The hazel dormouse (Muscardinus avellanarius) is one of Britain's most endearing but elusive mammals, and one facing severe conservation pressures. UK dormouse populations have declined by around 70% since the 1990s, with the species now largely restricted to ancient woodland and scrub in southern England and Wales.
Ecology
Dormice are arboreal, spending almost their entire lives in the canopy and shrub layer of woodland. They feed on flowers, berries, hazelnuts, and insects, preferring diverse woodland with species that provide food across the seasons (hazel, honeysuckle, bramble, rowan). They hibernate in nests on or near the ground from October to April — the longest hibernation period of any British mammal — living up to 5 years in the wild.
Causes of Decline
Habitat loss: Ancient woodland clearance and fragmentation has isolated populations, preventing recolonisation of improved habitats
Loss of coppice management: The abandonment of traditional woodland coppicing has reduced the diverse, low-level structure dormice require
Climate change: Warmer, wetter autumns disrupt hibernation; late springs reduce early food availability
Connectivity: Dormice cannot cross open ground; fragmented woodlands become isolated populations
Legal Protection
Dormice are protected under Schedule 5 of the Wildlife and Countryside Act 1981 and the Conservation of Habitats and Species Regulations 2017. Any development affecting dormouse habitat requires a survey, EPS licence, and mitigation including translocation where necessary.
Conservation Actions
Dormouse nest box programmes: box networks in suitable woodland enable population monitoring and support nesting
Coppice restoration: reinstatement of traditional coppice management in historically managed woodland benefits dormice directly