Glis glisfat dormouse

Geographic Range

Fat dormice are found throughout most of Europe and parts of western Asia. The range expands as far south as Italy and northern Turkey, and as far north as Latvia. The westernmost range lies in northern Spain, extending throughout Europe and into portions of western Russia and northern Iran. Populations have also been found on several Mediterranean islands, including the British Isles. Range elevations have been recorded from sea level to 2,000 m. (Amori, et al., 2008)


Prime habitat conditions include deciduous and mixed forested regions with large volumes of mast seeding trees. A dense understory with tall, “well-connected” tree canopies is ideal. Beech (Fagus) and oak (Quercus) habitats are preferred, whereas coniferous forests are avoided. Caves, tree cavities, and houses are also frequently inhabited (Krystufek, 2010). Lower altitudes, approximately 1200 to 1300 m above sea level, provide less thermal stress and higher tree strands, proving to be more desirable (Milazzo et al., 2003). Fat dormice shelter in the hollows of trees, rock crevices, burrows among tree roots, animal cavities, piles of debris, attics, barns, and nest boxes. They line their shelters with grass or other vegetation. (Kryštufek, 2010; Milazzo, et al., 2003; Myers and Poor, 2012)

  • Range elevation
    0 to 2000 m
    0.00 to 6561.68 ft
  • Average elevation
    1200 m
    3937.01 ft

Physical Description

Dormice are small to medium sized rodents with short limbs, compact bodies, and bushy tails, bearing some resemblance to squirrels. They have four digits on their front feet and five on their hind feet, containing short, curved claws. They are myomorphous, but differ from other myomorphs in that their zygomatic plate is not as developed. Dormice have a dental formula of 1/1, 0/0, 0-1/0-1, 3/3 with a total of 16 or 20 teeth. (Myers and Poor, 2012). Characteristics of fat dormice that distinguish them from other dormice include lack of spines on the lateral pads of the glans penis, loss of sphenofrontal and stapedial foramina, shortened lateral pterygoid process and fossa pterygoida, concealment of m3 by the coronoid process in the lower jaw (lateral view), lack of perforation in the angular process of the lower jaw, and separation of protoloph and metaloph (Krystufek, 2010). (Kryštufek, 2010; Myers and Poor, 2012)

Glis glis is the largest of the dormice with a typical body length of 160 to 190 mm, tail length of up to 168 mm, and small ears relative to its body size. Differentiation in body size between sexes is not apparent (monomorphic). Individuals are gray in color with a white underside/belly and four to six pairs of nipples (Krystufek, 2010). Fat dormice gain substantial weight before entering hibernation seasonally. (Kryštufek, 2010)

  • Sexual Dimorphism
  • sexes alike
  • Range mass
    120 to 150 g
    4.23 to 5.29 oz
  • Range length
    160 to 190 mm
    6.30 to 7.48 in


Fat dormice are polygamous and promiscuous breeders. Females are territorial and remain within their home range. Males are not, allowing them to pursue available mates. (Kryštufek, 2010)

Unlike many mammals, fat dormice do not mate every year. Instead, reproduction occurs only in years with sufficient mast production. Mating season ranges from June to August, resulting in a single litter approximately one month after copulation. The average litter size is typically 5 young. (Kryštufek, 2010)

  • Breeding interval
    Fat dormice breed based on food availability rather than time intervals.
  • Breeding season
    Breeding season ranges from June to August.
  • Average number of offspring
  • Average gestation period
    1 months
  • Average time to independence
    30 days
  • Range age at sexual or reproductive maturity (female)
    351 to 380 days

Little is known about parental care in this species. However, as in most mammals, females take on the majority of parental care through gestation and lactation. (Myers and Poor, 2012)

  • Parental Investment
  • altricial
  • female parental care
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female


Wild fat dormice have been known to live up to 12 years (Myers and Poor, 2012) but on average live approximately 9 years (Krystufek, 2010). (Kryštufek, 2010; Myers and Poor, 2012)


Like most dormice, fat dormice are arboreal and nocturnal, spending most of the daytime hours in nests or tree cavities (Krystufek, 2010; Myers and Poor, 2012). A significant feature of their behavior is that they practice all three types of dormancy: daily torpor, hibernation, and aestivation. Daily torpor is present throughout the year in coordination with the other two dormancy types. Fat dormice are considered true hibernators, staying in their hibernacula from autumn to spring, living solely on fat stores (Wilz and Heldmaier, 2010). Their hibernacula are located in soil cavities. Despite the fact that dormice are primarily non-social, they do hibernate and occasionally share nests with close relatives (Krystufek, 2010). (Kryštufek, 2010; Wilz and Heldmaier, 2000)

Home Range

Dormice rarely travel, except when searching for food. Males, however, have significantly larger home ranges than females (females are territorial). Home ranges in fat dormice are density dependent, depending on food availability rather than reproduction (Kryštufek, 2010). (Kryštufek, 2010)

Communication and Perception

Acoustic communication includes twitters, chirps, shrieks, churrs, whistles, tooth-chattering, and buzzing (in juveniles) (Hutterer and Peters, 2001). When and why these communications occur has not been extensively studied. Olfactory communication consists of marking territories with glandular excretions (Myers and Poor, 2012). (Hutterer and Peters, 2001; Myers and Poor, 2012)

