Bill Streever was on NPR today talking about his new book Cold and talking about hibernating arctic ground squirrels. Full transcript isn't up yet but here's the gist:
"As [the squirrel] hibernates, he begins to cool off. In fact, he cools off to a temperature that's just below the freezing point of water, so around 30 degrees Fahrenheit," says Streever. "When he hits that temperature — when one would think this animal is, for all intent and purposes dead ... he spontaneously starts to shiver," and his temperature rises.
Of course, You Tube has you covered with this video of the process which is great on many, many levels: