Every child is familiar with this mousesized
rodent from its appearance at the Mad Hatter’s tea party, but few people have
seen them ‘in the flesh’ because of their
scarcity and nocturnal habits. A plump,
mouse-sized animal with a distinctive long
bushy tail, the adult dormouse is a golden
or orange brown. They have prominent black eyes, long whiskers, and short furred ears. The feet and nose are naked. Animals with white tips to their tails are not uncommon, and occasionally tails may be short or absent altogether, presumably following some injury. During the summer adult dormice weigh 16 to 20 g but they can double in weight in the autumn as they prepare for hibernation.
Dormice feeding on hazel open the nuts in a characteristic way with their tooth marks following the line of the shell. Nuts are dropped beneath the branches of the tree rather than stored. Dormice spend daylight hours in domed woven nests assembled from fresh leaves and honeysuckle bark in scrub and low trees. These grapefruit-sized nests have no obvious entrance hole; larger nests may be built for breeding and the dormouse may also use convenient cavities such as bird boxes or old squirrel dreys. Dormice build their hibernation nests at ground level, making small
tightly woven nests in moist places such as hazel stools, under logs or leaf piles or even in rockeries.
Hazel nut opened by dormouse
Images © Jen Bousfield
© Jenny Stuart
Where dormice are present they occur at naturally low densities due to their habitat and food
requirements, so they are vulnerable to habitat fragmentation and
damage. Dormice and their habitat are protected under European and British legislation and any disturbance must be licensed by Natural England. They are listed as a priority species under both the UK and Cornwall BAPs. Dormouse populations at 338 sites across the country are currently studied under the National Dormouse Monitoring
Programme coordinated by the People’s Trust for Endangered Species. Reintroduction programmes have taken place in 11 counties where the animal used to occur.
Dormice are perhaps our most unusual rodents - eschewing the ‘live fast, die young‘
strategy of mice and voles, they can survive for 5 or 6 years in the wild. Although often considered to be an inhabitant of woodlands with a well-developed shrub layer, more exhaustive surveys have found them in hedgerows, coniferous woodland, heathland
and coastal scrub. Dormouse do not eat much plant material since they lack the
digestive capacity to break down cellulose, instead they rely on a variety of invertebrates, fruits, nuts and flowers. Hazel nuts are considered to be an important food source for dormice, especially as they build up reserves to hibernate. Uniquely among similar mammals, they build a winter nest in a hazel tree stool or stone bank and spend the winter months in a deep torpor, slowing their metabolic rate and allowing them to survive when little food is available.
In April or May they emerge and, feeding on flowers and seeds, rapidly increase in
weight to prepare for breeding. They prepare day nests, which they may use for
temporary hibernation if the weather is poor, or food is in short supply. A larger nest is built for breeding, where the first litter of 2 to 7 young are born in July or August. Male dormice appear to be territorial during the breeding season, but their social structure is unclear. The young are independent at about 6 weeks. A second brood of young may be born, but these often fail to grow to a sufficient weight to survive their first hibernation.
Although owls, weasels and cats may all take dormice, their nocturnal arboreal habits and their relative rarity mean they form only a tiny proportion of the prey of any predator. Most dormice deaths probably occur during hibernation as a result of
insufficient fat reserves, or from starvation in early summer.
Did you know?:
Hazel dormice are also known as the common dormouse or chisel mouse. At the time when Lewis Carroll wrote about the sleepy dormouse many country children would have been familiar with the animal as a pet. The edible dormouse (Glis glis) is a larger introduced species which occurs in the Chilterns but is not found in Cornwall.
Jen Bousfield monitors dormice at several sites in North East Cornwall. She met her first dormouse in 1995 when she was woken by the sound of a small mammal falling from her windowsill to the bedroom floor. She carefully returned the animal to the hedge outside. She later found its nest in the ivy growing by the window - the dormouse had taken a wrong turn, but inspired Jen’s obsession.
Hazel dormice occur mainly in east and central Cornwall. Their secretive nature and low numbers may meanthat they are under-recorded, despite extensive surveyactivity. Elsewhere in England the hazel dormouse isfound from north Wales to the south coast with scattered populations in Cumbria and Suffolk. In Europe they are found from Brittany east to Russia, and from Swedensouth to Greece.
Ground searches for hazel nut feeding remains. Searching for nest sites in
winter hedgerows. Monitoring nest tubes and boxes. Camera traps and footprint tracking systems at feeding stations. Cat kills and incidental reports.