In the UK hedgehogs hibernate over winter as the environmental temperature drops and their food supply diminishes. Hibernation can start any time from October to January (depending on environmental conditions) and usually lasts until March/April. To safely hibernate hedgehogs need to have built up enough body reserves to keep them alive over winter. In recent years a lot of hoglets have been born later in the year and are not big enough to survive hibernation, a hedgehog needs to be an absolute minimum of 450g ideally greater then 600g to go safely into hibernation.
For adult hogs going into hibernation they build nests (hibernacula) with thick insulation, usually of leaves in a quiet corner of the garden such as amongst tree roots, hedgerows, compost heaps, woodpiles etc., purpose made hedgehog houses are also available offering a simple way to provide alternative winter accommodation. If you know you have hedgehogs in your garden and are keen to help them providing them with food (ideally hedgehog food, but cat or dog food can also be used) and water in shallow dishes can help them build their fat reserves. Once the food is no longer being taken just leave out water until the warmer weather returns, mid March onwards, ready for the hog/s when they come out of hibernation hungry and weakened. A hibernating hedgehog should not be disturbed as rousing them will cause them to use up more of their energy, if you accidently come across a hibernating hog it is best to quickly cover it back up and leave it alone. We at Holmer Veterinary surgery are keen to help support the sadly declining hedgehog population, if you see a small hoglet or an adult out in the day, especially in the winter months, or if you see a weak, wobbly, sick or injured hedgehog please do not hesitate to call us, we routinely examine, treat and then refer sick and injured hedgehogs to experienced volunteers for rehabilitation.