The BBC wildlife presenter stressed the importance of the species to the wider ecosystem
Chris Packham is telling people to "get on and do it" after being bowled over by the actions of two Devon schoolgirls.
The best friends from Tiverton High School have pulled off a remarkable wildlife rescue mission, breeding and releasing hundreds of harvest mice in an effort to save the species from vanishing from English fields.
Eva Wishart and Emily Smith, both 13, have spent two years raising the tiny rodents in tanks at home after discovering the animals were in steep decline. On Wednesday, August 27, the pair released 250 mice into a newly created nature reserve near Eva's home in Tiverton.
Harvest mice are Britain's smallest rodent, growing to just 70mm long, and were once common across farmland. But their numbers have plummeted over the past half-century, largely due to pesticides and modern harvesting methods that strip fields of cover and food.
The project drew the support of naturalist Chris Packham, who travelled to Devon to help with the release. He said he was struck by the girls' determination: "It's not every day you get an email from two young people saying they're doing something enormously imaginative, innovative and that might make a real difference for conservation. It's bold and it's brave and they've put an enormous amount of time, effort and energy into it".
Mr Packham stressed the importance of the species to the wider ecosystem. "Harvest mice were once very numerous and played a very important role in the ecology of the UK countryside. But in the last 50 or 60 years, the intensification of agriculture has meant their numbers have crashed.
"They're not surviving, having a happy time as a harvest mouse, or being eaten by kestrels, barn owls, weasels and foxes. And that's part of their job. When we are trying to rebuild ecosystems, it takes all sorts. Reintroducing animals like this is part of the portfolio of tools we have as conservationists. We've just got to get on and do it".
While the release was a moment of celebration, Packham was realistic about what lies ahead. "I'm going to be very honest with you, some of these mice are going to get eaten. But then there are going to be some happy animals that have eaten them. What I really hope is that enough survive to get through the winter and breed next year.
"Today could be the nucleus of a population that, in a few years, spreads out into the surrounding countryside. Wouldn't that be a thing? What a great legacy for two young people to leave behind before they're even twenty".
Eva said it had been "amazing and unbelievable" to have Packham involved. "Saying goodbye, well, they're going to a much nicer life even though they won't have wheels anymore, which is obviously a great tragedy, but it's much better for them," she joked.
Emily described the day as "epic", adding: "It's sad that they're gone, but good to move on. I really want to do lizards next, but that's unlikely because of licences. I definitely want to get into conservation work."
Mr Packham said the girls' attitude should inspire others. "Be bold, be brave, be inventive. Ask people who know more than you do, and if they're doing less, then get on and do it yourself. Ultimately, the old punk rocker in me is a do-it-yourself person. If someone says no, I say yes. Eva and Emily said yes, and they've done it. Top work".
The girls will return to the site next autumn to search for nests to check if the colony has bred. They hope to release another 80 mice in spring.
Chris added: "I'm tired of listening to old conservationists saying, 'We listen to young people.' Let's empower those young people to take decisions.
"Give them opportunities to see projects like this through, because they aren't risk averse. There's too much red tape, too much pontificating. Just get on with it. Make a difference for life on earth".