Water voles have returned to every county in England following a reintroduction programme in Cornwall, the Environment Agency has said.
Hundreds of captive-bred water voles have been released in the county over the past year.
Water voles used to be widespread but have declined because of habitat loss and predation by American mink.
The agency released the final 65 animals near Bude, which means every county now has a breeding colony.
'Evidence of breeding'
Alistair Driver from the agency said the voles were a "key part of the food chain" and "one of our most popular animals".
Mr Driver said: "Over the past year, several hundred animals have been released in a project run by the Environment Agency and Westland Countryside Stewards."
Conservationists decided to reintroduce the animals because it was deemed unlikely the species would naturally recolonise from the next nearest population in East Devon.
Mr Driver said: "I've seen clear evidence of them breeding in Cornwall and spreading out from where they were released."
He added that for the first time since 1989, Cornwall had an established breeding colony.