Inter- and Intrapopulation Variation in Bottlenose Dolphin Mating Strategies

Abstract

Bottlenose dolphins (Tursiops spp.) live in complex societies with high fission-fusion dynamics and exhibit a polygynandrous mating system in which both sexes mate with multiple partners. The benefits of polygynandry vary between the sexes; males likely increase their reproductive success by maximizing the number of mating partners, whereas females may reduce infanticide risk and/or increase the genetic quality of offspring by mating with multiple males. Socio-ecological theory states that mating strategies are dictated by the distribution of females and the ability of males to monopolize them. However, the tactics that males use to achieve reproductive success vary within and across populations. Although some male bottlenose dolphins appear to use a solitary approach to gain mating access, males in several populations demonstrate a relatively rare mating tactic: cooperative mate guarding within alliances. Male alliances generally consist of a pair or trio of males that work together to sequester a fertile female. However, nested or multilevel alliances have been documented in two populations to date (i.e., Shark Bay, Australia, and Jacksonville, Florida). The complexity of male alliances may vary in response to a suite of specific ecological, demographic, and/or morphological variables that promote male-male cooperation and reduce intrasexual competition. In this chapter, we review population-specific examples of male bottlenose dolphin mating tactics and examine several hypotheses that may explain inter- and intrapopulation variation in alliance complexity. We also explore the sociosexual behavior and potential countertactics used by females.