University of Western Australia
A new study has found male bottlenose dolphins form the largest known multi-level alliance network outside humans.
The research focused on 121 male dolphins in Shark Bay, 750 kilometres north of Perth, and involved scientists from The University of Western Australia, University of Bristol, University of New South Wales and University of Massachusetts.
Co-lead author Dr Stephanie King, an Adjunct Research Fellow from UWA’s School of Biological Sciences and UWA Oceans Institute, said cooperation between allies worked well for humans as a species as well as Shark Bay dolphins.
“The cooperative relationships between groups, rather than alliance size, allows males to spend more time with females increasing their chances of reproductive success,” Dr King said.
Co-author Dr Simon Allen, an Adjunct Research Fellow at UWA and UWA Oceans Institute, said Shark Bay dolphins formed first-order alliances of two to three males to cooperatively pursue mating opportunities with females.
Second-order alliances of four to 14 males competed with other alliances over opportunities to consort female dolphins, and third-order alliances occurred when different second-order alliances teamed up.
“The duration these teams of male dolphins consort with females is dependent upon being well-connected not just within the second-order alliance but also with third-order allies, that is, social ties between alliances are important and lead to long-term benefits in terms of mating opportunity,” Dr Allen said.
He said researchers were concerned about the impact of climate change and recreational fishing in Shark Bay, a Marine Protected Area and UNESCO-listed World Heritage site.
“This dolphin society is uniquely complex and that is almost certainly related to the enormous seagrass beds that support an incredibly rich, diverse ecosystem,” Dr Allen said.
“Resilient ecosystems need nurseries, like seagrass meadows, just as they need apex predators, like big fish and sharks.”
The paper, Strategic intergroup alliances increase access to a contested resource in male bottlenose dolphin was published in The Proceedings of the National Academy of Sciences.