Science Saturday IV: Whistling While They Work

We've long known that dolphins are evolved critters, but now comes convincing word that they can call each other by name, making them the only animals besides humans who can recognize such information.

Scientists have long known that dolphins' whistling calls include information thought to be their names, but a new study indicates dolphins recognize these names even when voice cues are removed from the sound.

For example, a dolphin might be expected to recognize its name if called by its mother, but the study found most dolphins recognized names -- their signature whistles -- even when emitted without inflection or other vocal cues.

Laela Sayign, one of three authors of a paper published in the Proceedings of the National Academy of Sciences, told CNN that:

The scientists already knew that dolphins responded to whistles, but wondered if something in the actual voice of the whistling dolphin was making the identity clear, or if the name itself was enough for recognition.

To find out, they studied bottlenose dolphins in Sarasota Bay, Florida. Instead of playing recordings of actual dolphins making signature whistles, the researchers synthesized signature whistles with the caller's voice features removed and played them to dolphins through an underwater speaker.

In nine out of 14 cases, the dolphin would turn more often toward the speaker if it heard a whistle that sounded like a close relative's.

"It's a very interesting finding that encourages further research, because they are using whistles as referential signals -- that's what words are," said Sayigh. "Dolphins appear to be using these arbitrary signals to identify another dolphin."

In case you're wondering, Sayigh stopped short of saying dolphins might have a human-like language.