Name That Dolphin.

If you want to meet a dolphin in the wild, just whistle. New research shows that bottlenose dolphins (one of 26 dolphin species) use "signature whistles" to greet one another or identify themselves across distances. "They always use the same call. You might call it a name," says biologist Vincent Janik at the University of St. Andrews in Scotland. Janik used three hydrophones (underwater microphones) to eavesdrop on dolphins swimming in the Moray Firth off the northeast coast of Scotland.

At an early age each dolphin adopts a personalized call--a unique whistle of rising and falling tones that emanates from nasal sacs below the blowhole (the single nostril atop a dolphin's head). Janik's computer analysis of 1,700 adult dolphin whistles reveals that dolphins separated by a distance of up to 599 meters (.36 miles) routinely imitate one another's signature calls--often repeating the exact whistle tones within seconds. Guess that's one way to find a pal in a giant pool!

How did Janik know he was hearing a true dolphin exchange? To count as a vocal match, each response had to occur within three seconds of the original call and originate from at least several meters away. Since sound moves faster under water (about 3,600 miles per hour) than dolphins can swim (18 to 25 mph), these rapid-fire exchanges must come from two individual dolphins, Janik concludes. "If you can copy another animal's signal, you can address that animal." Now if only he can figure out what dolphins gab about underwater!

* For more on how dolphins and other animals use sound for communication and navigation, see "Listening to Bats" on page 8.