Hazel dormice facts
Hazel dormice are small, native rodents with golden-brown fur, large black eyes, long whiskers and are the only small British mammal with a furry tail. They’re active late spring, summer and early autumn in trees and shrubs and hibernate in nests on the ground in winter.
Dormice are found in various landscapes, particularly old managed woodlands linked by continuous hedgerows. Their long-term decline reflects the loss of many old woodlands over the last century, the lack of management of those that are left, and the removal and neglect of hedgerows no longer needed to enclose stock.
(Non-native fat or edible dormice are also present in Britain, introduced from Europe in 1908 and living around Tring in Hertfordshire. These dormice can occupy houses and damage trees and can be a pest.)
Diet, behaviour and habitat
Hazel dormice feed on shrub flowers in spring, insects over summer and fruit and nuts in autumn. Their specialised diet isn’t available over winter, so they hibernate on the ground for about five months until spring.
Such a long hibernation reduces their active period and they generally produce only a single litter, occasionally two, of four young usually in August or September. On average dormice live for three years but they can live up to five.
Active hazel dormice are fully arboreal and nocturnal. Given the challenge of moving at night through often poorly connected trees and shrubs, dormice don’t travel very far to feed and are relatively sedentary in their woodland homes. When they disperse as juveniles they need good tree, shrub and hedgerow connectivity either within their home woodland or beyond it.
Dormice prefer the new growth of woody vegetation that arises after woodland management such as coppicing, ride widening, thinning or glade creation. In the UK, they tend to favour old coppice woodland but they’re also found in scrubland, old hedgerows and sometimes conifer plantations.
See more on woodland and hedgerow management for dormice
Population and distribution
Hazel dormice used to be widespread in Britain but there’s evidence they’ve been in decline over at least the past 100 years. In 2016 we published The State of Britain’s dormice, based on our national monitoring records, which showed a decline of 38% since 2000. And more recent analysis suggests a decline on average of 5.8% per year.
Their range has shrunk significantly and they’re now confined predominantly to southern England and Wales. Even where dormice remain, their distribution is patchy.
See more on the declining extent of the hazel dormouse range and the efforts to restore them to their native areas
Problems for hazel dormice
Dormice are thought to be declining because of:
- inappropriate or absent long-term woodland and hedgerow management
- fragmentation of woodlands and hedges
- our variable maritime climate of warm winters and wet springs that sometimes leads dormice to wake frequently from hibernation and feed poorly in spring.
See more on the problems facing dormice.
Find out how to identify a dormice, how they open nuts, what to do if there’s a nearby local planning applications, and much more at frequently asked questions.