Never has hibernation seemed so attractive as during the last winter period. The thought of going to sleep in November 2020 with a full belly and ample fat reserves and then being woken up in early spring 2021 by someone waiting to give you a Covid jab seemed perfect! There is much to recommend hibernation as a survival strategy even without a pandemic to worry about. The ability to reduce metbolic rate and body temperature saves energy and helps animals through periods when food is scarce – but it can have its downsides.
Half of all hedgehogs, for example, fail to reach spring. It is often late-born youngsters who don’t survive because they have been unable to find enough food to fatten themselves up before winter arrives.
There is also the risk from reduced vigilance, which can make a poorly hidden hibernator easy prey. Although the significant reduction in movement while hibernating makes animals much harder to spot, they have very little chance of escape if they are unlucky enough to be discovered by a predator.
Some female bats even wake up to discover that they are pregnant, having been taken advantage of in their sleep.
Apart from a few small mammals – hedgehogs, bats and dormice – the majority of our hibernators are insects. There are no birds in Britain that are known to hibernate – in fact, there is only one in the world: the common poorwill, a North American relative of the nightjar, which spends most of the winter in a torpid state beneath a pile of stones. However, right up until the 18th century, people accounted for the winter absence of birds such as swifts, swallows and martins – which of course had migrated to warmer climes – by believing they had gone to the bottom of ponds to hibernate!
The big question is ‘Could humans ever learn to hibernate?’ We have better ways to survive the winter, of course – fire, clothing and human-controlled food sources mean that we have never needed to hibernate in order to survive from year to year. However, large mammals (most famously, bears) do hibernate – and it was recently demonstrated that primates can, too. Our closest hibernating relative (and the only primate known to do so) is the fat-tailed dwarf lemur, a native of Madagascar.
There are a few unsound reports of people buried in snow avalanches or falling through ice-covered ponds and being revived after having been technically dead for some hours. And there’s a study of French peasant life, published in 2017, which suggested that, until recently, they took to their beds after harvest and re-appeared in the spring ‘dishevelled and anaemic’ – which sounds a bit like me every morning!
Although the possibility of the human race collectively and voluntarily taking a long winter nap is not on the horizon, learning how to safely mimic (and return from) a state of hibernation could bring significant benefits, including improving the survival rates of trauma patients, advancing the treatment of diseases and even allowing humans to travel deeper into space – and it is an area of active study.
Failing that, you could try joining Walt Disney in the Cryogenic Chamber!