Hazel Dormouse

The Hazel Dormouse or Common Dormouse (Muscardinus avellanarius (Linnaeus, 1758)) is a small mammal. It is the only living species current classified in the genus Muscardinus. It is 6-9 cm long with a tail of 5.7-7.5 cm. It weighs 17-20g, although this increases to 30-40g just before hibernation. The Hazel Dormouse hibernates from October to April-May.

The hazel dormouse is native to northern Europe and Asia Minor. It is the only dormouse native to the British Isles (though the edible dormouse, Glis glis, has been accidentally introduced and now has an established population), and is therefore often referred to simply as the Dormouse in British sources.

The UK distribution of the hazel dormouse can be found on the National Biodivestity Network website here

Protection status
The Hazel Dormouse is a European Protected Species and is protected in the UK under the Wildlife and Countryside Act

Natural history
Hazel dormice are the only small mammals in Britain to have a completely furry tail. They have golden-brown fur and large black eyes. They are nocturnal creatures and spend most of their waking hours among the branches of trees looking for food. They will make long detours rather than come down to the ground and expose themselves to danger.

In winter (early October), dormice hibernate in nests beneath the leaf litter on the forest floor. When they wake up in spring (late April or early May), they build woven nests of shredded honeysuckle bark, fresh leaves and grasses in the undergrowth. If the weather is cold and wet, and food scarce, they save energy by going into torpor; they curl up into a ball and go to sleep. Dormice, therefore, spend a large proportion of their lives sleeping; either hibernating in winter or in torpor in summer.

Identification signs
Examination of hazel nuts may show a neat round hole in the shell. This indicates that it has been opened by a small rodent, e.g. the dormouse, Wood mouse, or Bank vole. Other animals such as squirrel or jay will either split the shell completely in half or make a jagged hole in it.

Further examination reveals that the inner rim of the hole has toothmarks which are at an angle to the hole for the dormouse. The toothmarks are parallel with rough marks on the nut surface for a wood mouse, bank vole leaves parallel grooves with no rough marks.

Diet
It feeds on a wide variety of aboreal foods:


 * flowers for nectar and pollen
 * fruits - berry and nuts
 * insects - especially aphids and caterpillars
 * buds of young leaves
 * Hazel - the main food for fattening up before hibernation, although the tree is also an important provider of insects.
 * Hornbeam and blackthorn fruit where hazel is scarce

A variety of different food sources available at different times of year is required to ensure the hazel dormouse survives.

Habitat

 * Woodland
 * Hedgerows - that are species rich and connected to woodland. Ideally they are 3 to 4 metres high, and left at least 7 years before cutting - because many shrubs do not begin to fruit until that time period has passed.
 * nestboxes
 * They usually only travel less than 70 metres from their nest (2)

Trees and shrubs of value to dormice

 * Hazel - principal food source, supports insects. Forms an understory of poles, especially when coppiced, which makes it useful for its arboreal activity.   The hazel dormouses Latin name avellanarius means 'hazel'.
 * Oak - insect and flower food. Acorns of little value
 * Honeysuckle - bark is nesting material. Flowers and fruit are food.
 * Bramble - flowers and fruits provide food over a long period. Thorns give protection for nests. Dormice thrive on blackberries.
 * Sycamore - insect and pollen, and a habitat. However they cast a dense shade which decreases the understory.
 * Ash - seed keys whilst they are still on the tree
 * Viburnum lantana - fruits and flowers
 * Yew - fruits are a favoured food
 * Hornbeam - seeds
 * Broom - flowers (in early Summer)
 * Sallow - unripe seeds, supports many insects
 * Birch - seeds
 * Sweet chestnut - chestnut an excellent foodsource, the flowrs are eaten as well
 * Blackthorn - Fruits are eaten
 * Hawthorn - flowers are an important food in the spring. Fruit eaten occasionally

Threats

 * Predation from Eurasian badger, fox, stoat, weasel
 * Trampling, e.g. deer, human
 * Lack of food source e.g. from too frequent hedge-trimming, or competition from other species e.g. squirrel
 * Destruction of forest and hedge-row habitat, or their diverse range of species as a broad spectrum of food is required across the calendar year.