Edible dormouse (Glis glis)
|Also known as:||fat dormouse, sleeper, Spanish rat, squirrel-tailed dormouse|
|Size||Head-body length: 12 - 22.5 cm (2)|
Tail length: 11 - 20 cm (2)
|Weight||70 - 250 g (2)|
- The edible dormouse is the largest dormouse species.
- The edible dormouse hibernates for seven to eight months of the year, remaining dormant underground and surviving on its fat reserves.
- The edible dormouse was considered a great delicacy in Roman times, leading to its common name.
- Unusually for a small rodent, the edible dormouse is long-lived and does not breed every year.
The edible dormouse is classified as Least Concern (LC) on the IUCN Red List (1).
Also known as the fat dormouse, the edible dormouse (Glis glis) is the largest dormouse species and the only member of its particular genus (3). Somewhat squirrel-like in appearance, this rodent has short, thick fur and a long, bushy tail (2) (3) (4) (5) (6) (7), which is generally held flat (5) (6). Its legs are short and the soles of its feet have naked, rough pads which help with grip as the edible dormouse climbs about in trees (3) (4).
The edible dormouse’s fur is greyish-brown to silvery grey on the upperparts, with slightly lighter flanks, and the underparts of the body are white to yellowish (2) (3) (5) (7). The tail is usually slightly darker than the back (3), and there are dark stripes down the outside of the legs (2) (6). The edible dormouse usually has a dark ring of fur around each eye (2) (3) (6) (7), making the eyes look quite large (7), and its ears are quite short and rounded (3).
The male and female edible dormouse are similar in size and appearance, while juveniles are a slightly duller grey than the adults (3).
The common name of the edible dormouse comes from the ancient Roman practice of fattening this species up to be eaten as a delicacy. Colonies of edible dormice were kept in enclosures planted with nut-bearing trees, and prior to a feast the animals were confined to earthenware pots to be fattened up on acorns and chestnuts (3) (4) (7).
The edible dormouse occurs across much of Europe, except for the westernmost coasts, most of the Iberian Peninsula and Scandinavia. This species occurs on a number of Mediterranean islands, including Sardinia, Corsica, Sicily and Crete, and its range extends eastwards to the Caucasus, northern Iran, and the Volga River in Russia (1) (2) (3) (4) (5).
In 1902, the edible dormouse was deliberately introduced to England, and a population now occurs in a small area around the Chiltern Hills, to the northwest of London (2) (3) (4) (5) (6) (7).
An arboreal species, the edible dormouse typically inhabits deciduous and mixed woodland with plenty of nut-bearing trees, such as beech (Fagus species) and oak (Quercus species) (1) (3) (4) (5). It can also be found in parks, gardens and orchards (1) (2) (3) (4) (5), as well as in Mediterranean shrubland (1) (3), but tends to avoid coniferous forest and pine plantations (3). This species has also been found sheltering inside caves (3).
The edible dormouse often occurs on the outskirts of towns and even inside some cities (3), and it frequently enters houses (1) (2) (3) (5) (7). This rodent occurs at elevations from sea level to around 2,000 metres (1) (3).
The edible dormouse is mainly nocturnal, spending the daylight hours sheltering in a tree hollow, in a nest constructed from plant material, in a rock crevice, or inside an artificial nestbox or human dwelling (2) (3) (4) (6) (7). It will also take over abandoned bird nests and squirrel dreys (3) (7). An agile climber, the edible dormouse is capable of moving down tree trunks head first and can cling from branches by its hind feet. This species spends most of its life in the trees, rarely coming to the ground (3).
The diet of the edible dormouse consists mainly of plant matter, particularly nuts and seeds such as acorns, hazelnuts and beech mast. The edible dormouse also eats berries and other soft fruits, as well as buds, leaves, bark and fungi. Insects are taken occasionally, and this species is also known to eat bird eggs and nestlings (2) (3) (4).
The edible dormouse communicates through a range of squeaks, chirps, whistles and squeals, and it also uses scent to mark its territory (3) (4) (5). Individuals can be quarrelsome and males have been reported to fight aggressively during the breeding season, although small groups of this species have been known to hibernate together (3) (4).
The edible dormouse has a long hibernation period that begins between September and November and lasts until May or June (3) (4) (6) (8). Unlike some small mammals, this species does not store food for the hibernation period, instead surviving on large fat reserves accumulated in late summer and autumn (3) (7). The edible dormouse usually hibernates in a burrow or cavity underground, often under the roots of trees (3) (6) and sometimes as much as a metre below the surface (4). It can also sometimes be found in cellars and attics (3) (6).
The mating season of the edible dormouse occurs soon after individuals have emerged from hibernation, between about June and August (3) (4). Males usually mate with more than one female (3) (5). The female edible dormouse gives birth to a single litter of young (2) (3) (4) (5) (8) after a gestation period of around 20 to 31 days (3). Litter size ranges from about two to ten (4), but nests may contain more young than this as females sometimes share the same nest and nurse each other’s offspring (3) (8).
