APPLIANCE OF SCIENCE: Why do some animals hibernate and could humans?

APPLIANCE OF SCIENCE: Why do some animals hibernate and could humans?
Hedgehogs have left the nest and are foraging to put on weight to hibernate.

With the changing of the clocks and the colder, darker days, it is understandable that some of us wish we could curl up in a warm place and do very little. Maybe hibernation wouldn’t be such a bad idea. Why do some animals hibernate while others don’t? Would humans be able to if we chose to?

A look at hibernation

Hibernation is an extended period of torpor, a state of reduced physiological activity resulting in a significant decrease in body temperature, heart rate, breathing and other metabolic processes. It is often thought of as an extended sleep but scientists believe it has no real association with sleep at all. Recent research suggests that animals have to frequently rouse themselves from hibernation to catch up on sleep, before returning to the state again.

Why do animals hibernate?

Animals will hibernate for a number of reasons: to avoid extremes in temperature, because of a lack of food supply, to escape predators or simply to wait for more adequate living conditions.

We associate hibernation with cold weather and cold climates but this is not always the case. Lots of types of animals hibernate … insects, reptiles, amphibians, mammals and even a small number of primates hibernate. Some will do so in tropical or hot climates and this is known as aestivation; they may do so to avoid drought or extremes in temperatures.

Hibernating animals are very difficult to detect as they give off little, if any, heat or odour and do not move around. It is a very good way to stay safe from predators, especially if those predators are seasonal. The pupae of large white butterflies of southern Spain hibernate for a few months in the summer to avoid a certain type of parasitic wasp.

Studies on the edible dormouse show it can hibernate for 11 months. Researchers have associated this extended period of hibernation with a poor year for one of its primary food sources, European beech trees. Somehow, the dormice predict a lean year for the tree and hibernate through most of that time.

Not humans

Why do we not hibernate? If we follow the path of our evolution back to its origins we would find our early ancestors lived in warmer climates with a relative abundance of food so they did not need to hibernate. We devised efficient ways to hunt, farm, shelter and keep warm. Hibernation was not necessary.

Most hibernating animals are small but scientists believe we can learn much about possible human hibernation from large hibernating animals, like bears. Studies on Alaskan black bears have revealed some unique hibernating methods. They hibernate for up to seven months a year without the need to eat, urinate or defecate. While reducing their metabolic processes considerably, their core body temperature does not drop as much as in smaller hibernating animals.

Just for sci-fi?

There is now more interest in the processes that control hibernation and if it can be induced in humans. One reason for this is space travel. The possibilities of humans travelling further and longer into space are not as farfetched as heretofore.

Large research programs, like a current Nasa-funded project to put humans into hibernation for space flight, may take the idea of human hibernation out of sci-fi books and movies and make them a reality.

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