Dolphins form structured boys’ groups to improve mating chances

Dolphins appear to pick up their courtship strategies from 1970s romcoms, with researchers finding male bottlenose dolphins form courtship alliances with their buddies to maximise their chances of wooing a partner.

It means maybe humans aren’t as special as we think – at least when it comes to certain behaviours – with a long-running study finding male bottlenose dolphins in Western Australia build significant social networks.

The study shows male bottlenose dolphins organise themselves into cooperative duos and trios to enable more effective courtship of single dolphin females.

They then organise-up into second-order alliances of between four and 14 which compete with others of similar size over females.

These second-order groups may also band together to form larger third-order alliances which further strengthens their ability to compete against others – a phenomenon rarely observed in non-human species.

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Dolphins show behaviours thought of as human-exclusive

The formation of these groups further reinforces the complex social behaviours shown among dolphins. Not even chimpanzees – the closest human relative – organise themselves into cooperative social structures like this.

Alliance-building forms part of a broader society characterised by ‘chimpanzee-like’ mating behaviours and life cycles. 

But it’s the strategic nature of these groups that allows them to maximise reproductive success.

Unlike other animal species, dolphins are willing to build social alliances with non-relatives and shift allegiances to improve their chances of reproduction.

“Male bottlenose dolphins form the largest known multilevel alliance network outside humans,” says Dr Stephanie King, a co-lead author of the researcher published in PNAS, the journal of the National Academy of Sciences in the USA.

“Cooperative relationships between groups, rather than simply alliance size, allows males to spend more time with females, thereby increasing their reproductive success.”

Aerial photo of six allied males and a female consort
Six allied males and a female consort / Credit: Simon Allen

It also suggests the hypothesis that human cooperation is tied to male-female bonding may not hold true. 

“Our work highlights that dolphin societies, as well as those of non-human primates, are valuable model systems for understanding human social and cognitive evolution,” says King.

These findings add to the long-term research out of the Shark Bay Dolphin Research hub on Australia’s western coast, which has studied the region’s dolphin populations since the 1980s.

Earlier this year, members of the researchers group found male-male bonds increased the chances of individual reproductive success. It also found males maintain their social bonds, including within the alliances described in the new research, by whistling.

It adds to well-known understandings of dolphin behaviours like parallel swimming, petting, flipper-holding and male-to-male support behaviours aiding courtship.

Dr Simon Allen from Bristol University contributed to the study and says that the strength of male alliances can determine the extent of long-term benefits for individuals.

“The duration over which these teams of male dolphins consort with females is dependent upon being well-connected with third-order allies,” says Allen.

“That is, social ties between alliances leads to long-term benefits for these males.”

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