How the pine marten became an unlikely hero in the fight against scourge of grey squirrels

SCOTLAND’S pine martens have been garnering some impressive column inches lately. The handsome creatures – cat-sized mustelids with a chestnut brown coat, creamy yellow or orange chest bib, round ears and a long bushy tail – are most often in the news being lambasted for preying on fellow protected species, the capercaillie.

Clearly, though, the pine marten has employed a top-notch PR company. The kind of juggernaut publicity machine that wayward footballers and fallen starlets utilise to boost their beleaguered image. In short, the pine marten has gone from villain to hero with a new mantle: saviour of the red squirrel.

It is well documented that the Scottish population of red squirrels has been decimated since the introduction of non-native grey squirrels in Victorian times, largely because greys carry the squirrelpox virus, which leaves them unharmed, but is fatal to the reds.

But grey squirrels are on the march.

For the first time, they have been found north of Dunkeld in Perthshire and they are also moving north from Angus into Aberdeenshire. In 2021, grey squirrels were recorded in Pitlochry and north of the River North Esk. The fear is that the central belt population of grey squirrels will join up with the established Aberdeenshire population to pose an even greater threat to red squirrels.

According to research, the presence of pine martens helps control grey squirrel numbers. In north Scotland, red squirrels have co-existed with pine martens since the early 1980s. Forestry and Land Scotland (FLS) announced last week that it is installing artificial pine marten dens in forests along the east coast of Scotland and the A9 corridor in a bid to halt the advance of grey squirrels.

The plan is to position around 30 dens along grey squirrel migration routes and use pine martens as what are being dubbed wildlife “bouncers”. Gareth Ventress, FLS environment forester, said: “We need to stop grey squirrels in their tracks.”

How do pine martens control grey squirrel numbers? The exact process 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, and this increases their chance of escape.

In Scotland, the presence of field voles could also act as a buffer between red squirrels and pine martens by providing a food source for the latter.