Hazel (or Common) dormouse
Native and localised. Rare and vulnerable to extinction
Hazel dormice have golden-brown fur and large black eyes and, distinctively, they are the only small British mammal with a furry tail. They are nocturnal and spend almost all of their time in the branches of trees during the summer, rarely coming down to the ground. They have sometimes been found asleep in old bird nests but they weave their own nests (often in brambles or other shrubs) from strips of honeysuckle bark or a similar plant, surrounded by a layer of green leaves. When conditions are cold or wet, or if food is scarce, dormice curl up into a ball and go into a state similar to hibernation for a short time (called torpor) in order to save energy. Between October and May dormice hibernate in nests beneath the leaf litter on the forest floor or in the base of hedgerows.
Head-body length: 6 – 9 cm
Tail length: A little shorter than the body
Weight: 15 – 35 g
Lifespan: Up to five years
Litters of three to seven pups are typically born in July or August but may be as early as May or as late as October. Juveniles leave their mother’s nest after about two months and must be at least 15 g in weight to survive hibernation. Dormice usually have a single litter each year but if the summer is long, may produce a second.
Flowers, honeysuckle and pollen in spring; fruits, hazelnuts, beechmast and sweet chestnuts in the autumn. They will also eat small insects such as aphids.
Deciduous woodland with new growth, scrub, and large, overgrown hedgerows. They are sometimes found in conifer plantations.
Occasionally owls, weasels and cats but they have few natural predators.
Habitat loss and fragmentation; climate change.
Status & conservation
Native and localised. Hazel dormice are rare and vulnerable to extinction in the UK. They are a priority species in the UK Biodiversity Action Plan. They are protected under the Wildlife and Countryside Act 1981.
Population size & distribution
UK population 45,000. There has been a long-term decline in numbers, which continues. There is an indication however that the decline in recent years is less steep. Hazel dormice are patchily distributed, mostly in southern counties of England and in Wales.
Did you know?
Wood mice, bank voles and hazel dormice feed on hazelnuts by gnawing a round hole in the shell and each leaves distinctive marks. The tooth-marks of dormice run parallel to the edge of the hole, rather than outwards from its centre, so that the rim looks smooth, and there are few tooth-marks elsewhere on the nut. In contrast, the tooth-marks of mice and voles run outwards, so that the rim of the hole looks like the milled edge of a coin.