Did You Know

Why do Some Animals Hibernate?

Some animals including bears and bats hibernate in the colder months.

What is Hibernation?

Hibernation is an adaptation utilized by some animals by which they conserve energy by remaining inactive for long periods of time. During winter, it is difficult for many animals to find food. Hibernating animals adapt themselves into a kind of deep sleep to save energy and survive the cold winter times. The word “hibernation” has its origin in the Latin word “hibernare” which means "to pass the winter”.

Hibernation is triggered in animals by the seasonal changes like the shortening of days and the reduction in temperatures. When certain external stimuli are noticed by the animals, they produce a hormone called "hibernation-specific protein". This protein initiates a metabolic slump which results in hibernation “sleep”.

What Happens During Hibernation?

Hibernation is associated with decreased metabolic activities. It is a sleep-like state intermixed with short spells of wakefulness. During these brief out-of-sleep periods, the animal's body resumes metabolic processes at a normal pace. It should be noted that if someone wakes up a hibernating animal, it may not cause any long-term trauma to the animal.

During hibernation, an animal enters a different state of metabolism. Animal's heart beats and breathing rates slow down. The blood supply gets restricted and non-essential organs go into stasis. The creature may not walk, eat, or drink for weeks. A distinguishing feature of a real hibernator is that its body temperature drops very low, generally as low as the surrounding temperature. The purpose of hibernation is to save energy and pass through the difficult time.

Different animals prepare differently for the hibernation. Some store food in their dens. They eat this stored food when they are awake (for short spells during their hibernation). Other animals eat extra food before hibernation and store this food as body fat. They use this extra fat to get energy during hibernation.

Hibernation periods vary from species to species and also within a given species. For example, individual British bats begin their hibernation at different points between November and March.

Examples of Hibernating Animals

Most species have evolved in a manner where they do not need to hibernate. Animals which hibernate generally have a high surface area to volume ratio. These animals have a large body area from which the heat radiates out but they have a small volume of body cells from which they generate energy.

Animals which hibernate include bats and rodents. Some species of reptiles, fish, amphibians, and birds are also known to lie dormant during winter. Hibernators include hamsters, ground squirrels, woodchucks, jumping mouse, little brown bat, lemurs, wood frog, deer mice, skunks, European hedgehogs, eastern chipmunk, white-tailed prairie dogs, and a bird species called the gray and white poor. During hibernation, a Woodchuck for example reduces its heart beats from 80 per minute to about 4 or 5, and its body temperature drops 60 F. Bears are famous for their hibernation because they do not drink, eat, urinate, or excrete during their hibernation.

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