Whale Killer.(sonar)

Visitors to beach resorts on Spain's Canary Islands were greeted to an ugly sight last September: 14 beaked whales washed ashore and lay dying on the sands. It wasn't the first time this had happened. Since 1991, environmentalists have been accusing navy fleets the world over of killing marine life with their powerful sonars. Strandings in the Canaries, as well as in Greece in 1996, the Bahamas in 2000 and last May off Puget Sound, all coincided with sonar tests. Even the U.S. Navy has acknowledged that sonar can put marine life at risk.

Nobody, though, has been able to explain why sonar is apparently so destructive. Last September Antonio Rodriguez, a scientist at the University of Las Palmas in Gran Canaria, performed necropsies on the Canary whales. His conclusions, published last week in the journal Nature, have shocked biologists and created a mini controversy. Rodriguez and his colleagues found that the whales died of the "bends"- -the same decompression sickness that strikes divers who surface too quickly.

Here's what scientists think happens. When a navy vessel uses sonar, it sends out powerful sound waves through the water and waits for the echo to return. When a beaked whale is hit by the sound waves, it gets disoriented and flees to the surface, like a panicked diver, often from 1,000 meters deep. The effect: gas bubbles appear in the ...