No one is sure where the beavers on the River Otter come from, the Guardian reported. Devon Wildlife Trust began a reintroduction project in 2011, but its beavers, a male and female, remain in a secure enclosure miles away.
Tom Buckley, a retired environmental scientist, began to suspect beavers in the Otter when he spotted trees that appeared to have been gnawed by beaver teeth last year. He worked with David Lawrence, a local landowner, to install motion-activated infrared cameras along the river.
"We'd seen bits of trees chewed and cut down and I was starting to think that it was a sign of beavers even though I couldn't believe it," Buckley said.
The cameras have captured three adults and suggest there is a breeding population.
The fashion for beaver hats and the belief that castoreum, a secretion beavers use to mark territory, was medically valuable led to their extinction in the 16th century in England. The animal was also wiped out in many other areas in Europe and the slaughter continued in North America with the American beaver becoming locally extinct in much of the continent.
A re-introduction program began in 2009 in Scotland and one is being considered for Wales.