Why and when do they hibernate?
Hedgehogs survive well in the cold but cannot survive without food. During the winter months, hedgehogs’ food sources become scarcer and scarcer until the energy required to forage in the colder weather outweighs the energy gained from the remaining food available. This triggers hedgehogs to enter into a state of hibernation, which typically lasts from October or November until March or April, depending on the severity of the winter. Some of their food sources such earth worms, ladybirds invertebrates and caterpillars have gone into various states from pupa to chrysalis to dormancy.
In the preceding months, hedgehogs will be more active and increase their fat stores in order to survive the winter. During hibernation, their heartbeat slows from 190 to 20 beats per minute and their body temperature drops dramatically to match that of their surroundings to conserve energy for the long sleep. Due to their heightened vulnerability during hibernation, most hedgehog deaths occur in the winter.
Once hibernating, a hedgehog may wake up for short periods of time and forage, particularly in bouts of warmer weather. We have noticed in areas where people feed that some hedgehogs don't hibernate at all or may just sleep for odd days. It may be that feeding has changed their habits and is the factor that inhibits hibernation. In arid climates, hedgehogs may respond to the extreme conditions and reduced food availability by undergoing a similarly dormant state called aestivation.