Dormice

(Myoxidae)

Class Mammalia

Order Rodentia

Suborder Sciurognathi

Family Myoxidae

Thumbnail description
Variable in size; thick fur on body and bushy tail (except for Myomimus), large eyes, short, curved claws

Size
Body 2.4–7.5 in (6.1–19 cm); tail 1.6–6.5 in (4–16.5 cm); weight 0.5–7 oz (15–200 g).

Number of genera, species
8 genera; 26 species

Habitat
Woodland and forest, steppe and rocky areas.

Conservation status
Critically Endangered: 1 species; Endangered: 4 species; Vulnerable: 5 species; Lower Risk/Near Threatened: 5 species.

Distribution
Europe; Africa; central and western Asia; Japan.

Evolution and systematics

The earliest fossil remains of this family were discovered in Europe and date from the Eocene era (about 40 million years ago). Pleistocene fossils of Leithia, a giant dormouse, have been found in Sicily and Malta.

Phylogenetically, dormice have been grouped with the mountain beaver, Aplodontidae, and squirrels, Sciuridae: in appearance and behavior, dormice most closely resemble squirrels.

Taxonomically, this family is made up of three subfamilies, 8 genera, and 26 species. The largest subfamily, Graphiurinae, consists of a single genus Graphiurus, the so-called African dormice, whose 14 species are all found in sub-Saharan Africa. The subfamily Leithiinae has four genera; forest dormice Dryomys; garden dormice Eliomys, mouse-tailed dormice Myomimus, and desert dormice Selevinia. The latter genus, consisting of a single species, Selevinia betpakdalaensis, has been the subject of some taxonomic debate. This naked-tailed rodent has been placed either within the Muridae, in a distinct family, or as a subfamily of the Myoxidae. Holden (1993) believed it was most closely related to the mouse-tailed dormice and put it within the same subfamily.

Physical characteristics

In appearance, dormice have a squirrel or sometimes chipmunk-like shape. They vary considerably in size between species: an edible dormouse (Myoxus glis) is nearly two and a half times the length of a Japanese dormouse (Myoxus japonicus), for example. Most dormice are highly adapted to a predominantly arboreal existence—only mouse-tailed dormice appear to live exclusively on the ground. The feet are well adapted to grasping on to trees. On the soles, they have cushioned pads for gripping, and the four toes on the front feet and five toes on the hind feet all have strong, curved claws. The hind feet can be turned backwards, like those of a squirrel, enabling the animal to hang head-first from a branch to feed on the lowest fruit, and to run down stems with some dexterity.

The fur is generally soft and thick and in most species, the tail is bushy and long. Its primary function appears to be in assisting with balance, since it is not prehensile. Dormice will readily shed their tails to escape from predators. Ground-dwelling mouse-tailed dormice have thin, naked tails.

Adaptations for a largely nocturnal existence usually include large eyes, sensitive vibrissae, and an acute sense of hearing; the rounded ears are not, however, especially large.

Distribution

This Old World family is found through most of Europe apart from far northern parts; North Africa and the rest of the continent south of the equator; and western and more patchily, central Asia. The single species in the Far East is the Japanese dormouse, found only, as its name suggests, on islands of Japan. The two Balearic dormice species in the Hypnomys

genus are probably extinct, extirpated from these western Mediterranean islands by human settlers and their animals about 5,000 years ago.

Habitat

Most dormice occupy forest, woodland, or scrub habitat. True to their name, forest dormice are among the most arboreal, living in dense forests at up to 8,200 ft (2,500 m) in altitude. Hazel dormice (Muscardinus avellanarius) are also reluctant to come to ground, preferring to stay in the canopy of largely deciduous woodland. They may remain high in tall trees for several days at a time, or spend long periods feeding on low-hanging fruits close to the ground.

Edible dormice inhabit deciduous or mixed woodland. Both this species and the garden dormouse (Eliomys quercinus) are also found in orchards. The latter species, also called the orchard dormouse, is also able to live on the ground, since small numbers are discovered in fields, swamps, steppe, and even places where there are no trees. However, their title is something of a misnomer, since most live in forest habitat.

