Each year at this time, thousands of gray whales in the Pacific swim north on their annual migration from warm, shallow lagoons off Mexico, where they breed and give birth, to their summertime feeding grounds in the chilly depths of Arctic seas. It is one of the most epic journeys in the animal kingdom, and something may be going wrong along the way.
Then again, the opposite could be true: The rash of deaths may be an encouraging sign of growth for the species, which in the past few decades has made a strong comeback from the brink of extinction. No one knows.
About two dozen gray whales, which as adults extend over 30 feet long and weigh as much as 40 tons, washed up over hundreds of miles of shoreline from Southern California to San Francisco Bay last month. The tally is higher than it was last year - midway through the migration season. By the end of the last migration season, 47 gray whales had been found dead on the California coast.
The rising number of whale deaths worries and puzzles many scientists. Last year's total was three times higher than the annual average for the past decade. And the total in 1998 was about double what the average had been.
"No one is pushing the panic button yet," said Joseph Cordaro, a biologist for the National Marine Fisheries Service in Long Beach, Calif. "But we have to find some definitive answers, because this is unusual."
The detective work is daunting. By the time they are found in the sand, whale carcasses usually are decomposing, which makes necropsies difficult. There also seems to be no clear pattern to the latest deaths. Gray whales are not being found dead in roughly the same spots along the coast, nor do most of them appear to be victims of man-made hazards such as fishing nets or boats. Biologists also say that many of the whales do not look extremely malnourished. Those being found are both young and old, male and female.
The lack of consistent clues is even prompting some biologists to wonder whether the deaths may be no cause for alarm. The rising number of beached whales, they say, may only be a natural side effect of their population boom.
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