Walruses breed in the Bering Sea in the winter time. Calves are born in late April or early May.
In spring, when ice retreats, males generally remain in the Bering Sea. But females migrate north with their pups through the Bering Strait and traditionally stay with the ice edge in the Chukchi Sea.
Walruses feed on clams, snails and other bottom creatures. As the ice edge moves over the relatively shallow continental shelf, females can nurse their calves on ice and reach productive feeding areas as the ice edge moves north.
However, extreme ice retreats in recent years have put the ice edge far north of the continental shelf, over water that's too deep for the females to feed.
A maximum dive for a walrus to scour the sea bottom is about 630 feet and the Arctic Basin can be several thousand feet deep or more.
But this year the sea ice withdrew much further from shore than normal over the course of the summer. As a result, large numbers of females have used Alaska's Arctic coast for hauling out:
Thousands of walruses since late summer have congregated in haulouts on Alaska's northwest shore, a phenomenon likely connected to record low Arctic sea ice.
Joel Garlich-Miller, a walrus expert with the U.S. Fish and Wildlife Services in Anchorage, said Wednesday animals began showing up on shore in late July, a month earlier than usual. By August, several thousand animals far more than normal were bunched up in haulouts in a stretch of coastline from Barrow, America's northernmost community, to Cape Lisburne, about 300 miles to the southwest on the Chukchi Sea.
This could lead to increased mortality:
The agency's immediate concern is that groups of walruses congregated on land are susceptible to additional human contact, whether a low-flying airplane or a hunter's boat, that could can panic the group, setting off a deadly stampede to the water.
Juvenile survival rates may drop:
But having animals concentrated on land instead of the vast expanse of the Arctic ice pack also raises stress issues, said Chad Jay, a U.S. Geological Survey biologist.
Walruses on shore may be forced to swim farther to forage, expending more energy. Researchers would expect increased mortality to calves, Jay said, if they try to stay with their mothers during feeding rather than resting on a platform of sea ice over feeding grounds.
"You can imagine access to traditional foraging areas is diminished," Garlich-Miller said. "That is cause for concern."
We'll have to wait to find out what happened:
It may take until spring to determine if there are animal deaths associated with the Alaska haulouts, Garlich-Miller said.
Walruses are expected to remain on shore until they move south as the Chukchi Sea freezes in November. Information from flights will be limited by snow cover and the Alaska winter darkness.
"We may have to follow up this next spring to see what the final chapter of this was," Garlich-Miller said.