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Why Do Animals Hibernate?

Ashwini Kulkarni Sule
In some animals, hibernation is a mechanism of coping with cold months that are characterized by paucity of food.
You must have heard the story of ants and grasshopper. Wise ants work hard throughout the summer and fall to store food for winter, while grasshopper just sits back, enjoys good weather, and gorges on food. As winter arrives, the ground gets covered with snow and there is no food to eat. In the absence of stored food, grasshopper fails to survive long, cold winters. However, ants judiciously use their food storage and make it through the winter months.
The point is that, some animals know how to adapt to environmental changes and survive through rough weather. Hibernation is one such mechanism that is adopted by some animals to cope with freezing cold and scarcity of food.

What is Hibernation?

In simple words, hibernation is a state of deep sleep. It differs from normal sleep though, and too, in several ways. Hibernating animals take a long time to wake up from their slumber. They are not disturbed by loud noises. Even after they wake up, they take some time to resume their normal activities. Some people refer to hibernation as death-like sleep, wherein the animal's heart rate slows down and some of the non-vital organs become entirely inactive. It's a state in which body uses minimal energy.

Why Do Animals Hibernate in the Winter?

As mentioned above, winter is the time when food is less and weather rough. Animals have to spend a lot of energy finding food. Even if they succeed in finding anything, which is very unlikely, it is seldom sufficient to compensate for the energy lost in searching for it. Extreme weather is also an issue, and it may even lead to death at times. A much better option is to reduce the demand for food by reducing activity, which is exactly what these animals do when they hibernate throughout the winter.
Before the onset of winter, when there is ample food, animals eat excessively and store this excess food in their body in the form of fat. As winter arrives, they return to their dens or winter nests, where they spend the rest of winter hibernating. As animals hibernate, their body temperature starts dropping due to the lack of activity and metabolism.
At one point, it is only a few degrees higher than the ambient temperature. Blood circulation drops as heart begins to slow down. Whatever energy the body needs to perform certain minimal tasks, is derived from the fat storage.
Due to lack of activity, the fat burning process is slow and steady. The energy from fat is sufficient enough to keep the animal alive for the rest of the winter.
Hibernation differs from species to species. While black bears sleep throughout the winter (approximately seven months) without waking up in between, squirrels wake up after every 4 days to eat some food and excrete. Hibernation in domestic animals may vary from that of their wild counterparts. As there is no food shortage for domestic animals, their hibernation period is not marked by long periods of inactivity. Domestic animals hibernate as a result of their natural instinct, but with more active periods in between.

Which Animals Hibernate?

Hibernation is commonly found in warm blooded animals. They usually choose safe, well-hidden places to hibernate, as this state makes them vulnerable to predators. GivenĀ ahead is a short list of animals that hibernate
  • Bears
  • Hedgehogs
  • Badgers
  • Hamster
  • Dormouse
  • Prairie dogs
  • Fat-tailed lemurs
  • Groundhogs
  • Ladybird
So, hibernation is a useful mechanism which protects animals from cold, dreary winter. A similar mechanism, which is known as estivation, is seen in cold blooded animals, wherein they sleep through hot dry weather. All warm blooded animals do not feel the need to hibernate. Some of them resort to other mechanisms of dealing with food scarcity and cold weather, like migrating to warmer regions in winter.