ANCHORAGE, Alaska - Thousands of walrus have appeared on Alaska's northwest coast in what conservationists are calling a dramatic consequence of global warming melting the Arctic sea ice.
Alaska's walrus, especially breeding females, in summer and fall are usually found on the Arctic ice pack. But the lowest summer ice cap on record put sea ice far north of the outer continental shelf, the shallow, life-rich shelf of ocean bottom in the Bering and Chukchi seas.
Walrus feed on clams, snails and other bottom dwellers. Given the choice between an ice platform over water beyond their 190-metre diving range or gathering spots on shore, thousands of walrus picked Alaska's rocky beaches.
"It looks to me like animals are shifting their distribution to find prey," said Tim Ragen, executive director of the federal Marine Mammal Commission. "The big question is whether they will be able to find sufficient prey in areas where they are looking."
According to the National Snow and Ice Data Center at the University of Colorado at Boulder, September sea ice was 39 per cent below the long-term average from 1979 to 2000. Sea ice cover is in a downward spiral and may have passed the point of no return, with a possible ice-free Arctic Ocean by summer 2030, senior scientist Mark Serreze said.
Starting in July, several thousand walrus abandoned the ice pack for gathering spots known as haulouts between Barrow and Cape Lisburne, a remote, 480-kilometre stretch of Alaska coastline.
The immediate concern of new, massive walrus groups for the U.S. Fish and Wildlife Service is danger to the animals from stampedes. Panic caused by a low-flying airplane, a boat or an approaching polar bear can send a herd rushing to the sea. Young animals can be crushed by adults weighing 900 kilograms or more.
Longer term, biologists fear walrus will suffer nutritional stress if they are concentrated on shoreline rather than spread over thousands of kilometres of sea ice.
Walrus need either ice or land to rest. Unlike seals, they cannot swim indefinitely and must pause after foraging.
Historically, Ragen said, walrus have used the edge of the ice pack like a conveyor belt. As the ice edge melts and moves north in spring and summer, sea ice gives calves a platform on which to rest while females dive to feed.
There's no conveyor belt for walrus on shore.
"If they've got to travel farther, it's going to cost more energy. That's less energy that's available for other functions," Ragen said.
