Just like hibernation, torpor is used by animals to survive during the winter months. It too involves a lower body temperature, heart rate, breathing rate, and metabolic rate. However, unlike hibernation, torpor is typically an involuntary state that an animal enters into as the conditions determine. Plus, unlike hibernation, torpor only lasts for short periods of time. It can sometimes last through the night or day depending upon the feeding pattern of the animal (diurnal or nocturnal). While active, body functions are normal. However, during sleep, they enter into a much deeper resting period that allows them to conserve energy.
Waking from torpor takes about an hour and the critter typically experiences violent shaking and muscle contractions. This uses energy, but this loss of energy is offset by how much is saved while in the torpid state. Torpor is set off by ambient temperature and the availability of food. Raccoons, bears, and skunks all use torpor to survive the winter.