African dormice live in a wide range of forested habitats, ranging from thick forest where they may even be diurnal, to thinly wooded riverbanks of mountainous, rocky areas. The desert dormouse lives in desert scrub. Only the little-studied mouse-tailed dormice appear to live on or under the ground. In southeastern Europe, Roach's mouse-tailed dormouse (Myomimus roachi) has been trapped in a variety of open habitats, but never in forest.

Behavior

Dormice live at lower densities than most rodents of equivalent size. Outside the mating season, they appear to show little territoriality. Most species studied coexist in small groups, with juveniles typically making up half their number. Artificial nest boxes are often found with several inhabitants of both sexes inside. Families tend to stay together through winter hibernation; but a wild male, probably leaves a female after mating, in order to pursue other estrous females.

Home feeding ranges are very variable. At one extreme, hazel dormice rarely venture more than 230 ft (70 m) from their daytime nest. African dormice range far wider, and, in common with most species, males travel greater distances than females. In spectacled dormice (Graphiurus ocularis), the male occupies an average of 34.3 acres, (13.9 ha) while the female roams over 21 acres (8.5 ha).

At the start of the mating season, males exhibit territorial aggression towards each other. The hazel dormouse flicks its tail like a squirrel as a warning sign to intruders. Edible dormice mark their space with glandular secretions and fight with great savagery. Garden dormice share sleeping and feeding sites. Males adopt a dominance hierarchy shortly after the animals emerge from hibernation.

All species studied communicate using a range of calls. Five or six separate calls have been identified for forest dormice, including an alarm squeak. Other calls have sexual or aggressive functions.

During periods of inactivity, dormice seek a variety of places in which to shelter. Day nests are often constructed in

tree hollows, with the animal weaving a round ball of vegetation, consisting of leaves, grass, moss, lichen, and shredded bark, bound together with saliva, and lined with hair or feathers. Sometimes, a ball nest is made in the branches of a tree; at other times the animal will use a bird or squirrel nest as a foundation for its own nest, or it will tuck the nest behind the bark of the tree. Garden and African dormice in particular also use rock crevices. Artificial nestboxes are adopted readily by many species.

Ironically, it is during the period of sustained inactivity that dormice are most likely to come into contact with humans. Their search for a secure, enclosed hibernation site with stable temperatures leads them into some bizarre places. While hazel dormice make their winter nests in tree stumps or on the ground, rather than in trees where temperatures fluctuate and desiccation is a threat, edible dormice may also choose woodpecker holes, artificial nest boxes, and barns. Japanese dormice are known to select cottage roofs and birdhouses while African dormice sometimes winter inside house furniture.

Most species undergo periods of hibernation in response to food shortages and low temperatures. Hibernation in Europe may extend from September until May. The animal curls itself into a ball, with the tail covering the mouth to reduce water loss. Although hibernation is thought to occur in most species, climactic variation means that in some milder areas such as Israel, dormice do not go into true hibernation, but have several hours of torpidity each day during the winter.

Feeding ecology and diet

Dormice are nocturnal and crepuscular foragers, with most species taking their food from trees. Although they are nominally omnivorous, they are the only rodent family lacking a cecum. Consequently, their consumption of low grade plant food is minimal.

Most species are specialized in taking advantage of seasonal food. Typically, buds and tree flowers are eaten in spring and early summer; insects and other arthropods, small rodents, birds' eggs and insects in summer; and fruit, berries, seeds, and nuts in late summer and the fall. The extent to which individual species depend on one source varies—edible and hazel dormice have a largely vegetarian diet, whereas garden, forest, and African dormice are predominantly carnivorous. Yet each species can alter its diet in response to particular needs. "Vegetarian" dormice eat insects in the summer period of

shortages before fruits and seeds have ripened. "Carnivorous" dormice switch to nuts and seeds in the fall, so that their fat intake increases in preparation for hibernation. Only the desert dormouse is thought to be purely carnivorous.

Reproductive biology

Lengthy hibernation periods at either end of the year mean that for a number of species, the breeding season is very short.

In temperate zones, it lasts typically from May to October with one litter producing on average four young. Hazel dormice sometimes attempt—usually unsuccessfully—a second litter. Forest dormice appear to be exceptional in raising three litters. Productivity in Africa, where breeding seasons are much longer, is largely unknown.

