Common dormouse (Muscardinus avellanarius)

Common dormouse on maple leaf
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Common dormouse fact file

Common dormouse description


This attractive rodent can be easily distinguished from mice by its long, fluffy tail. The common dormouse (Muscardinus avellanarius) is one of the smaller members of the family of dormice, it has bright golden fur on its back and a pale, cream-coloured underside. The dormouse has large eyes which betray its strictly nocturnal existence.

Also known as
hazel dormouse.
Tail length: 55 - 80 mm
Head-body length: 60 - 90 mm
15 - 30 g

Common dormouse biology

Dormice are well known for their habit of sleeping for much of the time. Their popular English name is thought to derive from the French word 'dormir' meaning 'to sleep'. Dormice are known to hibernate for as much as seven months of the year. At the onset of colder weather in October, the animals will select a suitable site close to the ground to build a nest. They then curl up and go to sleep until April. During hibernation, dormice slow down their bodily functions and enter a state of extreme torpor. In this state they feel cold to the touch and take some time to rouse themselves when handled. However, they do wake up periodically for a few hours at a time. They survive extended periods without food by living off stored reserves of fat laid down in the fruitful autumn months.

Dormice feed high up in the trees on a variety of food. They eat flowers and pollen during the spring, fruit in summer and nuts, particularly hazel nuts, in autumn. It is thought that insects are taken too. This variety of food must be available within a small area, a requirement which limits the suitability of some sites for dormice.

Dormice become sexually mature at one year old and their breeding season is from May to September. They produce between two and seven young and can raise two litters a year. The young dormice stay with their mother until they are about ten weeks old. As well as their grass-woven nests, dormice are known to use tree cavities and boxes for rearing young. They hibernate in nests built just below ground.


Common dormouse range

The dormouse is found across Europe as far east as the Ural mountains and south to the Mediterranean. In the UK its range is largely restricted to the south of England and Wales. Even here it is threatened by loss and fragmentation of its habitat.

You can view distribution information for this species at the National Biodiversity Network Atlas.

Common dormouse habitat

The dormouse lives in dense, deciduous woodland, coppice and thick shrubbery. Hazel coppice is a preferred habitat and the dormouse builds spherical nests of grass and honeysuckle bark situated a few feet from the ground. Here it spends the greater part of the day before emerging after dark to forage high in the canopy.


Common dormouse status

The common dormouse is classified as Least Concern (LC) by the IUCN Red List and Vulnerable in the UK. Listed under Appendix III of the Berne Convention and Annex IV of the European Habitats Species Directive.

IUCN Red List species status – Least Concern


Common dormouse threats

In addition to the effects of habitat loss, dormice have declined as a result of the isolation of their woods and inappropriate woodland management. The animals are reluctant to cross open ground and consequently are vulnerable to local extinctions when woodland is lost. The grubbing out of hedgerows in recent decades has removed these wildlife 'corridors' between woods that might have allowed dormice to move more freely to alternative sites. Because of their specialised diet they are unlikely to be found in recently established woodland or isolated old woods of less than 20 ha in size.


Common dormouse conservation

The common dormouse is no longer 'common'. Because of its serious decline, it is listed as a UK Biodiversity Action Plan (UKBAP) species. English Nature has also included it in their Species Recovery Programme (SRP). The initial objectives for saving the dormouse included gaining more knowledge as to its range and numbers, securing the existing populations, promoting suitable woodland management and re-introducing animals to appropriate sites.

Because of its popularity with the public and its potential as an excellent 'indicator species' the dormouse became the centre of a publicity campaign designed to draw attention to the threat to the animal and its habitat. This included producing information on the value of old, well managed woodland, establishing a National Nest-box Recording Scheme on computer database and involving the public and school children in 'The Great Nut Hunt'.

Part of National Dormouse Week, the Great Nut Hunt encouraged people to search their local woods for signs of nibbled hazel nut shells. Unlike squirrels which open nuts by splitting them, dormice nibble a small hole and extract the kernel piecemeal. The discovery of these nuts, indicating the presence of dormice, showed that the wood was still in a favourable condition. The last Great Nut Hunt took place in 2001.

In 2016, 38 dormice were reintroduced into a woodland area in the Yorkshire Dales in an attempt to stem the decline of the species.

The UK Biodiversity Action Plan for this species is available at UK BAP.
There may be further information about this species available via the National Biodiversity Network Atlas.
View information on this species at the UNEP World Conservation Monitoring Centre.

Find out more

For further information on the common dormouse see:



Information supplied by English Nature.



Coppicing is a traditional form of woodland management in which trees are cut close to the base of the trunk. Re-growth occurs in the form of many thin poles. Coppiced woodlands are cut in this way on rotation, producing a mosaic of different stages of re-growth.
A plant that sheds its leaves at the end of the growing season.
Indicator species
Any species that provides a guide to the condition of its habitat.
A sleep-like state in which the body processes slow to a fraction of their normal rate.



Image credit

Common dormouse on maple leaf  
Common dormouse on maple leaf

© Bengt Lundberg /

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