Saving England's most threatened species from extinction

The Pine Marten and squirrel conundrum…

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 [1]. 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 [2].

 

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!

 

Lizzie Croose

Mustelid Conservation Officer

 

References

[1] 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.

[2] 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.

 

Keep up to date with our latest events here, or get the latest updates through our Twitter and Facebook pages - follow us: @naturebftb.

5 thoughts on “The Pine Marten and squirrel conundrum…

  1. We will be visiting the valley Nr Llanthony (S Wales) for a week in May. A local Farmer has told us there are Pine Martens there. Where is it best to site Trail camers?

  2. I would like to know what constitutes the 75% of the pine marten diet that is not squirrel and more importantly what do you know will be the impact on other species in those areas – you surely must know this before you can support release programmes and should be informing the public?

    1. Pine Martens have a very varied diet, which includes small mammals (voles and mice), fruit and berries, insects, carrion and small birds and eggs. As Pine Martens are a generalist predator, they don’t have an impact on any particular native prey species at a population-level.

  3. (1) Is there any objective evidence that pine martens will choose to eat grey squirrels and not reds? (2) Even if that were to happen initially whilst greys are most prevalent, surely the risk that PMs pose to reds, will only increase as the population of greys reduces? (3) Grey squirrels predate bird nests pushing songbirds into serious decline, recent evidence also shows that they predate the endangered dormice. What evidence is there that these creatures will not suffer the same or worse if pine martens are introduced?

    1. Hi Glyn,
      Thank you for your questions, below are the responses from our fab Pine Marten team:

      (1) Is there any objective evidence that pine martens will choose to eat grey squirrels and not reds?
      There is indeed. In a study in Ireland, grey squirrels comprised 15.6% of pine marten diet, whereas red squirrels only comprised ~2% of the diet. You can read more in the full paper here- https://www.researchgate.net/publication/257997086_A_non-invasive_approach_to_determining_pine_marten_abundance_and_predation

      (2) Even if that were to happen initially whilst greys are most prevalent, surely the risk that PMs pose to reds, will only increase as the population of greys reduces?
      There’s no evidence that this will happen. In the Scottish Highlands, where grey squirrels have always been absent, there are healthy populations of red squirrels, as pine martens only eat very small numbers of red squirrels (making up <2% of their total diet). Pine martens and red squirrels also co-exist across much of the rest of Europe and have done so for thousands of years.

      (3) Grey squirrels predate bird nests pushing songbirds into serious decline, recent evidence also shows that they predate the endangered dormice. What evidence is there that these creatures will not suffer the same or worse if pine martens are introduced?
      Pine martens can actually help to restore the balance in woodland ecosystems. By potentially reducing the number and density of grey squirrels, pine martens could help to reduce the predation pressure grey squirrels exert on songbirds and other potentially vulnerable prey species.

      BftB

Leave a Reply

Your email address will not be published. Required fields are marked *

Donate now