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August 03, 2010

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“Crying” walrus pups may be orphaned thanks to global warming

April 16, 2006
Courtesy Woods Hole Oceanographic Institution
and World Science staff

Melting Arctic Ocean ice may be leaving walrus pups stranded, according to researchers.

A walrus pup alone in the Arctic Ocean, one of nine calves seen swimming far from shore and presumed to have died. (Photo by Carin Ashjian, Woods Hole Oceanographic Institution)

“We were on a station for 24 hours, and the calves would be swimming around us crying. We couldn’t rescue them,” said Carin Ashjian, a member of the research team studying the animals.

Most scientists believe widespread melting of polar ices is due to global warming, a gradual increase in the Earth’s temperature caused by human use of fossil fuels.

Last December, researchers claimed the melting may be pushing polar bears to suicidal swims and cannibalism.

Ashjian’s group reported seeing an unprecedented number of lone walrus calves. The melting may be forcing mothers to abandon them as the mothers follow the rapidly retreating ice edge north, according to the scientists.

Researchers aboard the U.S. Coast Guard icebreaker Healy reported seeing nine lone pups swimming in deep water far from shore during a cruise in the Canada Basin, two summers ago. The calves were likely to drown or starve, the scientists said. 

Lone walrus calves far from shore had not been described before, the researchers wrote in the April issue of the research journal Aquatic Mammals.

The strandings could cause “a significant population decline of this species,” the paper warned. The lead author is Lee W. Cooper, a biogeochemist at the University of Tennessee in Knoxville, Tenn.

Warmer oceans may have melted ice over a shallow continental shelf north of Alaska where walruses dive for clams and crabs, the researchers wrote. Walrus use the ice as a resting platform, and mothers leave the young there while they dive.

Pacific walrus, Odobenus rosmarus divergens, forage for food by diving as far as 200 meters (about 630 feet) to the seafloor.

“The young can’t forage for themselves,” said Ashjian, a biologist with the Woods Hole Oceanographic Institution at Woods Hole, Mass. “They don’t know how to eat,” and depend on their mothers’ milk for up to two years.

The researchers reported a mass of water as warm as 44° F (7° C) moving onto parts of the shelf from the Bering Sea to the south in 2004. This warm-water intrusion was more than six degrees higher than temperatures at the same time and place in 2002, they wrote.

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