In October 1986 a beach in Reykjavik, Iceland, was the scene of an apparent massacre: 148 pilot whales lay dead on the shore. They died because in following their leader, or pilot, they swam onto the beach could or would not escape back into the sea.
What in mysterious about this destructive behavior is that it has often happened before. In September 1975 more than 200 pilot whales were found on the beach at Bonavista Bay, Newfoundland. In January 1983, 87 killer whales stranded themselves on a beach in eastern Victoria, Australia. And from 1963 to 1980 at least 169 whales of different species stranded themselves on the coast of southern Africa alone.
The most popular explanation among laymen is that the whales are committing suicide intentionally: when attempts have been made to head them off, or return them to deeper water, they still struggle to suicide.