Naturalists have confirmed that more than 150 beavers are now living and breeding successfully in the wild in the southern Highlands of Scotland after escaping from nearby private collections.
The Eurasian beavers, which were once native to the UK, have been found living across hundreds of square miles of lochs and rivers in Perthshire and Angus after they began escaping from private collections nearly a decade ago.
An expert report for Scottish Natural Heritage said the beavers were adapting very easily but were posing serious challenges for farmers, landowners and drainage systems in some places along the river Tay which could require intervention.
Hunted to extinction around 400 years ago, they were disease-free and adapting well, the researchers said, suggesting they would be an ideal group to use to reintroduce the species Scotland-wide if ministers agreed.
“Genetic tests tell us that they would be suitable for permanent reintroduction to Scotland, because they are Eurasian rather than North American beavers,” said David Bale, chair of the Tayside beaver study group.
“They are also varied enough genetically to make a reasonable first step towards a full reintroduction if that was the decision of the Scottish government.”
Confirmation that such a large number of beavers has now established itself naturally and without official intervention makes this one of the largest natural repopulations by a once native mammal in the UK, comparable with wild boars now living freely in parts of southern England.
It is likely to spur on campaigns in other parts of the UK for beavers to be reintroduced, with the latest report coming after Natural England agreed in January to allow wild beavers living in Devon to remain at large following a campaign by conservationists.
The beavers’ spread in the Tay and Earn catchments, reaching as far north as Loch Rannoch and as far south as Crieff and Bridge of Earn, has been occurring naturally even while zoologists have had mixed success in their project to officially reintroduce beavers under controlled conditions at Knapdale in Argyll.
The Knapdale project, a multimillion-pound programme under the auspices of the Royal Zoological Society of Scotland and Scottish Wildlife Trust, released 16 beavers in four family groups trapped in Norway in 2009 and 2010.
Six animals shipped over from Norway in the first batch died in quarantine or could not be released. Of those that were, a number of animals disappeared or died, with breeding less successful than hoped, leaving a total population last year of 13 beavers.
Scotland’s powerful salmon fishery and farming lobbies have repeatedly resisted or criticised beaver reintroductions, including blocking a plan for a second official release scheme at Insh Marshes national nature reserve near Kingussie in the Cairngorms – only 35 miles north of Loch Rannoch.
The beaver study confirmed there were impacts on farming. It suggested that the animals near heavily cultivated farmland on the lower river Isla where it met the Tay might need to be captured and relocated, because they could cause drainage systems to fail and cause widespread flooding.
Bale, a regional manager for SNH, said that in general the beavers were causing little significant damage.
“Our work documenting the impacts of beavers on land management interests has shown that in many situations, beavers are likely to cause few concerns,” he said. “But if they were to be permanently reintroduced, efficient, effective and affordable ways of managing and reducing potentially significant impacts on intensively farmed land and other interests would have to be found.”
