Ice melt causing death of polar bears, say experts

November 24th, 2007 - 1:59 pm ICT by admin  

Washington, Nov.24 (ANI): Biologists have predicted that polar bears will struggle to survive as summer comes sooner to the Arctic.
Less time spent on icy hunting platforms means the bears are slimming down before winter sets in, they said.
A study of the polar bear population in Canada’s Hudson Bay revealed that these animals rely on ice shelves as hunting grounds before winter sets in.
Anecdotal reports in 2005 say bears were found swimming far out at sea; a few were found floating dead, presumably drowned.
So far no evidence has directly linked the trend of melting sea ice associated with climate change to bear deaths.
Now, looking at 20 years of data from bears captured along the coast of Hudson Bay, a team of scientists from the United States and Canada has found that fewer of the youngest and oldest bears survived in years when the ice broke early.
“Survivorship has dropped in the cubs, sub-adults and very old animals and is directly related to the date of break-up,” said Ian Stirling, a biologist with the Canadian Wildlife Service in Edmonton, Alberta, and an author on the report.
Although the timing of ice break-up varies from year to year, the trend has been towards more days of open water. Historically, ice has filled Hudson Bay for eight months each year. Now the ice is clearing nearly three weeks earlier than it did 30 years ago.
Since 1984, wildlife managers have captured some bears that spend their summers on the western shore of the bay, releasing them with ear tags and lip tattoos.
The marks allow biologists to recognize individual bears, track their fate and estimate how many survive each winter.
It was found that over a period of two decades, this population has declined by more than 20 percent.
According to Eric Regehr of the US Geological Survey in Anchorage, Alaska, adult bears in their prime those between 5 and 19 years old seem unaffected by the changes in ice cover. But cubs, sub-adults and old bears captured in years when the ice broke the earliest weren’t spotted again.
Polar bears fast through their summer by stocking up on weanling ring seals. In early spring, the bears feast on unwary seal pups until the ice breaks up, storing up much of the energy they’ll need to get by. In years when the ice breaks early, the less-able hunters catch fewer seals than they need.
It seems the hunger is leading to deaths. “It’s scary,” says Martyn Obbard, who keeps tabs on polar bears at the southern edge of Hudson Bay for the Ontario Ministry of Natural Resources in Peterborough, but did not participate in this study.
That’s the main reason behind the population decline, Stirling and colleagues report in the November issue of the Journal of Wildlife Management 1.
The United States is considering listing polar bears as threatened under the Endangered Species Act; a decision on this is expected early next year. (ANI)

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