Our work looking after dormice

Dormouse at Hembury Wood, Dartmoor — Dormouse numbers have dwindled over the past half a century | © National Trust Images/Ross Hoddinott

Loss of woodlands and competition for food mean that hazel dormice are in trouble, with numbers tumbling in the last century. But rangers and volunteers have been working hard to restore woodland habitats and protect the species so they can survive.

Hazel dormice

Hazel dormice are no bigger than an avocado stone, and with their golden-brown fur, large black eyes and furry tail it’s easy to see why they’re one of the UK’s most appealing small mammals. However, many people will have never seen a dormouse in the flesh, as they’re nocturnal and spend much of the spring and summer up high among tree branches or in hedgerows. Their numbers have also declined as traditional woodland management techniques have died out and the dormice’s habitat has been lost.

A close up of a ranger's cupped hands holding a torpid dormouse at Killerton, Devon — Ranger holding a torpid dormouse | © National Trust Images / Emma Jones

Dormice in winter

During the winter dormice leave the tree canopy to hibernate on the ground, often under logs and piles of leaves, in grass tussocks or at the base of trees. Dormice will also sleep through cold and wet weather whatever the time of year, so they actually spend a large proportion of their time unconscious. In fact, their name comes from the French word ‘dormir’, which means ‘to sleep’.

When they are awake, dormice spend much of their time in search or buds, hazelnuts, berries and insects to eat. Hazelnuts provide a great source of fat for dormice; so hazel trees are an ideal habitat.

Hazel dormice are listed as a priority species in the government’s Biodiversity Action Plan and are strictly protected by both UK law and European law,. You need a licence to be able to check nesting boxes and handle them.

Our work to protect dormice

Read on for more details on some of the projects we have undertaken to help protect dormice:

Dormouse boxes ready to install at Parke, Devon | © National Trust Images/Mick Jones

Hunting nibbled nuts at Wenlock Edge, Shropshire: In October 2015, a dormouse feeding signs project was started on Wenlock Edge, to see if signs of dormouse feeding could be found in every area where there is fruiting hazel. The project ran for a number of years between September and December. Nut searches are the most effective method of establishing dormouse presence where there is fruiting hazel.
Snoring dormouse discovered at Holmwood Common, Surrey: Rangers searched for rare hazel dormice in the 50 dormouse nest boxes at Holmwood Common. Ranger, Sophie Parker, discovered female dormouse whilst checking the boxes under the supervision of a licensed handler from the Surrey Dormouse Group. The data collected was submitted to the National Dormouse Monitoring Programme run by the People’s Trust for Endangered Species to help monitor the national population. Friends of Holmwood Common donated money for 50 nest boxes on the common, after volunteers from the group found a dormouse hibernating in dead leaves beneath the trees.
Hedgerows for dormice on the Holnicote Estate, Somerset: In 2017, the Holnicote Estate on Exmoor received a £5,500 Heritage Lottery Fund grant to fund their Healthy Hedgerows project. It helped fund a study of the endangered dormice in hedgerows. The grant assisted the study of farmland hedgerows in Porlock Vale, assessing the general health of the hedgerows, working out where the dormice are and who else is calling the hedgerows ‘home’. With large variations of land types including moor, wood, farm and coast, Holnicote offers an ideal place to develop understanding of links between hedgerows and high conservation value woodlands. The information gathered allowed us to assess how connected the dormice habitats are, contributing to the National Trust’s strategy aims of creating sites that are bigger, better and more joined up for nature.
Building nest boxes at Stourhead, Wiltshire: In 2008, Stourhead secured funding for a survey of its 2,650 acre estate, to find out whether or not it was home to hazel dormice. The project monitors and protects resident dormice and their habitat.

With the help of a team of volunteers, ranger and licensed-handler Tamsin Holmes built 167 dormouse nest boxes and erected them in targeted woodland areas. Box checks first took place in May 2009 when four dormice were found.

A survey in November 2011 showed 33 out of now 183 nest boxes were occupied, with sightings of dormice nesting in each of them.

Stourhead is registered with the Peoples’ Trust for Endangered Species as a dormouse monitoring site. Results of surveys are sent to them for the National Dormouse Monitoring Programme.