Living Organisms / Animalia / Craniata / Mammalia / Rodentia / Myoxidae / Muscardinus / Species
Muscardinus avellanarius - Hazel dormouse (Click photographs/illustrations: full picture & further details)
Click Photo for full-page view Click Photo for full-page view








Return to top of page

General and References

Alternative Names (Synonyms)

  • Common dormouse
  • Hazel mouse
  • Sleeper
  • Muscardin (French)
  • Haselmaus (German)

Alternative species names (the second part of the binomial species names): [Genus] abanticus; [Genus] angilicus; [Genus] corilium; [Genus] kroecki; [Genus] muscardinus; [Genus] niveus; [Genus] pulcher; [Genus] speciosus; [Genus] trapezius; [Genus] zeus (B141).

Names for new-borns / juveniles

Names for males  
Names for females  

Return to top of page

General Appearance

Orange-brown, mouse-sized rodent with a slightly bushy tail, prominent large black eyes, largish ears, short muzzle and long whiskers (B142, B144, B153, D30).

Similar Species

  • Distinguished from other mouse-sized rodents by bushy tail.
  • Much smaller (half size) than Myoxus glis - Fat dormouse, which has larger bushier tail and is grey-brown not orange-brown.

(B142, B153, D30)

Sexual Dimorphism
  • Males and females similar.
  • Longer ano-genital distance in male, and testes may be noticeable in breeding season.


Return to top of page


Species Author

Debra Bourne

Major References

Husbandry references:
B151, D24

(UK Contacts)

(Further Reading)
Click image for full contents list of ELECTRONIC LIBRARY

Return to top of page

TAXA Group (where information has been collated for an entire group on a modular basis)

Parent Group

  • Dormice (Rodents)

Specific Needs Group referenced in Management Techniques

  • Dormice (Rodents)

Return to top of page

Husbandry Information


Individual Techniques linked in Wildpro

Return to top of page

Appearance / Morphology

Measurement & Weight

Length Head-body length: 60-90mm, usually 80-85mm for adults in summer (B142). 68-85mm (D30); 60-90mm (B147); 2.6-3.4 ins./6.5-8.5cm (B144).
Height --
Adult weight General 15-20g (B142); 15-40g (B147); 0.5-1.1 oz. / 13-32g (B144); about 17g (15-22g), but 25-40g pre-hibernation, 15-20g post-hibernation (B153).
Male --
Female May be about 26g when pregnant (B142)
New-born weight --
Growth rate 10-13g for sub-adults at end of winter (B142); juveniles 40-50mm, 7-14g; may be 18-28g pre-hibernation and 12-16g post-hibernation (B153)

Return to top of page


General --


Nose: short blunt muzzle, long whiskers (B142, D30).

Ears: relatively small, rounded (B142, B147).

Dentition (Teeth) I 1/1, C 0/0, P 1/1, M3/3. Four cheek teeth in each row, numerous transverse ridges on each large cheek tooth (molars), which are multiple-rooted. Premolars small, single-rooted (B142, B153).
Eyes Large, prominent black eyes (B142, B147, D30).

Return to top of page

Legs and Tracks

Hind foot 15-18mm. Feet slender and very prehensile, pads large (B142, B143).

Return to top of page


Slightly bushy, similar length to head and body (B142, B144, D30)

Length: 57-68mm (B142); 55-75mm (B147); 2.4-3.4ins. / 6-8.5cm (B144).

Return to top of page

Coat / Pelage

Adult Female Soft dense coat.
  • Dorsal and tail: uniform orange-brown (also described as yellowish-brown, sandy-yellow or yellowish-red).
  • Ventral: pale buff/pinkish buff; throat white, may extend onto abdomen in thin line.
  • Tail: Dorsal brown, ventral paler (B147).

(B142, B144, B147, B153, D30)

Variations (If present)
  • Tail tip white (about 10% of population) (B142, B153).
  • Albino individuals rare (B142, B153).
Moult Winter pelage in October (B142).
New-born / Juvenile
  • First coat grey. Moulted about 18 days old. (B142).
  • Juveniles (second coat) grey-brown rather than orange-brown (B142, B153).

Return to top of page

Neonate (New-born) Characteristics

Blind, hairless, pink, helpless (B142, B153).

Return to top of page

Detailed Anatomy Notes
(Summary information provided for pertinent species-specific data cross-referenced in Wildpro)

  • Reproductive: Four pairs of nipples (B142, B147).
  • Scent Glands: near anus (B142).

Return to top of page

Life Stages / Natural Diet / Physiology

Reproductive Stages

Breeding Season --
Oestrus / Ovulation --
Gestation / Pregnancy
Parturition / Birth
  • Britain: May to September (exceptionally October).
  • Continental Europe: peaks late June/early July and late July/early August.
  • (B142).
Neonatal development
  • Birth: blind, pink, helpless.
  • 7 days: grey fur.
  • 13 days: coat well developed.
  • 18 days: eyes open, moult first grey coat.
  • 30 days: start to leave nest.
  • 40 days: independent; may remain with mother to 8 weeks.

(B142, B153)

Litter size
  • Average about 4, but 2-7 and even up to 9 recorded (B142); 1-7, mainly 3-5 (B144); usually 4-5, occasionally 7-8 (B153).
Time between Litters / Litters per year
  • Usually one, sometimes two litters per year (B142, B153)
Lactation / Milk Production --
Sexual Maturity
  • Year following birth (B142); one year (B144)
  • 4 years recorded in wild, 6 years in captivity (B142); four years (B144); may reach 4-5 years in wild (B153).

Return to top of page

Natural Diet

  • Hazelnuts, seeds, buds, berries, delicate leaves, insects, possibly bird eggs and nestlings.

