25 May 2023

Reintroducing dormice to the UK

Rare British hazel dormice have been given their final check-up by our vets ahead of their planned release into the wild next month - as part of our on-going conservation work to protect this tiny, vulnerable mammal, once common across England and Wales.   

Led by our expert vets at Institute of Zoology, images and footage show yesterday’s check-ups ensuring that these sweet-natured rodents are fit and healthy before their release to a secret woodland location - part of a long-term project to rebuild populations and restore the range of this native species. 

Hazel dormouse health check
Hazel dormice sleeping anaesthetic

Hazel dormouse weight

During each 20 gram dormouse’s 10-minute appointment with the expert team, 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 our 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.” 

Hazel dormouse vet care
Hazel dormouse Stethoscope

Breeding dormice

Since 1993, we've worked alongside a group of conservation charities led by People’s Trust for Endangered Species (PTES), to reintroduce carefully bred dormice annually to sites across the country as part of Natural England’s Species Recovery Programme. Through meticulous organisation and expert care, the project has come to be praised by conservationists as a benchmark of wildlife reintroduction 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.”  

Hazel dormouse sleeping
Hazel dormouse healthcheck

Protecting dormice from disease


Alongside the health checks, our DRAHS team play a wider key role in disease risk management, helping to plan the reintroductions to ensure that not only do the small golden-furred rodents have the best chance of survival in their new homes, but that the species currently living in those habitats are not at risk of being introduced to new infections. 


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.”

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The furry-tailed dormice are currently staying at our headquarters at London Zoo where they receive expert care and regular monitoring in the lead up to next month’s release by PTES, ZSL and partners.  
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.”