Polar bear cubs' ranks declining off Alaska, U.S. reports

ANCHORAGE — Far fewer polar bear cubs are surviving off Alaska's northern coast, a federal government report released Wednesday has concluded.

The study of polar bears in the south Beaufort Sea, which spans the northern coasts of Alaska and western Canada, also found that adult males weigh less and have smaller skulls than those captured and measured two decades ago.

A decline in sea ice is a likely reason for fewer surviving cubs and smaller male adults, one of the three researchers said.

"We can't say unequivocally that sea ice is the only thing involved," said Steven Amstrup of the U.S. Geological Survey. "However, the trends we observed are consistent with changes in nutritional status that are likely to be associated with declines in sea ice."

The population of polar bears in western Hudson Bay, Canada, dropped 22 percent in 17 years from 1,194 in 1987 to 935 in 2004.

The report estimates the Beaufort Sea polar bear population at 1,526, down from a previous estimate of 1,800 bears. The report compared data on cubs collected from 1990 through last spring to studies from 1967-89.

For polar bears measured during autumn months, the number of surviving cubs born that spring declined from a mean of 61 per 100 females to a mean of 25 per 100 females.