Fewer Gray Whales Migrating to Warmth of Mexico

The number of gray whales making a yearly migration from the icy North Pacific to breed in Mexico’s warm lagoons has dropped this year, possibly because of changing weather patterns, scientists say.

Whale food shortages near Canada and Alaska mean that some of the thousands of whales that make the 5,000-mile journey have departed late or even stayed behind this year, researcher William M. Megill said.

Other researchers said Thursday that varying temperatures in the Bering Sea could be changing migration patterns.

Megill, a lecturer at the University of Bath in Britain, said the whales might be undernourished and many could die on their return trip north later in the year.

In British Columbia, “there was nothing to eat until well into September,” he said. “I wouldn’t be surprised to see carcasses up and down the coast because they didn’t have enough food.”

According to Megill’s latest census, about 90 whales had made it to San Ignacio on the Baja Peninsula by February, down by about half compared with February 2005.

The whales arrive in the lagoons from December to February and start their return journey in April.

Studies of feeding grounds in the northern Bering Sea between Alaska and Siberia show an abrupt rise in temperatures since 2000 and a decline in the worm and shrimp colonies that nourish the whales.

The principal oceanographer at the University of Washington, Sue Moore, said the whales appeared to be adapting to changing environmental conditions in the north by feeding in new areas and heading south later.

“I do not think they are suffering starvation at this point -- gray whales are very resilient and can feed on a variety of prey all along their migration route,” she said.

The whales were removed from the U.S. endangered species list in 1994 for the region including the Bering Sea.

They can grow 50 feet long and weigh up to 40 tons.