Dormice become sexually active after their first hibernation and bouts of wakefulness towards the end of hibernation may be caused by hormone changes that trigger sexual activity. Vocal calls are important in courtship as each sex entices the other with a range of squeaks and whistles. Once mated, the female builds a globular nest and gives birth to pink, blind young weighing just 0.07 oz (2 g). At seven days, they gain gray fur. By 18 days, the fur is brown and the babies can both hear and see. Shortly after, the young are able to accompany their mother on foraging trips. They reach independence after four to six weeks. Longevity is up to about 5.5 years in the wild. A captive garden dormouse lived for five years and six months.

Conservation status

A number of factors conspire to make more than half of all dormouse species at risk under IUCN criteria. The exclusively forest-dwelling species have poor mobility and this makes them highly vulnerable to habitat loss and fragmentation. Furthermore, a nocturnal, arboreal existence makes both survey and research work difficult. The little-understood

Roach's mouse-tailed dormouse was only discovered in Europe in the mid-twentieth century. Despite years of concentrated research, scientists in the United Kingdom only discovered at the end of the twentieth century that hedges were an important habitat for the hazel dormouse.

Dormice may be adversely affected by climate change, which causes habitat alteration and temperature fluctuations. Arousal from hibernation during mild winters forces an animal to expend considerably greater amounts of energy than if it maintained consistently low internal temperatures.

Concerted efforts to understand the complex ecology and difficulties of protecting this vulnerable family have led to a series of international dormouse conferences, where scientists have been able to share information on the appealing but enigmatic Myoxidae.

Significance to humans

The ability of dormice to store reserves of fat in their bodies has made them desirable to humans as food. Their appeal dates back millennia—the Romans kept edible dormice in darkened enclosures called glisaria. Dormouse eating is well documented in southern Africa, Slovenia, and Yugoslavia and there is good reason to suppose it has taken place wherever humans have come into contact with these mammals.

Dormice are also famous for their sustained periods of hibernation and torpor. Indeed, the name comes from the French dormir—to sleep. The hazel dormouse—known in rural England as the sleep-mouse—gained wider notoriety when it was portrayed in Lewis Carroll's book Alice in Wonderland and in the Disney movie nearly a century later.

Species accounts

List of Species

Spectacled dormouse

Graphiurus ocularis

subfamily

Graphiurinae

taxonomy

Graphiurus ocularis (Smith, 1829), Cape Province, South Africa.

other common names

French: Graphiure spectaculaire; German: Brillenschläfer.

physical characteristics

Head and body length 2.7–6.5 in (7–16.5 cm), tail 1.9–5.3 in (5–13.5 cm); weight 0.6–1 oz (18–30 g). Color is grayish with markings on the face, paler underneath.

distribution

Cape Province and southwestern Transvaal, South Africa.

habitat

Wooded rocky areas, generally near water.

behavior

Territorial pairs and their young occupy sizeable areas of up to 34.5 acres (14 ha).

feeding ecology and diet

Seeds, nuts, fruits, grain, insects, eggs, and small vertebrates.

reproductive biology

Breeds in spring or summer with 4–6 young per litter.

conservation status

Classified as Vulnerable on the IUCN Red List and declining.

significance to humans

Formerly more common around human habitation and eaten. Now largely absent because of competition with rats.

Forest dormouse

Dryomys nitedula

subfamily

Leithiinae

taxonomy

Dryomys nitedula (Pallas, 1778), lower Volga River, Russia. Fifteen subspecies.

other common names

French: Lerotin; German: Baumschläfer; Spanish: Muscardino balcanico.

physical characteristics

Head and body length 3.1–5.1 in (8–13 cm), tail 2.35–4.5 in (6–11.3 cm); weight 0.6–1.2 oz (18–34 g). Color is grayish to yellowish brown, buffy white underneath.

distribution

Central Europe and western Asia to Tien Shan mountains.

habitat

Forests and shrubs in gardens and fields.

behavior

Arboreal and highly agile—able to leap distances of up to 6.6 ft (2 m) between trees.

feeding ecology and diet

Carnivorous in summer, eating spiders and other small invertebrates, eggs, and young birds. Otherwise subsists on seeds, buds, and fruit.

reproductive biology

Nests colonially, either in one tree or in adjacent trees. Three litters south of its range and one litter of usually 2–5 young in temperate areas.

conservation status

Classified as Lower Risk/Near Threatened on the IUCN Red List. Loss of forest habitat has caused declines in central Europe.

significance to humans

Causes damage to crops in apple orchards.

