Whether it’s the cold weather, the economic crisis, the hordes of Christmas shoppers or the short days and long evenings, the idea of hibernation takes on a particular appeal at this time of year. Wouldn’t it be wonderful to pull the duvet over your head and sleep through the Christmas frenzy, the New Year hysteria and the February gloom, and wake up when spring is on the point of reappearing? I suppose you’d regret missing out on all the fun bits, but in weaker moments it’s a very tempting thought all the same.
Unfortunately, hibernation just isn’t an option for humans. While for some years scientists have been experimenting on ways of producing a state of reversible hibernation or suspended animation in humans, which could help protect patients with serious injuries from the effects of oxygen deprivation, this procedure is still in the realms of science fiction rather than fact.
Though some of us might have enough body fat to keep us going without food over the winter, it’s our metabolic rate that would prevent us sleeping – and surviving – all that time. We humans can’t adjust our metabolism, but animals that hibernate are able to slow down their system to conserve energy and keep their bodies ticking over just enough to stay alive: when they enter a state of hibernation their body temperature and pulse rate are reduced and their breathing becomes slower. Hibernation can last for different periods, depending on the species of animal and external factors such as air temperature. Hedgehogs, for example, perhaps our best known native hibernators, don’t sleep continuously from autumn until spring: they tend to wake up several times during the winter, potter about for a while and then curl up again. They prepare for winter by storing a particular kind of fat around their shoulders and necks, and settle into a nest (known as a hibernacula ) that they make from fallen leaves, which provide good insulation. These nests are often built near or under piles of fallen branches or twigs – so if you have a bonfire during the winter it’s worth checking that you’re not going to incinerate an unsuspecting hedgehog.
The Big Sleep
Other animals that hibernate include bats and rodents. Dormice, for example, sleep for more than half their lives, hibernating for six months of the year. The Anglo-Saxon name for a dormouse is “dormeus”, which means “sleepy one”, and Lewis Carroll was obviously aware of the dormouse’s predilection for sleeping – the character in Alice in Wonderland wasn’t exactly the life and soul of the Mad Hatter’s tea party. “‘You might as well say,’ added the Dormouse, who seemed to be talking in his sleep, ‘that “I breathe when I sleep” is the same thing as “I sleep when I breathe”.’ ‘It is the same with you,’ said the Hatter.”
As a rule, birds do not hibernate (though in past times there was a belief that the swift slept through winter ): instead they use what’s known as torpor, a periodic state of reduced metabolic activity, which usually happens at night in autumn and winter, and which enables the bird to cut down the amount of energy it uses. During the day, however, they are wide awake and functioning as normal. But there is an American bird, the poorwill (which is related to the nightjar ), that enters a state of torpor so close to hibernation as to be almost indistinguishable from it.
Scientists reckon that there isn’t physiologically much difference between torpor and hibernation apart from the length of time involved, hibernation being a long-term state and torpor a short-term one. Now there’s a thought...