As our gardens start to fade into their winter state, it's important to remember that they could become a vital hibernation place for many species over the colder months. Mammals, reptiles, amphibians and insects can all use our gardens for winter shelter and protection, so let's see what we can do to aid and assist them at this tricky time of year.
Hedgehogs can start to hibernate during November if temperatures drop significantly. During hibernation, they become immobile, their bodies cool and their normal physiological activities are slowed down. Their heart rate decreases considerably from approximately 190 per minute to a faint 20 per minute, the body temperature, which is normally 35°C drops to 10°C or less and respiration almost stops (they will breath about once every few minutes). Hedgehogs may well be searching for hibernation nests, called hibernacula, around now. Favourite sites include leaf piles and compost heaps, so it's a big help to leave these undisturbed in your gardens during the winter. They also like to crawl under spaces such as sheds and decking, so make sure access to these is not blocked.
Amphibians and reptiles also like to find a winter home in our gardens. Take the common frog for example. They like to spend the winter in compost heaps or under piles of logs or rocks. Some adult male common frogs spend the winter in garden ponds, nestled among rotting leaves and mud at the bottom. This is a risky strategy, as smaller ponds can freeze over and frogs can sometimes die through a lack of oxygen. But clearly for some frogs, the benefit of being first in the pond when females arrive in spring means the risk is worth taking. For reptiles and amphibians, the term often used is 'brumation', differing from hibernation in that although reptiles and amphibians enter a period of low metabolic function and activity, they may sometimes move around for brief periods of activity on warmer days.
You can even build your own hibernaculum for reptiles and amphibians!
Nick Cunard (rspb-images.com)
Certain insects will also survive winter in a dormant state in our gardens. These include bumblebees, the queen bees of some species, ladybirds and some adult butterflies (such as small tortoiseshell and peacock). These insects find shelter in garden sheds, holes in trees, in leaf litter, under logs and under rocks. Like mammals, they enter a state of torpor, called diapause when referring to insects. Their metabolism slows and their temperature drops, while their heart rate slows. Some insects even produce anti-freeze chemicals that enable them to become “super-cooled”. These chemicals work to prevent build up of ice, which can rupture and destroy the insects delicate cells and tissues. In very low temperatures however, these chemicals can fail and the insect is killed by ice.
Small tortoiseshell Aglais urticae, spending winter in a shed
Phil Cutt (rspb-images.com)
So as you look around your garden this November, have a look out for potential hibernation sites and be sure to keep them in place for the winter. The wildlife around you will be very grateful for the shelter, warmth and protection given by your compost heap, leaf pile, log piles, tree or shed over the coming months!