The social function of synchronous displays in allied male bottlenose dolphins

Abstract

Forming multiple strong social bonds can increase an animal’s fitness and resilience to environmental and social stochasticity. However, as an individual forms more social relationships, they must commit more time to maintaining them. Therefore, evolution likely selects for lower cost mechanisms of bond maintenance. Evidence suggests that in humans, synchrony - or the precise coincidence of behaviours in time - can bond multiple individuals at once. Consequently, it has been theorised that human synchronous ability evolved in response to an increasing number of social relationships. However, to better test this hypothesis, a comparative approach should investigate if different species use synchrony for a social function. In Shark Bay, Western Australia, male Indo-Pacific bottlenose dolphins, form multi-level alliances to cooperate for reproductive opportunities. The core alliance unit is the second-order alliance, comprising 4-14 males that compete with other second-order alliances over access to females. From within the second-order, males recruit pairs or trios to cooperatively herd single oestrus females, in events termed ‘consortships’. Additionally, multiple second-order alliances can form weaker but still significant ‘third-order’ alliance relationships, where they provide additional support in the pursuit and defence of females. Across all alliance levels, males need to maintain multiple strong bonds to increase their access to reproductive opportunities. To maintain bonds, males engage in physical affiliative contact behaviours, vocal exchanges, and synchrony. Allied males perform displays of synchronised turns, leaps and surfacing bouts, typically during consortships. Here, I show that males perform synchronous displays for longer after engaging in affiliative contact behaviour. Additionally, I find that the precision of synchrony is greatest in males with weaker social bonds. These findings provide evidence that male dolphins use synchrony to maintain their multiple bonds, specifically strengthening weaker social bonds. This thesis provides new insights into the evolution of synchrony in a cooperative context.

Date of Award	13 May 2025
Original language	English
Awarding Institution	University of Bristol
Supervisor	Christoph Grueter (Supervisor) & Stephanie L King (Supervisor)