30 June 1989
Vol 244, Issue 4912

About The Cover

An arctic ground squirrel, Spermophilus parryii, newly emerged from its hibernaculum in Alaska. During hibernation, arctic ground squirrels spontaneously and reversibly adopt core body temperatures as low as —2.9°C without freezing. See page 1593. [Photo by Steve Moffitt, Department of Biology and Wildlife, University of Alaska, Fairbanks, AK 99775]