Pine martens drafted in to fight grey squirrel incursion
Artificial pine marten dens are being installed in forests along the east coast of Scotland and the A9 corridor to try to halt the advance of grey squirrels.
Forestry and Land Scotland (FLS) plans to install over 30 pine marten dens along the grey squirrel migration routes in a bid to protect red squirrels.
For the first time, grey squirrels are being found north of Dunkeld in Tayside and moving north from Angus into Aberdeenshire. In 2021 they were recorded in Pitlochry, Perthshire and north of the River North Esk.
The threat, according to FLS, is that the central belt population of grey squirrels will join up with the established Aberdeenshire population found around Aberdeen, endangering the red squirrel populations.
Gareth Ventress, environment forester at FLS, said:
“We need to stop grey squirrels in their tracks.
“Grey squirrels from the central belt can bring squirrelpox with them, which is what decimates reds alongside competition for food. Grey squirrels in Aberdeenshire don’t currently carry squirrelpox.
“We plan to install artificial pine marten boxes along the grey squirrel migration route, particularly in forests like Craigvinean in Perthshire or Inglismaldie just north of the River North Esk along the A90."
Research has shown that the presence of pine martens helps control grey squirrel numbers. In north Scotland, red squirrels have coexisted with pine martens since the early 1980s in large areas of native species and mixed plantations.
The exact process of how pine martens control grey numbers is not fully understood. One hypothesis is that red squirrels have evolved to be smaller and lighter, so they can use small, fine branches that heavier pine martens can’t access. This increases their chance of escape.
In Scotland, the presence of field voles could act as a buffer between red squirrels and pine martens - the voles, which aren’t present in Ireland and some other countries, are the main food source for pine martens.
FLS already has some artificial dens installed in Galloway Forest Park and some Aberdeen woods.
Installing artificial dens will support pine marten populations in the areas where grey squirrels are advancing.
“We’re not introducing pine martens to these areas, they’re already there. The artificial dens provide safe and secure natal sites and help improve the winter survival of kits, which are baby pine martens. That increases their local density.
“The dens are installed around four or five metres off the ground. They’re basically wooden boxes with roofs to keep the rain and wind out, and we put wood shavings inside them to make them cosy.
“We check the boxes in May and we can tell when pine martens have used them - they circle like dogs when they lie down, which disturbs the wood shavings. They also have a tendency to scat on the roof of the den boxes.
“Pine martens are slow breeders. Plantation forests, where the trees are relatively young, do not offer an abundance of the safe, warm and dry tree cavities that the martens prefer to den in. Therefore artificial dens can help improve breeding success locally."
Gareth says the pine marten boxes are one tool to help stop the advance of the greys, but other measures will still be necessary.
“We’ll still have to carry out grey squirrel control, but the presence of the artificial dens should support pine marten numbers and the survival of the reds.
“Pine martens are funny little things and it’s always exciting to see one. They have such pretty faces, but they also have quite sharp teeth. They are also legally protected from disturbance, so it’s best to keep a distance unless you are trained in handling them and have protective gloves on.”
The FLS team has begun installing the artificial dens in several forest locations between Dunkeld and Pitlochry along the A9 and from Brechin up to and around Aberdeen along the east coast. The boxes will be checked in May to find out whether pine martens have used them.
Notes to editors
- Forestry and Land Scotland (FLS) manages forests and land owned by Scottish Ministers in a way that supports and enables economically sustainable forestry; conserves and enhances the environment; delivers benefits for people and nature; and supports Scottish Ministers in their stewardship of Scotland's national forests and land.