Bottlenose dolphins (Tursiops truncatus) can use copying of signature whistles as a way of addressing or labeling animals on an individual basis, according to new research reported in the journal Proceedings of the National Academy of Sciences.
Study authors Dr Stephanie King and Dr Vincent Janik, marine biologists from the University of St Andrews, conducted sound playback experiments with wild bottlenose dolphins on the east coast of Scotland.
Their earlier study 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.
The 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 biologists 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.
“Animals have been found to use calls to label predators or food but these calls are inherited and not influenced by learning,” Dr King said.
“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.”
Bibliographic information: Stephanie L. King, Vincent M. Janik. Bottlenose dolphins can use learned vocal labels to address each other. PNAS, published online before print July 22, 2013; doi: 10.1073/pnas.1304459110