Seasonal changes in the stability of male-male bonds in Indian Ocean bottlenose dolphins (Tursiops sp.)

Abstract

In Shark Bay, Western Australia, males cooperate in alliances of two or three individuals to herd females. In one closely observed alliance of three males, only two of the three males participated in any given herding event, but there were frequent changes, called ‘partner changes’, in which two males herded together. The frequency of partner changes was strongly seasonal. In each of two consecutive years the frequency of partner changes was high prior to the breeding season but low during the breeding season. We test the hypothesis that the males had fewer opportunities to change herding partners during the breeding season. This hypothesis was not supported, so we conclude that the high frequency of partner changes prior to the breeding season reflects instability of social bonds. We evaluate these results in reference to hormonal data from a captive study.