Torpor is a (usually short-term) state of decreased physiological activity in an animal, usually characterized by a reduced body temperature and rate of metabolism. Animals that go through torpor include birds (even tiny hummingbirds) - notably Cypselomorphae - and some small mammals such as bats. During the active part of their day, these animals maintain normal body temperature and activity levels, but their body temperature drops during a portion of the day (usually night) to conserve energy.… (More on Torpor)