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Hibernation: How it works, why animals do it, and the creature that can sleep for up to 11 months

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Dormice sleep for months, hedgehogs snore in quilts of moss and wooden frogs flip to ice — a spellbound John Lewis-Stempel investigates the annual thriller of hibernation.

The world in winter: when the earth is chilly and unforgiving, the days quick and meals scarce; when the thoughts of the animal is preoccupied by a single thought — survival. Some, comparable to the swallow, flee to hotter climes; a few of the much less fleet-of-wing enter a state of diapause or dormancy: the winter sleep of forgetting and sanctuary. Birds don’t do it, however ladybirds do, likewise the bumblebee, the painted woman butterfly, the grass snake, the frog and three of our mammals — the bat household (all 17 varieties of them), the hedgehog and the dormouse.

Hibernate is from the Latin hibernationem, ‘the action of passing the winter’, though the dry logic of Latin fails pitifully to embody the thriller and the miracle of the suspended animation by which the tiny dormouse can sleep soundly for greater than half a yr and wooden frogs flip to ice, then revive.

Hibernation: when the residing are lifeless, a pure phenomenon to be distinguished from ‘torpor’: hibernation is protracted and voluntary, torpor is the involuntary, occasional winter snooze of badger and squirrel. There are completely different ‘switches’ that flip dormancy on, the commonest being linked with temperature and the size of daylight. That pest of potato crops, the Colorado beetle, begins its preparation for hibernation when daylight dips beneath 15 hours a day.

Hibernation is a course of, with the slumber preceded by feasting. The hibernator’s essential pantry is its physique. Thus the Colorado beetle greedily devours potato leaves earlier than beginning the zombie state, queen bees regale on pollen and nectar and hedgehogs pig out, fattening up by ½lb; 30% of its physique weight will probably be fats. The dormouse doubles down on meals, doubling its weight. Like the dormouse, the British mammals that hibernate to keep away from the laborious, hungry occasions are insect-eaters, or part-insect eaters; in winter, the huzz and buzz of the bugs is all however gone, changed by the sound of silence. Bats can be seen hanging the other way up in the darkish locations from November to April, clustering collectively for heat.

Dormice could start their winter sleep as early as October. Quite our champion snoozer, the dormouse — therefore, in fact, the identify, from the French dormir. The edible model (Glis glis) holds the mammalian report for hibernation, at a teenager-envy-inducing 11 months.

Hibernating, mammals stay at a decrease temperature and gradual their our bodies down. A hedgehog’s coronary heart charge drops from 190 beats per minute to 20 throughout the lengthy lethargy; a dormouse’s blood temperature sinks to simply above freezing; bats cut back their respiration to 5 breaths a minute.

Greater Horsehoe Bats (rhinolophus ferrumequinum) hibernating.

So chilled out are bats throughout hibernation that they could be saved in a fridge, though a extra traditional winter roost is the church steeple, cottage attic or hole tree. Some hand around in the authentic bat cave.

Hedgehogs and dormice, in the meantime, choose their winter quarters at floor stage, typically in the cranny base of a brambly hedge. Dormice weave nests, hedgehogs wrap themselves round in moss and grass, however each cosy options are quilts of heat and camouflage. Inert, inside a cloak of concealment, with metabolism suppressed by 90%, little of the hibernating dormouse or hedgehog is left for a predator to detect. Except that Mrs Tiggy-Winkle typically snores in her hedgerow ‘hibernaculum’.