ROBERT SIEGEL, HOST: Dolphins are like humans in many ways, the size of their brains, for example, and their complex social networks. And now, a new study tells us about another similarity. As NPR's Rhitu Chatterjee explains, dolphins may be using something like names to identify one another.

RHITU CHATTERJEE, BYLINE: Every bottlenose dolphin has its own unique whistle. And it sounds something like this.


DR. STEPHANIE KING: In the underwater environment, animals use their own signature whistles to broadcast their identity, to say, I'm here, I'm here.

CHATTERJEE: Stephanie King is a marine biologist at University of St. Andrews in Scotland and an author on the new study. Earlier this year, King and her colleagues showed that when bottlenose dolphins in captivity get separated from each other, they call out to their loved ones by imitating their whistles.

KING: They were calling the unique identity signal of a friend they wanted to reunite with.

CHATTERJEE: But what she couldn't tell was whether the other dolphin really answered the calls and also whether this happened in the wild. To try and find out, she and a colleague recorded the identity whistles of 12 dolphins living off the east coast of Scotland, then they modified those whistles slightly so it would sound like another dolphin making the sound and played back these modified whistles using underwater speakers.

KING: And it was very, very exciting to see that every time a dolphin heard a copy of its signature whistle, it called back, sometimes multiple times.

CHATTERJEE: Not only did the dolphins call back, King says they even swam towards the source of the sound, the speakers. It was what you might expect if two friends were trying to find each other in a crowd. Peter Tyack is a marine biologist also at University of St. Andrews.

DR. PETER TYACK: This new study shows that when a dolphin hears an imitation or a copy of its own signature whistle, it will respond immediately.

CHATTERJEE: He says both of King's recent studies show that dolphins do label each other with these whistles. But are these whistles the dolphin version of human names? That's harder to tell, says Tyack.

TYACK: To get at the issue of naming, I think we need to get beyond the function of the communication to a more cognitive question.

CHATTERJEE: For example, he says, does hearing someone's whistle bring up in a dolphin's mind an image of that particular animal? Questions like these might be hard to answer, but Tyack says it's well worth trying. Rhitu Chatterjee, NPR News.



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