The tumbling temperatures of winter present a stiff challenge to Devon’s wildlife. Some species opt out, choosing migration in search of warmth and food. But for most the strategy must be to stay put and do the utmost to survive.
This is true of one of our most familiar, but sadly most rapidly declining mammals, the hedgehog. Hedgehog’s rely on invertebrates – insects, worms, slugs, snails, etc. – as their main food source. Because their prey is small in relation to their own body-size, they are voracious feeders, requiring huge numbers of invertebrates just to keep going.
Winter presents the hedgehog with a conundrum. Cold weather demands more energy to stay warm and on the move. At the same time there are fewer invertebrates around to feed on – many insects perish in the first frosts, others including slugs and snails hide themselves away. The answer to this food shortage for hedgehogs (like those other invertebrate-reliant mammals, the bats) is to hibernate.
Hibernation is not the snug, cosy, deep sleep depicted in children’s story books. It represents a time of risk, a state from which some hedgehogs will never re-emerge. Hibernation opens the hedgehog to discovery by predators, accidental disturbance and harm from humans, frost bite and freezing, even flooding and drowning.
As a consequence, hedgehogs will go on leading active lives as long as the autumn and early winter weather and their food supply allows.
When the time does come to hibernate, a nest of dry leaves or grass is favoured, often under the cover of a hedge or cover such as brambles. Once settled an extraordinary change occurs in the animal. Hedgehogs will rely on the fat reserves that they spent autumn and the early winter months building up. But they also look to minimise their energy use. Their metabolism will slow dramatically, brain activity will almost cease and the animal will not move from its familiar ball position. An active hedgehog will take between 40-50 breaths per minute, but during hibernation this will drop to just 9. A heart beat that runs at 190 per minute in summer is slowed to 20, while the body temperature falls from 34°C to as little as 6°C.
A hedgehog’s problems don’t end when they emerge from hibernation. The animal will wake when its body’s fat supplies are running low. At this time it must find water and food quickly. If it fails then dehydration and starvation may strike.
There are things that we can all do to help hogs negotiate the coming winter. These include leaving part of your garden ‘wild’, and putting out food sources and water at key times of year. For this and many more tips on supporting local wildlife take a look at the wildlife gardening pages of:
by Stephen Hussey of the Devon Wildlife Trust