Number Of Pregnant Polar Bears Denning On Shore Nearly Doubles Since 1994 - ADN

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More pregnant polar bears in Alaska are digging snow dens on land instead of sea ice, according to a federal study, and researchers say deteriorating sea ice due to climate warming is the likely reason. From 1985 to 1994, 62 percent of the female polar bears studied dug dens in snow on sea ice. From 1998 to 2004, just 37 percent gave birth on sea ice. The rest instead dug snow dens on land, according to the study by three U.S. Geological Survey researchers.

Bears that continued to den on ice moved east in the Beaufort Sea off Alaska's northern coast, away from ice that was thinner or unstable. "We hypothesized that the sea ice changes may have reduced the availability or degraded the quality of offshore denning habits and altered the spatial distribution of denning," said wildlife biologist Anthony Fischbach, lead author of the study. "In recent years, Arctic pack ice has formed progressively later, melted earlier, and lost much of its older and thicker multiyear component."

The study makes no predictions of harm in the short term but suggests the Beaufort Sea bear population could be harmed if warming continues. Though bears are powerful swimmers, at some point they might face daunting distances of open water to reach denning habitat on shore.

"If Arctic sea ice continues to decline, we predict that the proportion of coastal denning will continue to increase until the autumn ice conditions prevent pregnant bears foraging offshore from reaching the coast in advance of denning," Fischbach said.

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