Our reporter Fiona Marley Paterson went to meet the water voles reintroduced in Cumbria.
Water voles have been introduced to the Lake District in a bid to save Britain's fastest-declining mammal from extinction.
The 350 water voles, in Haweswater and Lowther, are the Lake District's first.
Water voles were once widespread across Cumbria, but are now on the brink of extinction: endangered in the UK and so a protected species.
In the last century, they've disappeared from 94% of the places where they used to live. An estimated UK population of eight million is now down to just 132,000.It was such a significant moment in history that the voles' first dip into the bog stream waters of Cumbria was surrounded by cameras.
Ten older voles were released straight into the environment in what's called a hard release.
Jenny Tratt, an Ecologist from vole specialists Derek Gow Consultancy explained: "The older animals tend to be able to get on with it a little bit quicker. Get straight into digging burrows."
Two hundred and six younger voles had a slower introduction to their new home in Haweswater, being put into cages that were then spread 40 meters apart so they populate the whole valley, in a soft release.
The distance is calculated with science: it's close enough for them to breed, but far enough that they won't fight.Dr Ashley Lyons, RSPB Haweswater's Conservation Scientist explained more about the soft releases: "So they're in these cages in small sibling groups, so they know a few of the others that are about. They will be in the landscape for a few days.
"We'll feed them some apples and some carrots so that they've got enough to eat. And then in a couple of days' time, we'll open the cages for them to go and start exploring. And then from next week, they're hopefully on their own in the landscape and doing well."The voles have been raised in captivity on the border of Devon and Cornwall.
They were then marched into the Cumbrian bog in their cages by a team of volunteers, excited to do their bit for this moment in history.
Volunteer Jane Porter told ITV Border it was tough-going.
"It's miserable trekking them through this ground because it's really, really boggy," she said.
"It's very tussocky. So it's really quite hard work, they're quite heavy. And this is possibly one of the hardest tasks we've done."Her teammate Ben Challis, another volunteer continues: "But knowing that water voles are doing really well somewhere in Cumbria because of something we've all been part of is really gratifying. It's just remarkable, you just feel like you're walking on air."The volunteers will keep checking on them and monitoring their progress. There was a lot of excitement.
Volunteer Chris Jerome said: "I've done lots of work for water vole conservation over the last year and a bit, but I've never actually seen one until today. So this is the most exciting thing I've been involved in."
Eden Rivers Trust Intern Isaac Pullan explains why they put fern and vegetation on the top of the cages: "It's just to make it blend in really and give them a bit more security so they don't feel as threatened."
There have been years of preparation for this big day, lovingly creating their new home: re-wetting the bog and using cattle to encourage wildflowers to grow for the voles to eat.The voles will now also be ecosystem engineers: improving it for other animals.Dave Greaves from Eden Rivers Trust says the voles like that landscape because diverse vegetation of a nice length means they can hide away, "and then they've also got bits of areas of higher ground and tufts where they can hide from predators."David Morris, Area Manager for the RSPB explains the work they've been doing for the last few years: "So we've made it much wetter by sort of damming up the water, creating more wildflowers and some of the kind of plants and vegetation here that the voles eat.
"In future, this'll get wetter, more plants and maybe beavers one day, connecting up the beavers that are down the valley at Lowther and that will be the first time water voles and beavers have been together in Cumbria for about 400 years."Beavers and voles live well together as the voles love the dams the beavers love to create. But there's one animal that's no longer welcome here. The team has spent years culling the voles' main predator: non-native American mink.Bill Kenmir from Cumbria Connect explains why the mink have been so disastrous for voles in the UK: "They were introduced as part of the fur trade. They haven't evolved together and it's just been too much for the voles.
"We've been able to reduce that mink population to such a low level that we think the water voles have a good chance and will start to thrive."Voles only live for about five months in the wild, and the team now hopes enough will survive, as Jenny Tratt explains, "a fair amount of the population will be lost over the winter, just due to water levels rising, food getting less.
"But we hope that enough will overwinter and then start breeding again so that there'll be still a population here in the spring ready to thrive."
Voles do breed quickly, so in a year's time their grandchildren and great-grandchildren may have turned the fate of voles in the UK.
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