Field Guide
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Hazel Dormouse
Muscardinus avellanarius
Not yet photographed by the community
Chestnut-golden; hibernates Oct–April; declining woodland species.
Species Profile
UK Red List (Near Threatened); protected under the Wildlife and Countryside Act 1981; a Protected Species under UK law.
- Lifespan
- 4–5 years in the wild, up to 9 years in captivity
- Size & Weight
- 12–15 cm body length, tail 6–8 cm; 15–30 g
- Habitat
- Deciduous and mixed woodlands, hazel coppices, hedgerows, and scrubland with dense undergrowth and climbing vegetation.
- UK Distribution
- Resident throughout southern England, Wales, and southern Scotland, though with a highly fragmented range. Absent from most of northern England and Scotland. Distribution has contracted significantly.
- Diet
- Omnivorous, feeding on hazelnuts (particularly favoured), berries, seeds, insects, and occasionally bird eggs or nestlings, especially in spring.
- Predators
- Owls (tawny and barn owls), weasels, stoats, foxes, and domestic cats.
- Mating Season
- June to August
- Breeding
- Single litter of 4–7 young born June–August after a gestation of 22–24 days. Young are weaned at 6–8 weeks; only one brood per year.
- Behaviour
- Solitary and nocturnal, arboreal and skilled climbers that nest in shrubs and small trees. They enter torpor (a hibernation-like state) in winter, typically from October to April, during which they lose up to 50% of their body weight. Highly specialized habitat requirements make them vulnerable to woodland fragmentation.
- •Hazel dormice build elaborate spherical nests woven from honeysuckle bark and grass, typically placed 1–3 metres high in shrubs.
- •They are one of only three British mammals that enter torpor, alongside hedgehogs and bats.
- •The name 'dormouse' derives from the Old French 'dormir' (to sleep), reflecting their lengthy winter dormancy.
- •In spring, male dormice produce a distinctive churring or purring vocalisation to attract females.
- •Hazel dormice have declined by approximately 95% since the 1950s due to habitat loss, with fewer than 10,000 individuals estimated remaining in the UK.
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