They combine warm- and cold-blooded animals in one. ~ Russian American physiologist Elena Gracheva
Leopard ground squirrels (shown) and golden hamsters are comfortable in the cold. This makes hibernation easy: they don’t have to fatten themselves up like bears for an extended slumber during the winter.
These rodents manage by having a specialized cold-sensing protein that does its job of signaling bodily functions but allows an imperviousness to the cold: aware but unperturbed. Other, related adaptations in metabolism, heart rate, and breathing afford a cold body hibernating in comfort.