Dolphins Whistle in Unison

Learning to whistle the same tune may help gangs of male bottlenose dolphins stake a claim on females. Researchers have long known that small groups of male dolphins form alliances to scare off rivals for the attentions of females. And they have recognized that individual dolphins appear to adopt a distinctive "signature" whistle by the time they are 6 months old. But studying how they communicate in the wild is tricky, as it can be impossible to pinpoint which animal in a swirling school is producing a particular whistle.

In the shallow inshore waters of Shark Bay, Western Australia, however, wild dolphins allow researchers to wade among them and record their calls. Behavioral ecologists Rachel Smolker of the University of Vermont, Burlington, and John Pepper of the University of Michigan, Ann Arbor, took advantage of these conditions in the late 1980s, listening in on the chatter of one three-dolphin alliance over a 4-year period. Now, after comparing almost 1700 whistles produced by the trio, they've found that over time, the members gave up their own whistles and converged on a new, shared signal.

Learning the common voice probably allows the gang to announce "that they represent a formidable competitive force," say the authors, whose study will appear in Ethology later this year. Bioacoustics expert Bill Evans of Texas A&M University in Galveston calls the discovery "interesting," as it means that dolphins are among the few types of vertebrates--the others being birds and humans--capable of learning new vocalizations throughout their lives.