Dozens of rare hazel dormice are being released into a wood in Warwickshire as part of efforts to boost the fortunes of the tiny British mammal.

A reintroduction of 20 breeding pairs or trios of dormice into an undisclosed woodland location south of Coventry is being led by the People’s Trust for Endangered Species (PTES) and Warwickshire Wildlife Trust.

Volunteers prepare to release dormice (Ben Birchall/PA)

It follows a successful release last summer of dormice in the county and forms part of a wider landscape scheme, with the hope to one day connect the two populations to create a stronghold in Warwickshire for the mammals.

A new assessment of British mammals published this week has listed the hazel dormouse, immortalised as a sleepy guest at the Mad Hatter’s Tea Party in Alice In Wonderland, as being at risk of extinction in Britain.

Hazel dormice have become extinct from 17 English counties since the 19th century and have seen populations fall by a third since 2000, according to a report published by PTES in 2016.

A dormouse prepares to return to the wild (Ben Birchall/PA)

Loss of their natural woodland and hedgerow habitat and changes to traditional countryside practices such as coppicing trees are thought to be to blame for their declines.

The tiny dormice, which have been bred in captivity and given a full health check before the reintroduction, are being released on site in pairs or trios in their own wooden nest box, fitted inside a mesh cage secured to trees.

The cages are filled with food and water and allow the dormice to acclimatise to their new wild home, before being opened after around 10 days to allow them out into the woodland.

A volunteer holds a box containing a dormouse (Ben Birchall/PA)

Ian White, dormouse and training officer at PTES, said: “Our annual reintroduction programme has been running since 1993.

“Since then, over 900 dormice have been released into woodlands in 12 English counties where they once existed, in an effort to rebuild lost populations.

“This year’s reintroduction is the second phase of a wider landscape project we started in Warwickshire last year, so we hope that by returning to the same county, albeit to a different woodland, that we can connect the two populations in the future, creating a larger, self-sustaining population which we hope will help bring this species back from the brink.”

A dormouse prepares to return to the wild (Ben Birchall/PA)

Chris Redstall, from Warwickshire Wildlife Trust, said: “This year’s woodland has been chosen as it is well-managed with a mixture of mature and coppiced woodland, which is the perfect habitat for hazel dormice.

“This, combined with ongoing sympathetic woodland management and a drive to improve surrounding hedgerow links, should help ensure the successful establishment of this new population.”