Dolphins use 'signature whistles' that act as names to identify and communicate with each other, according to a new study conducted by marine biologists from the University of St. Andrews in Scotland.
This evidence, published Monday in the Proceedings of the National Academy of Sciences, also indicates that other species started calling each other by names way before humans did.
Previous studies conducted on bottlenose dolphins revealed that individual dolphins use the 'signature whistle' in big group settings, like when several pods of dolphins meet at sea.
Whitney Friedman, a dolphin-behavior expert at the University of California, San Diego said that this study shows a dolphin's response to the signature whistle by repeating the whistle back, as if to say, 'Yup, I'm here-did you call my name?'
Past studies on dolphins revealed that they can follow 'recipes,' help other species in sorrow, and possibly do math.
The biologists arrived at the conclusion after observing a group of wild dolphins on a boat off eastern Scotland. For more than four months, the team observed different groups of wild dolphins, and identified and recorded the whistles of 12 dolphins living off the east coast of Scotland.
Then they modified those whistle sounds slightly so it would seem like a second dolphin was making the first dolphin's whistle sound. The researchers played back these modified whistles using underwater speakers.
When one of the dolphins whistled a name, the equivalent of "Joey!" for example, the researchers recorded the sound at the time. Later, when they played back the whistle to the dolphins, the dolphin they named Joey by the biologists, responded immediately with the same whistle-as if to say, 'Yup, I'm here.'
"It was very exciting to see that every time a dolphin heard its signature whistle, it called back, sometimes multiple times," said, Stephanie King, the study leader.
Similar tests conducted on other dolphins also produced similar results. Some of them even approached the boat soon after responding and swam toward the speakers that were playing the sound.
"This new study shows that when a dolphin hears an imitation or copy of its own signature whistle, it will respond immediately," said, Peter Tyack, another marine biologist at University of St. Andrews.
Friedman, who was not part of the study, said that for dolphins, whistles are not just noises but a crucial communication tool for them. King said that these signature whistles are effective as it helps lost animals reunite with their pod.
"Having sounds that express identity might be a way for the group to know where each group member is at a given time, and the specific identity of that dolphin," said, Jeremy Karnowski, a UCSD dolphin-communication expert who was not involved in the new study.
Laela Sayigh, a marine biologist at Woods Hole Oceanographic Institute in Massachussetts, who was not part of the study, said that no two signature whistles are similar. Dolphins are estimated to create a name for them similar to those of their mothers or combine together scraps of different whistles, or they simply produce them spontaneously
"We don't really have an exact answer," Sayigh said.
