Up to 200 dead walruses have been spotted on the shore of Chukchi Sea on Alaska's northwest coast.
Federal wildlife researchers from the U.S. Geological Survey on their way to a walrus tagging project spotted 100 to 200 carcasses near Icy Cape about 140 miles southwest of Barrow.
They report the dead walruses appeared to be mostly new calves or yearlings. However, neither the age of the dead walruses nor the cause of death is known, said Bruce Woods, spokesman for the U.S. Fish and Wildlife Service.
"It's just too early to say until we can get someone on the ground," Woods said.
About 3,500 walruses were reported last week at the Icy Cape haulout site, where walruses rest from feeding forays.
Young animals can be crushed in stampedes when a herd is startled by a polar bear, human hunters or even a low-flying airplane.
This is the second time in three years that walruses have congregated in large numbers on the Alaska shore rather than the edge of the sea ice, which moves north in the summer as temperatures rise and south in the fall as temperatures cool.
Walrus cannot swim indefinitely and historically have used sea ice as a platform for diving in the Bering and Chukchi seas for clams and other food on the ocean floor.
In recent years, however, sea ice has receded far beyond the outer continental shelf, forcing walruses to choose between riding the ice over waters too deep to reach clams or onto shore. New research Thursday showed the ice cap this summer was slightly larger than in 2007 or 2008. But scientists with the National Snow and Ice Data Center, which released that information, said a slower melt-off of sea ice has occurred in given years before without changing the strong downward trend of recent decades.
USGS researchers left this week to begin a tagging project using satellite transmitters to study foraging habits of walruses gathered on shore. Researchers fear animals congregating on shore instead of the sea ice edge could eventually exhaust food within swimming range, leading to a crash in the population.
On a flight along the coast Monday, the USGS researchers spotted the dead animals. They did not have a chance to land.
Veterinarians working for the U.S. Fish and Wildlife Service will try to reach the site to learn what caused the die-off, said Joel Garlich-Miller, a walrus expert for the agency.
The agency also hopes to fly the coast to see if deaths occurred at other sites where walruses have gathered.
"The weather, I must say, has been very uncooperative," he said. "A lot of airplanes are stuck on the ground. Information is coming to us very slowly."
Researchers and veterinarians will have to approach the site cautiously to avoid causing a stampede themselves, Garlich-Miller said.
The nearest Inupiat coastal villages are 50 miles away -- Point Lay to the southwest, and Wainwright to the northeast.
Environmental groups calling for measures to slow greenhouse gas emissions say walruses on shore are evidence that global warming is altering the Arctic and forcing major changes in wildlife behavior.
The Center for Biological Diversity has petitioned the Fish and Wildlife Service to list walruses as a threatened or endangered species because of the threat from sea ice loss, and the agency has opened a 60-day public comment period. Retreating sea ice might have taken away some of the platforms walrus use to hunt and rest, pushing to walrus to shore.
Shaye Wolf, spokeswoman for the Center for Biological Diversity, said the walrus deaths were alarming.
"It provides another indicator that climate change is taking a brutal toll on the Arctic," she said.
Walruses for years came ashore intermittently in Alaska during their fall southward migration but not so early and not in such numbers.
Herds were in the tens of thousands at some locations on the Russian side of the Chukchi Sea. Russian biologists in 2007 reported 3,000 to 4,000 walruses died out of a population of perhaps 200,000, mostly young animals crushed in stampedes.