Chinese dormouse

Dryomys sichuanensis

subfamily

Leithiinae

taxonomy

Dryomys sichuanensis (Wang, 1985), north Sichuan Province, China.

other common names

French: Lerotin du Sichuan.

physical characteristics

Head and body length 3.5 in (9 cm), tail 3.6–4 in (9.2–10.2 cm); weight 0.8–1.2 oz (24–36 g). Color is grayish to yellowish brown, buffy white underneath.

distribution

Northern Sichuan.

habitat

Subalpine mixed forests.

behavior

Nocturnal; little other data available.

feeding ecology and diet

Thought to be largely gramnivorous.

reproductive biology

Nests in small trees.

conservation status

Classified as Endangered on the IUCN Red List.

significance to humans

None known.

Garden dormouse

Eliomys quercinus

subfamily

Leithiinae

taxonomy

Eliomys quercinus (Linnaeus, 1766), Germany. Fourteen subspecies.

other common names

English: Orchard dormouse; French: Lerot; German: Gartenschläfer; Spanish: Lirón careto.

physical characteristics

Head and body length 3.9–6.9 in (10–17.5 cm), tail 3.5–5.3 in (9–13.5 cm); weight 1.5–4.2 oz (45–120 g). Color is gray to brown, cream to white underneath.

distribution

Europe from France to western Russia, south to southern Spain and Portugal.

habitat

Despite its name, the garden dormouse is most often found in forests. Also cultivated fields, rocky areas, and marshland.

behavior

Although an agile tree climber, this species can also live without trees. Recorded feeding and sleeping together in groups.

feeding ecology and diet

Largely carnivorous, with insects making up to 89% of diet. Also fruit, especially in fall.

reproductive biology

Highly vocal during courtship, with female attracting male using whistling calls.

conservation status

Loss of forest habitat has meant this species is classified as Vulnerable on the IUCN Red List.

significance to humans

Historically, eaten for food by humans.

Roach's mouse-tailed dormouse

Myomimus roachi

subfamily

Leithiinae

taxonomy

Myomimus roachi (Bate, 1937), Mount Carmel, Israel.

other common names

English: Dormouse; French: Loir myomime, loir d'Ognev; German: Mausschläfer; Spanish: Lirón colipelado.

physical characteristics

Head and body length 2.4–4.7 in (6.1–12 cm), tail 2–3.7 in (5.3–9.4 cm); weight 0.7–1.9 oz (21–56 g). Color is ocher and gray, white underneath.

distribution

Southern Bulgaria and western Turkey.

habitat

Open areas with trees, such as the edges of fields and gardens.

behavior

Not a specialized tree dweller, this species appears to spend most of its time on the ground.

feeding ecology and diet

Seeds, nuts, fruits, grain, insects, eggs, and small vertebrates.

reproductive biology

Seven pairs of mammae suggest large numbers of offspring. Breeding biology largely unknown.

conservation status

Classified as Vulnerable on the IUCN Red List.

significance to humans

None known.

Desert dormouse

Selevinia betpakdalaensis

subfamily

Selevinia

taxonomy

Selevinia betpakdalaensis Belusludov and Bashanov, 1939, south Kazakhstan.

other common names

French: Loir du desert.

physical characteristics

Head and body length 2.9–3.7 in (7.5–9.5 cm), tail 2.3–3 in (5.8–7.7 cm); weight 0.6–0.9 oz (18–25 g). Fur is grayish above and whitish underneath.

distribution

Kazakhstan.

habitat

Shrubby thickets in desert, especially wormwood and Spirianthes.

behavior

Thought to emerge at twilight to feed, sheltering from the sun under cover, or possibly in a burrow by day. When threatened, moves in a succession of short jumps.

feeding ecology and diet

Probably wholly carnivorous, feeding on insects and spiders. Can eat three-quarters of its own body weight in one night.

reproductive biology

Nothing is known.

conservation status

Classified as Endangered on the IUCN Red List.

significance to humans

None known.

