Can Pine Martens ‘control’ Grey Squirrels?
There has been a lot of interest and media coverage recently on the fascinating relationship between Pine Martens, the non-native Grey Squirrel, and the native Red Squirrel; and the impact that Pine Martens are having on Grey Squirrels.
We explore this story a little more in relation to our Back from the Brink Pine Marten project.
What we know so far.
Grey squirrels are a non-native, invasive species in Britain. They have had a detrimental impact on Red Squirrel populations, causing them to become extinct across much of Britain, and cost the timber industry millions of pounds a year by bark stripping of trees.
A study in Ireland found that where Pine Martens are present at high densities, Grey Squirrels are absent . A strong negative correlation was found between these two species presence, whereas a positive correlation was found between Pine Martens and Red Squirrels. Furthermore, Grey Squirrels made up ~15% of Pine Marten diet, in woodlands where both species occur, whereas Red Squirrels featured in the Pine Marten’s diet only occasionally, making up ~2% of the diet.
This research was built on by a recent study in Scotland .
Will Pine Martens control Grey Squirrels in northern England?
The short answer is, we don’t know and only time will tell.
It appears that for Pine Martens to have an impact on Grey Squirrels, martens have to have been present for several years and at relatively high densities. Therefore, it’s likely it will be several years before any impact on Grey Squirrels is seen in northern England and other parts of Britain where Pine Martens are slowly recovering or present in small numbers.
The recovery of Pine Martens in England will be dependent on several factors, including suitable woodland habitat and connectivity between woodlands and low mortality. Ultimately, if the return of this mammal to England can have a knock-on effect on Grey Squirrels, that’s all the more reason to support the conservation of this species.
How can I help/encourage Pine Martens?
You can get involved in the Back from the Brink Pine Marten project by volunteering with us.
If you live in an area in which Pine Martens might be nearby (contact us to find out), you can put out a camera trap with some bait to see if a marten visits (Pine Martens love peanut butter, jam, raisins and eggs!). You could also consider installing a den box, which acts as a purpose-built/artificial den site for them to rest and sleep in.
We hope to hear from you!
Mustelid Conservation Officer
 Sheehy, E. & Lawton, C. 2014. Population crash in an invasive species following the recovery of a native predator: The case of the American grey squirrel and the European pine marten in Ireland. Biodiversity and Conservation. 23(3), 753-774.
 Sheehy, E., Sutherland, C., O’Reilly, C. & Lambin, X. 2018. The enemy of my enemy is my friend: native pine marten recovery reverses the decline of the red squirrel by suppressing grey squirrel populations. Proc. R. Soc. B. 285: 20172603.