Dormice in Bottom Wood

Because dormice are active in the dark and are agile climbers, they are almost impossible to see. In the past, they were sometimes found asleep by woodsmen, but otherwise they were rarely encountered. Luckily for those, like us, who wish to study them, it's been found that they readily use nest boxes. Many woods today have a shortage of natural tree holes and although dormice may weave nests in dense cover, they will also do so in a nest box.

A dormouse nest box is very like a bird nest box, but with the entrance hole facing the tree trunk. The boxes we use have a removable inspection lid and boxes like this are proving very helpful in dormouse research.

Licensed to peer

Dormice are protected by law and MUST NOT BE DISTURBED in any way. People who carry out dormice surveys and inspect their nest boxes must have a licence from Natural England. Bottom Wood's dormice are monitored for the National Dormouse Monitoring Project and we are licensed to carry out the work.

A note on edible dormice

The edible dormouse, Glis glis, is not native to Britain, but was introduced in 1902 by Lord Rothschild in Tring Park, Hertfordshire. Ever since, the species has been slowly spreading out across the Chilterns. It was seen in Bottom Wood for the first time in 2005.

The edible dormouse is much bigger than the common dormouse, more like a small squirrel, with grey fur and up to 17.5cm (7") head and body, plus another 15.cm (6") of tail. It also has black markings on the face. On the continent, where common and edible dormice live together, the common dormice tend to live in the lower layers of the wood with the edible dormice higher in the trees.

Like its smaller relative, the edible dormouse hibernates, and has an interesting life history. Unfortunately, it can be a pest, sometimes taking bark off of trees and coming into houses, where it can play havoc in lofts. It will also use nest boxes, sometimes those intended for common dormice, and may compete for some of the same foods. We are not especially pleased by its arrival in Bottom Wood!

Dormice

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.

Dormouse chiselled 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.