Bottlenose Dolphins Use Signature Whistles to Call Each Other

Bottlenose dolphins use distinctive signature whistles to identify themselves when they are engaged in a social interaction, new research suggests.

The researchers came to this conclusion based on data accumulated over a decade by tracking the population of wild bottlenose off the east coast of Scotland and recording each individual's whistle.

 Copying sounds is common in several animals and birds and they also produce complex displays, mostly for mating purposes. But to link specific sounds with particular individuals is not common in many species, reports Guardian.

Researchers noticed that different dolphins produce their own unique whistles and interact with other individuals in their social group by producing their own unique sound or signature whistle.

These signature whistles of dolphins were noticed in 2006 by a pair of biologists, Stephanie King and Vincent Janik, at the University of St. Andrews, Scotland.  They noticed that dolphins were more likely to head toward the audio speaker that was emitting the whistles of a relative rather than an unrelated bottlenose.  Further exploring  this, King and Janik came up with another study in February 2013 that stated mothers were more likely to copy the distinctive whistle of their offspring to locate them, reports Smithsonian.com.

But this latest study provides further evidence that the bottlenose dolphins create unique signature whistles to distinguish themselves from each other and to identify themselves by the sound of their own chirps.

Dolphins depend heavily on sound production in order to navigate, hunt food, communicate and avoid predators. And interestingly the bottlenose dolphins can produce both clicks and whistles simultaneously. The sounds vary not just in volume but also wavelength, frequency and pattern and are produced at anytime and at considerable depths. The frequency of the signature whistles range from 7-15 kHz and last for less than one second, reports SeaWorld.

In the new study, the researchers played the recorded signature whistles back to the bottlenose dolphins and noticed that the dolphins responded to the sound by producing the exact copy of the whistle.

In the second trial they randomly played the records of whistles and then carefully watched the response of the dolphins. They found that animals were more likely to copy the sound or call back on hearing their own whistles rather than unrelated whistles.

This makes the researchers believe that the bottlenose dolphins act like humans when they hear their own names.

In eight trials that used a member group's signature whistle they noticed at least one dolphin in the group responded  to the whistles compared with just two in the 22 trials that used chirps of unfamiliar dolphins within the group. If the chirp belonged to their group they moved toward the speaker indicating they were responding to a well known stimulus.

The study details were published in the journal Proceedings of the National Academy of Sciences.