We all find ourselves having a chat to our cats and dogs at home sometimes, but they don't normally talk back. This week however, a paper in PNAS looks at communications between dolphins that suggests that they used learned names to address one another. Kate Lamble spoke to Vincent Janik from the University of St. Andrews.
Kate - So Vincent, what have you discovered?
Vincent - We've studied signature whistles of bottlenose dolphins for a while now and these are very unusual signals, in that every animal develops its own specific sound early in life and then uses that to broadcast where it is and who it is. These sounds also are occasionally copied by other dolphins and when we first found that, we thought that this might be a kind of labelling system or as has been discussed as a kind of naming system perhaps. In subsequent studies, we looked at who copies who and it turned out that it's mainly animals that are very close to each other like mothers and calves or also close associates.
In this a new study now, we've put this to the test by going out into the wild and playing back signature whistles to animal's here off the east coast of Scotland. What we really wanted to do was to find out whether we can address one animal just with a copy of its signature whistle. So, for that to be the case, we had treatment calls which were the signature of animals, but also other whistles from their repertoire and signature whistles from other animals. The result of the study was that the animals really only responded when we copied their own signature whistle, but did not to all the control sounds.
Kate - And you sent us a few of those signature whistles over. (CLIP) Those two whistles were obviously very different. How do we know that those are signature whistles as opposed to any other sort of random collection of clicks?
Vincent - This is an interesting question because indeed when you have an animal in captivity for example and you can isolate it from the group then the signature whistle is the most common whistle that the animal makes, it is producing it almost constantly. Now in the wild, this is a little trickier. We do know that about half of the whistles they produce are signatures, but the other half, other kinds of whistles, the way we found out what the signatures were in these wild animals here was using a study that we published earlier this year, showing that you can find out what signature whistles are by looking at the specific temporal patterns of whistles. So, if dolphins repeat whistles then the interval between these whistles for signature whistles have very specific values and you can look for those and you can identify then which of the whistles are signature whistles and which ones are not.
Kate - You mentioned that these whistles are learned by the animal when it's quite young. So, does each dolphin create its own nickname in a way?
Vincent - Yes, so one of the big differences we called as names to humans is that the animals develop them themselves, so they're not given to them. The way it happens is it is kind of a creative process in that the animal listens to other whistles in its environment and then maybe chooses one of the model, but then starts to change their whistles efficiently so that it becomes a new signal. So, the animals really do label themselves first in a way and then produce that whistle repeatedly when they are trying to contact the group. And only through this repetition do other members of the group of course learn that this new signal stands for a particular individual.
Kate - How do we know what these whistles are used for? Are they just being used to say hi and let other animals know that they're there or they're used as a warning like we hear other animals sort of scream warnings? Baboons tell other baboons that leopards are near for example.
Vincent - These whistles really just label the identity of the animal, so there isn't any additional information in the shape of the whistle. Now, there is of course additional information always in the voice of an animal, also of a human when we communicate. So, if an animal is afraid for example, then certain parameters change and those can also be extracted from receivera and they can recognise what state the animal is in. And so, through that, the animal can also convey for example whether there is danger eminent.
However, these signature whistles do not function the same way as alarm calls where they label particular predators for example. These whistles really just kind of stand for the individual that's producing them. For other calls that the animals might have, there are food calls that we found as well which kind of seem to be standing for food. But we need further research to see to what extent they really are labels rather than just a kind of excitement call by animals who encounter large schools of fish.
Kate - Is this naming unique to dolphins?
Vincent - The only other animal in which we find something comparable perhaps - apart from humans - are perhaps parrots. There's various studies from parrots that suggests that they may also have a signature call system that works in a similar way. But there's only very few studies so far and this is one of the rare cases where we actually have more information about dolphins than we have about birds even though birds as a group are studied much more extensively than dolphins.
Kate - Why does dolphin communication in particular fascinate us so much?
Vincent - I think there's different reasons for this fascination. On the one hand, people are fascinated with dolphins because they are beautiful animals and you encounter them in the wild.
The other fascination is the scientific one which really comes more from the fact that these animals have these advanced cognitive skills which really rival those of the non human primates. It is a puzzle to find this in an animal that clearly evolved in a completely different environment from ours. So, to have similarities in communication skills between humans and dolphins, like vocal learning for example, or also in other skills like social memory and recognition tasks is kind of a surprise in such a uniform environment.
What it really tells us and one of the interesting aspects about this is probably, a lot of these skills actually evolved primarily in social contexts rather than in perhaps tool manufacturing or tool use context which is one of the other possible origins of advanced cognition that we find in primates.
Kate - So, you're suggesting that us understanding how dolphins communicate can help us understand how our own language evolved?
Vincent - Yes, I think these comparative studies with animals that are quite far away from our own lineage are very useful in highlighting what could perhaps be common reasons for the evolution of complexity. In this case in particular, in communication but I think also beyond this in cognition in general. The fact that dolphins don't have opposable thumbs, don't produce complex tools is something that kind of hints at the more dominant role of social aspects.
Kate - What are the next steps in your work, now that you understand the role of these signature whistles?
Vincent - One of the interesting observations we've made is that if you follow a group of dolphins, every so often, you hear signature whistles of animals that aren't present in the group and one of the next questions really is, whether these are attempts of the animals in the group to find these other individuals or whether they perhaps really use them as referential labels to exchange information about third parties.
We're quite a long way away still to kind of make that discovery I think if it's there, but I think it's a very interesting question to see to what extent perhaps these learned signals could serve as truly referential signals which could only be shown if we show that they are conveying information to a dolphin about another dolphin.