May 10, 2006 — Dolphins create a signature whistle for themselves that researchers believe is comparable to a human name, suggests a new study.
The study, published in this week’s Proceedings of the National Academy of Sciences, focused on bottlenose dolphins, Tursiops truncatus. But the researchers believe other dolphin species, including the common dolphin and the Pacific white-sided dolphin, also possess the signature whistles.
Dolphins now join spectacled parrotlets as the only animals other than humans known to name themselves, though researchers think there may be others.
The researchers played dolphin whistles to bottlenose dolphins at Sarasota Bay, Fla. The scientists stripped each whistle of everything but the basic frequency contour, resulting in a kind of generic dolphin voice analogous to a computerized human voice with no uniquely defining qualities.
Nine out of 14 dolphins turned their heads toward the speaker when they heard a synthesized version of a whistle delivered by a close relative.
The signals vary greatly, with some dolphins repeating sounds or altering patterns. Sayigh told Discovery News that the variations suggest the whistles may encode information beyond the name-like signatures, such as emotion.
While there is no convincing evidence that dolphins exhibit dialects in the way that people and birds show regional accents, the scientists have not ruled it out.
"Dolphins in Australia do seem to produce more simple whistles, while Florida dolphin whistles appear to be more modulated," she said. "Right now, we don’t know why that happens."
It's also unclear whether dolphin communication qualifies as language.
"Language by the standard definition must have syntax- or structuring of words- and reference," Sayigh explained. "Dolphins do have the ability to use artificial signals to refer to objects, but it is unclear at present if their vocalizations involve syntax."
Jim Oswald, spokesman for The Marine Mammal Center in the Marin Headlands of California, told Discovery News that the new finding is "incredible, but not entirely unexpected."
In 2004-2005, Oswald's center helped rehabilitate and release a bottlenose dolphin.
"The dolphin wound up in the wrong pod upon release, but when he found his correct group, there were all sorts of signal vocalizations," Oswald said. "It was as though they were having a conversation, so it appears they really do communicate very specifically with each other using the sounds. Now that it is possible they have unique names, I wonder what else they name?"
