A decision to let wild beavers stay on the River Otter in Devon permanently is the culmination of a wildlife saga that has run for more than a decade.

But now that as many as 15 family groups are free to swim, build dams and breed on the river and its tributaries, a bigger question looms about the future of wild beavers across England.

Conservationists say the origins of the beavers on the River Otter are unclear, but reports of the semi-aquatic mammals living wild on the waterway started in around 2006.

By 2013, video evidence of beaver young, or kits, showed the animals were successfully breeding.

Officials intended to catch the beavers and put them into captivity, but Devon Wildlife Trust put forward plans for a five-year trial monitoring them in the wild, with the support of local people.

The Trust applied for a licence for the trial from government agency Natural England in 2014, and, after four adults and a kit were captured, tested and found to be clear of disease in 2015, they were released back on to the river.

DNA tests had also confirmed they were Eurasian beavers, a species found in the UK before being hunted to extinction several hundred years ago, rather than North American beavers – but also that they were inbred.

So a new pair of beavers was released on to the catchment in 2016 to boost the population’s genetic diversity, and a further two beavers were released into different parts of the river in May 2019.

The five-year River Otter Beaver Project, a partnership led by Devon Wildlife Trust and involving Clinton Devon Estates, Derek Gow Consultancy and the University of Exeter, measured the impact of the animals on the local landscape, economy, communities and wildlife.

A report on the trial, published earlier this year, revealed a range of benefits, including reducing the risk of flooding for downstream properties, and benefiting wildlife including fish, water voles and birds.

The mammals caused some localised problems for several landowners, including flooding land and damaging trees, but these could be addressed successfully with “active management”, the study said.

Professor Richard Brazier, who led the University of Exeter research team, said benefits also included water quality improvement, carbon storage, and a boost to local businesses through wildlife tourism.

“We show that any conflicts can be managed swiftly and efficiently and also that the benefits of beavers far outweigh any costs associated with their management,” he said.

Now attention is turning to the national strategy for releasing and managing beavers in England, amid reports that the rodents are already living wild on other rivers and with many being introduced into enclosures in the countryside.

James Wallace, director of the Beaver Trust, said: “Having shown through research and community engagement many of the benefits, challenges and ways of living alongside beavers, it is time to apply the learning from the River Otter Beaver Trial across the rest of the country.”

He said the Beaver Trust, Devon Wildlife Trust and other conservation, fishing, farming and forestry stakeholders are developing proposals for an English beaver strategy.

“We invite the Government to collaborate with us on planning, resourcing and supporting the future management and restoration of beavers across suitable river catchments in England,” he said.

Wildlife groups back the wider return of the aquatic mammals, which manage the landscape by cutting down trees and damming rivers, for the benefits they can provide.

There are high levels of public support for beavers returning to England, and some landowners are keen to use the landscape engineering they perform to help “rewild” parts of the countryside to help nature.

But farmers have raised concerns that they can damage farmland.

There have also been calls for funding for landowners to support them to make space for beavers, which are now classed as an endangered native species, in the landscape.

The Government is planning a consultation later this year on the national strategy for beavers in England and how to manage them.

But for the beavers in East Devon, at least, although they are unaware of it as they take to the river at dusk to forage on willow and check out the occasional wildlife watcher on the banks, the future is secure.