Mammals · Rodentia · Gliridae

Hazel Dormouse

Muscardinus avellanarius

Least Concern

The species is abundant and widely distributed; it faces no significant short-term risk. See full glossary

A tiny rodent with a stocky body and dense fur, with a striking contrast between the warm cinnamon-coloured back and the white belly. Its tail is long and bushy, unlike the scaly tail of mice. It is the only living species in the genus Muscardinus.

Weight

17 g – 40 g

Size

6 cm – 9 cm

Diet

Omnivore

Combines animal and plant food depending on availability.

Activity

Nocturnal

Active mainly at night.

Social structure

Solitary

Lives and hunts alone, joining others only to breed.

Sighting difficulty

Easy

Omnivore Nocturnal Solitary Mammal

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Fun facts

It spends most of its life asleep: it hibernates from October to April or May and, if the summer is cold and food is scarce, it also goes into torpor.
Its specific epithet, avellanarius, comes from the hazel, its main source of fat before hibernating.
You can tell it has eaten a hazelnut by the clean round hole it leaves in the shell: a squirrel would smash it and a vole would leave a ragged gap.

Life cycle & biology

Skeleton type: Vertebrate - internal bony skeleton (mammal)
Habitat & environment: Deciduous woodland, hedgerows and gardens of Europe and Asia Minor, from France to the Urals and from Sweden to Greece and northern Turkey. It depends on tall hedgerows well connected to woodland
Size at birth: The young are born naked and blind
Sexual maturity: In the year after the one they were born in
Gestation / incubation: 22 - 25 days
Litter / clutch size: 3-7 young as a rule, with a maximum of 9, and one or two litters a year

Sources consulted: IUCN Red List (e.T13992); Wachtendorf 1951 (tipología de nidos); Armitage et al. 2025, Oecologia; People's Trust for Endangered Species; Antropocene.it