The Dormouse had been recorded in Victorian times from several South Lakeland valleys, but was thought to have become extinct in the region. However,the discovery of a Dormouse skull in the regurgitated pellet of a Barn Owl in the early 1970's led to the discovery of a viable population in the Duddon Valley, although numbers recorded here in recent years have been very small. A much bigger and more stable population is also known from the Cartmel peninsula (parts of Roudsea Wood being managed for the species) and a nest was recently found in limestone scrub to the south-east of the county just east of the M6, opening up the possibility of more populations in this overlooked habitat. Even better news was the discovery of dormice in Grizedale Forest in 2007, when two adults and three young were found to be using nestboxes installed by the rangers.

The Common Dormouse is a globally threatened species that has virtually disappeared from most of northern England; even in the south it only has a patchy distribution. It is one of the species in English Nature's Species Recovery Programme.

The Dormouse has suffered from the destruction of semi-natural woodland and the decline in coppicing. The loss of hedgerows is another unfavourable factor, as Dormice do not readily cross open ground, preferring to spend their time in tress and shrubs.

The winter nest, occupied from October to April, is below ground or in a hollow tree stump. Emerging in May in Cumbria, the Dormouse initially finds food in short supply. It does not really begin to put on weight again until August when fruit and berries become available and green hazel nuts appear; bramble is particularly important. Natural summer nests comprise a ball of grass, leaves and honeysuckle bark about 15 cm in diameter and woven to entirely surround the animal and wedged in a forked branch, but increasing conservation efforts have provided nest-boxes, which the species uses willingly.

Evidence from the monitoring of nest-boxes has shown that the Dormouse can become comatose and cold in the early part of the day, regaining body temperature later in the day. This obviously helps to conserve energy, especially if food is in short supply, and confirms the Dormouse's reputation as a sleepyhead. In Cumbria, the first litters are usually born in August, which leaves little time for the young to put on enough weight before hibernation. Dormouse are nocturnal foragers, often for as little as three hours per night, and wet weather in autumn can exact high infant mortality.

Hazel nuts are a vital part of the autumn diet, but the plant does not provide a good crop of nuts if it becomes shaded. Coppicing is essential to allow light into the wood; it also promotes a good variety of shrubs in the understory, which is necessary to produce food earlier in the season as the Dormice emerge from hibernation. Deer can be a problem as they eat this vital understory.

The Dormouse has a plump 8 cm long body and the tiny weight of 15 to 30 grams. Its facial features are squirrel-like and it is the only small mammal with a bushy tail. The upper parts have orange-brown fur, while underneath it is yellow white with a white throat. In the right habitat an individual can live for four years.