Which British mammal is dependent on woodland to survive, can fit into the palm of your hand and spends much of its life asleep? It’s the hazel dormouse, a fascinating, but increasingly rare, rodent that has already disappeared from much of the UK. Here's everything you need to know about dormice and what we're doing to help the species survive.

Dormouse identification

Also known as the common dormouse, this is one of our most distinctive rodents, with golden brown fur, large black eyes and a notably furry tail. The latter is the easiest way to distinguish the species, as no other small rodent has such a thick bushy tail. In terms of size, they are roughly in between the house mouse and wood mouse.


You’ll need to be very lucky to spot a dormouse in the wild. They are primarily nocturnal and tend to stick to thick cover, making the species hard to see. However, you may come across the places they call home. Dormice rest and raise their young in nests weaved from bark and leaves. These are often built in tree holes or within brambles and hedges.

In periods of bad weather or during food shortages, dormice will enter their nests and go into a state of ‘torpor’ – essentially a mini hibernation that will end when conditions improve.

From October to May it’s the real deal, with the species entering full hibernation. A new nest is constructed for the winter months, usually at ground level and sheltered by dead wood, moss or leaf litter.

It's against the law to disturb dormice, so if you think you’ve found a nest, be careful to only observe it from a distance.

Dormice in decline

Woodland is a key habitat for the species and dormice spend most of their time among tree branches, rarely venturing down to the ground. Ancient woods that are managed using traditional practices such as coppicing and selective felling are ideal for the rodents, as this creates a diverse habitat that provides both food and shelter.

Sadly, the decline of such practices and the loss of woodland in general – 50% of ancient woodland has been lost or damaged since the 1930s – has had a disastrous impact on dormice numbers.

The species is now found in only 32 English counties, down from 49 in 1885, and the population is thought to have dropped by 38% since 2000 alone.

Dormice numbers are highest in southern England, with lower numbers in the Midlands and Wales and just a handful of scattered populations in the north.

The woodland we have left is increasingly fragmented, causing further problems for dormice. The loss of connecting features such as hedgerows means the small rodents have no way to travel between woods, as they will not cover large distances on the ground. As a result, individual populations become isolated, lose genetic diversity and ultimately become more vulnerable to extinction.

Pursuing protection

We have contributed to the National Dormouse Monitoring Programme (NDMP), which is tracking the status of the dormouse population across the country. A key part of this is the use of dormice nest boxes or tubes, which are used to detect the presence of this secretive species. Please note it is illegal to check a nest box where dormice are known to be present without the relevant licence.

Dormice are just one of the species that benefit from our tireless action to protect ancient woodland across the UK. We’ve saved over 1,000 woods from destruction since 1972, but with ancient woodland covering just 2% of the UK and hundreds of woods under threat right now, it’s never been more important that this irreplaceable habitat receives the legal protection it deserves.

By safeguarding these centuries-old woodlands, we can help to ensure dormice have a future in the UK.

Explore ancient woodland and the wildlife that lives there

Trees woods and wildlife

Ancient woodland

Home to myth and legend, where folk tales began. It fuelled our ancestors and still houses thousands. Ancient woodland has grown and adapted with native wildlife, yet what remains only covers 2.5% of the UK.

Find out more about ancient woodland