The young dormice are born relatively late in the year, from around July to September (3) (4) (8), when food is most available (3). The young, which are helpless, naked and blind at birth, open their eyes at about 21 to 23 days old and leave the nest at 30 days old (2) (3). As the young edible dormice are born late in the year, they must grow rapidly to be able to survive the winter (3).
The edible dormouse can sometimes breed in the year following its birth, but some females may not give birth until their third year. This species is unusually long-lived for a small rodent, having a life expectancy of about nine years (3) (8). Some of the key tree species on which the edible dormouse relies for food, including beech and oak, only produce large seed crops every few years, with seed production in the intervening years being low or even failing entirely (3). The edible dormouse’s long lifespan and relatively large litter size compensate for the fact that this species does not usually breed in years of low food availability (3) (8) (9). In non-reproductive years, the edible dormouse has been found to sometimes return to a dormant state underground, being active for only a few weeks of the year (9).
The edible dormouse is a widespread and abundant species, and is not currently considered to be at risk of extinction (1). However, populations in the northern parts of its range, such as in Poland and Lithuania, are thought to be declining (1) (3) (10). In countries such as Lithuania, the main threat to this mammal is the destruction of its forest habitat (1) (4) (10).
As well as being a delicacy in Roman times, the edible dormouse has more recently been hunted for food, fur and medicinal uses in a number of countries, and it is still a game species in Slovenia and Croatia (1) (3). The exact impacts of hunting on the edible dormouse are not known (3).
In both its native range and its introduced range in England, the edible dormouse is often considered to be a pest species. In some areas, it is viewed as an agricultural pest (1), causing damage to fruit trees and vineyards and also stripping bark from trees (2) (3) (4) (5). It can also be a nuisance in houses, gnawing rafters, pipes and wiring, as well as fouling surfaces with its droppings and being quite noisy (2) (5) (6). In some areas, the edible dormouse may compete with hole-nesting birds for nest boxes, and can potentially threaten some species by eating their eggs and young (3).
The edible dormouse is protected under Appendix III of the Bern Convention, meaning that any exploitation of this species should be regulated (11). It also occurs in many protected areas throughout its range (1). In Lithuania, the edible dormouse is protected and has been chosen as the symbol of the Lithuanian Fund for Nature (10), while in Poland a reintroduction programme for the species began in 1997 (3).
Where the edible dormouse has become a pest, measures have sometimes been taken to control it (3). In the edible dormouse’s non-native range in England, it is an offence to release the species into the wild or to allow it to escape (6). However, the legal status of the edible dormouse in the UK is confusing, as it is also legally protected and cannot be trapped without a licence (12).
Find out more about the edible dormouse:
BBC Nature - Edible dormouse:
People’s Trust for Endangered Species - Edible dormice:
GB Non-native Species Secretariat (NNSS): Factsheet - Edible dormouse:
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- Arboreal: an animal which lives or spends a large amount of time in trees.
- Deciduous woodland: woodland consisting mainly of deciduous trees, which shed their leaves at the end of the growing season.
- Genus: a category used in taxonomy, which is below ‘family’ and above ‘species’. A genus tends to contain species that have characteristics in common. The genus forms the first part of a ‘binomial’ Latin species name; the second part is the specific name.
- Gestation: the state of being pregnant; the period from conception to birth.
- Hibernation: a winter survival strategy in which an animal’s metabolic rate slows down and a state of deep sleep is attained. While hibernating, animals survive on stored reserves of fat that they have accumulated in summer.
- Nocturnal: active at night.
- Territory: an area occupied and defended by an animal, a pair of animals or a colony.
IUCN Red List (October, 2013)
- Long, J.L. (2003) Introduced Mammals of the World: Their History, Distribution and Influence. CSIRO Publishing, Collingwood, Australia.
- Kryštufek, B. (2010) Glis glis (Rodentia: Gliridae). Mammalian Species, 42(865): 195-206.
- Nowak, R.M. (1991) Walker’s Mammals of the World. The Johns Hopkins University Press, Baltimore and London.
GB Non-native Species Secretariat (NNSS): Factsheet - Edible dormouse (October, 2013)
GB Non-native Species Secretariat (NNSS): Identification Sheet - Edible dormouse (October, 2013)
- Burton, M. and Burton, R. (2002) International Wildlife Encyclopedia. Third Edition. Marshall Cavendish, New York.
- Morris, P.A. and Morris, M.J. (2010) A 13-year population study of the edible dormouse Glis glis in Britain. Acta Theriologica, 55(3): 279-288.
- Bieber, C. and Ruf, T. (2009) Summer dormancy in edible dormice (Glis glis) without energetic constraints. Naturwissenschaften, 96(1): 165-171.
Lithuania Fund for Nature - Edible dormouse (October, 2013)
Council of Europe: Bern Convention (October, 2013)
- Morris, P.A. (1997) A review of the fat dormouse (Glis glis) in Britain. Natura Croatica, 6(2): 163-176.