GREY squirrels are likely Scotland’s most familiar non-native species.
Walk into almost any park in the central belt and you’re almost guaranteed to spot at least one of the invasive rodents.
Yet their introduction to the UK in the late 19th century has led to the significant decline of our only native squirrel species - the red squirrel.
Indeed, the red squirrel’s contemporary association with the Scottish Highlands is largely down to the fact that the species has been all but wiped out in England, Wales and much of the central belt.
Now, more than a century since grey squirrels were first released into the grounds of innumerable stately homes and public parks in the UK, conservation efforts may mean their days are numbered in some areas of Scotland - including a major city.
The problem with grey areas
“THERE are currently approximately 287,000 red squirrels in the UK, with about 80% of the population residing in Scotland,” said Katie Berry, communications and engagement officer at Saving Scotland’s Red Squirrels (SSRS).
“Grey squirrels pose the greatest threat to reds, outcompeting them for food and living space.
“Some also harbour the squirrelpox virus, which is lethal to red squirrels without affecting greys.
“These factors mean that when greys and reds and both present in an area, reds find it very difficult to breed successfully and survive, and without intervention can be totally replaced within 15 years. This rate significantly increases when squirrelpox is present.”
A map of squirrel sightings, both grey and red, on SSRS’s website gives a decent picture of their distribution in Scotland.
While red squirrels have held on in the Highlands and the Borders, the central belt appears like a grey barrier to the two populations ever meeting.
“In the Central Lowlands, our main aim is to defend the core red-only populations of the Highlands by carrying out conservation activities across the diagonal east-to-west Highland Boundary Fault Line, which at the moment is the uppermost point that grey squirrels have reached (bar Aberdeen),” added Berry.
“In time, we very much hope to move this line southwards, creating more areas for reds to thrive in and allowing for conservation activities in more southerly locations within areas such as Angus, Tayside and Stirlingshire.”
Why the grey squirrel’s days in Aberdeen might be numbered
VANI is a 14-year-old volunteer for SSRSs in Aberdeen.
Every week or so, her father accompanies her to 10 locations across Bieldside and Deeside to check, clean and collect data from squirrel feeder boxes.
Using special stickers attached to the underside of the feeder, Vani is able to see which animals may have paid a visit.
“We replace the bait for the squirrels and check the stickers for squirrel hair,” she told the Sunday National.
“We also have to do some slightly less glamorous tasks like cleaning out slugs.
“Then I record all of the data based upon whether we’ve seen any red squirrel hairs and the SSRS can use that for further analysis.”
The granite city is the northernmost stronghold of grey squirrels in the UK.
At least, it was.
Volunteer efforts in both monitoring and lethal control mean that ridding Aberdeen of grey squirrels now looks like a distinct possibility, with their numbers dropping from hundreds into the tens.
In 2024, SSRS has reported just 12 detections of grey squirrels in Aberdeen city centre.
“In Aberdeen and the surrounding area, we are aiming to achieve complete eradication of greys, enabling reds to thrive,” said Berry.
“This is possible because this population of greys is isolated geographically from the rest of the UK, being the result of a single accidental introduction in 1971.
“Although a challenging task we very much believe this is possible, having seen a significant reduction in grey population as a result of substantial staff and volunteer efforts in the region in recent years.”
The fact that it may be possible to entirely eradicate grey squirrels from a Scottish city is undoubtedly encouraging, particularly when other harms caused by the species are factored in.
Alastair Boston, a deer officer at the Forestry Commission, said 2024 had been “the worst year” for grey squirrel damage to trees in England.
Unlike their red brethren, grey squirrels have a habit of stripping bark from trees, which can weaken and even kill them.
And yet for decades, the environmental problems caused by grey squirrels have seemed largely insurmountable.
After all, how does one go about getting rid of more than two million rodents which are spread far and wide across the UK?
As it stands, volunteers like Vani may be the best bet.
The Great Scottish Squirrel Survey
THE lethal control of invasive species can sometimes spark controversy, particularly when the species being controlled garners some affection from the public by being long-standing or cute.
It’s why education about the damage caused by non-native critters is so integral.
“Research has found that grey squirrel control is particularly accepted by those with knowledge of the impact of greys on red squirrel populations and trees, and those residing in areas where red squirrels are present,” said Dr Michael Dunn, a senior social scientist with Forest Research.
“Only a small minority of the public disagree with the need for grey squirrel control, with a majority in favour of non-lethal approaches to management such as habitat alteration or fertility control.”
While lethal control will be necessary in some cases, Berry states that the easiest way to help the cause of red squirrels is simply by reporting sightings.
The Great Scottish Squirrel Survey, an annual week-long campaign which encourages Scots to report any sighting of both squirrel species on the SSRS website, is set to run from September 30 to October 6.
It presents the opportunity for researchers to build a national picture of squirrel distribution and concentrate their efforts accordingly.
“SSRS has been collecting public squirrel sightings since 2010 - last year, we received a massive 17,016 sightings with the help of the Great Scottish Squirrel Survey, giving us our second-highest recording year to date,” said Berry.
“Collating as many sightings as possible during the one-week survey provides us with a week-long snapshot of current species distributions, and the data gathered directly informs conservation action on the ground by helping staff, volunteers and partners understand how distributions are changing over time, where on the ground efforts should be prioritised, and alerting the project to situations where grey squirrels are posing an immediate threat to existing red squirrel populations.”
It’s safe to say that squirrel conservation doesn’t sit high on the list of political priorities for the Scottish Government, particularly at a time when the purse strings are being tightened.
Yet the case of Aberdeen shows just what can be achieved when action is concentrated in the right areas.
Last month, a red squirrel was filmed in Bishopbriggs, the furthest south within the central belt the species has been spotted in decades.
At present, there are no plans for grey squirrel eradication in the area. But even a single sighting helps make the case for future intervention.
“It might seem like such a small thing to do,” said Vani.
“But with so many people taking the time to report sightings, it makes a big impact.
“Just look at what we’ve managed to achieve in Aberdeen.”
