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 whale’s organs, damaging tissue.
Not everybody is buying this thesis. For one thing, little is known about beaked whales–they’ve never been kept captive. “In order to say a situation is pathological or abnormal, you have to have pretty good idea of what is normal,” says James Mead, a whale expert at the Smithsonian National Museum of Natural History. Other scientists think that the tissue damage may have occurred when the whales were knocked around in the shallows when they beached. “It would be premature to say that we have one cause that explains all the traumas that have been reported,” says biologist Darlene Ketten at Woods Hole Oceanographic Institution in Massachusetts.
While the scientific debate rages, environmentalists seem to be winning in the courts. Last year the Natural Resources Defense Council sued to prevent the U.S. Navy from fully deploying a new low-frequency active sonar. This week, the two sides were expected to announce an agreement, as ordered by a federal judge, to restrict testing to an area that won’t result in harm to wildlife. But it’s not clear to what degree the regulation of sonar will reduce strandings, most of which are due to natural causes. The creatures of the deep, it seems, continue to baffle policymakers and marine biologist alike.
