Same-Sex Socio-Sexual Interactions Among a Group of Captive Bottlenose Dolphins (Tursiops truncatus)

Bottlenose dolphins (Tursiops truncatus) frequently engage in non-reproductive sexual behavior, including homosexual encounters. In order to better understand the nature and function of these interactions, a longitudinal study of the patterns of association and the dynamics of initiator/recipient role exchange was conducted. Underwater video footage of a colony of bottlenose dolphins housed at the Roatan Institute for Marine Sciences (RIMS), collected between March of 2010 and May of 2013, was analyzed. Associations occurring during homosexual interactions were transitory for most individuals. Nonetheless, subsequent analyses allowed the rejection of the null hypothesis of random association, suggesting the existence of preferred associations. A symmetry analysis showed that most pairs shared a symmetric relationship, as only five of 22 dyads were significantly asymmetric. Evidence of association preferences and overall symmetry suggest that homosexual interactions in this population promote social bonding. Alternative explanations, including reconciliation, dominance assertion, tension reduction, and practice for future mating, might also play a role in the occurrence and maintenance of these interactions.