There may not be the clarity on the numbers of beavers in the waterways of central Scotland but there is evidence to show they are now remarkably widespread only 10 years after the first population was spotted in Strathmore.
Meetings of farmers and land managers in Coupar Angus and Crieff last week were shown a distribution map illustrating the growth of the population, with groups of beavers identified right through the Tay system and its tributaries including the River Earn.
One group has settled at Tentsmuir at the mouth of the Firth of Tay and others have built lodges and dammed watercourses 120 miles away at Crianlarich near the headwaters of the river system.
Other groups are now in the Forth system as far inland as Aberfoyle in the Trossachs.
Another group has mysteriously appeared in Clackmannanshire.
Andrew Bauer, policy director for Environment and Land Use Policy at NFU Scotland, said: “That one is a real puzzle.
“The catchments do not connect so did the beavers hike over the Ochil Hills?”
All the beavers apart from a small officially sanctioned population in Knapdale, in Argyll, have originated from illegal releases, most likely in the River Isla and River Dean run through prime arable land in Strathmore before joining the Tay.
It is believed Scottish Natural Heritage (SNH) estimates numbers in the low hundreds.
Those at the meetings last week believe that would be a considerable underestimate and the actual number would be more than 1,000.
Leaving the Coupar Angus meeting, one disgruntled farmer said: “Beavers are going to end up being a bigger problem than rabbits. We are continually having to remove dams and inspect river banks for breaches.
"Those who are worried about Lynx being released should take warning from this. Once a population becomes established the genie really is out of the bottle.”
Farming’s battle with beavers
NFUS called the member-only meetings to outline management plans likely to appear soon in an SNH document.
Although the original releases were illegal, beavers will now have protection under the EU Habitats Directive. Until now farmers and land managers have been able to destroy dams and lodges where they are blocking waterways and to control numbers by shooting.
Mr Bauer suggested that from now on lethal control will only be allowed under licence granted by SNH.
Land, fishery and forestry managers will have to demonstrate they have tried other methods of control and that shooting will not affect the conservation status, the natural range and the population trends of the beavers.
Licences are likely to be granted on an individual basis and only after a site visit.