7/21/2011 3:19:05 PM

Long Distance Swims Take Toll on Polar Bear Cubs

Polar bear in open water

As polar bears are forced to embark on longer and longer swims to reach sea ice, more polar bear cubs are dying, a new study shows. On one swim, a mother bear swam for nine days straight and 426 miles (687 kilometers)—the distance from Washington, D.C. to Boston. In the process, she lost 22% of her body weight and her cub. PBI Chief Scientist Steve Amstrup, a co-author of the study, says the long swims are having a negative impact on cub survival.

"We're pretty sure that these animals didn't have to do these long swims before, because 687-kilometer stretches of open water didn't occur very often in the evolutionary history of the polar bear," he said.

The scientists collared 68 female polar bears from 2004 to 2009. They tracked their time at sea and correlated this with cub survival rates.

Five of the 11 mothers that had cubs before they began their lengthy swims lost their young by the time the researchers observed them again on land, according to the research, presented July 19, 2011, at the International Bear Association Conference in Ottawa, Canada.

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