They have not been introduced to the wild for more than 400 years.
But yesterday two families of beavers were released in Britain – to the anguish of anglers and the delight of environmentalists.
This implies that beavers were "introduced to the wild" more than 400 years ago, when I'm pretty sure that they just happened to live there.
The Mail Online version of the story uses different wording, although the page title reads: "Beavers released into the wild for the first time in 500 years". Again, that suggests they were released into the wild 500 years ago.