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Dolphins 'name' friends to recognise them

10 June 2018

It's already well known that male dolphins often form alliances with each other - sometimes lasting for a few decades.

Dolphins call each other by name when they chat, according to a new study.

The 30-year study of male dolphins set out to understand the role of vocal communication in their social behaviour.

The fact that the individual "names" are kept helps males to keep track of their many different relationships and distinguish between friends, friends of friends, and rivals.

The analysis showed that males in an alliance retain vocal labels that are quite distinct from one another, suggesting that those calls serve a objective similar to an individual name.

Research from 1989 shows that female bottlenose dolphins maintain signature whistles or names for at least 12 years in the wild.

The researchers also found that since the dolphins did not share a call sign, they used other means to strengthen relationships.

A trio of allied male bottlenose dolphins (Tursiops aduncus) from Shark Bay, Western Australia.

"It's an usual finding because across the animal kingdom many animals make their calls more similar when they form strong social bonds".

"Dolphins employ these kinds of behaviour in order to advertise alliance unity", she said.

"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. However, this is also in contrast to previous studies, which found that dolphins refer to each other using shared vocalizations as a way of advertising their membership to that partnership or group.

Dr King said bottlenose dolphins were different, instead retaining their unique call even when forming "incredibly strong bonds".

Interestingly, researchers also found no evidence of any genetic relatedness influencing signature whistle similarity between males. This shows the importance of names among the dolphin community.

Signature whistles of two different male dolphins from Shark Bay, Western Australia. This way they're able to negotiate a complex social network of cooperative relationships. It's not clear if this behavior is restricted only to bottlenose dolphins.

The alliances can be so close that the male dolphins will begin to touch each other.

After collecting the recordings, the team were able to determine the "names" or individual vocal label of each male.

"At the moment we're looking more closely into the relationships among the males in an alliance to find out whether or not they're equally strong between all the individuals involved", explains Krützen.

Convergent vocal accommodation is used to signal social proximity to a partner or social group in many species.

Dolphins may be more similar to humans than previously thought, with a University of Western Australia (UWA)-led study on Friday confirming that the ocean creatures use individual "names" to identify their friends and rivals among social networks.

Dolphins 'name' friends to recognise them