They are all mobilised in the bitter cold. Officers of Scottish Natural Heritage (SNH), the police and local enthusiasts are scouring the countryside for furry creatures amid fears that they could reclaim their ancient territory and undermine the grand beauty of our wild places.

The revelation last week that 20 beavers had been set loose in the forests around Perth and Tayside has sparked a desperate recovery operation. Along the banks of the river Tay a volunteer trapper is laying traps to round them up. The man from SNH was reluctant to let journalists spend time with him. I was savouring a weekend with my Davy Crockett hat and moleskin boots, but Calum MacFarlane is adamant: "He is one of our volunteers and I want him to focus on the job in hand. He didn't sign up to be questioned by the press."

The story begins, though, on three dark lochs near Knapdale forest in neighbouring Argyll. In May 2008, three families of beavers were gently reintroduced into the wild. It marked the first reintroduction of a mammal species in the UK. Wildlife enthusiasts and lobbyists were jubilant.

According to them, beavers had been an integral part of Scotland's ecosystem more than 400 years ago before they had been hunted to extinction. This could be the start of something that would transform Scotland's rural glory and raise its global profile to a plateau only currently occupied by the great wildernesses of North America and Africa. Soon there might be lynxes, wolves and bears. Others, though, view the relentless campaign to reintroduce beavers to Scotland as a prime example of urban busybodies and political apparatchiks foisting something unnecessary and possibly very damaging upon the people who must eke a living in the countryside.

There is no real proof, they argue, that the beaver was ever native to Scotland. The creature's ability to clear significant parts of forest to build its lodges, they say, will ruin part of the beauty and grandeur of Scotland.

MacFarlane, however, sees few problems with their reintroduction and he believes the unauthorised recent releases in Perth and Tayside can be contained. "The reintroduction around Knapdale Forest is part of a five-year experiment. A report is due before the middle of next year which will give us some indication of how well this is working.

"The beavers that have been released recently we do not believe will breed easily and such is their behaviour and habits that they are not very difficult to catch. We and the National Species Reintroduction Forum were very meticulous about this project."

Opponents of the scheme refuse to be charmed by the prospect of Scotland's ecosystem being changed by the mammal. At a public meeting in Argyle several years ago the local MSP, Jamie McGrigor, spoke for many when he challenged SNH's claim that a wide consultation of interested parties and experts had taken place. "Were any residents of this area actually consulted?" he asked. No, they hadn't been.

The previous Labour administration had blocked moves to conduct the beaver experiment. They were not satisfied that, if the experiment failed, Scotland wouldn't have hordes of beavers running amok destroying forests. The SNP, though, successfully applied European law to make it happen.

One senior government source forcibly rejected the opposition to the beavers' reintroduction. "Frankly, I just don't see what the naysayers are worried about. We have successfully introduced some spectacular birds of prey smoothly and effectively. The beaver will help complete our ecosystem and I would expect to see lynxes in the not too distant future.

"The salmon lobby fear that the beavers' dam building will harm the king of Scotland's rivers. But the Norwegian salmon fishers were entirely relaxed about similar schemes there. In fact, there was evidence to show that they improved some river systems favoured by the salmon."

Lynxes running wild in the Scottish Highlands has a wild and romantic aspect to it. This too, SNH argues, will benefit Scotland and not just in attracting more ecotourists. Lynxes are the natural predators of red deer. "And anyway, hardly anyone will ever see them," added the Holyrood source.

Farmers complain that after a team of beavers has been about its business a forested area can take on a blasted aspect. Others, however, point to the dark green shadow of fir trees that has enveloped large parts of the Scottish Highlands. If some of these wooded areas were to become the playgrounds of beavers who could complain? These cleared areas can also become home to different types of species of birds and insects.

And although SNH believes that up to 20 beavers have escaped private collections in Angus and Perthshire in recent weeks, privately locals think it may be as few as six. The plan is for the animals to be trapped and then passed on to the Royal Zoological Society of Scotland to be "rehoused".

SNH is keen to point out that trapping will take place in collaboration with Tayside police and local landowners.

The hills around Tayside and Perthshire that I visited yesterday were gently covered with a patina of snow and it is easy to see why feelings can run high about how best to preserve and enhance such splendour.

Resident after resident, though, seemed entirely nonplussed about the issue. In the summer there were sightings in Invergowrie, near Dundee. "I saw the beaver beside the water munching on some vegetation," David Leckie, who works at a local pet shop, told the Dundee Courier. "It was like a huge rat with a large flattened tail. I couldn't believe it! I stood there for a couple of minutes and then went to get my camera but it wasn't there when I got back."

Those I spoke to remained unconvinced. "I think it was a dog," said one elderly walker.

I kept to the footpaths and scanned the rivers, but then it got a bit chilly. Any beavers worth the name will be deep in their lodge.