A captive bottlenose dolphin develops its own distinctive whistle during the first few months of life. The animals can easily reproduce each other's signatures, and they often do this so-called whistle-matching when out of sight from one another. But no one knew whether whistle-matching was something dolphins did only in captivity.
To eavesdrop on dolphins in the wild, behavioral ecologist Vincent Janik of the Woods Hole Oceanographic Institute in Massachusetts analyzed recordings from an array of underwater microphones in Scotland's Moray Firth. And whistle-match the dolphins did. Because Janik recorded from many points in the firth, he could pinpoint the source of the whistles. If a dolphin sang a matching whistle within 3 seconds of another's call, Janik counted that as a response. If the whistles were far enough away that one dolphin couldn't have swum from one site to another in the time between the whistles, Janik knew they were made by two different dolphins. On average, given the interactions that fit the definition, dolphins mimicked each other from about 179 meters away, Janik reports in the 25 August issue of Science.
That the wild dolphins whistle-match, Janik says, "is a clear indication that they address each other individually." Christopher Clark, a bioacoustician at Cornell University in Ithaca, New York, agrees: "This is some of the first information about how dolphins are communicating in natural, wild populations." And it may not be just simple call and response, he adds. "I don't think dolphins just go around saying, 'peanut butter,' 'peanut butter;' 'rhubarb,' 'rhubarb;' 'jelly,' 'jelly.'" Instead, Clark considers whistle-matching a prelude to more complicated conversation.