Scotland's native red squirrels are one of our most threatened mammal species. Once the UK’s most common squirrel now there are only around 140,000 left in the UK - with more than 75 per cent of them estimated to be in Scotland.
There's one outstanding reason for that: the introduction in the late 19th century of the grey squirrel from North America. Perhaps no one could have known back then how far the grey critters would spread.
But nowadays, for anyone like me living in Glasgow or in the Central Belt, these creatures are the only ones we know, running around our parks and green spaces. There are some 2.7million greys in the UK, including at least 200,000 in Scotland.
Notoriously, however, they have been very bad news for their red Scots cousins - overwhelming them by sheer force of numbers, stealing their food and nesting spots and spreading disease.
That’s why I headed up to Loch of the Lowes, near Dunkeld in rural Perthshire, to one of Scotland’s safe havens for red squirrels.
It’s also, quite literally, the frontline in the fight to protect them from the grey invaders.
Loch of the Lowes sits right on a great red line across the map of Scotland, from Montrose to Loch Lomond, drawn up by conservationists and policymakers. And it's a line grey squirrels are not meant to pass.
Hazel Forrest, who is Species Advocacy Manager for the Scottish Wildlife Trust (SWT), talks about the situation a little like it’s a war.
She told the Record: “Dunkeld and Loch of the Lowes are in one of our main priority areas for red squirrel conservation because it forms part of the frontier between the grey squirrel-only zone in the Central Belt and the red squirrel-only zone of the Highlands.
“So we're really conscious that we need to keep that line in place and not allow grey squirrels to leak any further north than they have already.
“But unfortunately, grey squirrels have been spotted in Dunkeld and in Pitlochry. There’s a potential migration route here where they could leak into the Highlands. It’s really important that we keep on top of grey squirrel control in this area.”
This week officially marks Invasive Non-Native Species Week - aimed at raising awareness of the huge threat nature faces from alien species imported by humans into local ecosystems.
Plants like Rhododendron and Japanese knotweed are well-known culprits, infamous for strangling flora and fauna in our native woods and gardens.
Perhaps not as many people would lump cute little grey squirrels in with these offenders.
Talk of culling these animals might leave some feeling a little squeamish, particularly in the Central Belt.
Unfortunately, as things stand, there is no realistic alternative to population control measures for greys in the areas where they most threaten reds.
That means finding humane ways of catching them - such as with live cage traps - and disposing of them with minimal distress. Gamekeepers can also shoot grey squirrels as pests.
And the successful reintroduction of pine martens to parts of Scotland is having an effect - they are natural predators to grey squirrels while generally preying less on reds.
But the reality is, if left unhindered, greys would likely wipe out our native reds within 15 years. Worse still, they carry a disease - squirrelpox - which doesn’t impact on them but is fatal for red squirrels, killing them in a matter of days.
That’s why, says Hazel, there is no choice but to continue to intervene in controlling the greys population.
Leading all of this work is the Saving Scotland’s Red Squirrels (SSRS) campaign, launched in 2009, a coalition led by the SWT and other partners, which has transformed efforts to control greys and save reds into a national mission.
She said: “Saving Scotland’s Red Squirrels has been running for 14 years now and has developed a tried-and-tested blueprint for landscape-wide invasive species control.
“The methods, the system and everything are there, they’re in place and we know that it works. We know that targeted grey squirrel control can halt regional decline of red squirrels and actually help them expand into new areas.”
The SSRS network spans the country with a team of grey squirrel control officers, supported by a network of volunteer monitors and trappers and grant-funded landowners.
As well as bidding to halt the advance of greys from the Central Belt further north, in the south of Scotland they’re combatting an influx of the critters from the north of England into reds territory.
And the problem isn’t just that greys pose an existential threat to reds - if numbers get too great, they can destroy woodland as well by stripping the bark off trees.
Hazel said: “The damage they cause can lead to disease and stunt the growth of trees.
“In England, where grey squirrel densities are much higher and broad-leaved trees are much more common, this bark-stripping behaviour costs the forestry sector there £31million annually.”
Red squirrels are shy. They’re very different from their curious, cocky grey counterparts I know so well from walks about Glasgow.
Until yesterday, I had never seen one in real life. At the loch’s nature reserve, we had to wait a while for a sighting of the elusive creature.
But eventually, one showed up, taking advantage of the feeders installed on trees - he or she was a coppery colour with little pointed ears.
Nature-watchers at the peaceful reserve will happily wait hours to see the adorable creatures, whether they’re flying through the trees or scampering through the woods.
Hazel’s advice to Scots if they spot a grey squirrel in this neck of the woods is simple.
“The best thing we can do is visit the Save Scotland's Red Squirrels website and submit a sighting via their sightings page," she said.
“The team uses sightings to inform them when grey squirrels pop up in new areas with reds. They might need to respond quickly to new squirrel occurrences.”
Deborah Long, chief officer at eco coalition Scottish Environment LINK, said: “Invasive Non-Native Species are already one of the key risks to Scottish nature, and they will pose an increasing risk as habitats become fragmented and climate change impacts ecosystems.
"The impact of grey squirrels on reds, or the enormous damage caused by Rhododendron ponticum to our native woodlands, is profound – and underlines how important it is to act.
“It is vital that we act early to tackle potential new invasive species and prioritise prevention and rapid response.
“Once a species becomes established it can be very difficult to remove them – and piecemeal removal can be entirely ineffective, with invasive species simply returning unless removed at an ecological scale.
“If we are serious about tackling the nature crisis, we need serious and strategic action on invasive non-native species.”
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