Hazel dormouse

Once common across the UK, hazel dormouse populations have been decreasing. At ZSL, together with partners, we're working to reintroduce dormice back into woodlands. 

What do hazel dormice look like? 

Hazel dormice have golden-brown fur, and they are the only small British mammal with a furry tail. 

There are three dormouse species living in the UK, the native hazel dormouse and two invasive species, the garden dormouse and edible dormouse. Each of these species are from mainland Europe, and are much bigger than our native hazel dormouse. 

What do hazel dormice eat?  

Hazel dormice eat berries, seeds, flowers, pollen and nuts as well as any insects they find. They change their diet in preparation for hibernation, focusing on fattier foods like hazelnuts. The hazel dormice we reintroduce to the wild are supplemented with food after release to help give them the best start possible.  

Hazel dormouse habitat and distribution 

In the UK, hazel dormice are most common in the woodland within the south of England at places like Sussex, Devon, and Kent. They are nocturnal and hibernate for five months of the year, from late October through to April, making them very difficult to find. But you might be able to spot the woven straw nest of a hazel dormouse amongst thick bushes. They are also found in most of mainland Europe.

Hazel dormice threats  

Populations of hazel dormice have decreased by 55% over the last twenty-five years, and they are now extinct in 17 counties in the UK. 

The loss of woodland and hedgerows, and changes to traditional countryside management practices have lead to these declines. Climate change also has the potential to disrupt their long hibernations. Predators like the domestic cat, owls and weasels can catch them as they forage, whilst badgers can eat them in their nests during hibernation, but predators do not have a major impact on their populations.  

Hazel dormice conservation

Hazel dormice are a priority species in the UK Biodiversity Action Plan and are protected under the Wildlife and Countryside Act 1981. 

Dormice health checks

At ZSL, we’re working towards creating healthier, better connected, and bigger populations of hazel dormice, so hopefully one day they will be commonly found across the UK again. We provide health checks which are crucial to the project, to ensure healthy dormice are released to give them the best start possible as they return to the wild, whilst protecting local wildlife. 

our work protecting wild animals from disease 

Dormice reintroductions

Currently, the hazel dormouse reintroduction programme is striving to improve post-release monitoring methods, as well as ensuring the dormice involved continue to produce heathy, viable offspring to supplement the wild population.  

Follow the journey of 30 hazel dormice that we reintroduced to British woodland, from quarantine at ZSL to their new forever home:

Thanks to the National Dormouse Monitoring Programme, dormouse nest boxes at each reintroduction site are checked every month. This post-release health surveillance can make a difference between success and failure because we can tackle disease threats before they become a problem. If a dormouse dies, we carry out a full post-mortem examination to understand those threats. We have built a database of pathological diagnoses from free-living dormice and continue to carry out scientific research to safeguard wildlife health.   

The results from the post release monitoring and any subsequent post-mortem examinations not only inform the dormouse reintroduction programme but also provides an insight into how small populations of highly threatened species function in the face of changing conditions (including habitat destruction and disease). 

Partners & Sponsors 

• People’s Trust for Endangered Species

• Natural England

• Paignton Zoo

• Common Dormouse Captive Breeders Group