Food Habits

Fat dormice are primarily herbivorous, but can be carnivorous. Beech mast, acorns, and hazelnuts are their main source of nutrition. Fleshy fruits (blackberries, apples, pears, etc.) also comprise a significant amount of their diet, especially in the summer months. Other sources of food include flowers and leaves, arthropods, fungi, mosses, invertebrates (slugs, caterpillars, aphids, myriapods, and beetles), and hole-nesting birds, but these are uncommon and tend only to be an option when primary food sources are not available (Krystufek, 2010). (Kryštufek, 2010)

  • Animal Foods
  • birds
  • eggs
  • insects
  • terrestrial non-insect arthropods
  • Plant Foods
  • leaves
  • wood, bark, or stems
  • seeds, grains, and nuts
  • fruit
  • flowers
  • bryophytes
  • Other Foods
  • fungus


There are at least 14 known vertebrates that prey on fat dormice. Owls are their main source of predation, including barn owls (Tyto alba), Eurasian tawny owls (Strix aluco), long-eared owls (Asio otus), and little owls (Athene noctua). Other predators include golden eagles (Aquila chrysaetos), roof rats (Rattus rattus), gray wolves (Canis lupus), red foxes (Vulpes vulpes), brown bears (Ursus arctos), European pine martens (Martes martes), wildcats (Felis silvestris), and wild boar (Sus scrofa) (Krystufek, 2010). The typical response to alarm is a bite, but may also include hissing, spitting, and leaping. Dormice also have the capability of tail regeneration if lost to predators (Myers and Poor, 2012). (Kryštufek, 2010; Myers and Poor, 2012)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Dormice are primary consumers, eating nuts, fruits, mosses, and fungi. They can also be considered secondary consumers due to their occasional consumption of small invertebrates. In turn, they fall prey to owls and small carnivores (Krystufek, 2010). They are hosts to a wide variety of parasites. (Kryštufek, 2010)

Commensal/Parasitic Species
  • squirrel fleas (Ceratopsyllus sciurorum)
  • lice (Siphonaptera)
  • mites (Acari)
  • protists (Apicomplexa)
  • trematode worms (Trematoda)
  • nematode worms (Nematoda)
  • sucking lice (Anoplura)
  • bed bugs (Cimex)

Economic Importance for Humans: Positive

Fat dormice are trapped and hunted for their soft fur as well as for meat (Myers and Poor, 2012). Some hunt this species recreationally (Amori et al., 2008). (Amori, et al., 2008; Myers and Poor, 2012)

  • Positive Impacts
  • food
  • body parts are source of valuable material

Economic Importance for Humans: Negative

Fat dormice are sometimes seen as a nuisance species, inhabiting homes and gardens. (Amori et al., 2008). They have also been known to strip trees of their bark, leading to decay and possible infection (Montecchi et al., 2010). (Amori, et al., 2008; Montecchio, et al., 2010)

  • Negative Impacts
  • household pest

Conservation Status

Fat dormice are considered "least concern" by the IUCN because they are widespread, common, and tolerate human disturbance.

Other Comments

Glis glis was formerly referred to as Myoxus glis. It is the only extant species of the genus Glis (Krystufek, 2010). (Kryštufek, 2010)


Katie Fitzke (author), University of Wisconsin - Stevens Point, Christopher Yahnke (editor), University of Wisconsin-Stevens Point, Tanya Dewey (editor), University of Michigan-Ann Arbor, Shaina Stewart (editor), 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


having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.


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.

female parental care

parental care is carried out by females


union of egg and spermatozoan


A substance that provides both nutrients and energy to a living thing.


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


an animal that mainly eats fruit


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


an organism that obtains nutrients from other organisms in a harmful way that doesn't cause immediate death


having more than one female as a mate at one time

scent marks

communicates by producing scents from special gland(s) and placing them on a surface whether others can smell or taste them

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

stores or caches food

places a food item in a special place to be eaten later. Also called "hoarding"


living in residential areas on the outskirts of large cities or towns.


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


living in cities and large towns, landscapes dominated by human structures and activity.


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.


Amori, G., R. Hutterer, B. Kryštufek, N. Yigit, G. Mitsain, L. Muñoz, H. Meinig, R. Juškaitis. 2008. "Glis glis" (On-line). The IUCN Red List of Threatened Species. Accessed August 21, 2013 at

Hutterer, R., G. Peters. 2001. "The vocal repertoIre of Graphiurus parvus, and comparIsons wIth other specIes of dormIce" (On-line pdf). Accessed August 21, 2013 at‎.

Kryštufek, B. 2010. "Glis glis (Rodentia: Gliridae)" (On-line pdf). Accessed August 21, 2013 at

Milazzo, A., W. Falletta, M. Sara. 2003. "HABITAT SELECTION OF FAT DORMOUSE (GLIS GLIS ITALICUS) IN DECIDUOUS WOODLANDS OF SICILY" (On-line). Accessed August 21, 2013 at

Montecchio, L., L. Scattolin, R. De Battisti. 2010. "Dormouse injuries predispose beech to infection by Neonectria ditissima" (On-line). EBSCOhost. Accessed August 21, 2013 at

Myers, P., A. Poor. 2012. "Gliridae:dormice and hazel mice" (On-line). Animal Diversity Web. Accessed August 21, 2013 at

Wilz, M., G. Heldmaier. 2000. "Comparison of hibernation, estivation and daily torpor in the edible dormouse, Glis glis" (On-line pdf). Accessed August 21, 2013 at