ZÜRICH, Switzerland — For dolphins looking to mate, a new study finds it helps to be “the cool kid.” Researchers from the University of Zurich say male dolphins who are more “popular” in their social groups produce more offspring than their peers.
Unlike other species where age or strength may be the determining factor in which males father children, the team found that dolphin social bonds are more important. Researchers examining male dolphins in Shark Bay, Western Australia say these marine mammals live in very complex social groups with other males.
Groups within groups
More specifically, the males live in large, stable “alliances” where they form long-lasting bonds and cooperate with each other. However, inside these alliances, the males also form smaller and less stable groups of two or three dolphins which look to mate with females. These small packs also look to steal female dolphins from other alliances and help each other defend against similar attacks.
“This kind of male cooperation for the purpose of reproduction is highly unusual in the animal kingdom. It’s only been observed in a much less complex form in some other primates,” says Livia Gerber, a former PhD student in Zurich’s Department of Anthropology in a university release.
To find out whether popularity is a bigger factor in reproductive success than other traits of dominance, the team analyzed 30 years of data on the behavior of 85 male dolphins. They also examined genetic data to conduct paternity tests on more than 400 of their offspring.
Simply put, the results show that the popular males have all the luck with the ladies. Well-integrated (or popular) males with strong social bonds to several members of the alliance produced more offspring than their dolphin peers. Both partner stability within the smaller groups of two or three dolphins and the age of the mammals did not play a role in mating success.
Being popular can even keep dolphins healthier
Previous studies have also found that strong social bonds can improve the animals’ longevity, increase their immune responses, and boost their chances of survival in the wild.
“Well-integrated males might be in a better position to harness the benefits of cooperation and access crucial resources such as food or mates. They may also be more resilient to partner loss compared to those with few, but closer partners,” Gerber says.
“Our study is the first to show that social bonds among male dolphins positively impact their reproductive success and are, therefore, directly linked to fitness,” adds senior author Michael Krützen. “This had previously only been observed in male chimpanzees and some other primates. Our study expands upon previous findings on land mammals and provides compelling evidence that such highly complex, multi-level social systems also developed independently in the ocean.”
The findings appear in the journal Current Biology.