Muscardinus avellanariushazel dormouse

Geographic Range

Hazel, or common, dormice, Muscardinus avellanarius, are found throughout Europe, but are found more often in the south western regions of Europe. Hazel dormice are also found in regions of Asia Minor. ("Hazel, or common dormouse", 2002; Amori, et al., 1999; "Common dormouse, Hazel dormouse", 2002; Corbet and Ovenden, 1980; Corbet, 1966)


Muscardinus avellanarius inhabits deciduous forests that maintain a thick layer of scrub plants and underbrush. Being agile climbers, hazel dormice spend much of thier time in the tree canopy searching for food. They also inhabit hedge rows in rural areas of Britain. ("Common dormouse, Hazel dormouse", 2002; Corbet and Ovenden, 1980; Corbet, 1966)

Physical Description

Muscardinus avellanarius is the smallest of the European dormice and has a head to tail length of 115 to 164 mm. The tail makes up about one half of overall length. Hazel dormice weigh from 15 to 30 g. ("Hazel, or common dormouse", 2002; Amori, et al., 1999; "Common dormouse, Hazel dormouse", 2002; Corbet and Ovenden, 1980; Corbet, 1966; Haberl, 1999)

Looking similar to many other mouse-sized mammals, they have prominant black eyes and small, round ears, but can be distinguished by a thick, bushy tail. Coloration of hazel dormice is a brown to amber color on the dorsal side of the body, and white on the ventral side. Young hazel dormice lack the identifying color of the adults and are a duller and greyer in coloration. ("Hazel, or common dormouse", 2002; Amori, et al., 1999; "Common dormouse, Hazel dormouse", 2002; Corbet and Ovenden, 1980)

The feet of hazel dormice are very flexible, and are adapted for climbing. ("Hazel, or common dormouse", 2002; Amori, et al., 1999; "Common dormouse, Hazel dormouse", 2002; Corbet and Ovenden, 1980)

The dental formula of the hazel dormouse is (I 1/1, C0/0, P1/1, M 3/3 = 20). The cheek teeth of the hazel dormouse have a unique pattern of ridges. ("Hazel, or common dormouse", 2002; Amori, et al., 1999; "Common dormouse, Hazel dormouse", 2002; Corbet and Ovenden, 1980)

  • Sexual Dimorphism
  • sexes alike
  • Range mass
    15 to 30 g
    0.53 to 1.06 oz
  • Average mass
    20 g
    0.70 oz
  • Range length
    115 to 165 mm
    4.53 to 6.50 in
  • Average basal metabolic rate
    0.351 W


The mating system of this species has not been reported. However, males are very territorial, and so these animals are probably polygynous.

Muscardinus avellanarius has 1 or 2 litters per year. Birth rates peak from June to early July and from late July to August. Litter size in hazel dormice is from 1 to 7 young, but most litters are of 3 or 4 young. The eyes of neonates are sealed shut, but will open at about 3 weeks of age. Young become independant at about 5 weeks of age. Reproductively maturity is not reached until the summer following an individual's first hibernation. ("Hazel, or common dormouse", 2002; Corbet, 1966; Haberl, 1999)

  • Breeding interval
    Hazel dormice apparently can breed twice per year.
  • Breeding season
    Breeding typically occurs from June to October.
  • Range number of offspring
    1 to 7
  • Average number of offspring
  • Range gestation period
    22 to 28 days
  • Average gestation period
    24 days
  • Average time to independence
    35 days
  • Average age at sexual or reproductive maturity (female)
    1 years
  • Average age at sexual or reproductive maturity (female)
    Sex: female
    335 days
  • Average age at sexual or reproductive maturity (male)
    1 minutes
  • Average age at sexual or reproductive maturity (male)
    Sex: male
    335 days

Hazel dormice are altricial, being born with eyes shut. They are cared for in a nest by their mother, who provides milk, protection, and grooming. M. avellanarius females care for the young for about 5 weeks, after which time the young become independent. The young hazel dormice are raised in a nest that is usally in a stump or hollow tree. ("Hazel, or common dormouse", 2002; Corbet, 1966)

