Dormouse Biology and Species Information

Family, Appearance and Lifestyle    

Dormice (the Gliridae) are a distinct family of rodents found across Europe, Africa and Japan which have a very different biology from other “mice”. There is only one native species of dormouse in Britain, the common or hazel dormouse, a rich sandy chestnut coloured mouse-sized rodent which has large dark eyes and a furry tail. The common dormouse is nocturnal and arboreal and spends a considerable period of the year in hibernation.  Dormice also live at low densities, around 7 per ha. For these reasons this species is rarely seen.

Range, Habitat, Territory and Home

From late April until late October, dormice are predominantly arboreal, building tightly woven summer nests in bushes and shrubs or in more robust places such as tree hollows or old bird nests. They rarely come down to the ground and require arboreal connectivity which allows them to move between the understorey and canopy without difficulty.

Food

Dormice are unable to digest green food, so eat nectar and pollen, insects, mainly in the form of aphids and caterpillars, nuts and fruit. Most of the currently available literature suggests that a wide variety of food species are necessary for them to thrive and these must provide successive food sources, especially in the spring and early summer. Later in the year, many nuts and fruits ripen at about the same time when an abundance is necessary to enable dormice to amass sufficient fat for a successful hibernation. Dormice are a sedentary species and rarely travel more than 70m from their nests, so a wide range of food species must be available in a relatively small area.

Activity (including hibernation) and Social System

Hibernation begins in late October or November and is spent in a thin nest constructed just under the ground beneath a mat of ivy or moss, in a moist place where the temperature will remain cool and stable. Dormice wake from hibernation enough to eliminate waste on a regular basis. They emerge from hibernation in late April or early May when they feed on flowers and nectar. They may breed as early as the beginning of June and as late as early October. In the autumn with their metabolism changes and they put on large amounts of weight in a short time in preparation for hibernation.

Breeding – mating, season, numbers

Dormice usually have only one litter of up to seven young a year so they do not reproduce rapidly. In good years they may produce two litters although the second rarely survives. While they reproduce slowly, they are long lived for small rodents and may survive for up to six years.

Threats

The British population of dormice is about 40,000, equivalent to the human population of Yeovil, Llanelli or Inverness, and is still in decline. This can be attributed to habitat loss and fragmentation, to climate change and, to a lesser extent, to predation from domestic cats.

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