This autumn, thousands of hedgehogs will curl up and sleep through the winter blues, with the hope of emerging next March to see the blossom on trees and the return of life to the gardens, woodlands and fields. Hibernation, though, is a perilous practise and not to be taken lightly. Many hedgehogs will never wake up.
The common hedgehog, Erinaceus europaeus, is the only British mammal with spines. It is typically covered in up to 6,000 brown and white bristles, which are hollow and springy. They last about a year before falling off and being replaced. The spines give hedgehogs much needed protection from predators such as foxes. When they are scared or intimidated, they can simply roll up into a ball and hide beneath their sharp armour.
Baby hedgehogs, which can be called hoglets or even hedgehoglets, are born with only a thin layer of fine spines in order to protect the mother. A few days after birth, their secondary layer will spike through. A litter may be anywhere between one and seven hoglets, and each one must grow to at least 500g to be able to survive the cold winter.
To put on the necessary weight, they will eat pretty much anything available. Worms, slugs, frogs and sometimes snakes are on the menu, but there’s one catch, foraging can only take place in the dead of night. Using their long snouts, exceptional sense of smell and night-time vision, hedgehogs forage in 2 kilometre parameters.
By November, the average hedgehog weighs around 1,200g. At this weight, they are ready for hibernation. As the nights become increasingly colder and the insects begin to die, the little hog is left no option but to find a safe burrow and begin settling down. But hibernation is not just sleeping; it is a physiological miracle. Their metabolism slows down to retain fat reserves, their outer body temperature drops from 35°c to around 10°c and they will take only one breath every few minutes. To the outside observer this animal will appear dead. Protected only by their spines and a hidden burrow, hibernation is a risky business.
By springtime, when the hedgehogs wake up, they may only weigh about 400g and will be desperately thirsty. Many do not survive due to cold temperatures, insufficient fat reserves, predators and even careless human activity. Unfortunately, their numbers are in decline and hedgehogs were declared a priority conservation species in 2007. So spare a little thought for these wonderful creatures as they sleep their way through winter.