Rare Hazel Dormice in Top Health Ahead of Wild Release

A group of rare hazel dormice have undergone their final health check before they make their way back to the woodlands in the coming weeks. Vets from ZSL’s Institute of Zoology carried out the health checks to ensure the mice are ready for a life in the wild.

The release is part of ongoing works to restore this threatened species across Britain. All of the mice which were confirmed as fit and healthy will be released in to a secret woodland location. This is one of many steps in a long-term project to rebuild populations and restore the range of this species.

Each of the tiny dormice spent 10 minutes with the vet during which time they were placed under a miniature dormice-sized dose of general anaesthetic while their heart and lungs were checked with a stethoscope, their eyes, ears, nose, teeth and fur were visually examined, and a tiny microchip was gently placed under their skin to allow for easy identification in post-release monitoring.   

Dr Elysé Summerfield-Smith, health-check co-ordinator and wildlife veterinarian for ZSL’ Disease Risk Analysis and Health Surveillance Team (DRAHS), said: “Hazel dormice were once found in woodlands and hedgerows across Britain, spending their nights feeding on berries and hawthorn flowers and their days curled up asleep in nests made from honeysuckle bark.  

“While still common in mainland Europe, UK dormice number have drastically fallen over the last 100 years - linked to the loss of habitats - and the British population is now mostly confined to southern England and Wales, leaving these iconic native rodents vulnerable to extinction. Dormice are flagship species for their habitats, so by working to restore their homes and rebuild their populations, the birds, bats and butterflies that they live alongside will also benefit.” 

ZSL have worked alongside a group of conservation charities led by People’s Trust for Endangered Species (PTES) since 1993 to restore carefully bred dormice at selected sites across Britain. Through its careful management the program has become a benchmark for reintroductions done well.

Elysé continued: “Through our health checks we play a key role in fighting this ongoing decline, and for the last 30 years we have helped reintroduce over 1,000 dormice to 25 different sites across the UK – making the hazel dormouse one of the most successfully reintroduced species in the UK.”  

Along with being a health check this exam also helps ensure that the dormice do not introduce new diseases to the animals already living in the habitats to which they will be reintroduced.

Elysé explained: “The team’s careful planning, health checks and long-term post-release health surveillance aren’t just important for protecting the dormice, but it will also protect the health of the species that they will be living alongside. Any new disease that is accidently brought into a habitat can be disastrous for local wildlife, it’s vital we do everything we can to guard against it.  Dormice are just one of the 30 species that ZSL’s DRAHS team work with, using our expertise in disease mitigation to support reintroduction projects both across the UK and beyond as part of ZSL’s wider work protecting species.” 

Ahead of their release the dormice are being housed at ZSL's base in London Zoo. They will continue to receive monitoring and care ahead of their release.

Maya Folkes, ZSL DRAHS Pathology and Field Technician explained: “During their 8 week stay with us, our tiny guests are getting the specialist attention needed to ensure they’re in top shape for their big day – from weekly check-ups with our vets to munching on salads of blueberries, carrots, and mealworms carefully designed by the zoo’s expert nutritionist. It’s exciting to know that in a few weeks’ time they’ll be starting their new lives, joining a long line of dormice now flourishing across the country as we work to restore this precious native species.”