You talking to me? Click here to hear a signature name whistle from a bottlenose dolphin.© Getty

We are not the only animals to give ourselves names, says research on bottlenose dolphins. The dolphins' distinctive whistles may function as individual calling cards, allowing them to recognize each other and even refer to others by name.

The research reveals that bottlenose dolphins (Tursiops truncatus) each have their own personalized whistle, which is recognized by other dolphins even from a synthetic version played through a speaker. This suggests that the creatures recognize these as names in their own right, rather than identifying individuals based simply on the sound quality of their voice.

The dolphins have also been heard using each others' names in their 'conversation' — meaning that they may be able to call their comrades during social interactions. The calls may be used to bind groups together in the wild where individuals cannot always see each other, or to coordinate their delicately complex hunting manoeuvres.

Something to talk about

The effect was revealed in bottlenose dolphins living at in Sarasota Bay, Florida. The individual whistles of these dolphins are well known, as they have been involved in capture and recording studies since 1975.

Researchers created artificial versions of specific dolphins' signature calls and played them to other dolphins from the group. Dolphins were more likely to turn towards the speaker if it was playing the call of a close relative, rather than an unrelated dolphin, the team reports in Proceedings of the National Academy of Sciences¹.

"The calls mostly seem to be for negotiating social relationships," says Vincent Janik of the University of St Andrews, UK, who led the research. "When travelling they can be very quiet, but when they meet up there is a lot of chattering."

The signature whistles are just a small part of a huge vocabulary of whistles, clicks and other calls, Janik adds. In the wild, name calls seem to make up around 50% of all communication. In a tank, where dolphins can all see each other, they drop out of the repertoire almost entirely, replaced by other whistles with meanings that remain enigmatic.

Dolphins are renowned for their communication skills — although the assumption that they possess fully formed language has never been proved. Nevertheless, they produce a bewildering range of different noises, says dolphin expert Richard Connor of the University of Massachusetts, Dartmouth. "They squeal and growl and make a whole bunch of sounds."

Call me

Many animals, such as songbirds and monkeys, have distinctive calls. But these usually convey a message, such as a warning or a call for a mate, rather than a name. Among such animals, recognition of individuals is usually based on the quality of the voice, rather than the specific call.

Dolphins are different, Janik explains. He suspects that only parrots are capable of similar levels of sophistication.

The dolphin's facility for mimicry might even mean that they can talk about other group members in their absence, Connor suggests. "If they can talk about others behind their backs, that would be really interesting."

Such a discovery would be an immense surprise, Janik says. But he adds that we still know very little about dolphin communication. Some loud calls have been observed in contexts that suggest threats between rivals, or invitations to feast on a food source. For the most part, however, dolphins' whistles, and the constant snick-snick of their clicks, remain a fascinating puzzle.

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University of Massachusetts, Dartmouth

• References

  1. Janik V. M., Sayigh L. S.& Wells R. S. . Proc. Natl Acad. Sci., doi:01.1073/pnas.0509918103 (2006).