• Alex Taylor

The Tale of the Greys, the Reds, and the Pine Martens

A fascinating interplay is at work among these three species. A tale of two native species, one non-native, and a potentially happy ending that achieves two conservation objectives at once.

A grey squirrel in Scotland (taken from my bedroom window!)

Red squirrels once numbered around 3.5 million throughout the UK. Pine martens were once the country’s second most common carnivore. Both of these native species have suffered dramatic population declines. Pine martens have been persecuted for their fur and by gamekeepers protecting their poultry and game birds, and lost habitat through woodland clearance. Our actions have reduced their numbers so that only a few isolated populations exist in England and Wales, and around 1,000 individuals remain in Scotland.


Red squirrels have been impacted by a different species. The North American grey squirrel is a non-native, invasive species. Their introduction in the 1870s has had a devastating impact on them, with around 200,000 left in the country. Grey squirrels carry a deadly squirrel pox virus – well, it is not deadly to them, but it is to the reds, as they have evolved no defences against it. The greys also out-compete the reds for food. (It should of course be pointed out that this is our fault too, after all, it was us who introduced the greys in the first place.)


So, where there are high numbers of grey squirrels, there are low numbers of red squirrels. Now let’s introduce our third species. The pine marten has made a bit of a comeback recently, with their populations on the increase, particularly in Scotland. Legal protection gained in 1980 helped with this. Research initially in Ireland, and backed up more recently with research in Scotland, has shown that the resurgence of pine martens has been great news for red squirrels – they have come to their rescue!


The Scottish study, by University of Aberdeen (my alma mater) researchers, involved 200 feeders to attract squirrels and pine martens, with sticky tape attached to collect fur samples for DNA analysis. Their results showed that, where pine martens are common, red squirrels were much less likely to use the feeders. The red squirrels, being a native species, evolved with pine martens, and know them to be predators. The greys on the other hand did not avoid the feeders. It seems that, being non-natives, they are naïve to the threat. Having no similar predators in their own range, they are vulnerable to predation by pine martens.


The red squirrels’ bodies also helps them. They are smaller and light enough to scamper to the very ends of branches to evade the pine martens. But grey squirrels are heavier and slower, so can’t escape the pine martens in that way. And they are an easier target, as they spend more time foraging on the woodland floor. The result is that the more pine martens there are, the lower the number of grey squirrels and the higher the number of red squirrels.


This is great news for conservationists, as it not only means that numbers of a native species, the pine marten, are increasing (and will lead to higher numbers of reds too), it means that it is a more natural solution to the problem of the invasive grey squirrels. Lots of time and money is spent on controlling the greys, which could now be saved. Not having to kill grey squirrels is a huge bonus in my book.


It seems like encouraging the natural recovery of the pine marten is the best long term solution to controlling greys and helping red squirrels to increase. This won’t happen quickly though, the spread from the pine marten’s stronghold in Scotland down to England and Wales will take a long time, and by then we may have lost all of our red squirrels. So some intervention is required, and reintroductions are a pretty good way of speeding things up a bit.


This has already begun in Wales, with 50 pine martens being reintroduced from Scotland into mid-Wales who are currently thriving. And I’m happy to report that The Vincent Wildlife Trust just this month received funding from the Postcode Lottery to expand the project. They will now be able to educate local communities about the pine marten, as well as hire volunteers to monitor the animals and their offspring.


There are also plans to reintroduce some into the Forest of Dean in England. A community consultation (with 71% in favour, 26% undecided and just 3% against the plan), along with a scientific study that shows that the area has abundant suitable habitat, has already been submitted.


A plan to give grey squirrels oral contraceptives (hidden in Nutella) to prevent them breeding, with apparent backing from Prince Charles himself, is still underway. If I hear of any results, I’ll let you know…


Some good news in the conservation world for once, and it just goes to show that an ecosystem with its native predators present offers much greater resistance to invasive species.


#invasivespecies #greysquirrel #redsquirrel #pinemarten #reintroductions