Reintroducing the hazel dormouse

by ZSL on

ZSL works all over the world to protect some of our most threatened species, including right here in Britain. Species like the common – or rather not so common – dormouse. 

Dormouse undergoing health checks
ZSL monitored the health of the dormice for 10 weeks before they were released into the wild

The common, or hazel dormouse (Muscardinus avellanarius) was once widespread across England and Wales. But with the loss of woodland and hedgerows, as well as changes to traditional countryside management practices, populations are declining. 

Through a collaborative project, led by the People’s Trust for Endangered Species (PTES), ZSL has played a key role in reintroducing captive-bred dormice into the wild to help to combat this decline. 

Reintroductions like this are important conservation tools, but the risk of disease has to be taken into account, both to the species being released, and also to recipient populations. At ZSL’s Institute of Zoology, the Disease Risk Analysis and Health Surveillance (DRAHS) team, along with veterinary nurses and animal keepers at ZSL London Zoo, work to reduce this risk. 

21 dormice were held in quarantine at ZSL for 10 weeks where their health was regularly monitored to give them the best chance of forming a healthy population in the wild, and to minimise the chance of them passing on non-native diseases. During a detailed health examination under anaesthesia, all dormice were microchipped so that individuals can be recognised after their reintroduction. Their body weight and other physical features were also recorded, so that it was ensured they were healthy when released into the wild. 

After the health checks were complete, the dormice were then moved to a woodland in Warwickshire. The dormice were put in pairs or trios alongside the dormice kept in quarantine at Paignton Zoo, and subsequently over 17 breeding pairs of dormice were formed.  They were initially reintroduced in 'soft-release’ cages – a wooden nest box inside a mesh cage filled with climbing branches as well as food and water. They will be monitored daily to help them adjust to their new environment, before the soft release cages are opened and they are free to explore the surrounding woodland.

This Warwickshire reintroduction marks the 27th dormouse reintroduction led by PTES, and is the result of nearly two months of work by multiple partners (ZSL, Natural England, Paignton Zoo, Warwickshire Wildlife Trust and the Common Dormouse Captive Breeders Group). It’s hoped that these dormice will establish a viable and lasting population to combat the species’ decline. 

Learn more about DRAHS

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