  • Parental Investment
  • no parental involvement
  • altricial
  • pre-fertilization
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female
  • pre-independence
    • protecting
      • female


Little is known about the longevity of M. avellanarius in the wild, but research suggests that individuals live an average of 3 years, at the end of which their teeth show heavy wear. The longest known lifespan of a wild individual was 4 years. In captivity they generally live for about 4 years, and up to 6 years. (Corbet, 1966; Haberl, 1999; Juskaitis, 1999; Morimand, et al., 1997; Obuch, 1998; Sorace, et al., 1999)


Muscardinus avellanarius is strictly nocturnal. Days are spent sleeping in a spherical nest that is made of grasses, stripped bark, and moss, that is held together by a sticky saliva. The nest is about 15 cm in diameter and completly surrounds the individual mwhihc occupies it. The nests are usally located about 2 meters off the ground. Common dormice spend their nights up in the trees foraging for food. Their prehensile feet are very helpful when jumping between branches. (Corbet and Ovenden, 1980; Corbet, 1966; Haberl, 1999; Juskaitis, 1997)

Hibernation occurs from October to April, although early hibernation can be initiated if the external temperature drops below 16'C. Hazel dormice spend this time in a hollow stump, beneath the debris on the surface of the forest floor or in the abandoned burrow of a fossorial animal. Winter nests are lined with moss, stripped bark, feathers and grass. During hibernation, hazel dormice will reduce their body temperature to 0.25 to 0.50 degrees C, the normal body temperature of the hazel dormouse is between 34 and 36 degrees C. (Corbet and Ovenden, 1980; Corbet, 1966; Haberl, 1999; Juskaitis, 1997)

Hazel dormice are solitary. During breeding seasons males will fiercely defend their territory against other males. (Corbet and Ovenden, 1980; Corbet, 1966; Haberl, 1999; Juskaitis, 1997)

Home Range

The home range of M. avellanarius is established within 360 meters of its birth place. Males establish a home range that is 1 hectacre, and females establish a home range that is about .8 hectacre. The home ranges of the male hazel dormice overlap often, but the females home ranges very rarely overlap. (Amori, et al., 1999; Haberl, 1999; Juskaitis, 1997)

Communication and Perception

Muscardinus avellanarius will produce chirping and whistling sounds, not unlike those sounds that are made by other species of dormice. It is also likely that these animals communicate with tactile signals, especially between rivals, between mates, and between mothers and their offspring. Visual signals and scent communication are important in other rodents, and probably play some role in communication in this species also. (Haberl, 1999)

Food Habits

Muscardinus avellanarius consumes a diet consisting mainly of fruits and nuts, but will also eat bird eggs, fledglings, insects and pollen if they are readily available. Hazelnuts are a favorite nut of hazel dormice. Nuts which have been opened by these animals are easily distinguished by a smooth, round hole that is unlike that made by other rodents. Hazel dormice specialize on nuts in the weeks prior to hibernation, but do not store food for the winter. ("Hazel, or common dormouse", 2002; Amori, et al., 1999; "Common dormouse, Hazel dormouse", 2002; Corbet and Ovenden, 1980; Corbet, 1966; Haberl, 1999)

Foods that are high in cellulose are avoided, as hazel dormice lack a cecum, and cannot digest the cellulose. ("Hazel, or common dormouse", 2002; Amori, et al., 1999; "Common dormouse, Hazel dormouse", 2002; Corbet and Ovenden, 1980)

  • Animal Foods
  • birds
  • eggs
  • insects
  • Plant Foods
  • seeds, grains, and nuts
  • fruit


Muscardinus avellanarius is fast and agile in the trees, allowing hazel dormice to escape predators among the branches and underbrush of the forest. Nevertheless, predation by raptors occurs. During hibernation, wild pigs and red fox will dig hazel dormice out of winter burrows to eat them. (Corbet and Ovenden, 1980; Corbet, 1966; Haberl, 1999)

Ecosystem Roles

Muscardinus avellanarius will aid in pollination when eating the pollen of a flower. Hazel dormice are preyed upon by raptors in the summer, and are easy winter prey for red fox and wild boar. (Haberl, 1999; Juskaitis, 1999; Morimand, et al., 1997; Obuch, 1998)

  • Ecosystem Impact
  • pollinates

Economic Importance for Humans: Positive

Muscardinus avellanarius is a really cute animals, and is a popular species for photographs that are used as postcards and as greeting cards.

