Last updated June 21, 2018 at 1:37 pm
Vocal labels a part of complex relationships.
We can now add social intelligence to the list of impressive dolphin traits.
Researchers from the University of Western Australia have discovered that male bottlenose dolphins can retain individual vocal labels or “names” to help recognise friends and rivals in their social network. No other non-human animals have yet been found that do that.
Working with colleagues from the University of Zurich and the University of Massachusetts, they studied 17 well-known dolphins in Shark Bay, about 800 kilometres north of Perth, where males are known to form alliances as strong as those between mothers and calves, and which can last a lifetime.
After recording the dolphins’ vocalisations using underwater microphones and determining the individual vocal label of each male, they measured the similarity of these signals within and between other alliances to see whether males that had stronger social relationships had unique vocal labels or not. And they did.
Dr Stephanie King, from UWA Centre for Evolutionary Biology, said it was an unusual finding because it was the opposite of the norm.
It is common for animals to make their calls more similar when they share strong social bonds – some parrots, bats, elephants and primates do it – but with male bottlenose dolphins it’s the opposite. Each male retains a unique call, even though they develop incredibly strong bonds with one another.
Keeping track of friends and competitors
Previous research has shown vocal labels are similar to human names; dolphins use them to introduce themselves or even copy others as a means of addressing specific individuals.
King said these “names” helped males keep track of their many different relationships: who their friends are, who are their friends’ friends, and who are their competitors.
“Retaining individual names is more important than sharing calls as it allows dolphins to negotiate a complex social network of cooperative relationships,” she said. “This formation of alliances within alliances is very unique and it’s the only example we have in the animal kingdom outside of humans.”
The researchers also observed how male dolphins used physical contact to strengthen their relationships with one another, including petting, stroking and synchronous behaviours, as an alternative means of advertising their strong social bonds.
The next step will be to study whether all cooperative relationships within alliances are equal. “This will further our understanding of the political landscape of dolphin alliances in Shark Bay,” King said.
The paper published in Current Biology.
