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Study: Dolphins Call Out Their Own Names


This is DAY TO DAY, I'm Madeleine Brand.


And I'm Noah Adams. Here is the way a bottlenose dolphin might say hello.

(Soundbite of dolphin)

ADAMS: A signature sound. A dolphin in effect saying, Hey, it's me, over here. Bottlenose dolphins when they are very young develop a whistle sound signature. They give themselves a name and they use it all their lives and other dolphins know these names. Joining us to talk about this is Vincent Janik of the Sea Mammal Research Unit at the University of St. Andrews in Scotland. He's the co-author of a new study on dolphin communication to be published next week in the Journal Proceedings of the National Academy of Sciences. Welcome, Dr. Janik.

Dr. VINCENT JANIK (Sea Mammal Research Unit, University of St. Andrews, Scotland): Hello.

ADAMS: Tell us about the study. What's new? There's been some research before about sound signatures, but what have you found out that's new?

Dr. JANIK: Well, we were really interested in the system because people have described these signature whistles and these very distinctive calls that dolphins make when they are isolated from the rest of their group. And that whole system reminds us so much of a situation in which humans use names that we were really curious to see whether these animals really do recognize the actual shape of that whistle as carrying the information of identity. And the other, the alternative of course is that they just recognize voice, that they just recognize a general voice feature just like you and I would recognize each other if we are really familiar with a voice of a speaker.

ADAMS: How do you separate out just the voice from the actual information that's being carried by the voice?

Dr. JANIK: Well, what we did is we did the equivalent of a dolphin computer voice that is just copying the actual shape of the call. We synthesized these whistles and then we looked at whether dolphins react to them in the same way as they do to the whistles when you play the original.

ADAMS: You're in a -- what sort of water situation in Sarasota, Florida where you did this research?

Dr. JANIK: Yes that's right. For the particular study where we tested this, we did underwater playbacks with underwater speakers to see how the animals react and actually were able to see the animals because we were holding them at the time in a net corral.

ADAMS: Let's go back just a bit. If I'm a dolphin I know my name and I know your name and we could recognize each other right away, even in dark murky water.

Dr. JANIK: Yes, that's right, exactly. And that's a big advantage of the system and most likely the context in which it evolved.

ADAMS: Now, what is left to find out about this?

Dr. JANIK: First of all, we wonder whether dolphins can recognize voices. Because it's so hard in water and to maintain voice features, one of the other aspects of this is that when you dive down the pressure increases, the water pressure increases and actually changes these air filled cavities and you have that influence voice characteristics quite a lot. So one thing that can happen is actually voice changes as you go down. So maybe voice isn't something that's reliable at all to these animals and one thing we are trying to find out at the moment is whether they actually do recognize voices by using original recordings that are not signature whistles to see whether the animals can recognize those as well.

And another question we're interested in is whether the animal actually has a mental picture of another dolphin when it hears a dolphin's signature whistle. And that's another, another ongoing study that we're working on at the moment.

ADAMS: Now, is there any way to tell how many names a dolphin could recognize?

Dr. JANIK: I think that, you know, they can easily recognize, probably quite well, ten to twenty animals that they come across quite frequently. But then the ones that they see less and less often, who knows? I think, you know, it's probably, there's probably a gray area just like you encounter someone and say, well, I know that person's name but I just can't think of it right now.

ADAMS: Yeah, I know that voice, but I can't place -- I can't place your name.

Dr. JANIK: Yeah, exactly.

ADAMS: Remind me of your name.

Dr. JANIK: That's right.

ADAMS: Vincent Janik is a biologist at the Sea Mammal Research Unit at the University of St. Andrews in Scotland. Thank you, sir.

Dr. JANIK: Thank you very much. Transcript provided by NPR, Copyright NPR.