Until very recently, everything we knew about bear hibernation could be fairly well captured in a single sentence: We're pretty sure they do it. They disappear into dens for months at a time, they emerge in the spring looking a whole lot skinnier, and we're reasonably sure they didn't send out for any food. Hibernation is the only thing that explains all of that.

Metabolism in the large hibernators of the bear family have remained unknown because of technical limitations