Individual 'names' reveal complex relationships in male bottlenose dolphins

Leslie Hanson
June 10, 2018

Conducted in Shark Bay, Western Australia, researchers collected recordings of 17 male bottlenose Dolphins, which are known for their formations of alliances.

It's not uncommon in dolphin society for males to form long-lasting alliances with other males, sometimes for decades.

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

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

The discovery paints a picture of the social intelligence of dolphins whereby no other non-human animals have been found to retain an individual "name" when they form long-term cooperative partnerships with one another. That's in contrast to findings in many other species where individuals with close relationships converge on shared vocalizations as a way of advertising their membership to that partnership or group.

The researchers wanted to know if allied dolphins shared similar calls as a way to advertise their alliance, or if they stuck to individual vocal labels. "Therefore, retaining individual "names" is more important than sharing calls for male dolphins, allowing them to keep track of or maintain a fascinating social network of cooperative relationships".

"With male bottlenose dolphins, it's the opposite - each male retains a unique call, even though they develop incredibly strong bonds with one another". In other words, dolphins that were related didn't necessarily have similar names.

"These alliances with one another retain individual vocal labels, or 'names, ' which allows them to recognize many different friends and rivals in their social network".

A bottlenose dolphin signature whistle.

She also learned that the dolphins can mimic each other's whistles, seemingly to address or call out to one another.

"For pairs of males that form alliances in Florida, it appears they do make their identity signals more similar".

"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. Scientists aren't sure how dolphins get their names but they develop signature whistle during their first few months of life.

To explore the role of these "vocal signals", the team measured the similarity of the signals between and out of alliances of male dolphins.

Male dolphins also use physical signals such as caresses, slaps and synchronized behavior to express their social bonds.

The corresponding author on the study Stephanie King says that synchrony has been linked with oxytocin release in humans.

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