Scientists at the University of St Andrews have shown that bottlenose dolphins can use copying of signature whistles as a way of addressing or labelling animals on an individual basis.
The research was carried out by marine biologists Dr Stephanie King and Dr Vincent Janik who conducted sound playback experiments with wild bottlenose dolphins on the east coast of Scotland.
Earlier work published this year in the Proceedings of the Royal Society by the same authors showed that dolphins often copy the signature whistles of their close relatives and friends. Signature whistles make up about 50% of an animal’s whistles and broadcast its identity to others. This new study tests whether animals that are addressed with copies of their signature whistles really react to them. It is the ultimate test whether addressing really works in dolphins.
The team followed groups of wild dolphins and recorded the dolphin unique ‘signature’ whistles using a novel signature identification method. They then played back either a computer version of an animal’s signature whistle, or control whistles of either an unfamiliar animal from a different population or a familiar animal from the same population. Each dolphin only reacted when hearing the computer version of its own signature whistle, but not to the other whistles played back to it. Showing that dolphins can be addressed in this way was the missing link to demonstrate that signature whistles function as names.
Dr King explains how these signals are different from those of other animals:
“Animals have been found to use calls to label predators or food but these calls are inherited and not influenced by learning. The use of new or learned sounds to label things is rare in the animal kingdom. However, it is ubiquitous in human society and at the heart of human language. There are good data showing the ability to invent new sounds and copy them in dolphins and this led us to design our experiments”.
Together with findings reported in previous publications, this new study really demonstrates that signature whistles are used like names.
Dr Janik added:
“Our results present the first case of naming in mammals, providing a clear parallel between dolphin and human communication. In experimental work, parrots are also good at learning novel sounds and using them to label objects. Some parrots may also use these skills in their own communication. Thus, both dolphins and parrots present interesting avenues of research for understanding labelling or naming in the animal kingdom.”