This week 204 water voles were released by conservation charities at Haweswater, after 161 had been rehomed on the Lowther Estate in July.

It was the culmination of the first reintroduction programme since they were almost eradicated.

It is hoped the rodents, which are smaller than rats, with more rounded faces and shorter, hairy tails, will create new habitats and boost diversity of plants that have been wiped out by monocultures.

Environmental organisations and landowners had been laying the groundwork by building up suitable river and wetland habitats and "controlling non-native predators".

Water voles have disappeared from 94% of sites where they once lived, including the Lake District. They are Britain's fastest declining mammal, with population numbers over the last century falling from an estimated eight million to around 132,000.

The numbers plummeted mainly due to habitat loss, pollution and the "rapid spread of the water vole's nemesis; invasive, non-native American mink", the conservation groups said.

"Defenceless against the mink, whole colonies were swiftly decimated."

The release of water voles was run by Eden Rivers Trust, the Environment Agency and the Cumbria Connect programme, on land managed by the RSPB and United Utilities.

Dave Greaves, species and habitat officer at Eden Rivers Trust said: "Control of invasive, non-native American mink had to be in place as they kill water voles and other native wildlife.

"Water voles didn't co-evolve with American mink, and so lack strategies to avoid predation."

He said the project had been facilitated by additional funding made available as "nature recovery rises up the agenda of government and nature-friendly farming and land management is adopted."

Bill Kenmir, Conservation Manager at Cumbria Connect, said the "charming creatures" wield "significant influence in delicately balanced ecosystems by engineering new habitats and increasing plant diversity along waterways".

It follows the release of beavers to the Lowther Estate in summer 2020.

Jim Bliss from Lowther Estate said the two species "co-exist happily".

"The more dams created by beavers, the higher the water table."

This gives voles greater access to wider feeding areas, and the voles and their burrows "help the growth of a variety of wetland plant species - species that have previously been out-competed by monoculture", he said.

"All this helps to create a diversity of soil structures which in turn brings in more diversity."

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