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'Wind In The Willows footage courtesy of YouTube/The Wildlife Trusts
Pupils at a school in South London have stepped in to help save an important part of Britain's countryside threatened with extinction.
Numbers of water voles are rapidly declining because of pollution and loss of habitat. If nothing is done this aquatic mammal could disappear forever.
Inspired by reading about water vole 'Ratty' in Wind In The Willows, Year 5 pupils at Rutherford House School are on a mission to save this unsung hero of the countryside.
"They are rapidly declining because of habitat loss... and pollution," said one pupil.
"They are a huge part of the environment... and contribute to wildlife more than people think," they added.
The water vole is the UK's fastest declining mammal, disappearing from around 70% of sites in less than a decade.
"We've probably got less than 80,000 water voles across the UK and in London there are very few rivers with them on at all," said conservationist Elliot Leeson from Citizen Zoo.
"They help support the food chain and burrow into the landscape which creates fantastic habitat for things like grass snake.
"And because they eats lots of different types of plant they're good at dispersing seeds across the river - they're the gardeners of our riverbanks," he added.
Pupils at Rutherford House School are taking their campaign to some of the more powerful people in the country by sending letters to MPs. They've also started a petition signed by more than 13,000 people.