Grey squirrel numbers are growing in North Angus and there could be a “population explosion’’ if they were to breed with greys in Aberdeenshire.
Tufty-eared red squirrels are native to Scotland, whereas grey squirrels, indigenous to North America, were first released in the UK in the 1800s.
The larger non-native breed has been spotted in Hillside, Montrose and the grounds of the House of Dun.
Saving Scotland’s Red Squirrels is enlisting the public’s help in reporting sightings of grey squirrels in the area to stop them breeding with greys in Aberdeenshire where they were introduced in the 1970s.
The main threat to red squirrels is the spread of the invasive grey breed.
Grey squirrels compete more successfully than reds for food and habitat, they are larger and more robust, and can digest seeds with high tannin content, such as acorns, more efficiently.
Greys also carry the squirrelpox virus, which causes them no harm, but is fatal to red squirrels.
Ken Neil, Tayside project officer for Saving Scotland’s Red Squirrels, said: “Grey squirrels have been slowly moving up the county for several decades but only reached the very north of Angus in the last 20-odd years. Until recently they were only occasional visitors north of the river South Esk but we have been getting increasing reports of them at the House of Dun and further east at Hillside, along with one or two reports from Montrose.
“The area between the North and South Esk represents the furthest north that the squirrels that were released in Dunfermline in 1920 have migrated.
“The importance of dealing with this is that we are trying to defend the Highland Control Line to stop any further movement into Aberdeenshire in years to come.
“If they were to breed with invaders from the south there would be a population explosion due to the introduction of new blood into the gene pool.”
Report sightings at http://scottishsquirrels.org.uk/squirrel-sightings.