Dolphins 'Use Sonic Booms To Kill Prey'
http://www.stuff.co.nz/inl/index/0,1008,623770a11,FF.html
2-2-01

Dolphins use sound booms and clicks to stun and kill their prey, according to scientists who say they have the first video recordings of dolphins attacking fish with the sonic weapon.

Stunning clicks: dolphins employ sonic weaponry to catch fish For more than 20 years, scientists have speculated that the friendly clicks dolphins make could actually be weapons, but no one had ever seen them in use, nor demonstrated that the sounds could kill fish. Two scientists in Hawaii and Florida now say they have evidence on videotape, New Scientist reports today.

In one study Ken Marten of Earthtrust, a conservation group in Hawaii, recorded a dolphin emitting a sequence of low-frequency "bangs" while pursuing a fish. Dr Marten noticed that dolphins near herring shoals emitted low bangs at the frequency the fish hear best. He suggested that the bangs were designed to damage the fish's hearing apparatus.

He said: "She was aiming right at him. Pow, pow, pow." Denise Herzing, of Florida Atlantic University, recorded wild Atlantic spotted dolphins emitting a medium-frequency buzz while searching for prey on the seabed. She said buried eels jumped out of the sand, and either stopped or moved sluggishly as if stunned, giving the dolphin time to catch them.

Other researchers remained sceptical. Pete Tyack, of the Woods Hole Oceanographic Institution near Boston, thought the dolphins might be using sound to locate their prey, not to stun it. He said: "The underwater world is unfamiliar to us and you have to be careful with interpretations."