The Hazel Dormouse is also known as the Common Dormouse or the Dormouse and it spends about three quarters of its life sleeping. It sleeps during the day in a resting nest that it has built for itself.

The resting nest is roughly spherical and approximately fifteen centimetres in diameter. It is constructed out of shredded honeysuckle bark, dry grass and moss which are held together by sticky saliva. The nest is lined with leaves, moss and grass. The Hazel Dormouse weaves its nest quite loosely, which gives the nest a rather untidy appearance.

Some resting nests have been found as high up in trees as twenty metres. However, most resting nests are built approximately two metres above the ground in thick undergrowth beneath trees. When a Hazel Dormouse sleeps in a nest, it curls itself up and pulls its tails over its face and head. It looks really sweet.

If a Hazel Dormouse can’t get to food because the weather is too cold or severe, it reduces its body temperature to become ‘torpid’. 'Torpor' is a state of sleep in which the Hazel Dormouse slows down its metabolism to conserve its energy. It is a form of semi-hibernation.

Hazel Dormice usually hibernate between October and April when the first signs of frost appear. Hibernation is a period when Hazel Dormice sleep right through the cold winter months. During hibernation Hazel Dormice reduce their body temperature to under one degree Celsius! The normal body temperature is approximately thirty six degrees Celsius. Hazel Dormice also reduce their heart and breathing rates by ninety percent (or more) to conserve energy.

During hibernation the Hazel Dormouse sleeps in a winter nest. Winter nests are the same as resting nests, but they are lined with leaves, grass, moss, stripped bark and feathers. Winter nests are often built under leaf litters on the ground in woodlands.