How Scots are dealing with red alert

I VISITED the Cairngorms for Red Squirrel Week, courtesy of Visit Scotland.

On guided forest walks, visitors were shown the little rodent, which is loved in Scotland but almost gone from England and Wales. The famous Caledonian pine forests are the last British stronghold; they seem to support a thriving population. Squirrels were easy to spot around Aviemore, where I was based, but there’s concern for their future.

Edward Longshanks, king of England in the 13th Century, was known as the ‘Hammer of Scots’. Now another ‘hammer’ is on the march. In 1876, grey squirrels from America were introduced to Henbury Park in Cheshire and releases took place elsewhere in subsequent decades. The newcomers thrived in British woodlands and parks. The resourceful invaders, willing to cross open ground between stands of trees, have conquered most of our neighbouring island.

We have a similar problem in Ireland; next year sees the centenary of the arrival of greys here. In 1911, six squirrels, a gift to the bride, were released during a wedding breakfast on the lawn of a great house at Castleforbes, Co Longford. The march of the foreigners has been relentless, although the Shannon has obstructed their westward expansion.

In 1978, a grey was seen at Áras an Uachtaráin, the first such sighting in Dublin’s Phoenix Park. The last red was recorded there nine years later. Being twice as heavy its cousin, the grey, forages lower in trees and is also at home on the ground. American forests have more broadleaved species than European ones and the grey’s digestive system evolved to exploit the rich seed crops. Trees produce tannins to upset squirrel tummies but the resourceful greys have stayed ahead in the gastric arms race. Red squirrels eat acorns and nuts in small quantities but they can’t live exclusively on them. They need their choice food; conifer seeds. The two species, therefore, occupy somewhat different ecological niches and so, on the face of it, should be able to coexist amicably. But they don’t and the reasons why have been something of a mystery.

Greys don’t attack their smaller cousins, nor do they interfere with nests or young. Given the difference in food preferences, it’s hard to believe that greys eat the reds out of house and home, so what causes the demise?

A mysterious illness was recorded among reds in the south of Scotland soon after the arrival of greys there. A ‘squirrel pox virus’ was isolated; it was present in about 60% of animals tested. Greys are immune to its effects but reds are not. A red coming into contact with a carrier grey develops symptoms similar to those of myxomatosis in rabbits. But, as with any epidemic, the population should have individuals which are unaffected by the virus. This minority should survive and ensure that a degree of immunity eventually develops. However, it hasn’t.

Dr Mairi Cole, a squirrel expert with Scottish Natural Heritage, believes the demise of the reds is due to a combination of factors. She told RTÉ’s Mooney Show habitat composition and the fragmentation of woodlands play a part. However, the main threat comes from greys. They can exploit a wider range of plant species and, by doing so, tend to become more numerous. If there are some broadleaf trees available, to provide them with a secure food base, greys will thrive and invade local pine forests to devour conifer seeds. As food becomes scarcer in this war of attrition, reds have progressively smaller litters and fewer of their kittens survive.

So what is to be done? By establishing a squirrel version of Hadrian’s Wall in the south of Scotland and targeting any greys found north of it, the march of the invaders, she hopes, can be halted. Squirrel Week attempted to alert the public to the problem.

* www.visitscotland.com