...but its bad news for walruses: Sea ice retreat dooms walruses (Dan Joling, Anchorage Daily News, Feb 25, 2007):
...Walruses breed in the Bering Sea in the wintertime. Walrus 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 continue to be associated with the ice edge in the Chukchi Sea, Kelly said.
"Basically, this ice edge is typically lying over relatively shallow continental shelf waters," he said. "That's really important if you're a benthic feeder, if you feed on clams and snails and things that live down on the bottom, which walruses do. So by using this ice edge in the summer and fall, the females have access to food directly below them, but they can nurse their calves up on the ice. So they split their time between nursing their young on the ice and diving down to the bottom to provision themselves.
"What we've seen in recent years with these extreme ice retreats is that the ice is going north of the continental shelf and takes the nursing habitat over water that's really too deep for the females to feed.
A maximum dive for a walrus to scour the sea bottom with their broad, flat muzzles is about 630 feet. Ashjian and the other researchers saw the abandoned calves [The abandonment by mothers who were only able to feed themselves is described elsewhere in the article - Ben], nine in all at seven locations, in water that was about 3,000 feet deep.
Walruses will not thrive in climate warming simply by moving farther north, Kelly said.
"It's not just the amount of area," he said. "It's the relationship of the ice to another feature, in this case water depth, and hence, food."