On 4 September, Herts and Middlesex Wildlife Trust, reintroduced 100 Water Voles to a stretch of the Upper River Lea, near Wheathampstead, in collaboration with the Ayot Estate and Verulam Angling Club, and supported by volunteers. It marks the species' return to the river after more than 20 years.

The project is part of a wider effort to reverse the dramatic decline of Water Voles in the UK—currently the country’s fastest-declining mammal, but a vital ecosystem engineer for our waterways. Once common across Hertfordshire, populations have dropped nationally by 90% since the 1960s due to habitat loss and predation by invasive American Mink.

This reintroduction project has been funded as part of the Projects for Nature Platform. 

A Carefully Chosen Site

The 1.5km stretch of the Upper River Lea, below Wheathampstead, on the Ayot Estate was selected for its continuous high-quality, American Mink-free habitat, and healthy stretch of river, backed by a more complex wetland habitat, including lakes, backwaters and a significant floodplain. Another factor, is the reintroduction site’s proximity to two of the Trust’s nature reserves – Lemsford Springs and Stanborough Reedmarsh, which have both undergone extensive habitat enhancement work over the last two years. Additionally, the Trust has been advising and supporting Harpenden Town Council with their plans for a Water Vole reintroduction due to take place in 2026 on the River Lea upstream at Batford. It is hoped that over time this ‘corridor’ will enable the spread of Water Vole populations, genetically mixing communities along the full extent of the river.

The Ayot Estate and Verulam Angling Club, both committed to wildlife conservation, have worked closely with the Wildlife Trust to prepare the site, creating a welcoming environment for this important native species.

Josh Kalms, Water Vole Conservation Officer at Herts and Middlesex Wildlife Trust, said:

“We’re thrilled to see Water Voles back on the Upper River Lea. These animals are vital to healthy wetlands - their burrowing and grazing helps maintain riverbanks and improve biodiversity. Water Voles eat a huge range of plants species and in doing so, they move seeds around, helping to maintain varied plant cover and creating lush and wild bankside vegetation. They are also a key food source for native species like Stoats, predatory fish, herons and birds of prey.”

“We are indebted to the Ayot Estate and Verulam Angling Club for offering this quality habitat for the release, and to our funders. I’d also like to extend a big thank you to our wonderful volunteers who provide essential support throughout, from habitat surveys and mink raft monitoring to their hands-on involvement during the release. Significant volunteer hours will be dedicated to monitoring the population after the reintroduction.

“As our collaborations with landowners, organisations and local authorities shows, we can get a wider spread of Water Voles through partnership work – the more people on board, the better for their future, fulfilling our goal of seeing Water Voles thriving on all of Hertfordshire’s rivers by 2030.”

The Water Voles, bred by Derek Gow Consultancy in Devon, were released into riverside pens to acclimatise, with volunteers and the Trust’s team supporting their transition. After a short period with supplementary food, the pens were removed and the Water Voles began establishing their own burrows. 

Tom McLaughlin of land agents Strutt and Parker on behalf of the landowners said:

“We are proud to welcome back water voles to our stretch of chalk stream. Their return is a symbol of what can be achieved when landowners, conservationists and the local community work together to restore nature. This project is about more than one species—it’s about bringing vitality back to the whole ecosystem.”

Barry Killinger, Fisheries Manager - Verulam Angling Club said:

“Angling and nature conservation are closely linked - our members recognise how important it is to protect the aquatic environment and its inhabitants. It is rewarding to know that the club, though our management and maintenance of the river’s health, we are contributing towards bringing Water Voles back into this area and overall, a more sustainable future for the river, angling and nature. Going forward we are happy to engage in any monitoring programme of the voles and also look forward to further introductions on stretches further upstream.”

Hope for the future

The Trust will continue to monitor the reintroduction through regular Water Vole surveys, helped by skilled volunteers and checks for American Mink. 

In December 2024, a report from The Wildlife Trusts highlighted a national decline in Water Vole populations, with a 39% reduction in occupied areas since 2006, but also identifies encouraging local successes in Hertfordshire due to sustained conservation efforts. Two areas in the counties have now reached 'Regional Key Area' status, denoting that they are playing a vital role in Water Vole recovery.

Over 23 years, Herts and Middlesex Wildlife Trust’s long-term commitment to Water Vole conservation —including reintroduction projects and habitat restoration through its Living Rivers project, and ongoing American Mink control—has contributed to population expansion. Collaborations with anglers and conservation partners have further supported recovery efforts. While national challenges remain, local progress shows that targeted action can help rebuild resilient Water Vole populations.

There is further good news for Hertfordshire’s Water Voles – Hertfordshire’s Local Nature Recovery Strategy, which launches in October identifies Water Voles as a flagship species, an indicator for the health of rivers, and aligns the work being carried out by the Trust to county-wide conservation goals.

If you are a landholder or land manager who would like advice on how to help in the recovery of Water Vole populations in Hertfordshire, please contact Josh Kalms - water.vole@hmwt.org.