`You might just as well say,’ added the Dormouse, who seemed to be talking in his sleep, `that “I breathe when I sleep” is the same thing as “I sleep when I breathe”!’ – Alice’s Adventures in Wonderland.
The Hazel or Common Dormouse can spend up to three quarters of their life asleep, hibernating during times of scarce food in order to save energy. They will even go to sleep during cold, wet periods of summer. This has given rise to it also being known as the Sleeper. Along with bats, they are the only British mammals to truly hibernate during winter. Despite being named ‘common’ they are now rare.
They are most often found in the Southern counties of England. The specimen pictured, for example, was discovered dead in its nest in Chiddingford, Surrey, in 1978. Although very rarely seen, the early autumn is when you are most likely to spot them, as they gorge on blackberries and other fruit and nuts in preparation for their six month hibernation in October.
Dormice depend on a wide variety of food in order to build up enough fat to last through their hibernation. Along with hedgerow berries and hazel nuts they also eat aphids and caterpillars, making them a useful natural pest controller. They use the interlocking branches of oaks and other traditional English woodland trees as aerial highways, using the leaves as cover from predators.
They leave the forest canopy to build their nests in the leaf litter on the forest floor (although they sometimes nest in hedgerows or in any vacant nest boxes they might chance upon). These nests are protected from the elements by a thick layer of moss and honeysuckle bark. The nests also help protect the dormouse from predation, and a nest has even been found dropped from a raven roost with the dormouse still happily sleeping inside.
The dormice were the dominant rodents throughout Europe during the Eocene-Oligocene period (56 – 23 million years ago), and evolved long before rats, mice and other Muridae appeared. They probably arrived in Britain around 9000 years ago, as the ice age glaciers were receding, but before the flooding of the English Channel. Historically widespread, their numbers have been dramatically reduced by human destruction of their habitats.
These include the felling of oak forests for building battleships during the Napoleonic Wars, destruction of hedgerows through changes in farming, and replacement of native woodlands with fast growing commercial spruce forests. They also face competition for their food from introduced species such as the grey squirrel.
Hazel dormice are now protected across Europe, and it is illegal to disturb, trap or kill them in Britain without a licence. They are widely regarded as one of Britain’s most adorable and popular mammals, and are often featured on the BBC’s Autumnwatch, which returns on 7 October.
Lee Ismail, Curator of Natural Sciences