Ice melt strands 10,000 walruses
The marine mammals, which usually spend their time resting on sea ice, are increasingly forced to haul out on land
NationalGeographic.com, Oct. 2, 2013
An estimated ten thousand Pacific walruses have huddled together on a remote island in the Chukchi Sea, an unusual phenomenon that's due to a lack of sea ice, experts say.
The giant marine mammal is known to "haul out"—literally haul its body onto ice or land to rest or warm up—on various places along Alaska's coast.
But with the Arctic warming up and melting much of its floating ice, there are limited areas for the walruses to gather. This forces them to cluster on land in huge aggregations rarely before seen.
In 2011, 30,000 walruses hauled out along a stretch of beach less than a mile long, according to the National Oceanic and Atmospheric Administration, which took aerial pictures of the most recent walrus gathering.
Scientists have noted that such large terrestrial haulouts have increased in the past five years, said Pam Tuome, senior veterinarian at the Alaska SeaLife Center in Seward.
That mirrors the effect of warming temperatures in the Arctic, which is in the throes of a "long-term, downward trend" in sea ice cover, according to the National Snow and Ice Data Center.
In 2013, the Arctic experienced its sixth lowest minimum extent, or the period when sea ice cover is at its smallest.
The walrus haulouts are "another one of the symptoms of the changes that are occurring in the Arctic Ocean," Tuome said, "that are having somewhat unexpected or cascading effects."
On Thin Ice
The Pacific walrus as a species is suffering due to its shrinking habitat—the animal's numbers are declining, and it may get protection under the U.S. Endangered Species Act, Tuome said.
Meanwhile, the large haulouts are putting individual animals at risk. For one, if something like an airplane flying overhead spooks one of the mammals, it may spark a stampede into the water. During their panic, the heavy animals—which can weigh up to 1.5 tons (1.4 metric tons)—may trample other walruses to death, especially young ones, she said.
"It's like yelling fire at a movie theater," she said.
In addition, so many animals in such close quarters could increase the likelihood of a disease outbreak. In 2011 a mysterious, fatal disease swept through a population of ringed seals in Alaska that may also have killed some walruses in another location, she noted.
The disease may have spread from one population of marine mammal to another—for instance, ringed seals in Russia—and they weren't mixed together in a dense aggregation. A disease outbreak in a crowded haulout could be even deadlier.