Originally created 02/17/99

Seals rely on sight, not sound, to hunt



Marine biologists have gotten their most detailed peek at the mysterious underwater life of seals as they hunt their prey far below the Antarctic ice.

Randall W. Davis of Texas A&M University and colleagues from the University of California at Santa Cruz and the University of Texas mounted equipment on Weddell seals to record sounds, sights and other data as the animals swam below the sea ice of the McMurdo Sound in the Antarctic.

The 1,000-pound seals seldom used sound underwater, indicating that they do not use sonar to locate their prey, as had been thought, the researchers write in the Feb. 12 issue of Science. Instead, the seals appear to rely on their sight. Seals were seen tracking silhouettes of cod swimming near the ice, dimly illuminated by sunlight penetrating from above. The seals, which typically remain submerged for 20 minutes at a time, also blew bubbles into the subsurface ice to flush out fish hiding in the crevices.

"What captures the imagination of both scientists and non-scientists in this research is the ability to vicariously travel with these animals as they descend to great depths," said Davis.