We have given names to many bottlenose dolphins, from Flipper to Darwin. But in the wild, these animals have their own badges of identityâ€”signature whistles that they develop during their early years and that are unique to them.
These whistles seem a lot like human names. The comparison isnâ€™t perfect, but itâ€™s now stronger than ever after Stephanie King and Vincent Janik managed to address individual wild dolphins with recordings of their own signatures. The dolphins responded by calling back, but only when they heard their own whistle. â€œI think our results do present the first case of naming in mammals, providing a clear parallel between dolphin and human communication,â€ says King.
The evidence that dolphins use signature whistles like names has been building since they were first discovered in the 1960s. They can convey a dolphinâ€™s identity, as well as its mood and motivation. Individuals invent their own whistles at a few months of age, possibly with some influence from their mums. Theyâ€™ll keep the same call for decades, although males sometimes change theirs to resemble the whistle of a new ally.
The whistles are clearly important, since they account for half of all the calls that wild dolphins make. They can mimic each otherâ€™s signatures, but they usually call with their own, perhaps to broadcast their identity and keeping in touch while swimming.
Working out how dolphins actually use these signatures in the wild has been very hard. These are fast-moving animals, whose calls blend together into a cacophonous mess. But Janik has developed a way of identifying individual whistles based on their distinctive rhythms. He can now follow free-swimming pods, record their calls using underwater microphones, and parse out the signatures of different individuals.
In 2011, he used this technique to show that groups of bottlenoses exchange signature whistles when they meet upâ€”a ritualised greeting, like saying hello or shaking hands. When I covered that study, I ended with: â€œ[Janik] also wants to try some playback experiments â€“ the cornerstone of animal communication research â€“ to see if he can provoke a specific response by playing a chosen signature whistle.â€