The sun is glinting on the waters of Loch Sween and, in the hills beyond, the oaks and alders shimmer a vivid green. Days like this seem perfect enough in Knapdale, the rolling expanse that runs down to Scotland's west coast. This morning, though, is extra-special. As the banner at the Cairnbaan Hotel puts it: “Welcome Home. After 400 years — the beavers are back”.

Overnight three families of European beaver, 11 animals in all, were released into this landscape, which forms a natural enclosure of hill and rugged coast. Every young they rear, every tree they fell, every dam they build will be accounted for by a team of conservationists.

The five-year project to reintroduce beavers to Scotland has not lacked controversy. The cost has risen from £750,000 to more than £1 million. The effects on salmon fishing could be even more expensive, it has been claimed, with game fishing organisations offering dire predictions about the long-term impact.

This morning, though, the mood in Mid Argyll is optimistic. Darren Dobson, who moved north from the Isle of Wight and took over the Cairnbaan Hotel ten years ago, is convinced that the arrival of the beavers should be welcomed.

“It’s great for the profile of the area. We’ve sea eagles and pine martens, and now beavers. It’s a wonderful day,” he said.

Mr Dobson is a keen angler and says that during research into the beavers’ impact on fishing stocks he has not found any evidence of harm. If he had, he says, he would stand “shoulder-to-shoulder with my fellow anglers”.

Though ecologists emphasise that this project is a trial, there is the unmistakeable sense that the beaver — hunted out of existence at the shores of Loch Ness in the 16th century — has returned to Scotland for good.

Duncan Halley, a Scottish ecologist who works for the Institute for Nature Research in Trondheim, has studied the relationship between beaver and salmon in Norway’s rivers for 15 years and is unequivocal: they co-exist happily.

On the peninsula close to Mr Halley’s adopted home town, a beaver introduction scheme began in 1981. Since then the animals have remained within the enclosed territory of their release area, migrating only to a second stream 100m away. He says that this evidence scotches the myth that beavers spread far and wide and forms an important comparison because Norway’s coastline and mountainous interior is strikingly similar to the Scottish western Highlands.

“Beavers have great difficulty in getting across watersheds — they are easily managed,” Mr Halley said. In other words, with their short, fat hairy legs, they are unlikely to spread to every salmon river in Scotland.

To ensure further that they do not escape, a research framework is in place that scientists from the Scottish Wildlife Trust, the Royal Zoological Society of Scotland and the Forestry Commission Scotland are certain will reassure sceptics. All the beavers are electronically tagged and should one seek to swim across the Sound of Jura, naturalists would soon scoop it up and take it home.

This tracking scheme could be extended for the benefit of tourists. The prospect has been raised of live video streaming from a Knapdale beaver dam, available online to viewers all over the world. A similar innovation at Loch Garten in Speyside, where an osprey nest is the focus of a video link, has been an outstanding success.

For now, Mr Dobson is revelling in his first sighting of a Scottish beaver. “I was there when they released the first three,” he says. “We were thrilled to see them. And you could tell that they were thrilled to be free. Not that they gave us a second look — they were into the water and off. I can’t wait to see them again.”

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