Late freeze of sea ice threatens Hudson Bay bears
A male polar bear walks along the shore of Hudson Bay near Churchill, Man. on Monday Aug. 23, 2010. (THE CANADIAN PRESS/Sean Kilpatrick)
Published Wednesday, December 8, 2010 1:47PM EST
Scientists say polar bear moms and their cubs near Churchill in northern Manitoba are suffering the worst effects of a late freeze-up of sea ice on Hudson Bay.
The bears are just now setting out for the sea ice they use as a hunting platform for seals, said University of Alberta researcher Andrew Derocher.
That's weeks later than usual -- and comes on top of an early spring thaw that drove the bears off their hunting ground nearly a month sooner than usual.
"This year's been pretty challenging on the population," said Derocher from Inuvik, N.W.T. "They were early off the ice and now they're late getting on.
"Some of these bears have had a very long on-land period. A lot of the bears are just running out of steam."
Polar bears tend not to hunt during the summer, which they spend on the land. They can burn up to a kilogram of fat a day as they wait to return to the sea ice.
Adult males are big enough to make it through the extended fast. But this summer was tough on mother bears and cubs, Derocher said.
"If you're a mother that's nursing cubs, if you run out of energy you stop producing milk," he said. "Your cubs then have to rely on their own fat stores and because cubs have such low fat stores it eventually means they're going to die.
"One of the things that was observed this year is that in at least some family groups the mothers stopped nursing and the cubs died on land. We don't usually see that."
Derocher said that means fewer cubs that grow to adulthood, further stressing a population that's been in decline for years.
Churchill's bears are frequently visited by tour groups in the fall and operators have reported that the population this year looked good.
But Derocher said the bears that are suffering aren't likely to be nosing up to tundra buggies.
"The bears that are not doing very well typically hunker down and don't move very much," he said. "What we've seen was a lot of the bears were in poor condition."
The worldwide population of polar bears is estimated at between 20,000 and 25,000. Of the 19 populations around the globe, eight are considered to be declining, three are stable and one is increasing. There isn't enough known about the other seven to assess their status.
The population around Churchill is estimated at about 1,000 bears.