Water voles have returned to every county in England following a reintroduction programme to bring them back to Cornwall, the Environment Agency said.
The final release of 60 captive-bred water voles, the mammal immortalised as Ratty in Wind in the Willows, means there is now an established breeding colony in Cornwall for the first time since 1989 – and in every county in England.
The reintroduction of water voles to Cornwall’s Bude river catchment was undertaken as the mammals were highly unlikely to recolonise the county naturally due to the distance to the next nearest population in East Devon, experts said.
The programme by the Environment Agency and Westland Countryside Stewards was started last year and, with the final release of 60 voles, some 540 captive-bred mammals have been released to establish the breeding colony.
Water voles were once widespread, but saw numbers crash by 90% in the 1990s as a result of predation by mink – which have established themselves in the countryside after escaping from fur farms – and loss of riverbank habitat.
Data released by the Environment Agency and Wildlife Trusts last year suggested the mammal may have declined by as much as a fifth in just the last few years since 2011.
But experts said reintroduction schemes, combined with programmes to control mink and manage habitats for water voles, were providing a lifeline for the species.
The Environment Agency’s national conservation manager Alastair Driver, said: “Habitat creation and restoration projects are hugely valuable for most wildlife, there are some species for which introduction programmes are necessary simply because populations have become so fragmented and the species is not very mobile.
“The Environment Agency has created nearly 5,000 hectares of wetland and river habitats in the last 10 years, and worked hard to tackle unsustainable abstraction from our rivers, to the extent that some 55bn litres of water each year is now returned to the environment.
“However we are keen to support carefully located water vole release projects as well, but only as long as there is rigorous control of American mink in the catchment.
“This is essential if the populations of water voles are to benefit from these healthier rivers and new habitats.”
Water voles were successfully released into the River Axe in Devon in 2009, thriving as a result of habitat management and mink control, the Environment Agency said.
John Duncan, chief executive of the charity Westland Countryside Stewards, said: “It has been a privilege to play a part in the release of water voles back into a Cornish habitat where they were once a common sight.”