Polar bear’s swim breaks long-distance record
Published 12:01 am Monday, February 7, 2011
ANCHORAGE, Alaska — On a summer day two years ago, polar bear 20741 decided to leave a remote Beaufort Sea beach. The 7-year-old, nearly 500-pound bear walked north into frigid Arctic Ocean water east of Barrow in search of sea ice.
She swam. And swam. And swam.
She covered 426 miles — farther than researchers have recorded a polar bear swimming without a break. After nine days, she reached pack ice and walked or swam another 1,118 miles, eventually looping south back to Alaska soil a few miles from the Canada border.
Researchers recaptured her after two months and learned her journey had come at an extraordinary cost. Her body mass was reduced 22 percent and her internal temperature had dropped. Her yearling cub was gone, likely drowned.
A paper on the bear, published last month in the journal Polar Biology by U.S. Geological Survey and University of Wyoming researchers, concludes that polar bears can respond to a changing Arctic, said USGS research zoologist George Durner, but that there are limits to that ability as sea ice diminishes.
“If we continue to see declines in the extant of Arctic sea ice, it’s hard to imagine that a bear would be capable of swimming much further than that,” Durner said. “I’m not saying that’s the limit, but it just boggles my mind.”
Diminished Arctic sea ice is at the heart of the debate on whether ice-dependent marine mammals should be listed as endangered species, with all the ramifications that accompany that decision, including debate on drilling for offshore Arctic oil.
Polar bears use sea ice for hunting their main prey, ringed seals. Their most important feeding time is mid-spring to early summer. The National Snow and Ice Data Center has tracked a steady decline in sea ice. Some models see summer sea ice disappearing by 2030.
The summer low for sea ice, measured each September, averaged 2.7 million square miles from 1979 to 2000.
Sea ice has fallen far below that in recent years, including a record low 1.65 million square miles in summer 2007. The 2010 low was 1.84 million square miles.
