As the weather gets colder it’s time for hazel dormice to start fattening up ready for hibernation. Dormice usually hibernate between autumn and spring, where they will enter a state of very deep sleep.
To survive through winter, dormice need to gain enough weight to have sufficient fat stores to draw upon during hibernation. Then, as temperatures drop and the first frosty mornings arrive, dormice will start to hibernate – usually at ground level in nests of leaves, bark or moss. During this time, they lower their body temperature, their heart rate halves, and their breathing rate reduces to just a couple of breaths per minute. They also curl up into a tight ball and tuck in their toes to reduce the risk of freezing. This allows them to save energy during the cold winter months when food is scarce.
Following hibernation, dormice can also enter a state called torpor if there is adverse weather or a food shortage during the months of the year when they are normally active. However, this state usually only lasts for less than 24 hours and is done to conserve energy.
During the summer, dormice build nests that usually consist of a double-layered structure with green leaves on the outside for camouflage, and an inner chamber of woven strips of bark or grasses. A helpful way to find out if dormice are present in a woodland is to install nest boxes or tubes, which dormice will use as a shelter to build nests in. A licence is needed to check these nest boxes, as dormice are a protected species.
