Hazel dormouse

Hazel dormouse
Temporal range: Middle Miocene – Recent
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Rodentia
Family: Gliridae
Subfamily: Leithiinae
Genus: Muscardinus
Kaup, 1829
Species: M. avellanarius
Binomial name
Muscardinus avellanarius
(Linnaeus, 1758)
Geographic range

The hazel dormouse or common dormouse (Muscardinus avellanarius) is a small mammal and the only living species in the genus Muscardinus.[2] It is 6 to 9 cm (2.4 to 3.5 in) long with a tail of 5.7 to 7.5 cm (2.2 to 3.0 in). It weighs 17 to 20 g (0.60 to 0.71 oz), although this increases to 30 to 40 grams (1.1 to 1.4 oz) just before hibernation. The hazel dormouse hibernates from October to April–May.


The hazel dormouse has golden-brown fur and large, black eyes. It is a nocturnal creature and spends most of its waking hours among the branches of trees looking for food. It will make long detours rather than come down to the ground and expose itself to danger.

Distribution and habitat

The hazel dormouse is native to northern Europe and Asia Minor. It is the only dormouse native to the British Isles, and is therefore often referred to simply as the "dormouse" in British sources, although the edible dormouse, Glis glis, has been accidentally introduced and now has an established population. Though Ireland has no native dormouse, the hazel dormouse has recently been found in County Kildare,[3] and appears to be spreading rapidly, helped by the prevalence of hedgerows in the Irish countryside.[4] The first record of the dormouse in Ireland was noted in Co. Kildare in 2010.[5]

The United Kingdom distribution of the hazel dormouse can be found on the National Biodivestity Network website. A 2016 study finds that hasel dormice in Britain have declined by over one third since 2000. Woodland habitat loss and management and a warming climate are seen as material threats to their future status.[6]


Protection status

The hazel dormouse is protected in the UK under the Wildlife and Countryside Act.[8]


In winter (October to November), the hazel dormouse will hibernate in nests on the ground, in the base of old coppiced trees or hazel stools, under piles of leaves or under log piles as these situations are not subject to extreme variations in either temperature or humidity. Dormice are almost completely arboreal in habit but much less reluctant to cross open ground than was thought even recently. When it wakes up in spring (late April or early May), it builds woven nests of shredded honeysuckle bark, fresh leaves and grasses in the undergrowth. If the weather is cold and wet, and food scarce, it saves energy by going into torpor; it curls up into a ball and goes to sleep. The hazel dormouse, therefore, spends a large proportion of its life sleeping − either hibernating in winter or in torpor in summer.

Examination of hazelnuts may show a neat, round hole in the shell. This indicates it has been opened by a small rodent, e.g., the dormouse, wood mouse, or bank vole. Other animals, such as squirrels or jays, will either split the shell completely in half or make a jagged hole in it.

Further examination reveals the cut surface of the hole has toothmarks which follow the direction of the shell. In addition, there will be toothmarks on the outer surface of the nut, at an angle of about 45 degrees to the cut surface. Woodmice and voles bite across the nutshell leaving clear parallel toothmarks from inside to outside. Woodmice also leave toothmarks on the outer surface of the nut but voles do not.


The hazel dormouse requires a variety of arboreal foods to survive. It eats berries and nuts and other fruit with hazelnuts being the main food for fattening up before hibernation. The dormouse also eats hornbeam and blackthorn fruit where hazel is scarce. Other food sources are the buds of young leaves, and flowers which provide nectar and pollen. The dormouse also eats insects found on food-source trees, particularly aphids and caterpillars.

Plants of value to dormice



  1. Amori, G.; Hutterer, R.; Kryštufek, B.; Yigit, N.; Mitsain, G.; Meinig, H. & Juškaitis, R. (2008). "Muscardinus avellanarius". IUCN Red List of Threatened Species. Version 2008. International Union for Conservation of Nature. Retrieved 29 October 2009.
  2. Mitchell-Jones, A. J.; Amori, G.; Bogdanowicz, W.; Kryštufek, B.; Reijnders, P.J.H.; Spitzenberger, F.; Stubbe, M.; Thissen, J.B.M.; Vohralik, V. & Zima, J. (1999). The atlas of European Mammals. London: Academic Press. p. 484.
  3. Ahlstrom, Dick. (2013-07-16). "The dormouse makes first appearance in Ireland". Irish Times.
  4. Mooney, John. (2013-09-08). "Rare UK dormouse moved to Ireland". Sunday Times.
  5. Marnell, F. and Donoher, D. (2013). First confirmed record of Hazel Dormouse (Muscardinus avellanarius) in the wild in Ireland. Ir Nat J. 33: 77-78
  6. 1 2 Aldred, Jessica (9 September 2016). "Britain's dormice have declined by a third since 2000, report shows". The Guardian. London, UK. Retrieved 2016-09-09.
  7. The Dormouse Conservation Handbook published by Natural England
  8. Dormouse: European protected species. Natural England Species Information Note SIN005 (19 October 2007)
  9. Hedgerows for Dormice. Ptes.org. Retrieved on 2012-12-28.
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