The 1,000th water vole will be released this week as part of a reintroduction scheme for the species in a remote corner of Northumberland.
A batch of 240 water voles are being freed into streams flowing into the east end of Kielder Reservoir to link with a population released last year.
By the weekend, the latest release by the Restoring Ratty water vole project will take the total number released to 1,205 since June 2017.
The voles have been bred in captivity from individuals captured from viable populations in the North Pennines, North Yorkshire and Scotland.
Restoring Ratty is a five-year partnership project between Kielder Water & Forest Park , Northumberland Wildlife Trust, Forestry England and Tyne Rivers Trust.
The project is aimed at re-establishing water voles in the Kielder area and has all been made possible by National Lottery players through a grant of £421,000 from the National Heritage Lottery Fund.
By the end of the year, around 1,400 water voles will have been released.
The latest phase of the reintroduction comes as a conference is being held in Gateshead on World Environment Day today on the need to “rewild” landscapes where natural features and species have been lost.
The event, staged by the community interest company Climate Action North East at the Marriott Hotel at the Metrocentre, is a sell out.
All signs indicate that water voles released at Kielder in 2017 and 2018 are doing well with some travelling up to 12km from their release sites.
Graham Holyoak, Restoring Ratty project officer, said: “Over the past two years we have learned so much about water voles from the past four releases, such as the fact that water voles will happily stay where they have been released and form populations if they are in very narrow burns, while on bigger streams a few will stay but many tend to disperse more.
“This will help form our future water vole conservation efforts.”
The water vole was once a common mammal along ditches, rivers and streams but habitat declines, pollution of waterways, industrialisation of agriculture, housing development and predation by American mink have led to severe water vole declines since the 1960s.
It is thought that 94% of water voles have disappeared from places in the UK where they were once prevalent.
