It was a summertime saga that gripped the nation, for its poignancy and the troubling mystery it posed. Just as the sun rose over the languid beaches in the crook of the elbow-shaped playland of Cape Cod, early-morning strollers were astonished by surprise visitors. Lying helplessly in shallows near the town of Dennis, Mass., like so many black boulders, were 55 grounded pilot whales. Although nine of the whales soon died or had to be put down (with lethal injections of sodium pentothal), rescuers managed to push 46 others out to sea.
But this feel-good story quickly turned bad. During the night, the whales, all dutifully tagged in the morning, beached themselves again, in a salt marsh 25 miles away. By the time good seamaritans got to them, six of the whales were dead and nine others had such weak heartbeats that scientists knew they would not make it. Even those that could be refloated soon returned to shore, oblivious to the frantically splashing rescuers trying to shoo them off. By evening, all the whales--mostly females, some of them pregnant--were dead.
With its shallow waters and shifting sands, Cape Cod has long been a graveyard for both man and whale, especially pilot whales. In this treacherous terrain, the whales' critical echolocation system--those telltale clicks whales depend on for everything from avoiding predators to finding a mate--can easily become confused. Yet even after years of studying these big-brained creatures, scientists admit that's only an informed guess and doesn't explain groundings elsewhere. "I could give you an unlimited number of scenarios," says veteran Smithsonian cetologist James Mead, "and because we know so little about whale biology, any of them is possible."
These possibilities include fatal illnesses, perhaps contracted from eating poisoned fish. Or startled reactions to the cacophony of a ship's engine. Or the sudden appearance of a predator. Some scientists have even linked whale groundings to magnetic anomalies that can play havoc with the internal compasses on which whales seem to depend for navigation. One scenario, however, has been pretty much dismissed in this case: disruption by underwater sonic booms from the powerful new U.S. Navy submarine-hunting sonar that recently inflicted fatal hearing damage on beaked whales in the Bahamas--and prompted an outcry from environmentalists when the Bush Administration allowed these exercises to continue. "Extremely unlikely," says Woods Hole Oceanographic Institution's Darlene Ketten, an expert on marine-mammal hearing who found hemorrhaging and other signs of trauma in the beaked whales and is now examining tissue from the grounded pilots.
What is known for certain is that pilot whales (which are actually large dolphins) are highly social creatures. They travel in pods that can be several hundred strong, usually led by a dominant male. If the leader loses his way while hunting a favorite food like squid, the rest of the pod will follow, even onto a beach. The closely knit whales will also converge on a calf that has accidentally grounded and is clicking and squeaking in anguish. In neither case, however, do scientists regard the whales' behavior as a suicide impulse. "That's old folklore," insists Joseph Geraci of the National Aquarium in Baltimore, Md., "and should be forgotten."