RARE - and 'charismatic' - Hazel Dormice have been reintroduced to the Yorkshire Dales National Park.

Once a familiar site across England and Wales, over the past 100 years, their numbers have declined sharply, due to the loss of their natural habitat of woodlands and hedgerows.

They have also been a victim of changes to traditional countryside management practices, leaving the tiny mammals rare and vulnerable to extinction.

But following a partnership between wildlife charity, the People's Trust for Endangered Species (PTES) and the national park authority, some 38 hazel dormice have been released in woodland near Aysgarth.

Their exact location has been kept secret, but it is hoped they will settle, breed and help stem the decline of the species.

It follows a similar event in 2008 when dormice were returned to a nearby woodland after a 100-year absence from the Yorkshire Dales - and it is hoped the two separate populations will eventually link up and spread.

The charity has been working with the national park authority, and the local Bolton Estate to carefully select a suitable new site near the 2008 location which will provide the best chances for the long-term survival of the species.

Ian White, dormouse officer at PTES said: “The two reintroduction sites are close enough that the separate dormice populations will eventually be able to meet up and breed, creating a self-sustaining population. In addition, the programme of habitat management in the area will have great benefits for a number of other species too, such as birds and bats.”

Ian Court, the park authority's wildlife conservation officer, added: “It is fantastic that we are undertaking this additional release that will help build on the original successful re-introduction in the heart of Wensleydale.

“We look forward to working with landowners and managers to help create a network of managed hedgerows and woodlands within the lower Wensleydale area that will look to re-establish a species back into the Yorkshire Dales that has been missing for many generations.”

The reintroductions play an important role in the long-term conservation of the endangered species and are part of Natural England’s Species Recovery Programme.

The release marked the culmination of weeks of work by all of the partners involved in the different stages of the reintroduction process, which also include Natural England, Zoological Society of London, Paignton Zoo, Common Dormouse Captive Breeders Group, and the Bolton Estate.

The released dormice were bred in captivity through the Common Dormouse Captive Breeders Group.

Before being set free, they underwent a six-week quarantine at Zoological Society of London (ZSL) and Paignton Zoo in Devon, during which vets conducted a full health examination to check they were in top condition. It also would have reduced the risk of them passing non-native disease, ensuring they had the best chance of forming a healthy population in the wild.

Following the health checks, the dormice were released at the secret location in the national park in breeding pairs or in groups of three in their own wooden nest box fitted inside a mesh cage secured to trees.

The mesh cages, filled with food and water, are aimed at helping the dormice adjust to their new home in the wild. The cages are eventually removed once the animals have settled into the wood.

It was the 26th reintroduction of dormice led by PTES, which has released more than 750 at 19 different sites across 12 counties in England over the last 20 years.

Tom Orde-Powlett, manager of the Bolton Estate, said: “We are delighted to support the national dormouse reintroduction programme. Conservation is central to our work and lives at Bolton and we are very proud of the wildlife that thrives here. We look forward to continued work with the National Parks and other partners to increase biodiversity, alongside protecting the many existing species of flora and fauna that we are so privileged to enjoy.”

Tony Sainsbury, senior lecturer in wild animal health, Zoological Society of London, said it was important to manage the health of reintroduced species to ensure harm to the dormice and other woodland species was avoided.

"In this programme we invest considerable resource to evaluate the health of the hazel dormice health before reintroduction to endeavour to develop a healthy ecosystem.”

And Neil Bemment, curator of mammals, Paignton Zoo, added the zoo was very pleased to support another year of the species recovery programme.

“The individuals concerned have been carefully selected according to studbook recommendations. All in all it is a great example of cooperation between a range of organisations and landowners for the greater good one of our most charismatic native species.”