Rival teams of male dolphins form the animal world's biggest social networks, long-running study fin

Rival teams of male dolphins form the animal world’s biggest social networks, long-running study finds
Keeping track of male alliances may have driven the marine mammals to evolve bigger brains



A lone female bottlenose dolphin is guarded by four males in Shark Bay, Australia.SIMON ALLEN

Anthropologists have long celebrated and puzzled over humans’ ability to cooperate. Our special talent lies in forming nested cooperative networks that involve unrelated individuals: family, community, city, state, nation, and allied nations. Not even our closest relative, the chimpanzee, does this. But over the past 4 decades, researchers have shown that another animal does: the sea-going Indo-Pacific bottlenose dolphin (Tursiops aduncus) of Shark Bay in Western Australia.

Unrelated male dolphins deploy their social smarts to build complex alliances that boost their chances of reproductive success. A new study concludes these are the largest such complex cooperative societies outside of humans. Moreover, they appear to have evolved in a different way from our own. “It’s an exciting finding that helps bridge the immense, perceived gap between humans and other animals,” says Mauricio Cantor, a behavioral ecologist at Oregon State University who was not involved in the study.

In an exploration of dolphin society launched in 1982, behavioral ecologist Richard Connor, now affiliated with Florida International University, and his team have been following more than 200 male dolphins in the exceptionally clear waters of Shark Bay, recording which males spend the most time together. Over the years, they have found that males form close relationships with one or two other males, and that these partnerships are nested inside a larger alliance, which in turn are nested inside yet another alliance—rather like being a member of “a platoon, a company, and a regiment,” notes Harvard University primatologist Richard Wrangham, who is not part of the team. The male dolphins cooperate in order to capture and defend fertile female dolphins from other groups of males. A lone male cannot corral a female; he needs partners.

In the new study, the team analyzed data collected between 2001 and 2006 on 121 individual males, revealing a super-connected social network with every male connected to one another either directly or indirectly. The males even cultivate relationships with males outside of their three-level alliances, forming the biggest network known in any nonhuman species, and thereby increasing their reproductive success, the researchers report today in the Proceedings of the National Academy of Sciences. Each male had on average 22 allies; some had as many as 50.

More:
https://www.science.org/content/article/rival-teams-male-dolphins-form-animal-world-s-biggest-social-networks-long-running