Hazel Dormouse

Identification

The hazel dormouse is a tiny, endearing rodent with a body length of about 10 centimetres and a distinctive long tail adding a further 5.7 to 7.5 centimetres. It weighs a mere 17 to 20 grams in its active season, though this increases to 30–40 grams before hibernation. The animal is easily recognised by its reddish-brown fur, which can vary to golden-brown or yellow-orange-brown tones, becoming lighter on the underside. Its most striking features are its large, prominent black eyes and small, underdeveloped ears. The tail is notably long and completely covered in hair, giving the creature an elegant, squirrel-like appearance.

Range & Habitat

The hazel dormouse is native to northern Europe and Asia Minor, and is the only dormouse species native to the British Isles. It has recently been discovered spreading in Ireland, having appeared in County Kildare in 2010. The species thrives in deciduous woodlands but also inhabits hedgerows and scrub. Sites with abundant honeysuckle, yew, and birch trees support higher populations. Unfortunately, the species has suffered significantly, with populations estimated to have declined by 72% between 1993 and 2014, largely due to woodland habitat loss and climate change impacts.

Behaviour & Diet

The hazel dormouse is a nocturnal, almost entirely arboreal creature that spends most waking hours foraging among tree branches, rarely venturing to the ground. It hibernates from October through April or May, building ground-level nests at the base of old coppiced trees, under leaves, or log piles. Upon waking in spring, it constructs intricate woven nests from shredded honeysuckle bark, fresh leaves, and grasses. During cold, wet summers with scarce food, the dormouse enters torpor, curling into a ball to conserve energy. It seldom travels more than 70 metres from its nest.

The dormouse requires diverse tree foods to survive. Hazelnuts are its primary fattening food before hibernation, eaten with a characteristic neat, round hole left in the shell. It also consumes berries, fruits, nuts, buds, flowers providing nectar and pollen, and insects such as aphids and caterpillars found on food trees. Where hazel is scarce, it relies on hornbeam and blackthorn fruits, as well as alder buckthorn berries.

Best Time & Places to See It

The hazel dormouse is strictly nocturnal and spends much of its life sleeping, making encounters challenging. Late spring through early autumn, when the dormouse is active and building its summer nests, offers the best window for observation. Deciduous woodlands with healthy understory vegetation, particularly hazel coppice, hedgerows rich in honeysuckle, and scrubland in Britain and northern Europe are prime habitats. Look in areas where the recently expanding Irish population has been recorded, particularly in County Kildare.

Photography Tips

Photographing hazel dormice requires patience and nocturnal fieldcraft. Target woodlands and hedgerows during calm nights in late spring and summer when activity peaks. Position yourself quietly near productive food trees, particularly hazel, honeysuckle, and yew, using red-filtered torchlight to preserve night vision and minimise disturbance. A camera trap with infrared triggers set at nest sites or along regular travel routes may yield remarkable images of this elusive, delicate creature. Fast film and image stabilisation are essential for capturing this small, agile nocturnal forager among the branches.