Male Dolphins Use 'Names' to Identify Friends and Rivals

This photo shows allied male bottlenose dolphins swimming together. Simon J Allen at the Dolphin Alliance Project

A three-decade study of bottlenose dolphins off the coast of Australia has found that males of the species make use of individual vocal labels to identify each other, much like humans use names.

Previous research has shown that in dolphin society, males often form long-lasting partnerships with other males. The new study, published in the journal Current Biology, demonstrates how dolphins in these alliances use "names" to manage their social network.

"Our work shows that these 'names' help males keep track of their many different relationships: who are their friends, who are their friend's friends, and who are their competitors," Stephanie King from the University of Western Australia, one of the authors of the study, said in a statement.

The researchers wanted to learn more about the role that vocal communication plays in bottlenose dolphin society. After studying the dolphins for many years, it became apparent that males formed long-term cooperative alliances with one another, but it was not understood that they used vocal signals to maintain these relationships.

For their study, the scientists recorded vocalizations made by the dolphins using underwater microphones—known as hydrophones—to work out which individual labels were used by each of the males.

"We wanted to understand if allied male dolphins converged onto similar calls as a way of advertising their alliance membership, or whether they retained individual vocal labels," King said.

They found that males within an alliance use vocal labels that are quite distinct from one another, indicating that they serve a similar purpose to names among humans.

The next step for the researchers, according to King, is to examine the relationships between the males in greater detail. They will do this by playing the "names" of individuals back to the dolphins to see how they respond in different contexts.

"It will be interesting to reveal whether all cooperative relationships within alliances are equal or not," she said.