Arctic ground squirrel
Images copyright by Mark A. Chappell
Arctic ground squirrels are famous among physiologists for their ability to 'supercool' during their long winter hibernation period. During hibernation bouts, deep body temperature can fall a degree or two below the freezing point (feezing doesn't occur), but the animals still have the ability to spontaneously arouse and warm up. These squirrels were photographed in Denali Park, Alaska
