ANCHORAGE (AP) -- Scientists say gray whales are no longer dying by the hundreds along their migratory path from Alaska to Mexico.
But no one knows why.
When the final tally is complete, biologists expect to find that no more than 30 whales died this year. That is more in line with normal fatality figures and a steep decline from the previous two years, when between 270 and 300 dead whales turned up each year.
The high number of whale deaths had alarmed scientists, who thought the die-off might continue indefinitely. Then this summer, gray whales stopping dying in massive numbers.
The whales appear to be doing better all along their migratory path, not just in isolated areas. In Alaska this summer, biologists found just five dead gray whales, compared to 59 in the summer of 2000 and 73 in 1999, according to Kaya Brix, a biologist with the National Marine Fisheries Service in Juneau.
Oregon, Washington and California noted similar turnarounds. The official numbers are not in yet for Mexico, but biologists said fatalities there are also significantly down.
The die-offs only occurred within the gray whale population and did not affect other whales. Gray whale birth numbers also dropped from a high of 1,520 in 1997 to just a few hundred calves in 2000. Biologists said they are curious to see what happens this winter when the calves are born. Brix said the whales will leave Alaska soon for Mexico.
The reasons for the sudden increase in whale deaths and the current reversal of that trend are unclear, said Sue Moore, a program leader at the National Marine Mammal Laboratory in Seattle. ''It could have been starvation. It could have been disease. It's hard to nail down the cause.''
But there are several theories.
One is that the gray whale population might have grown beyond what its habitat and food supply could support. Another possibility is that food availability has declined due to climatic changes in the Bering and Chukchi seas.
Or both could have happened at the same time.
Another theory is that water conditions might have changed because of a naturally occurring biotoxin bloom like a red tide, which occur more often in warmer waters.
Biologists said they rarely got to the whale carcasses quickly enough to determine the cause of death. But they often noticed that the whales appeared to be thin.
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