Hibernation is a state of inactivity and metabolic depression in animals, characterised by lower body temperature, slower breathing, and lower metabolic rate. Hibernation conserves energy, especially during winter.
Hibernation may last several days or weeks depending on species, ambient temperature, and time of year. The typical winter season for a hibernator is characterized by periods of hibernation interrupted by sporadic arousals wherein body temperature is restored to typical values.
Hibernation allows animals to conserve energy during the winter when food is short. During hibernation, animals drastically lower their metabolism so as to tap energy reserves stored as body fat at a slower rate.
Have you seen many Hedgehogs recently?
When do hedgehogs hibernate?
It is not usually until November, December or January that larger hedgehogs finally settle down to hibernation, when they must realise that the greatest threats they face are floods, the cold or predators which can destroy them while they are inactive.
A great many will never survive until the spring so it's as a last resort, when they cannot stay out and about any longer, that they put the final touches to their hibernation nests. As long as their is still food to be had you will still see hedgehogs out and about.
In Britain the really hard frosts do not usually descend until the end of January with February and the first part of March being the time when any adult hedgehog out in the open is in trouble.