Fat dormouse  (Glis glis)

Classified as Lower Risk/ near threatened by the IUCN Red List 2002 (3).

The fat, or edible dormouse was introduced to Britain in 1902 (3). This is a fairly large dormouse, with a very bushy tail and short, thick silvery grey fur which is white or yellowish-white underneath (3); overall it has a somewhat squirrel-like appearance (2). The hands and feet have hard pads, which are adaptations for climbing (3). The name 'edible' dormouse arose as the Romans used to eat them as a delicacy (2); the alternative name of 'fat' dormouse refers to the appearance of this species before it goes into hibernation(4). Furthermore, the Romans used to fatten these rodents on chestnuts and acorns inside clay pots called 'glisaries' or enclosures prior to eating them (5).

In Great Britain, this dormouse has a small distribution that is restricted to the Chiltern Hills, but its range is expanding. It occurs throughout central Europe (4), but has declined in many areas and is uncommon (3).

Inhabits mature broadleaved woodland, gardens, houses and orchards (4).

The fat dormouse is nocturnal, and lives in groups with related individuals (4). Adapted for climbing and leaping through the tree canopy (3), this species feeds on nuts, fruit, bark and fungi as well as animal matter including insects, bird eggs and even small birds (4). The breeding season occurs between June and August, during this time, fighting between males may occur over access to females (3). Females attract males to mate with them by rubbing their anal area along the ground. This produces an odour trail, which the male sniffs and scent-marks (6). Whistling sounds also indicate readiness to mate. The male will pursue the female for a while; she may rebuff him aggressively, but when he gives up she often follows him, and mating occurs (6). Males usually leave the female after mating takes place in order to find more potential mates (6). Females produce one litter a year, consisting of 2-9 young (4), typically in a nest inside a hollow tree (3), lined with grass, feathers and hairs (6). The young are born blind, naked and helpless, and are weaned by about 4 weeks of age (3). Mother and offspring seem to learn to recognise each other by exchanging saliva (7). The fat dormouse hibernates underground or in grass-lined hollows in trees from October to April (4). Towards the end of summer they begin to construct tunnels in the ground; they enter these tunnels to hibernate as soon as the weather begins to get cold, and groups of fat dormice have been found hibernating together (6).

This introduced species is considered to be a pest of orchards and forestry, as it can damage fruit crops and its habit of bark stripping is very destructive (4). In houses they can cause serious problems by chewing through wires and wood. They are therefore controlled in some areas (4). They have declined in many parts of the European range as a result of deforestation (3).

In Great Britain there is no conservation action in place for this non-native mammal (4).

For more on this species see: The dormouse hollow:
http://www.glirarium.de/dormouse/dm-biology-glis.html And Macdonnald, D. W. & Tattersall, F. T. (2001) Britain's mammals- the challenge for conservation. The Wildlife Conservation research Unit, Oxford University. Available from
www.wildcru.org

• Hibernation: a winter survival strategy characteristic of some mammals in which an animal's metabolic rate slows down and a state of deep sleep is attained. Whilst hibernating, animals survive on stored reserves of fat that they have accumulated in summer. In insects, the correct term for hibernation is 'diapause', a temporary pause in development and growth. Any stage of the lifecycle (eggs, larvae, pupae or adults) may enter diapause, which is typically associated with winter.

1. National Biodiversity Network Species Dictionary (May 2002) http://www.nhm.ac.uk/nbn/
2. Burton, J. A. (1991) Field guide to the mammals of Britain and Europe. Kingfisher Books, London.
3. Fat dormouse, or edible dormouse. The dormouse hollow. (August 2002) http://www.glirarium.de/dormouse/dm-biology-glis.html
4. Macdonnald, D. W. & Tattersall, F. T. (2001) Britain's mammals- the challenge for conservation. The Wildlife Conservation research Unit, Oxford University. www.wildcru.org
5. Alderton, D. (1999) Rodents of the world. Blandford, London.
6. Animal Diversity Web (August 2002) http://animaldiversity.ummz.umich.edu/accounts/myoxus/m._glis.html
7. Macdonnald, D. W (2001) The New Encyclopedia of Mammals. Oxford University Press, Oxford.