(B144, B147)

Varies with season.

  • Early summer: flowers, pollen
  • Later: fruits, including ash keys, berries, nuts.
  • Also insects: may be particularly important in summer (mid-June to mid-August) (B153)
  • Before hibernation: chestnuts, acorns, hazelnuts (eaten while still green, on tree) important.

(B142, B153)

Return to top of page

Detailed Physiology Notes
(Summary information provided for pertinent species-specific data cross-referenced in Wildpro)

Temperature 34-36C; down to 0.25-0.5C during hibernation (B147)
Pulse --
Respiration --
Faeces --
Haematology / Biochemistry --
Chromosomes 2n = 46 (B142).
Other --

Return to top of page


Feeding Behaviour

  • Sequential specialist feeder - change diet according to seasonal food availability (B143, B153).

Return to top of page

Parental Behaviour

  • Prolonged maternal investment - juveniles remain with mother for 6-8 weeks (B153).

Return to top of page

Social Behaviour / Territoriality

  • Little known. Multiple occupancy of nests frequently recorded. B142
  • Range probably about 0.5 hectares, but may use larger area over whole season (B142)
  • May reach 8-10 individuals per hectare in favourable habitats (B143, B153)
  • Males strongly territorial in breeding season (B143).
Inter-specific --

Return to top of page

Sexual Behaviour

Some evidence pair bonds are persistent: same male and female may be found sharing nestbox in consecutive years (B142, B153).

Return to top of page

Predation in Wild

  • Foxes, badgers, weasels, corvids (crow, raven, magpie). 
  • Rarely owls or cats.
  • (B142). 
  • Owls (B144).
  • Rarely owls, sometimes weasels (B153).

Return to top of page

Activity Patterns

  • Mainly arboreal. In tree canopy and scrub.
  • Agile climber; run and jump.
  • Rarely on ground.
  • May travel about 250m per night.
  • Territory may be 0.7 square miles (2 square kilometres) (B147).
  • Home range typically only about 3,000square metres (B153).
  • Usually stay within 50m and certainly 70m of nest.
  • Males range more widely than females and home range of male may overlap those of two or more females.
  • May be two or more in same nestbox. Males will not share nestbox with one another during breeding season but will share with females.
  • Hibernate in nest, at or below ground level, from October to April in Britain; may arouse periodically, rarely leave nest.
  • In Russia may be August to May (B147).
  • Triggered when temperatures fall below 16C (B147); body temperature may be reduced to 0.25-0.5C (B147).
  • Summer torpor may be used in early summer when poor food supply and/or wet or windy nights (B153).

(B142, B147)

  • Nocturnal and crepuscular.
  • Active all night in summer, but only few hours per night in autumn.
  • Leave nest about one hour after sunset.
  • May reduce activity in bad weather.
  • Juveniles and pre-hibernation sometimes active in daytime.

(B142, B144, B147, B153)

Return to top of page

Habitat and Range

General Habitat Type

  • Mixed broadleaf woodland with ample secondary growth and scrub such as bramble.
  • Woodland edge and overgrown clearings preferred.
  • Trees with edible seed preferred (hazel, sweet chestnut, beech).
  • Coppice (particularly hazel coppice) commonly used, also hedgerows rich in tree species, damp woodlands, marshy areas and reed beds with alders and bramble present.
  • Coppice of 15-20 year rotation preferable (B153)
  • N.B. Physical structure of vegetation important, particularly requiring arboreal pathways as may be provided by climbing plants such as honeysuckle, and by sprawling coppice.

(B142, B143, B144, B147, B153, D30)

Return to top of page

Nests / Burrows / Shelters

  • Above ground in summer, usually 1-2m from ground, sometimes up to 10m high. In treeholes, bush or in lower branches of tree. Also behind loose bark. use old bird nests and squirrel dreys.
  • Availability of tree holes may limit dormouse numbers (B153).
  • Use nestboxes if provided (B153).
  • Globular nest constructed from shredded bark (occasionally grass), with outer layers of leaves.
  • 15cm diameter breeding nest (B142); 120mm (B147).
  • 10cm nests made by newly-independent juveniles, often in group only few metres apart. Individual nests 60-80mm (B147)
  • May use several nests in succession.
  • Hibernation nest also woven,: in burrow, in stump or tree hollow or beneath debris on ground. Vegetation bound with sticky salivary secretion. (B147, B153).

(B142, B144, B147, B153)

Return to top of page

Distribution and Movement (Migration etc.)

Normal Western Palearctic: Europe and northern Asia Minor. Widespread Mediterranean to southern Sweden and from Britain (not Ireland) eastwards to Russia, reaching about 50E. Not found Iberia. Present Corfu, Sicily. (B51, B143, B147).
  • In Britain: range decreased. Found locally in suitable habitats in mid-Wales, also western and southern England: Leicestershire, Suffolk and further south (B142, B143, B147, D30) (mainly south of line from River Thames to River Severn (B153).
Occasional and Accidental --


Return to top of page


Intraspecific variation

Five subspecies recognised; appearance of all rather similar (B143).

Return to top of page

Conservation Status

Wild Population -
  • In Britain: native, localised and declining population. Pre-breeding population estimate of about 500,000, with 465,000 in England, 0 in Scotland, 35,000 in Wales. Population estimate of this widely-distributed species was based on a limited amount of data and considered likely to be inaccurate by up to 50% in either direction (B221).
General Legislation
CITES listing --
Red-data book listing Lower Risk - near-threatened (B143, B147).
Threats In Britain: loss of habitat, particularly of ancient woodland, and management changes to woodland resulting in heavy shading, loss of shrub layer, loss of aerial pathways connecting feeding sites (B221).
Captive Populations --
Trade --

Return to top of page