Japanese dormouse

Glirulus japonicus

subfamily

Myoxinae

taxonomy

Glirulus japonicus (Schinz, 1845), Japan.

other common names

French: Loir du Japon.

physical characteristics

Head and body length 2.5–3.1 in (6.5–8 cm), tail 1.5–2.1 in (4–5.5 cm); weight 0.5–1.4 oz (14–40 g). Color is pale olive brown with a darker stripe along the spine.

distribution

Honshu, Shikoku, Kyushu Island.

habitat

Mountain forest.

behavior

Arboreal and nocturnal. Known to hibernate in buildings and birdhouses.

feeding ecology and diet

Seeds, fruits, insects, and bird eggs.

reproductive biology

An average of four young born in June–July after a month-long gestation.

conservation status

Classified as Endangered on the IUCN Red List.

significance to humans

None known.

Hazel dormouse

Muscardinus avellanarius

subfamily

Myoxinae

taxonomy

Muscardinus avellanarius (Linnaeus, 1758), Sweden. Six sub-species.

other common names

English: Common dormouse; French: Muscardin; German: Haselmaus; Spanish: Muscardino.

physical characteristics

Head and body length 2.35–3.5 in (6–9 cm), tail 2.1–2.9 in (5.5–7.5 cm); weight 0.5–1.4 oz (15–40 g). Color is yellowish brown or yellowish red, white to buff underneath.

distribution

Europe from southern England to western Russia, south to northern Turkey.

habitat

Largely deciduous woodland with varied canopy cover.

behavior

Probably exclusively arboreal. In temperate areas, may hibernate for up to nine months of the year.

feeding ecology and diet

Flowers, fruit, nuts, and seeds. Insects in summer.

reproductive biology

Long-lived species, normally producing a single annual litter of 4–5 young.

conservation status

Classified as Lower Risk/Near Threatened on the IUCN Red List.

significance to humans

Efforts to maintain populations have included reintroductions and nestbox schemes.

Edible dormouse

Myoxus glis

subfamily

Myoxinae

taxonomy

Myoxus glis (Linnaeus, 1766), Germany. Nine subspecies.

other common names

English: Fat dormouse; French: Loir, loir gris; German: Siebenschläfer; Spanish: Lirón (Castillian), lirón gris, rata durmidora (Catalan).

physical characteristics

Head and body length 5.1–7.5 in (13–19 cm), tail 4.3–5.9 in (11–15 cm); weight 2.4–6.3 oz (70–180 g). Color is silvery gray, white underneath.

distribution

Europe, Iran, and Turkmenistan.

habitat

Deciduous and mixed forests, orchards.

behavior

One of the most agile of arboreal dormice—recorded making tree-to-tree leaps of more than 23 ft (7 m).

feeding ecology and diet

Seeds, nuts, berries, and fruit. Insects in summer.

reproductive biology

Apparently a territorial species, with males scent-marking boundaries. Male assists in raising of young and families may stay together through hibernation.

conservation status

Classified as Lower Risk/Near Threatened on the IUCN Red List.

significance to humans

Historically regarded as a food source, particularly as a delicacy. Considered a pest of fruit and vine crops.

Resources

Books

Bright, P., and P. Morris. Dormice. London: The Mammal

Society, 1992.

Kingdon, J. The Kingdon Field Guide to African Mammals. San Diego: Academic Press, 1997.

Macdonald, D. European Mammals: Evolution and behavior. London: Collins, 1995.

——. The New Encyclopaedia of Mammals. Oxford: Oxford University Press, 2001.

Macdonald, D., and P. Barrett. The Collins Field Guide to the Mammals of Britain and Europe. New York: HarperCollins, 1993.

Other

Dormouse Hollow. <http://www.glirarium.org/dormouse>.

Dr. Paul W. Bright. <http://www.rhul.ac.uk/Biological-Sciences/bright/>.

Nowak, R. M. Walker's Mammals of the World Online. Baltimore: Johns Hopkins University Press, 1995. <http://press.jhu.edu/books/walkers_mammals_of_the_world/rodentia.myoxidae>.

Derek William Niemann, BA