Economic Importance for Humans: Negative

There are no known adverse affects of M. avellanarius on humans.

Conservation Status

Muscardinus avellanarius populations are declining in the northern areas of its range, due to loss of forest habitat. Hazel dormice are currently listed as lower risk in the IUCN red list, and has no special status on the CITES lists. (Amori, et al., 1999; Corbet and Ovenden, 1980; Corbet, 1966; Haberl, 1999)

Other Comments

Muscardinus avellanarius is known by the common names hazel mice, hazel dormice, and common dormice. ("Hazel, or common dormouse", 2002; Amori, et al., 1999; "Common dormouse, Hazel dormouse", 2002; Corbet and Ovenden, 1980; Corbet, 1966; Haberl, 1999)


Nancy Shefferly (editor), Animal Diversity Web.

Shawn Miller (author), University of Wisconsin-Stevens Point, Chris Yahnke (editor, instructor), University of Wisconsin-Stevens Point.



living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

World Map


uses sound to communicate


young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.


Referring to an animal that lives in trees; tree-climbing.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.


uses smells or other chemicals to communicate


active at dawn and dusk


animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.


union of egg and spermatozoan


forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.


an animal that mainly eats seeds


An animal that eats mainly plants or parts of plants.


having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.


the state that some animals enter during winter in which normal physiological processes are significantly reduced, thus lowering the animal's energy requirements. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals.


offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).


having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.


active during the night

seasonal breeding

breeding is confined to a particular season


remains in the same area


reproduction that includes combining the genetic contribution of two individuals, a male and a female


lives alone


uses touch to communicate


that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).


Living on the ground.


defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement


uses sight to communicate


reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.


British Broadcast Company. 2002. "Common dormouse, Hazel dormouse" (On-line ). Accessed 12/04/02 at

America Zoo. 2002. "Hazel, or common dormouse" (On-line ). America Zoo. Accessed 12/04/02 at

Amori, G., M. Andera, F. M. Angelici, M. Apollonio, R. C. van Apeldoorn. 1999. The Atlas of European Mammals. London: T & A D Poyser Natural History.

Corbet, G. B. 1966. The Terrestrial Mammals of Western Europe. London: G. T. Foulis & Co. Ltd.

Corbet, G., D. Ovenden. 1980. Mammals of Britain and Europe. London: Wm Collins Sons & Co Ltd.

Haberl, W. 1999. "The Dormouse Hollow" (On-line ). Accessed 12/04/02 at

Juskaitis, R. 1997. Ranging and movement of the common dormouse in Lithuania. Acta-Theriologica, 42(2): 113-122. Accessed 12/04/02 at http://library/Indexes/.

Juskaitis, R. 1999. Winter mortality of the common dormouse in Lithuania. Folia-Zoologica, 48(1): 11-16. Accessed 12/04/02 at http://library/Indexes/.

Morimand, F., F. Pezzo, A. Draghi. 1997. Food habits of the Lanner Falcon (Falco biarmicus feldeggii) in Central Italy. Journal of Raptor Research, 31(1): 40-43. Accessed 12/04/02 at http://library/Indexes/.

Obuch, J. 1998. Dormice in the diet of owls in Slovakia. Lynx-Prague, 29(0): 31-41. Accessed 12/04/02 at http://library/Indexes/.

Sorace, A., M. Bellaviat, G. Amori. 1999. Seasonal Differences in nest-boxes occupation by the Dormouse Muscardinus avellanarius L. (Rodentia, Myoxidae) in two area of Central Italy. Ecologia Mediterranea, 25(1): 125-130. Accessed 12/04/02 at http://library/Indexes/.