Water vole reintroduction on the Gwent Levels, Wales, UK

Summary

The European water vole vanished from the Gwent Levels in south Wales after American mink, introduced from the 1950s onward, drove the population down across the whole of the UK. In 2011, Gwent Wildlife Trust ran a feasibility study at its Magor Marsh reserve, confirming no water voles had been recorded since 2003, no nearby source population existed, and roughly 4.5 km of suitable ditch habitat was available once mink numbers were controlled. An existing mink trapping programme, running since 2006, was expanded across the wider landscape in 2011 and 2012 to both remove mink and give early warning of new arrivals before they reached the marsh. With mink held at low density, over 200 captive-bred, health-screened water voles of lowland genetic stock were soft released at Magor Marsh in stages during 2013 to mimic natural colonization. Twice-yearly surveys of ten ditches, following standard water vole survey methodology, show the population thriving and spreading over 10 km into the surrounding landscape, while continued mink trapping suggests the resident mink population has been eradicated and only occasional migrants are now caught. The project is rated highly successful, crediting years of preparatory mink control, a strong volunteer monitoring network and enough connected habitat to support a resilient meta-population able to withstand local setbacks such as flooding.