Hibernation provides a means for an animal to conserve resources when food is scarce. Most animals hibernate during cold winters, but some suspend bodily activity during periods of hot or dry weather.
Hibernation and hibernation-like states take many forms in the animal kingdom. Some rodents, such as ground squirrels, enter periods of deep sleep during which their body temperatures drop to the temperature of the air around them and respiration and heart rate lower dramatically. These animals also wake for short periods during hibernation.
The body temperature of bears does not drop as significantly as that of rodents. Bears, however, can go for six months or more without waking, eating or drinking.
Hummingbirds enter a hibernation-like state, or torpor, each night. Hummingbirds consume up to three times their weight in nectar and insects each day. Because of their tiny size and thin feathers, hummingbirds lose heat quickly. To survive the night, hummingbirds lower their metabolism and decrease their energy requirements by nearly 50 percent while they sleep.
Reptiles, which rely on the surrounding air temperature to influence body temperature, also undergo periods of inactivity and lower metabolism when weather cools. This process in reptiles is called brumation.
Animals that live in hot, dry climates also deal with harsh temperatures and food scarcity by lowering metabolic requirements. Aestivation is a hibernation-like state that occurs in organisms during dry seasons in hot climates. Aestivation also prevents some animals from drying out during dry conditions.