The hazel dormouse (Muscardinus avellanarius) is one of the UK's most charming and threatened small mammals, spending almost half the year in deep hibernation. Its extreme dependence on structurally diverse deciduous woodland and hedgerows makes it highly sensitive to habitat loss — and its welfare during both active and hibernating periods is closely tied to habitat quality.
Dormice enter hibernation from October through April — the longest hibernation period of any British mammal. During hibernation, body temperature drops to near-ambient levels, heart rate slows to a few beats per minute, and metabolic rate is reduced by 95%. Sufficient fat reserves accumulated during autumn feeding are essential for survival through winter. Poor habitat producing insufficient food in late summer results in underweight dormice entering hibernation with inadequate reserves — a major welfare and mortality risk.
Dormice require: ancient woodland or structurally diverse hedgerows with diverse shrub species, autumn berry crops (particularly hazel, honeysuckle, blackberries), undisturbed hibernation sites (ground level in dense leaf litter or low vegetation), and woodland with continuous canopy connections enabling arboreal movement without ground travel (where predation risk is high). Dormice rarely descend to ground level — isolated woodland patches with no canopy connectivity effectively trap populations.
Dormouse nest boxes (specialized oval boxes with entrance holes facing the tree) enable population monitoring and supplementary nesting sites. Woodland management maintaining structural diversity — coppice rotation, shrub layer retention, continuity of connections — directly supports dormouse welfare. Hedgerow management avoiding cutting during the active season protects animals within hedges.
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