Bringing the dormouse back to UK woodlands

Liam Fitzpatrick

Liam Fitzpatrick is currently undertaking research for his PhD, where he is examining the risk of avian malaria to birds in the Galápagos archipelago.

Many UK woodlands have been missing an endangered rodent for decades. Liam Fitzpatrick, Pathology Technician at ZSL’s Institute of Zoology, blogs about how ZSL and other partners are helping to reintroduce and conserve the hazel dormouse.

A sleepy common dormouse in quarantine at ZSL
A sleepy common dormouse in quarantine at ZSL

The common or hazel dormouse (Muscardinus avellanarius) is not quite as common in the UK as its name might suggest. Previously found in almost every county of England and Wales, common dormice have undergone a marked decline in both range and numbers over the last century - estimates from the Joint Nature Conservation Committee indicate a 52% decline over the last 25 years and the majority of dormice are currently found only in some parts of southern England and Wales.  

Why are dormice numbers decreasing so much? Unfortunately, as with a number of other species, the way in which we use land has altered their former habitats and made many of them unusable for dormice. The impacts of changes in woodland management techniques, loss of hedgerows and habitat fragmentation has led to the common dormouse being designated a protected species in Britain.

ZSL scientists releasing dormice into ‘soft-release’ cages in the Yorkshire Dales National Park
ZSL scientists releasing dormice into ‘soft-release’ cages in the Yorkshire Dales National Park

In order to help conserve this species, reintroductions of captive-bred dormice have taken place across England over the last 23 years, helping to bolster remaining populations, and release dormice back into areas they historically roamed. 

Here at ZSL’s Institute of Zoology, the Disease Risk Analysis and Health Surveillance team (DRAHS), along with veterinary nurses and animal keepers at ZSL London Zoo, have been looking after captive-bred dormice in quarantine and conducting health examinations prior to their release.

The dormice stayed with us for approximately 10 weeks, during which time we screened them for ‘novel’ parasites that dormice may have picked up in captivity, but they are not usually exposed to in the wild. This disease risk management is essential for a successful reintroduction, trying to make sure that the dormice were not released with pathogens that could cause issues for either the dormice themselves or other wildlife at the reintroduction site.

During their quarantine period, the dormice were microchipped, so that they could be easily identified after their release, and their weights and condition were continually monitored to ensure they were in the best possible shape for reintroduction.

ZSL scientists releasing dormice into ‘soft-release’ cages in the Yorkshire Dales National Park
ZSL scientists releasing dormice into ‘soft-release’ cages in the Yorkshire Dales National Park

Working in partnership with People’s Trust for Endangered Species (PTES) and Natural England, on Thursday 23rd June 2016 we released our 19 dormice, along with those kept in quarantine at Paignton Zoo, into a managed woodland in the Yorkshire Dales National Park. The dormice were matched up to make breeding pairs, and the hope is that over the coming years they will establish a viable and lasting population in a place where dormice were last recorded over 100 years ago.

For the first couple of weeks of the release, they will stay in their ‘soft-release’ cages, along with plenty of food and water to keep them going, and will be monitored daily to check that they are adapting to their new habitat. Once everyone is satisfied that they are doing well, the doors will be opened and the dormice allowed to roam free around their new wild homes. PTES and the Yorkshire Dales National Park will continue to improve the habitat in the surrounding areas, in particular focussing on hedgerows, aiming to connect this reintroduced population with a similar released population a few miles away.

Reintroduction programmes such as this are vitally important for the continued conservation of a number of different species, but must be carried out in a responsible and controlled manner. The DRAHS project aims to minimise the risk of disease to these reintroductions, and monitors the health of wild animal populations at the reintroduction sites. 

Learn more about the DRAHS project

Select a blog

Careers at ZSL

Our people are our greatest asset and we realise our vision for a world where wildlife thrives through their ideas, skills and passion. An inspired, informed and empowered community of people work, study and volunteer together at ZSL.

Nature at the heart of global decision making

At ZSL, a key area of our work is the employment of Nature-based Solutions – an approach which both adapt to and mitigates the impacts of climate change. These Solutions, which include habitat protection and restoration, are low-cost yet high-impact, and provide multiple benefits to people and wildlife. We ensure that biodiversity recovery is at the heart of nature-based solutions. 

ZSL London Zoo

A blog for lovers of ZSL London Zoo, bringing you extraordinary animal facts and exclusive access to the world's oldest scientific zoo.

ZSL Whipsnade Zoo

Do you love wildlife? Discover more about our amazing animals at the UK's biggest zoo!


We're working around the world to conserve animals and their habitats, find out more about our latest achievements.


From the field to the lab, catch up with the scientists on the cutting edge of conservation biology at ZSL’s Institute of Zoology.


A day in Discovery and Learning at ZSL is never dull! The team tell us all about the exciting sessions for school children, as well as work further afield.

Artefact of the month

Every month, one of the pieces held in ZSL’s Library and at ZSL Whipsnade Zoo will feature here as Artefact of the Month.

Wild About

Read testimonials from our Members and extracts from ZSL's award winning members' magazine, Wild About.

Chagos Expedition

The Chagos archipelago is a rare haven for marine biodiversity. Hear from the team about our projects to protect the environments in the British Indian Ocean Territory (BIOT).

Asia Conservation Programme

ZSL works across Asia, from the famous national parks of Nepal to marine protected areas in the Philippines. Read the latest updates on our conservation.

Remote Sensing in Ecology and Conservation

An Open Access journal for research at the interface of remote sensing, ecology and conservation.