Karen Hopkin: This is Scientific American’s 60-Second Science. I’m Karen Hopkin.

It’s great to have friends. Especially if you’re an Indo-Pacific bottlenose dolphin. Because new research shows that the males who are the most popular with the lads are also the most successful with the ladies. Researchers describe how these affable marine mammals maintain and leverage their complex social connections in a pair of papers in the journal Current Biology.

Stephanie King: Male dolphins form lifelong cooperative relationships.

Hopkin: Stephanie King of the University of Bristol. She’s been studying the dolphin population that inhabits Shark Bay…a UNESCO World Heritage site off the coast of western Australia.

King: By studying populations like the Shark Bay dolphins for many years, we start to see the complex ways they maintain their important social relationships.

Hopkin: These connections are more than casual acquaintanceships. They’re crucial for the dolphins to be able to fend off rivals and secure mates.

King: When navigating their social world, it is those males that are more adept at building strong friendships that are ultimately more successful.  

Hopkin: So what do these aquatic alliances look like?

Livia Gerber: In Shark Bay, every male is embedded in a social network consisting of 4 to 14 males.

Hopkin: Livia Gerber of the University of New South Wales, Sydney.

Gerber: These 4 to 14 males are also known as second order alliances and they are the core social unit of the male bottlenose dolphins in Shark Bay.

Hopkin: This dolphin party consists of unrelated individuals of a similar age that remain together for decades. Now, when one of these dolphins is looking for love, he’ll select one or two wingmen…or maybe fin-pals?... from this larger posse to help him find a fertile female.

Gerber: While it was previously known that males have to cooperate in order to sire offspring in Shark Bay, it wasn’t known which male is the most successful one.

Hopkin: Is it the male with the most experience? The one with the largest territory? Or is there something about the bromance that holds the key to reproductive success?

Gerber: To answer this question, I [therefore] looked at the genetic profiles of more than 400 dolphins in Shark Bay and carried out paternity tests.

Hopkin: Once she identified the daddies, she could determine what quality they shared.

Gerber: I was quite surprised by my results because they were contrasting to so many other species, where the oldest males sire the most offspring or the males with the largest territories. As opposed to what we see in these other species, male bottlenose dolphins that have the strongest social bonds and multiple strong social bonds—so the most popular males—sire the most offspring. 

Hopkin: Gerber says that the males with more friends are likely more often invited to cruise for females…giving them more opportunities for cooperative canoodling. Ok, so dolphins do better on group dates. But how do they establish and maintain these critical friendships?

King: Through physical contact much like hugging or holding hands in humans.

Hopkin: Or like grooming in other primates, like chimps or monkeys…

Emma Chereskin: …where individuals will devote a lot of time and energy into grooming their closest friends to strengthen those relationships.

Hopkin: Emma Chereskin of the University of Bristol. She says the problem with all this physical interaction is…there’s only so many hours in a day.

Chereskin: When group sizes become larger, this places a constraint on how much time is available for an individual to devote to grooming key social partners.

Hopkin: Enter the “social bonding hypothesis.”

Chereskin: In this hypothesis, vocal exchanges can serve as a replacement for grooming to maintain social bonds.

King: Like us chatting regularly with our circle of friends.

Hopkin: For dolphins, those chats take the form of exchanging “signature whistles.”

Chereskin: A signature whistle is a vocalization that is completely unique to each dolphin that functions much like a human name.

[Signature whistle from Kooks]

Hopkin: That was Kooks…a member of the Alley Cat alliance.

[Signature whistle from Pimento]

Hopkin: And that’s his pal Pimento.

Chereskin: So when they use their signature whistle they’re advertising their identity to those around them as a way to maintain group cohesion.

Hopkin: So Chereskin set out to determine which dolphins were getting physical…and which were more or less phoning it in.

Chereskin: The results were surprising. I had anticipated that the way dolphins use their signature whistles would be akin to the way that primates do.

Hopkin: For apes and monkeys, chit chat is more common between besties. But for dolphins?

Chereskin: …when we look at just that core alliance group, we see that increased vocal exchanges occur between those with weaker social bonds. So while we do observe that vocal exchanges are indeed occurring between friends, rather than strangers, they’re occurring between distant friends rather than best friends.

[A whistle exchange between Spirit and Guppy]

Hopkin: Like Alley Cats Spirit and Guppy. Which Chereskin says kinda makes sense.

Chereskin: I liken these results to living with a partner. So when you live with someone, you typically don’t have to call or text them as much because much of your bonding occurs together in your home.

Hopkin: But for friends who are more far flung, you might be more apt to send a shout out…rather than making the effort to get together to bump fists…or fins.

[Dolphin clicks and pops]

For Scientific American’s 60-Second Science, I’m Karen Hopkin.

[Signature whistle from Spirit]

[The above text is a transcript of this podcast.]