Ten polar bears, an unusually large number, were seen swimming in open water off the northern coast of Alaska recently, some heading for shore and some heading toward the retreating ice in the Chukchi Sea. Susanne Miller, the biologist in charge of the polar bear project for the U.S. Fish and Wildlife Service, said 8 of the 10 bears spotted in the aerial survey had been within 15 miles of shore. One was 35 miles from shore and another one 50, but neither was more than 20 miles from the nearest arctic ice. Bear sightings in open water were infrequent until about 2004, Ms. Miller said, but rising temperatures have melted much of the ice platform on which they live and hunt for seals. In May, the United States put the polar bear population under the protection of the Endangered Species Act, primarily because of the loss of its habitat. “It's not unusual for bears to be swimming,” Ms. Miller said, “but depending on their condition and how much time they're spending in the water, this could be problematic. It's going to cost them more energy to swim through water than travel on land.” In addition, more bears have been sighted on land in July and August than in the past - a possible result of the retreating of the sea ice. But “it's not a clear-cut situation,” Ms. Miller said, noting that most bears captured this spring on the ice in the Beaufort and Chukchi Seas have been in good condition. So have several bears caught on land. Biologists are concerned that bears, particularly pregnant ones, will exhaust themselves on long open-water swims. “There were some years when some bears may have had to swim as far as 100 miles,” Steven C. Amstrup, the senior polar bear scientist with the United States Geological Survey in Anchorage, wrote in an e-mail message. “Now the ice is much farther offshore, more consistently and for longer. So the possibility of long distances between land and sea ice is much greater.”
