THEY were the grey shadows of the ancient Caledonian forest, powerful predators who dominated their environment but then disappeared from Scotland centuries ago as their persecutors closed in.

Popular folklore has it that the last wolf was shot by Sir Ewen Cameron in 1680 in Killiecrankie, Perthshire, in 1680 - long after they had been driven from the lowlands by deforestation.

But in recent years a loud debate has erupted over plans to bring back these top carnivores to the Highlands, and let them run free to prey on the deer herds.

Now scientists say that rewilding the wolf could be more than a pipe dream and that a sustainable population is a possibility, but only if it is kept fenced in.

Researchers from the University of Sussex and the University of Kent, concluded that 80 wolves spread over an area of 1,000 square miles - roughly 24,000 acres - would be required to "reduce" deer herds which have been blamed for over-grazing and preventing the return of woodland.

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The Scottish Government estimates that there are around 375,000 red deer and 350,000 roe deer living in Scotland, and each year an annual cull has to be held to reduce their numbers.

Dr Christopher Sandom, lecturer in biology at the University of Sussex with a particular interest in rewilding, believes that wolves could be the answer to the problem, and that it is possible to ensure they do not cross paths with people using the land.

READ MORE: Should wolves be reintroduced to Scotland?

The issue of reintroducing wolves to Scotland has proven controversial in the past, with farmers and landowners saying that they would go after sheep and could even pose a danger to hikers.

But the University study found that the idea was viable if an area was created where their paths would seldom cross with people's
Dr Sandom said: “Reintroducing the wolf has long been suggested as part of the solution to large deer populations but there will always be concerns about how wolves interact with people in any rewilding project like this.

"This research shows that they could actually have an extremely beneficial impact in terms of making the rewilding process more effective.”

The research, which also involved scientists from Aarhus University and the University of Oxford (WildCRU), tackled the question of how many wolves would be needed in an area to bring down the number of red deer to allow ecological restoration.

It used computer models to simulate wolves impact on the landscape, and drew on previous studies of areas were the animals had been re-introduced or were already living.

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The team’s analyses found that a fence capable of retaining at least 75 per cent of dispersing wolves within the reserve would be optimum in allowing for rapid population growth that could lead to reduced deer numbers, without the risk of having so many predators that the red deer population would be threatened.

READ MORE: Conservation charity backs bringing back wild carnivores to Scotland's countryside.

However, it is unlikely any wolves leaving the area would get far if proper procedures were put in place.

In Finland, all wolves leaving an expanding wolf population into a reindeer management area were shot before being able to reproduce, while in the Białowieża National Park in Poland, surrounding human activity has created a barrier to wolf movement patterns.

Biologists found that the wolf population of Riding Mountain National Park in Canada had limited interbreeding with other wolf populations in nearby protected areas and no successful wolf dispersal from the park had been recorded over several multi-year tracking studies over 40 years.

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Dr Sandom said: “Fences are a common but unpopular tool in biodiversity conservation and would ideally be avoided. But where there are conflicting interests, compromise is needed.

"Fences particularly constrain animal dispersal but as Britain is an island, this is less of a problem. A fenced reserve in Scotland could be a fantastic opportunity to return large predators to Britain, ecologically restore a large part of the Scottish Highlands, and promote tourism.”

The researchers suggested that grey wolves, also known as timber wolves, would be the best candidates to be reintroduced in Scotland. 
A previous experiment in Yellowstone national park in the US found that bringing back wolves to cull deer herds led to forests coming back and more biodiversity. It has since been hailed a major success story.

READ MORE: Lynx should be brought back to roam Scotland

Dr Joseph Bull, lecturer in conservation science at the University of Kent, said: “Wolves are glorious animals, and were originally natives of these shores. The idea of them returning will be thrilling for many people.

“While our model offers insights into what is likely to happen, the crucial next step would be to test these ideas in practice – by creating a reserve, reintroducing wolves, and closely monitoring the system. 

"More generally and perhaps counterintuitively, barriers in some form might have a more important role to play in establishing modern wild areas than previously thought".

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Professor David Macdonald, Director of WildCRU and co-author of the study said “Scotland can lead Europe in thinking about how conservation, large fenced reserves and tourism can reframe rural economies.

"The role of fencing in the conservation of big predators is globally a hot topic. So far our results are just simulations made from the safety of a desk, but they offer a highly original way of thinking about restoring nature and natural processes”.