Devoted to the dormouse

Dormice have been absent from our counties for two decades, but a project to reintroduce them offers hope for the future. County Mammal Recorder Dr Helen O’Brien, who lead the feasibility study into their release, tell us more.

The common or hazel dormouse was once widespread in the UK but has declined a staggering 51% since the year 2000. Its range is now more restricted than ever, making the dormouse vulnerable to local extinction. These tiny mammals, weighing just 15-40g, are mainly found in the south of England and Wales, with sca ered populations in the Midlands and the north of England where they have been reintroduced over the past 30 years to improve the species’ chance of survival.

Though once present in parts of east Leicestershire and Rutland, the last record here is from 2004 and it was accepted they were absent from the two counties a er several local studies found no evidence of their presence.

Dormice are strongly dependent on woodland habitat and features such as hedgerows and scrub that connect sites and help them to disperse. The main reasons behind their decline are the fragmentation, deterioration and loss of habitat, and the changing climate. Inappropriate management of woodlands in the past has meant dormice are now absent from many counties. While many areas may now be more appropriately managed and be er suited to dormice, they are unlikely to return without some assistance due to their isolation from viable populations. How we manage our woodlands and connect them to the wider countryside will determine the survival of this species.

Changes in our climate generally mean warmer, we er winters. This is not good for dormice, which hibernate in winter when food is scarce. If they wake up during a mild spell, they may starve or become weak and in danger of predation. Conversely, an unseasonably cool summer may trigger an involuntarily semi-state of torpor, which if occurring during the breeding season or when offspring are young, could seriously impact a local population.

In late 2020 LRWT commissioned a study with the support of Twycross Zoo to investigate the feasibility of reintroducing dormice to our two counties. The study considered past and present records of dormice and identified the National Forest cluster of woodlands – both new plantations and ancient woodland – as offering high potential. The National Forest Company and Twycross Zoo supported further surveys to validate the findings, confirming the suitability of key sites within the vice-county boundaries of Leicestershire and Rutland.

The study supported evidence for a local reintroduction and 38 dormice were released into a large woodland at Calke Abbey on the edge of Leicestershire in summer 2023. The reintroduction was led by the wildlife charity People’s Trust for Endangered Species (PTES) alongside landowners, the National Trust and many partners, including LRWT.

National Trust rangers and volunteers helped to install large cages on trees within the woodland. The dormice and their nestboxes were then placed inside the cages and the dormice fed a mix of high-protein nuts, seeds and fruit over a 90-day period to ensure they gained weight and to help them se le into their new homes.

Introducing dormice in this way gives them the best chances of survival. We were able to monitor the amount they were eating and whether they were still using the cages over the 90 days. During that time 200 nestboxes were also installed around the wood for the dormice to use on leaving the cages.

Nest checks

Monthly nestbox checks for dormice and their nests have been carried out by rangers, volunteers and licenced

Hazelnuts are full of protein and a major source of food for small mammals. Dormice, bank voles and wood mice gnaw the nuts in di erent ways, leaving tell-tale signs of their presence.

51% Lost from 17 counties decline since 2000

Dormouse Monitoring Scheme, led by dormice handlers as part of the National Dormouse Monitoring Scheme, led by PTES. These inspections reveal whether dormice populations have increased and dispersed across the woodlands and hedgerows following their release. The signs so far are good; the dormice have produced offspring and are using boxes away from the release cages.

LRWT is working closely with its many partners, including landowners, to help improve woodlands and the connectivity between them. Taking this landscapescale approach to help dormice and other vulnerable species is part of the Trust’s overall strategy towards nature recovery and improving resilience to climate change. By ge ing this right, we can work towards a more promising outlook for dormice and support additional releases in the future.

1,078 dormice reintroduced since 1993

The Common Dormouse Captive Breeders Group is a unique partnership that includes the Wildwood Trust, Paignton Zoo, and the Zoological Society of London who together breed the dormice destined for release. The dormice undergo an eight-week quarantine and receive a full health check by veterinary sta prior to being released into their new environment.

• National Trust

• People's Trust for Endangered Species

• Leicestershire & Rutland Wildlife Trust

• Twycross Zoo

• The National Forest

• Zoological Society of London

• Paignton Zoo

• Leicestershire & Rutland Mammal Group

• Nottinghamshire Dormouse Group

• Derbyshire Mammal Group