Keeping warm is no sweat for a polar bear-in fact,sometimes its biggest problem is cooling off! Imagine running around outside in a winter coat.Even if it's cold out,you might start to feel too warm.And like you in that coat,a polar bear is so well insulated that it can easily become overheated,or too hot,by moving too fast.But ,polar bears know how to avoid overheating.For one thing,polar bear usually moves slowly and doesn't run very often.In addition ,"It will often grab a mouthful of snow to cool off,"says polar bear biologist Francois Messier."Or it may lie flat with its legs extended to expose its stomach directly to the snow,since belly fur isn't as thick.