Long considered a unique feature of human societies, researchers now claim that some dolphins can actually form multiple levels of alliances between their societies.
People establish cooperative strategic relationships at different social levels for various reasons, including economic advantage, international trade, and military operations. For the male bottlenose dolphins living in Shark Bay, Australia, the motivation is a little less complex: the ladies. These dolphins actually form at least three different levels of cooperative relationships between groups to increase male access to females, according to the new study led by Richard Connor, a Florida International University biologist and professor emeritus at the University of Massachusetts at Dartmouth, and Stephanie King. , Associate Professor at the University of Bristol.
Male dolphins in Shark Bay form first-order alliances of two or three males to cooperatively pursue alliances with individual females. Their second-order alliances can include as few as four and as many as 14 unrelated males to compete with other alliances on access to females. Their third-order alliances occur between cooperating second-order alliances. The research team analyzed association and consortship data to model the structure of alliances among 121 adult male bottlenose dolphins from the Indo-Pacific, demonstrating that dolphins have the largest known alliance network outside of humans.
One of the main conclusions of the study is the importance of intergroup cooperation for male success. Intergroup cooperation in humans was thought to be unique and dependent on two other characteristics that distinguish humans from chimpanzees – the evolution of pair bonds and parental care by males. However, Connor said research shows that intergroup alliances can actually emerge without these characteristics and from a social and mating system that is more chimpanzee-like. According to King, this means that cooperation between groups is more important than the overall size of the alliance in increasing access to women. In short, collaborative dolphins have greater reproductive success.
The research has been published in Proceedings of the National Academy of Sciences in the wake of the 40eanniversary of the start of Connor’s dolphin research at Shark Bay and the 30e anniversary of a major research study that announced the discovery of dolphins forming two levels of alliances there. This research has also been published in Proceedings of the National Academy of Sciences.
Simon Allen, lecturer at the University of Bristol, Michael Krützen, director of the Institute of Anthropology at the University of Zurich, and William B. Sherwin, professor at the University of New South Wales, have also contributed to the study.