1,000th hazel dormouse reintroduced to the UK

A hazel dormouse being held by a licensed handler. Credit Clare Pengelly.

This week, the 1,000th hazel dormouse (Muscardinus avellanarius) will be reintroduced to the UK by wildlife charity People’s Trust for Endangered Species (PTES), Natural England and the University of Cumbria.

PTES and partners will release 15 breeding pairs or trios of rare hazel dormice into an undisclosed woodland location in the Arnside and Silverdale Area of Outstanding Natural Beauty (a nationally protected landscape covering parts of north Lancashire and south Cumbria), in an attempt to save this endangered species from extinction in the UK.

Dormouse reintroductions have taken place annually since 1993, but excitingly the dormice reintroduced this June are part of a wider species recovery programme, ‘Back On Our Map’ (BOOM). Led by the University of Cumbria and Morecambe Bay Partnership and supported by The National Lottery Heritage Fund, BOOM is a multispecies, landscape scale project which aims to reinstate 10 locally threatened or extinct native species back into the area, including hazel dormice.

With their soft caramel fur, furry tail and big black eyes, hazel dormice are undoubtably endearing, but sadly their numbers have declined by a staggering 51% since 2000, according to PTES’ State of Britain’s Dormice 2019. They are also considered extinct in 17 English counties. Carefully releasing healthy, captive bred dormice into the right habitat (that is maintained via correct woodland management practices) is the key to bringing these charismatic creatures back from the brink.

Ian White, Dormouse & Training Officer at PTES, explains:

Reintroductions are crucial to the long-term recovery of many species, but particularly hazel dormice as their decline has been so dramatic. Our first reintroduction took place in 1993, so we are thrilled that this year we’re releasing our 1,000th dormouse. This is a great milestone for conservation and a huge moment for hazel dormice in Lancashire too, as there are no known populations currently living there.

Jo Sayers, BOOM Project Manager, University of Cumbria, says:

Dormice have long captured the hearts of everyone after finding fame through Alice in Wonderland, but despite their popularity they are incredibly rare, so it’s time to take action. This is the first of two hazel dormouse releases planned for the Arnside and Silverdale woodlands, and we hope by next summer there will be around 80 dormice living in our woodlands.

Jim Turner, Reserve Manager, Natural England, says:

Today’s activity is part of Natural England’s work with the People’s Trust for Endangered Species to provide an ongoing programme of funding, coordination and monitoring of the dormouse recovery project.

We know hazel dormice thrive in well managed woodlands, which is why we chose an area with a range of tree species and ages – from mature oaks to newly coppiced hazel – which will give the dormice plenty of food and opportunities to nest. The Arnside and Silverdale AONB is rightly proud of their fantastic woodlands, which have been cared for over many years by local landowners, conservation organisations, volunteers and woodland businesses.

This year’s reintroduction would not be possible without months of dedication from all organisations involved, including the Common Dormouse Captive Breeders Group (CDCBG), Wildwood Trust (a key member of the CDCBG) and ZSL (Zoological Society of London). Each partner plays a key role in the reintroduction programme:

  • This year’s woodland site has been carefully chosen by the BOOM team, Natural England and PTES, ensuring that the right habitat is in place and that it’ll be maintained correctly to secure the long-term survival of the reintroduced dormice.
  • All dormice being released have been captive bred by members of the Common Dormouse Captive Breeders Group, including Wildwood Trust.
  • Before being released into their new home, every dormouse undergoes a nine-week quarantine period at ZSL (Zoological Society of London), where vets conduct regular and thorough health checks. This ensures that each animal is fit and healthy prior to release, giving them the best chance of forming a healthy population in the wild.
  • Once all dormice have been given the green light, they are carefully transported to the reintroduction location, where staff from PTES, Natural England and the University of Cumbria, along with several volunteers, will be on hand to ensure the smooth transition from travel nest-boxes to their new woodland home.

Dr Deborah Brady, Research Fellow at the University of Cumbria, who is managing the reintroduction for BOOM, adds:

Once the dormice arrive they are placed into mesh cages that mirror the woodland. The cages are filled with the right mix of foliage, buds, berries, nuts, insects and water, and this is where the dormice will live for the first 10 days. Each cage is connected to a tree, so the dormice become acclimatised to their new surroundings. Our local volunteers will check each cage daily and will also act as monitors over the next two years to ensure all the dormice remain healthy.

After 10 days, the cage doors are opened to allow the dormice to explore their new home. In due course, when the dormice no longer need them, the mesh cages will eventually be removed.

PTES, Natural England and the University of Cumbria are aiming to coordinate a further two dormouse reintroductions in the area in June 2022, in partnership with the National Trust, the RSPB and the Arnside and Silverdale AONB.

Ian White concludes:

This is the start of a positive new chapter for hazel dormice. With two further reintroductions planned, we hope to see more dormice released in this area that can one day create a self-sustaining meta-population, which we hope in turn will result in stable populations once again living all across this beautiful region.


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