation of male alliances. We supplemented skin biopsy sampling with the collection of faecal samples from individually recognized wild bottlenose dolphins, T. truncatus, to assess the role of kin selection in alliance membership in the northeast Bahamas. Stable alliances between pairs of males were identified based on association analyses of individual photoidentification data collected over 4 years. Molecular genetic analyses of tissue samples revealed highly significant correlations between patterns of association and both mitochondrial DNA haplotype identity and microsatellite relatedness, indicating that males within long-term alliances are more closely related than expected by chance. These data reinforce the high degree of plasticity previously reported within the genus Tursiops, and suggest that social and ecological differences between populations can markedly affect the role of kin selection in determining social alliances between male bottlenose dolphins. (C) 2003 Published by Elsevier Ltd on behalf of The Association for the Study or Animal Behaviour.