The common dormouse, Muscardinus avellanarius, is usually nocturnal, rarely comes to the ground and is about 14cm (5½") long, nearly half of which is a 6.5cm (2½"), thick, bushy tail.
They’re usually found from shrub level up to the highest branches of woodland trees, have orange fur and weigh-in at just 17g (½oz) – double that before hibernation.
The name dormouse has its roots in the French word for sleep ‘dormir’, which they do from October to May, lowering their body temperature and slowing their heart rate and breathing. Even in summer, part of the day may be spent in this kind of torpor, thus reducing energy requirements when food is scarce.
Dormice eat pollen, nectar, insects and various fruits and nuts. Mostly these are high energy foods and differ from the seeds taken by other mice. Many foods that dormice eat are only available for a short period each year, so a varied habitat producing a succession of nourishment throughout their active season, is vital.
Most other types of mice produce many large broods a year, but these other mice rarely live longer than a year. Dormice normally have a single small brood late in the summer, but can live for five or more years.
The dormouse signature
Although dormice themselves are hard to find, there is one sure sign that they are present – they feed on nuts in the autumn to fatten up for hibernation and eat hazel nuts in a unique way.
If you look near hazel trees, you may find discarded shells that have been gnawed by squirrels, woodmice, voles, dormice and other animals. The way to tell if a dormouse has been at work is due to the fact that they gnaw into hazel nuts slowly with their small teeth, turning the nut as they work. The result is a round or slightly oval hole, usually in the side of the nut.
Around the hole there are often tooth marks at an angle to the hole. The cut face of the hole is scooped smooth, and slopes steeply towards the centre of the nut.
Woodmice also leave toothmarks on the shell. Voles do not. Both these mammals cut across the shell edge with their teeth. Squirrels often bite the shell in two, or leave it broken and jagged, as do woodpeckers and nuthatches.