At this point in the winter, most hibernating animals were already hibernating, according to Reeder, who has authored textbooks about mammals and mammal biology. (Bears and squirrels do not hibernate in the same sense as bats, because they don't lower their body temperatures the same way. But they do sleep for extended periods in their dens.) Some bats in the southern states, like tri-colored bats in Georgia and the Carolinas, might not have been hibernating just yet — but they sure are now, Reeder says. If the polar vortex had arrived in early November, more animals might have been caught off guard. But “they should be tucked in already,” as Reeder puts it.