The reproductive and ecological functions of the pair-bond between allied, adult male bottlenose dolphins, Tursiops truncatus, in Sarasota Bay, Florida

Alliances between mammalian males, especially between non-relatives, are challenging to evolutionary theory and provide an opportunity to further understand mechanisms of cooperation. Mammalian males have been documented to cooperate primarily to gain mating access to females. Animals may also cooperate in a variety of non-reproductive contexts, although, among cooperating mammalian males, observations of such behaviors have been less common.;This study focused on determining whether the long-term, stable alliances which form between pairs of adult male bottlenose dolphins, Tursiops truncatus, in Sarasota Bay, Florida serve reproductive and/or ecological functions, as has previously been hypothesized. Behavioral, health, ecological, genetic, and life history data were used to assess alliance function and to further our understanding of evolutionary mechanisms of alliance formation.;In any given year, about 40% of adult males are not members of an alliance (non-alliance males, NAMs). The majority of NAMs are either too young to have formed an alliance, or their alliance partner has died or disappeared and they have not formed a new alliance. Data suggest that alliance formation is the norm among adult males and that NAMs are a transitional stage rather than an alternative strategy.;Genetic analyses using nuclear (microsatellites) and mitochondrial DNA found that on average, alliance males (AMs) are no more related to their partner than expected by chance. Kin selection is therefore not driving alliance formation. Prior association and similar age seem to be more important parameters in partner selection for alliance formation than relatedness in the Sarasota Bay bottlenose dolphin community.;Comparisons between AMs and NAMs indicate AMs have greater access than NAMs to females for mating opportunities, and AMs may also receive significant ecological benefits. AMs spend more time than NAMs in habitats which may be more predatorand prey-rich. Enhanced vigilance and/or predator protection may provide AMs access to habitats where prey are more abundant, leading to a reduction in time searching for prey. AMs may also be more efficient foragers overall. This study thus presents evidence that long-term, stable pair alliances between non-related mammalian males can function in both reproductive and ecological contexts.