Water voles are Britain's fastest-declining mammal. Once widespread across the country's rivers, streams and wetlands, they have declined due to habitat loss, pollution, agricultural pressures and predation by non-native American mink. National estimates now stand at between 58,000 and 186,000 individuals, making every stronghold for the species increasingly important. 

The survey, carried out by Hampshire & Isle of Wight Wildlife Trust with the River Meon Conservation Volunteers, recorded extensive evidence of water vole activity including feeding stations and remains, burrow entrances and latrines. 

The findings suggest a healthy and active population during the breeding season and are thought to be among the strongest recorded at the reserve using a new monitoring method.

Andy Reeves, Reserves Officer (Central Rivers & Downs) at Hampshire & Isle of Wight Wildlife Trust, said: "What makes a survey like this so exciting is seeing just how much evidence water voles leave as they go about their daily lives. 

“Water voles can be difficult to spot, so we look for clues. We found feeding stations with neatly cut stems clipped at the distinctive 45-degree angle that water voles are known for, plus active burrows and characteristic latrines along the riverbank. Some of their green, tic-tac-shaped droppings have been flattened into what we call 'trampled latrines', where water voles stamp them down to scent mark their territory during the breeding season. Finding so many of these signs shows that the population is feeding, breeding and thriving here at St Clair’s Meadow Nature Reserve."

Rather than surveying solely from the riverbank, trained staff and volunteers now search the vegetation for field signs from within the river itself, following water safety procedures and wearing appropriate clothing and safety equipment. This has proved highly successful, enabling a much more detailed assessment of water vole activity and has significantly increased the number of sightings.

The results reflect a wider encouraging picture emerging along the River Meon. Survey data collected by the South Downs National Park Authority (SDNPA) and SDNPA volunteers in 2025 recorded water voles at 32 of the 35 sites surveyed, with evidence of breeding at 22 locations. 

The SDNPA results contribute to emerging evidence of a slight recovery in water vole populations at a national level. However, water voles remain the UK’s fastest declining mammal, and long-term continued conservation effort is essential. 

A key reason for the species' recovery on the River Meon has been the Meon Valley Water Vole Project. Launched in 2013 by the SDNPA and the Meon Valley Partnership, with support from Hampshire & Isle of Wight Wildlife Trust, the project saw more than 2,800 water voles released into the river system. It is the UK's largest water vole reintroduction within a river valley and the only project of its kind to have taken place in Hampshire.

The River Meon is one of the most important strongholds for water voles in Hampshire. Its clear chalk stream waters, well-vegetated banks and good habitat conditions provide an ideal home for the species. In addition to the reintroduction, years of partnership work to improve river habitats, reduce predation pressures, and support species have helped create the conditions for populations to recover and thrive.

Andy adds: “Water voles may be small, but they play a surprisingly important role in a healthy river ecosystem. Their feeding and burrowing behaviour helps shape riverbank habitats, benefiting a range of other species and helping maintain the rich wildlife that helps makes chalk streams like the Meon so special.”

Monitoring work is made possible through a long-standing partnership involving Hampshire & Isle of Wight Wildlife Trust, the South Downs National Park Authority and dedicated volunteers. The River Meon is believed to be one of the most intensively surveyed rivers for water voles in the country, providing valuable data on the species' status and recovery and contributing to national monitoring efforts.

Andy said: "Monitoring is absolutely essential. Conservation doesn't stop once a species has been reintroduced. We need to keep tracking populations to make sure they remain healthy and to identify any threats early.

“I'd like to thank the River Meon Conservation Volunteers, whose efforts collecting data feed into national monitoring programmes and help us understand how water voles are faring not just here on the River Meon, but across the country."

The survey is thought to be one of the most successful at the site to date using a new monitoring method, which records detailed field signs directly into a national monitoring programme. The National Water Vole Monitoring Programme helps conservationists build a better understanding of how the species is faring nationally.

Hampshire & Isle of Wight Wildlife Trust plays a leading role in water vole recovery, not only regionally but also nationally. The Trust is co-author of the  National Water Vole Database and Mapping Project, which collates records from across the UK which helps guide conservation action to the areas where it is needed most.

Visitors can also help protect water voles and other wildlife by staying on paths and keeping dogs on leads when near riverbanks to minimise disturbance to wildlife and sensitive habitats.

The success at St Clair's Meadow reflects Hampshire & Isle of Wight Wildlife Trust's aim to bring more land into nature recovery. Alongside managing existing wildlife-rich sites, the Trust is restoring habitat at nearby Court House Meadows. This newly acquired land, which has the River Meon running through it, is creating more space for nature and supporting the long-term recovery of water voles and other species across the wider landscape.

To help support the recovery of water voles and other wildlife, become a member of Hampshire & Isle of Wight Wildlife Trust today. Membership helps fund vital conservation work, habitat restoration and species monitoring across Hampshire and the Isle of Wight, including work along the River Meon. Join today here.