The water vole is the UK's fastest declining mammal, but in St Albans, the species is thriving along the River Ver.

Water voles were once abundant in rivers throughout Hertfordshire, but populations have declined by more than 90 per cent in the last 50 years, due to habitat loss and the threat of the American Mink, an invasive, non-native species.

The alarming drop in numbers has put the animal at risk of extinction, including on the River Ver, where they had not been seen since 1987.

That was until 2021, when 150 water voles were released in the St Albans beauty spot, and in the two years since they have thrived.

Herts Advertiser: A water vole along the River Ver dives into the water.A water vole along the River Ver dives into the water. (Image: Terry Whittaker)

2022 data showed a 238 per cent increase in the water voles' range along the river and its watercourses, with this year’s findings revealing the species occupancy in the Ver Valley has, on average, more than doubled each year.

Josh Kalms, water vole officer at Herts and Middlesex Wildlife Trust, led the Water Vole Surveyor Volunteers who collected the data, and is delighted to see the species thriving.

READ MORE: Where are the ULEZ cameras on the Hertfordshire border?

"Water Voles are a key species in wetland ecosystems and their actions are important for maintaining healthy wetland ecosystems – they are mini ecosystem engineers with their burrowing and feeding helping our river banks and wetlands stay in good condition," he said.

"It’s wonderful to see how well the water voles are doing on the River Ver, and it's testament to the private landowners who saw the ecological benefit of the reintroduction, and all the hard work that went in to managing the habitat prior to their release.

Herts Advertiser: Herts and Middlesex Wildlife Trust plans to reintroduce water voles to every river in Herts by 2030.Herts and Middlesex Wildlife Trust plans to reintroduce water voles to every river in Herts by 2030. (Image: Terry Whittaker)

"For that, I must extend huge thanks to the Ver Valley Society, whose volunteers have been instrumental in this project from the early planning stages of the reintroduction. Indeed, many of those are now trained water vole surveyors and continue to be guardians of both the river and the species.

"Water Voles are now occupying almost all of the River Ver between St Albans and Redbourn, with some travelling an additional 4.8km upstream. This year we counted more water vole field signs than the previous year and I’m thrilled to be able to share this amazing success story."

Herts and Middlesex Wildlife Trust have grand plans to reintroduce the water vole to every river in Hertfordshire by 2030, but they need your support.

You can visit to find out more and donate.