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Polar Bear Cubs Face Death As Arctic Ice Melts

July 20, 2011

As their icy Arctic habitat melts, polar bear mothers and their cubs are forced to swim long distances, which expose the cubs to higher mortality rates than cubs who do not have to swim as far, a study shows.

“Climate change is pulling the sea ice out from under polar bears’ feet, forcing some to swim longer distances to find food and habitat,” co-author of the study, Geoff York of World Wildlife Fund (WWF), told Reuters.

Polar bears are not naturally aquatic creatures. They rely on ice or land to hunt, feed and give birth, reports Reuters.

Previous studies found that individual animals have had to swim hundreds of miles to reach ice platforms or land, but this is the first to show how these long swims expose polar bear cubs to greater risks.

According to York, the current study is the first time these long swims have been quantitatively measured.

Researchers used satellites to track 68 polar bear females equipped with GPS collars over a six year span, from 2004 to 2009. Data was gathered to find occasions when these bears swam for more than 30 miles at a time.

Over those six years, there were 50 long-distance swims involving 20 bears, ranging up to 426 miles in distance, and with duration of about 12.7 days, according to the study presented at the International Bear Association Conference in Ottawa, Canada this week.

At the start of the study when the bears were equipped with the GPS collars, 11 of the bears that swam long distances had young cubs. Five of the polar bear mothers lost their babies during the long swim, which represents a 45% mortality rate, report the study.

For cubs that didn’t have to swim long distances with their mothers, the mortality rate was 18%.

“They can’t close off their nasal passages in rough waters,” York said in a telephone interview with Reuters. “So for old bears or young bears alike, if they’re out in open water and a storm hits, they’re going to have a tough time surviving.”

Steve Amstrup, a former scientist at the U.S. Geological Survey and current chief scientist at Polar Bear International, told Reuters, “Young bears don’t have very much fat and therefore they aren’t very well insulated and cannot cope with being in cold water for very long.”

Since they are leaner than their parents, Amstrup says that the cubs “aren’t as buoyant (as adult polar bears) so in rough water they’ll have more difficulty keeping their heads above water.”

Under the Endangered Species Act of the Bush administration in 2008, polar bears were listed as a threatened species. Reuter reports that the decision still holds true after being challenged last month, and Canada has listed polar bears as a species at risk this month.

The accumulation of greenhouse gases in the atmosphere has the Arctic warming up faster than lower latitudes, reports Reuters. In addition, the melting of sea ice in summer is accelerating the warming effect.

“Unless we take action to curb climate change and transition to low-carbon energy sources like renewable energy, we will consign our planet to a very perilous path,” York said.

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Polar Bear Cubs Face Death As Arctic Ice Melts


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