Male dolphins form lifelong bonds that help them find a mate, study finds

Dolphins form decades of social bonds, working together between and between cliques, to help each other find mates and fend off competitors, new research has shown — behaviors not previously confirmed in animals.

“These dolphins have long-term stable alliances and they have alliances between groups. Alliances of alliances of alliances, really,” said Dr Richard Connor, a behavioral ecologist at the University of Massachusetts Dartmouth and one of the lead authors of the paper. “But before our study, collaborations between groups were thought to be unique to humans.”

The findings, published Monday in the journal Proceedings of the National Academy of Sciences, appear to support the “social brain” hypothesis: that mammalian brains evolved to be larger for animals keeping up with their social interactions and networks. Humans and dolphins are the two animals with the largest brains in relation to body size. “It’s no coincidence,” Connor said.

Connor’s team of researchers collected data between 2001 and 2006 by conducting intensive boat surveys in Shark Bay, Western Australia. The researchers tracked the dolphins by watching and listening to them, using their unique identifying whistles to tell them apart.

They observed 202 Indo-Pacific Bottlenose Dolphins (Tursiops aduncus), also during the high season between September and November.

Back in the lab, they dug into data targeting 121 of these adult male dolphins to observe patterns in their social networks. And for the next decade, they continued to analyze the animals’ alliances.

Dolphins’ social structures are fluid and complex. The researchers found alliances between two or three male dolphins – as best friends. After that, the groups expanded to 14 members. Together, they helped each other find females to herd and mate with, as well as help females steal from other dolphins and defend themselves against any “theft” attempts by rivals.

“What happens when a man, you could be in a threesome herding a woman. And if someone comes to get that woman, the other men on your team and your second-order alliance come in to help you,” said Dr Stephanie King, professor of animal behavior at the University of Bristol and one of the authors of the study. “These guys have a very, very clear idea of ​​who is on their team.”

Six male bottlenose dolphins with one female.
Six male bottlenose dolphins with one female. Male dolphin alliances can last for decades. Photo: Simon Allen

These teams can last for decades and are formed when the dolphins are still young, although they don’t reap the benefits of fatherhood until mid-teens, King said. “It’s a significant investment that starts when they’re very young — and these relationships can last a lifetime.”

Sometimes, especially when dolphin groups feel there is a risk to themselves, two second-order alliances will also come together to form a larger team. As a result, among the dolphins observed by the scientists, each male was directly linked with between 22 and 50 other dolphins.

The researchers’ observations show that in these groups, the closer the clique — and the stronger the bonds between the dolphins — the more successful they are at attracting females.

It’s their cooperative relationship, rather than alliance size, that gives males more breeding success, King said.

It’s already well known that dolphins are highly sociable and cooperative, but also remarkably good at adapting and learning behaviors specific to their environment, he said. Stephanie Venn Watsonformer director of Translational Medicine and Research at the National Marine Mammal Foundation in San Diego, California, who was not involved in the study.

“One wouldn’t rule out the possibility that other cetaceans could develop similar alliances,” Venn-Watson said. “This complex behavior will likely be limited to large-brained mammals.”

According to the researchers behind the article, this is the only non-human example of this kind of multi-level strategic alliance that has been observed. But these findings also highlight the cognitive demands these animals face, suggesting that dolphins’ cerebrums help them keep track of the various relationships, Connor said.

“I’d say dolphins and humans have come together in the evolution of alliances between groups — an incredibly complex social system,” Connor said. “And it’s amazing because we’re so different from dolphins.”

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