April 14, 2006

Study Shows Melting Ice a Danger to Walruses

By JoAnne Allen

WASHINGTON -- Arctic researchers who discovered a surprising number of abandoned baby walruses say melting sea ice may be the culprit, according to a study in the April issue of Aquatic Mammals.

During an icebreaker cruise in the Canada Basin two years ago, researchers measured a unusually warm mass of water -- as high as 44 degrees F (7 C) -- moving into the area from the Bering Sea to the south. This warm water may have rapidly melted seasonal sea ice over the shallow continental shelf north of Alaska, the study said.

They also found nine lone and possibly abandoned walrus calves in the area, an "unprecedented number" for walruses since mothers tend to stay with their calves for two years.

"We were on a station for 24 hours, and the calves would be swimming around us, crying. We couldn't rescue them," said team member Carin Ashjian, a biologist at Woods Hole Oceanographic Institution.

Sea ice offers foraging walruses a place to rest. Mothers leave their calves on the ice while they dive to feed on animals on the sea floor such as crabs and clams.

But rising ocean temperatures may be forcing the walrus mothers to abandon their young as they follow the rapidly retreating ice edge north to colder waters, the study said.

Without their mothers, the calves likely drown or starve, according to the research team.

"The young can't forage for themselves," Ashjian said in a statement. "They don't know how to eat."

Sightings of solo walrus calves far from shore have not been reported before and suggest increased polar warming may take a toll on the walrus population, the study said.

"If walruses and other ice-associated marine mammals cannot adapt to caring for their young in shallow waters without sea ice available as a resting platform between dives to the sea floor, a significant population decline of this species could occur," the researchers concluded.

Funded by the National Science Foundation, the study investigated the impact of global climate change on the oceanic ecosystem over the continental shelf of Alaska.