Wednesday, June 14, 2006

Polar bears go cannibal as ice melts

In the competition for ever diminishing resources polar bears are turning to cannibalism as longer summers are melting the ice bridges to ringed seal colonies, their natural food source.

Observed Sea Ice 1979Observed Sea Ice 2005

Observed Sea Ice in Sep 1979 Versus 24 Years Later
Source: ACIA 2004:25.

Polar bears are predators, and they do kill each other for population regulation, dominance and reproductive advantage, but they are not known to kill each other for food. :::[SMH]

"During 24 years of research on polar bears in the southern Beaufort Sea region of northern Alaska and 34 years in northwestern Canada, we have not seen other incidents of polar bears stalking, killing, and eating other polar bears,"
Steven Amstrup
US Geological Survey Alaska Science Centre

A study documenting bears preying on each other for food has been published in Polar Biology.

Researchers in the northern spring of 2004 found more bears in the eastern portion of the Alaska Beaufort Sea to be in poorer condition than bears in areas to the west and north.

Researchers discovered the first kill in January 2004. A male bear had pounced on a den, killed a female and dragged it 75 metres away, where it ate part of the carcass.

Females are about half the size of males.

"In the face of the den's outer wall were deep impressions of where the predatory bear had pounded its forepaws to collapse the den roof, just as polar bears collapse the snow over ringed seal lairs," the paper said.

"From the tracks, it appeared that the predatory bear broke through the roof of the den, held the female in place while inflicting multiple bites to the head and neck. When the den collapsed, two cubs were buried, and suffocated, in the snow rubble."

In April 2004, while following bear footprints on sea ice near Herschel Island, Yukon Territory, scientists discovered the partially eaten carcass of an adult female.

Footprints indicated it had been with a cub.

The male did not follow the cub, indicating it had killed for food instead of breeding.

A few days later, Canadian researchers found the remains of a yearling that had been stalked and killed by a predatory bear, the scientists said.

The Centre for Biological Diversity petitioned the US federal government to list polar bears as threatened under the federal Endangered Species Act in February 2005. You can find out how it is going here: :::[]

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