Dolphins May Eavesdrop on Each Other, Study Suggests

Anna Petherick
for National Geographic News
January 18, 2006

Synchronized swimming in tight formations might help wild dolphins listen in on one another's mapping and foraging, according to a recent study.

Thomas Götz, a marine biologist at the University of Tübingen in Germany, reached that conclusion after analyzing the sounds made by dolphins swimming near the island of Gomera in the Canary Islands (see map).

By dragging a recording device behind a boat, Götz captured the echolocation signals of several small groups of rough-toothed dolphins (Steno bredanensis).

Like all dolphins, these marine mammals gather information about their environment by emitting high-pitched sounds, or clicks, and analyzing the returning echoes.

Götz's recodrings showed that when the dolphins swam in loose, scattered formations, several individuals produced echolocation signals.

But 80 percent of the samples from groups moving in close, synchronous clusters contained the clicks of just one animal.

"You can tell if there are two animals echolocating or if there's just one by comparing the sound spectrum and the interval pattern of different clicks in a recording sequence," he said.

The findings led Götz to suggest that wild dolphins can tune in on each other's signals and use the information to navigate as a group.

Language Barrier?

To make sense of others' echolocation, a dolphin would have to be able to link the returning echoes to the outgoing clicks.

Such a task would be much easier to perform if the eavesdropper stays close to the animal making the sound, Götz says.

"[The dolphins'] behavior almost looks like a military formation, because all the fins are in one line, and they go down and come up in exactly the same formation," he said.

Continued on Next Page >>




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