The researchers said dolphins copy the signature whistles of loved ones, such as a mother or close male buddy, when the two are apart. These “names” were never emitted in aggressive or antagonistic situations and were only directed toward loved ones.
The whistle copies also always had a unique variation to them, so the dolphins weren’t merely mimicking each other. The dolphins instead were adding their own “tone of voice” via unique whistling.
While researchers often hesitate to apply the “l word” -- language -- to non-human communications, bottlenose dolphins and possibly other dolphin species clearly have a very complex and sophisticated communication system.
“Interestingly, captive dolphins can learn new signals and refer to objects and it may be that dolphins can use signature whistle copies to label or refer to an individual, which is a skill inherent in human language,” King said.
Heidi Harley, a professor of psychology at New College of Florida, is a leading expert on cognitive processes in dolphins. She agrees with the new paper’s conclusions.
Harley told Discovery News that it can be challenging to study dolphin signature whistles, since it’s difficult to identify which particular dolphin is emitting the sounds, and whether or not the sounds are just mimicked copies.
“This study provides evidence that copies of signature whistles include elements that differ from the whistles of the original whistler, while still maintaining the changes in frequency over time that allow a listener to identify the original whistler,” Harley said. “In addition, that signature whistle copying occurs between close associates, suggesting it is used affiliatively.”
King and her team are now using sound playback experiments to see how wild, free-ranging dolphins respond to hearing a copy of their own signature whistle.