Unexpected results of global warming #102. Polar bears are turning to cannibalism.

Polar bears in the southern Beaufort Sea may be turning to cannibalism in response to nutritional stresses related to longer ice-free seasons, American and Canadian scientists have concluded.

The study reviewed three examples of predation from January to April 2004 by polar bears above Alaska and western Canada, including the first ever reported killing of a female in a den shortly after it gave birth to cubs.

Polar bears feed primarily on ringed seals and use sea ice for feeding, mating and maternity denning.

Polar bears kill other bears for population regulation, dominance and reproductive advantage, the paper said. The most common might be the killing of cubs by a male polar bear to interrupt a female's lactation cycle, said principal author Steven Amstrup of the U.S. Geological Survey Alaska Science Center.

Killing for food seems to be less common, he said Monday.

"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," the scientists said.

Our environmental footprint is crushing the creatures that share our planet beneath it.