Hazel Dormouse

Field guide to the most commonly encountered mammals and birds

Here, we provide some basic information regarding commonly observed species (plus some others about which we have had queries).

Feel free to contact us by email if you have any questions regarding species you have encountered on the site.

For more information about mammals, we recommend the Mammal Society's species hub, here, and MammalNet here. For birds, excellent resources are available from the RSPB (here) and the BTO (here).

Scientific name: Muscardinus avellanarius

Family: Gliridae

Appearance: The Hazel Dormouse has golden-brown fur and is the only British small mammal that has a furry tail. It has large black eyes and long whiskers. It also has long toes which are an adaptation for climbing.

Size: Head and body 6-9 cm; Tail 5.7 – 6.8 cm; Weight 15-35 g.

Natural history: Once widespread and relatively common the Hazel Dormouse has been in long-term decline and is now only patchily distributed - mainly in southern England in in Wales. Even before its decline the Hazel Dormouse was difficult to see as it spends over half the year in hibernation (October to May) and when active is strictly nocturnal. It typically occupies deciduous woodland with a diverse understorey but, may also be found in overgrown hedgerows or scrub. Its diet is mainly vegetarian and is extremely varied utilising a wide range of flowers, pollen, fruits, berries and nuts throughout the season. The females give birth to (usually) one litter of around four young a year in late July or August. Males play no part in raising the young which start to leave the nest after about 30 days.