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Dormice

  There are two species of dormouse in the UK, though they are seldom seen because of their limited distribution, their nocturnal lifestyle and because they hibernate from October to April. The name is presumed to be related to the French verb ‘dormir’ meaning ‘to sleep’, however a more obvious correlation would be with the French ‘dormeuse’ meaning ‘sleeper’. In many ways a sort of cross between true mice and squirrels, dormice have beautiful bushy tails and feed principally on nuts, fruit and fungi. Their summer nests are built, usually fairly high up in trees with inter-linking branches being used as aerial runways.

One species is non-native to Britain – the Edible dormouse (Glis glis – and also known as fat dormouse) was in fact farmed by the Romans as food for their dinner tables! This is the largest of all dormice and very similar to a young Grey squirrel. The Edible dormice in Britain today are the descendants from a group introduced from central Europe by the Hon. Walter Rothschild and released at Tring Park in Hertfordshire in 1902. They multiplied rapidly and, to this day, they are familiar in the attics, thatched roofs and similar places of dwellings throughout Hertfordshire and Buckinghamshire. They are still seldom seen but their noisy activities give away their presence. It remains a mystery, however, why they have never extended their range beyond the Chilterns.

Our native species is the Common Dormouse (other colloquial names include chestle-crum; derry-mouse; dorymouse; dozing-mouse; sleeper; sleep-mouse). It’s Latin name Muscardinus avellanarius relates partly to its habitat – being found, typically, among Hazel trees, avellanarius comes from Corylus avellana, the Hazel. Its main features, compared to other mice is a bushy tail, orange-brown back, pale buff to white underside, medium sized ears (about 12mm), a short muzzle, long black whiskers and prominent black eyes. 

 Its range has halved over the last century due to habitat loss changing land use and poisoning and pollution. Raising the awareness of Britains unique mammal heritage and protecting and enhancing key remaining sites is vitally important and is work that the National Trust can be involved in.

 Traditionally its prime habitat was always considered to be ancient woodland with a dense understorey including Hazel and honeysuckle as well as thick tall hedgerows. Its food being mainly hazelnuts and its nesting material stripped honeysuckle bark. More recently it has been found that it is just as likely to find dormice in reedbeds, coastal scrub, willow carr – even monocultures of gorse. As much as 60% of the summer diet could easily consist of insects and hedgerow fruit indicating less dependence on the hazel woodlands than previously thought.

With this in mind, The Mammal Society and Cornwall Wildlife Trust have initiated a study in Cornwall where landowners participate in a nest tube survey, putting out and checking a number of tubes on their property concentrating on scrub near the coast. (This can be done without a licence up until the first dormouse is found, dormice being fully protected under the 1981 Wildlife & Countryside Act). Having attended a workshop in the spring we were only too pleased to start a survey, choosing two sites – one in Boscastle and one nearer St.Genny’s.

Fortnightly checks were made initially and then monthly from June. This will continue until November. Site sketch maps and habitat notes are also submitted with the results. Take up has been slow, however I am pleased to say we have found a nesting dormouse on our Boscastle site and an ‘accidental’ find in one of the bird nest boxes in Valency Valley! So, they are about which is great news. It is now planned to put up more permanent wooden boxes as and when we get them made.

 A Dormouse year

Breeding will take place in late May and June. The short gestation period of just 22-24 days sees a small litter born – usually 3-5 young. At first pink, blind and helpless, the young take about 18 days to gain fur and sight. The mother will care them for for 6-8 weeks. Dormice have only one litter a year. This is no weakness of the species since they have a specific life strategy – specialist feeding; occupying rare and patchy habitat, slow breeding and living a long time (3-4 years). This is in complete contrast to other small mammals such as woodmice and voles.

Summer sees a period of nest building and feeding, depending on what’s available. There are times in early and mid summer when food can be short. Dormice have the ability to go into summer topor or hibernation in order to save energy to combat this.