Dolphins Are Smart Team Players That Learn 'Names' of Friends

Dolphins are smart team players. They size up their relationships and classify them into various alliances, based on how useful they can be when heading off to take on rivals.

Bottlenose dolphins actually form three levels of useful relationships. A new study from researchers at the University of Bristol in the United Kingdom analyzed how they classify and respond to their friends and allies in these three tiers.

Of the 40 or so species in the dolphin family, there are varied social systems. Some are well-studied, while researchers know very little about others, says study lead author, Stephanie King, senior lecturer from Bristol's School of Biological Sciences.

“The killer whale, for example, is the largest species in the dolphin family and their social system is characterized by very stable social relationships. Once born into the family, individuals tend to stay for life, being led by a matriarch,” King tells Treehugger. “Bottlenose dolphins, on the other hand, exhibit a fission-fusion grouping pattern, in which group membership can change on a minute-by-minute or hour-to-hour basis.”

For the study, researchers had been studying Indo-Pacific bottlenose dolphins in Shark Bay, Western Australia, for three decades. There, dolphins live in large, open social networks with many different relationships — much like humans do.

“Male bottlenose dolphins start to form long-term friendships with other males when they are juveniles and, by the time they are adults, these friendships crystallize into long-term alliances — tight bonds between males that last for decades,” King says.

They form all sorts of relationships ranging from casual acquaintances to best friends to archrivals. Male dolphins form three levels of alliances in Shark Bay which, King says, is “unparalleled in the animal kingdom and matched only by one other species, our own.”

With what is called their first-order allies, the male dolphins work together to herd receptive females. With second-order allies, they team up in contests over females with rival alliances. In third-order alliances, they work in even larger groups when more rivals appear.

“Given this complex, nested alliance formation and that friendships can occur across all three alliance levels, we set out to assess how dolphins classify their alliance relationships,” King says. “We wanted to assess how well-known individuals would respond to the signature whistles, equivalent to a human name, of their allies.”

They were curious if the dolphins would respond most strongly to allies in one of these specific groups.

Responding to Whistles

Dolphins make an array of high-pitched noises, including whistles. Dolphins develop a signature whistle in the first few months of life. They learn to respond to the unique whistles of their closest friends and allies.

For the study, researchers placed speakers underwater and played the whistles of males to other males in their alliances. The dolphins ranged in age from 28 to 40 years old and some had known each other for more than 28 years. While they were playing the whistles, scientists flew a drone overhead to record footage of their reactions.

The dolphins responded to all the males that had assisted them in the past, even if they weren’t close friends. But surprisingly, they didn’t respond most strongly to their first-order allies.

“Our results showed that males responded strongest to members of their second-order alliance – the team that have a shared, cooperative history in helping each other out in contests against rivals over access to females,” King says.

The results were published in the journal Nature Communications.

“All these male dolphins know each other, some are closer friends than others and some spend little time with others. The social unit that really counts though, is the second-order alliance,” she says.

“These guys consistently help each other out irrespective of whether or not they work together at the first-order alliance level or not. Third-order allies can also be friends, but there is less consistency in the cooperative acts, so it pays to always respond to your second-order allies — your team within this big social network of friends and rivals.”