'Survival of the fattest' for polar bears

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LONDON, March 20 (UPI) -- Fat may be the best friend a polar bear can have, say researchers studying the animals struggling to cope with climate-induced changes to sea ice in Canada.

A study published in the British Ecological Society's Journal of Animal Ecology focused on polar bears in western Hudson Bay in Manitoba, where sea ice melts completely each summer and typically re-freezes from late November to early December.

The bears have adapted to the annual loss of sea ice by migrating onto land each summer, researchers say.

"This poses an interesting challenge for a species that has evolved as a highly efficient predator of ice-associated seals," Seth Cherry of the University of Alberta said.

"Because although polar bears are excellent swimmers compared with other bear species, they use the sea ice to travel, hunt, mate and rest."

Having to move to land with the loss of sea ice in the summer means the bears cannot hunt seals and must rely on fat reserves to see them through until the ice returns.

The longer bears spend on land, the longer they must go without energy-rich seals important to their survival, a problem likely to increase with climate change, researchers said.

"Climate-induced changes that cause sea ice to melt earlier, form later, or both, likely affect the overall health of polar bears in the area," Cherry said. "Ultimately, for polar bears, it's survival of the fattest."