What is hibernation

Last updated: April 1, 2026

Quick Answer: Hibernation is a state of reduced metabolic activity that certain animals enter during winter to conserve energy when food is scarce. During hibernation, animals experience lowered body temperature, heart rate, and breathing.

Key Facts

Understanding Hibernation

Hibernation is a biological adaptation that allows animals to survive harsh winter conditions by dramatically reducing their metabolic rate. During this state, animals become nearly motionless, and their body functions slow significantly to preserve energy reserves accumulated during warmer months.

Physical Changes During Hibernation

When an animal hibernates, its body temperature drops substantially—often falling from a normal 98-100°F to as low as 30-40°F. The heart rate decreases dramatically, sometimes from 100+ beats per minute to just 2-3 beats per minute. Breathing becomes shallow and infrequent, with some animals taking only a few breaths per hour.

Preparation for Hibernation

Animals don't enter hibernation immediately when winter arrives. Instead, they enter a preparatory phase called torpor, where they gradually reduce activity and sleep more frequently. During autumn, hibernators consume significantly more food to build up fat reserves that will sustain them throughout the winter months without eating.

Types of Winter Sleep

Not all winter sleep is true hibernation. Some animals enter brumation, a lighter state where they remain somewhat alert and may wake occasionally. Other animals practice torpor, which is a temporary hibernation-like state from which they can wake more easily.

Common Hibernating Animals

Bears, ground squirrels, hedgehogs, and certain bats are among the most well-known hibernators. While many people associate bears with hibernation, bears actually enter a lighter sleep state where they can be awakened more easily than true hibernators.

Awakening from Hibernation

As winter ends and temperatures rise, animals gradually increase their metabolic rate and body temperature. This awakening process, called emergence, typically occurs over several days. Animals may appear sluggish immediately after awakening as their bodies return to normal functioning.

Related Questions

How long can animals hibernate?

Most animals hibernate for 3-8 months depending on the species and local climate conditions. Some ground squirrels can hibernate for up to 9 months, while other animals may only enter hibernation for shorter periods.

Can humans hibernate?

Humans cannot truly hibernate due to our body's inability to significantly lower metabolism without causing damage. However, humans can enter a state similar to torpor under extreme cold conditions, which is sometimes called hibernation by scientists studying hypothermia.

What do hibernating animals eat?

Hibernating animals don't eat during hibernation; they survive entirely on the fat reserves they accumulated before entering hibernation. This is why pre-hibernation feeding season is critical for their survival.

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Sources

  1. Wikipedia - Hibernation CC-BY-SA-4.0
  2. USGS - What is Hibernation Public Domain