Dolphins greet one another by “name,” using signature whistles to keep track of one another in murky waters and across distances, a researcher said today.
While he hesitates to say the dolphins are actually using language, the researcher said the study shows dolphins have a clear and consistent vocabulary and are able to identify one another as individuals.
“Each dolphin develops a very specific signature signal,” biologist Vincent Janik of the University of St. Andrews in Scotland, who conducted the study, said in a telephone interview. “They always use the same call. Some people call it a name.”
Like a Screen Name
But because the dolphins seem to develop their own signature whistles, Janik said the calls are more like Internet screen names or handles.
Janik studied wild bottlenose dolphins off the Moray Firth, on Scotland’s coast. He recorded 1,719 whistles using six hydrophones and a computer-based method for finding individual dolphins as they made the calls.
The dolphins were coming into the bay to catch salmon.
“You have lots of dolphins all over the place,” Janik said. “Obviously at some point they want to get together again.”
Each dolphin makes its own, distinctive whistle, Janik found. Other dolphins will imitate that whistle, presumably to contact and keep in touch with that particular dolphin.
“It’s like keeping in acoustic contact,” Janik said.
“It’s something that we know from birds and humans, too.”
To check his work, Janik used five human “judges” to confirm the calls were identical. People are very good at hearing differences in tone, he said.
“I used human judges because a computer is not up to the job yet,” he said.
“I can say the same word in a high-pitched voice or a low-pitched voice and it’s still the same word but the computer could confuse it.”
Janik has also found that, like monkeys and other primates, the dolphins use distinctive calls when they have found food. This one is a low-pitched “bray,” he said.
“It really sounds like a donkey bray,” Janik said.
“It was very clear that this was a feeding call. If one dolphin found food, they would produce this call. The others would rush in.”
So does it qualify as language? “I always try to avoid the term ‘language,“‘ Janik said.
“But it is certainly a complex communication system.”
Now Janik is working in Shark Bay, in Western Australia to see if mother dolphins and their calves use the distinctive signature calls. “We know they have to get back together again,” Janik said.