Polar bears’ swim a gloomy sign

Nine polar bears were observed in one day swimming in open ocean off Alaska’s northwest coast, an increase from previous surveys that may indicate warming conditions are forcing bears to make riskier long-distance swims to stable sea ice or land.

The bears were spotted in the Chukchi Sea on a flight Saturday by a federal marine contractor, Science Applications International Corp.

Observers were looking for whales but also recorded walrus and polar bears, said project director Janet Clark. Many were swimming north and ranged from 15 to 65 miles offshore, she said.

Interior Secretary Dirk Kempthorne in May declared polar bears a threatened species because of a loss of summer sea ice and because of forecasts that the trend will continue.

Polar bears spend most of their lives on sea ice, which they use as a platform to hunt their primary prey, ringed seals. Conservation groups fear that one consequence of less ice will be more energy-sapping long-distance swims by polar bears trying to reach feeding, mating or denning areas.

Steven Amstrup, senior polar bear scientist for the U.S. Geological Survey in Anchorage, said the bears could have been on a patch of ice that broke up northwest of Alaska’s coast.

“The bears that had been on that last bit of ice that remained over shallow shelf waters are now swimming either toward land or toward the rest of the sea ice, which is a considerable distance north,” he said in an e-mail response to questions.

It probably is not a big deal for a polar bear in good condition to swim 10 or 15 miles, Amstrup said, but swims of 50 to 100 miles could be exhausting.

“We have some observations of bears swimming in to shore when the sea ice was not visible on the horizon,” he said. “In some of these cases, the bears arrive so spent energetically that they literally don’t move for a couple days after hitting shore.”

Observers have no indication of the fate of the nine polar bears.