Alaskan Polar Bears Threatened…By Too Much Spring Ice

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polar-bearsFive meters of ice– about 16 feet thick – is threatening the survival of polar bears in the Southern Beaufort Sea region along Alaska’s Arctic coast, according to Dr. Susan J. Crockford, an evolutionary biologist in British Columbia who has studied polar bears for most of her 35-year career.

That’s because the thick ice ridges could prevent ringed seals, the bears’ major prey, from creating breathing holes they need to survive in the frigid waters, Crockford told CNSNews.com.

“Prompted by reports of the heaviest sea ice conditions on the East Coast ‘in decades’ and news that ice on the Great Lakes is, for mid-April, the worst it’s been since records began, I took a close look at the ice thickness charts for the Arctic,” Crockford noted in her Polar Bear Science blog on April 18th.

“Sea ice charts aren’t a guarantee that this heavy spring ice phenomenon is developing in the Beaufort, but they could be a warning,” she wrote, noting that they “don’t bode well” for the Beaufort bears.

“What happens is that really thick ice moves in because currents and winds from Greenland and the Canadian islands push it against the shore,” Crockford told CNSNews.com.

“The male seals arrive in the area in early spring to set up breeding territories. They drill a hole through the ice to maintain breathing holes close to the shore. But there’s a limit. They can drill through two meters (about seven feet) of ice. But too much beyond that and they’re in trouble.”

“The reason that’s important is that seals mate right after the pups, who are born in April, are weaned. So the male seal wants to be there, but he has to have breathing holes. If the ice is too thick, he has to move off someplace else,” she explained.

But this is the same time that female polar bears are just emerging with their newborn cubs from maternity dens either on or near the shore.

“When those bears come out of their dens in the spring, they need to find seals right away because they will have gone six months without eating,” Crockford said. “If there are no seals, they have to go further out, where there’s thinner ice.”

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