David Williams gave the Society a fascinating talk on the common or hazel dormouse (Muscardinus avellanarius) at our March meeting. David works for the Surrey Wildlife Trust on the recording and conservation of these endearing but endangered mammals. He illustrated his talk with some stunning and unusual pictures.
The hazel dormouse is a member of the Rodentia, family Gliridae. (Rats and mice belong to the Muridae.) It is distinguishable from the other mice by its thick bushy tail, orange-brown fur, pale underparts and white throat. Its teeth also differ in that it has four pairs of cheek teeth as opposed to three in rats and mice. It is widespread throughout Europe but is found mainly in the southern counties of Britain. It has suffered a decline in numbers in recent years due to loss of woodland habitat. Its cousin, the edible dormouse (Glis glis), is much larger and is not native to Britain but a few introduced colonies survive in the Chilterns.
In cooperation with landowners and farmers, Dave records the presence of dormice, and in selected areas sets up 50 day-rest boxes on trees about 5 feet above the ground, which he monitors at regular intervals. The dormouse is arboreal, feeding in the canopy at night and resting up during the day. It does make a natural nest but these are difficult to see among the foliage, and it readily adopts a box where it constructs a cosy nest of leaves and shredded bark, often with honeysuckle. The boxes have a concealed entrance at the back but Dave has often found tits, wrens and bats in residence. The dormouse is protected by law and a licence is required to handle them. The `sleepy' dormouse can in fact move very quickly, so checking the boxes without losing the occupant requires some skill. Dave measures and weighs the animals, most of which weigh between 15 and 30 g. The day nests are also used for rearing young.
The dormouse is a woodland species and mature coppiced hazel, with a good understorey, is ideal. They feed mainly on fruit, seeds and nuts with blackberries and hazel nuts the most common dietary items. The way the dormouse opens a hazel nut is very characteristic and is often the first sign of dormouse presence in an area. The dormouse leaves a very smooth rim to the opened nut whereas the wood mouse (Apodemus sylvaticus) and squirrels leave tooth marks on the rim. Dave brought a selection of opened nut shells for us to examine.
The dormouse is a truly hibernating mammal, slowing its heart rate and temperature to a very low level. It usually hibernates in a nest at ground level in a deep bed of leaves, a hole in a tree, or a dense bramble thicket. It goes into hibernation at the end of October and re-emerges at the beginning of May. It is relatively safe from predators as when hibernating it gives off very little scent.
We have had other talks on dormice over the years, in particular from Dr Pat Morris. This occasion not only gave us an update and an insight into current research, but also entertained us with candid and beautiful pictures of an elusive mammal few of us will ever see in the wild. Dave also runs a limited number of training days for those who want to take part in dormouse monitoring.
Chris Brading