By Leah Rambadt, American Forests
How do most wildlife survive the cold, winter temperatures? A few ideas may immediately come to mind: Mammals growing another layer of fur, birds migrating south, bears hibernating, etc.
Well, it turns out bears aren’t easily classified as hibernators and not all birds migrate for the winter. Instead, some birds enter a scaled-down version of hibernation known as torpor.
There are three types of sleeping techniques wildlife may use to escape bad weather conditions: hibernation, torpor and estivation. All three allow an animal’s bodily functions to slow down, so its energy is used to sleep through periods of extreme temperature instead of looking for food.
Hibernation is a voluntary state triggered by day length and hormone changes within an animal that indicate the need to conserve energy. An animal enters hibernation when food is scarce, and to reduce the need to go out and face the winter conditions. Most animals store fat before entering hibernation, and may wake up briefly to eat, drink or excrete waste during hibernation. A hibernating animal remains in a deep sleep that mimics a death-like state.
Characteristics of Hibernation:
- Triggered by day length and hormone changes
- Lowered body temperature — may become as low as the surrounding air.
- Slowed breathing and heart rate — an animal may breathe once every five minutes, and heartbeats may occur four or five times a minute.
- Lowered metabolic rate
- Duration: An animal tries to remain in hibernation for as long as possible. Depending on the species, an animal can remain in hibernation for several days, weeks or months at a time.
- Waking: It takes several hours for a hibernating animal to wake up, and it uses most of its conserved energy reserve to do so.