Polar Bears

Up to three meters high and 1500+ pounds in weight, polar bears can still run at up to 40 mph short bursts.  Fierce predators who live mainly off seals, they can also manage a walrus for breakfast in a stomach with a capacity of 7150 pounds!   How are they adapted to survive in such inhospitable environments? Is man's contribution to global warming the greatest threat to the last refuge of the polar bear-the Arctic?