Pine Marten Reintroduction: The Unlikely Saviour of the Red Squirrel?

On the 2nd of October, the Devon Wildlife Trust announced that 15 European pine martens have officially been reintroduced across Dartmoor National Park. This is the first step in their plan to reintroduce the species after their extinction in the South West about 100 years ago. Once a prominent native species of the UK, pine martens had, until recently, all but disappeared, except in the North of Scotland. However, with new legal protection and a growing number of reintroduction programs (such as in Wales and the Forest of Dean) the UK population has been making a slow recovery in recent years.

The pine marten, a relative of ferrets and otters, is an adorable but voracious predator — and a big item on their menu is squirrels. Surprisingly, their reintroduction is actually very good news for the iconic red squirrel. Red squirrel numbers in the UK have suffered greatly since the introduction of the invasive grey squirrel — thanks in part to the squirrel pox virus they carry, which is lethal to red squirrels. Add to this that grey squirrels are much better at competing for food and you can see why red squirrel populations are suffering. However, not all hope is lost. 

Scientists have found that in Scotland, where pine marten populations are recovering and expanding, their presence decreased grey squirrel population numbers without affecting red squirrels. In fact, red squirrel abundance was found to correlate with a greater chance of their encountering a pine marten. To investigate why this could be, researchers at Queen’s University, Belfast experimented on whether each species of squirrel would avoid a feeder with pine marten scent on it. They found that grey squirrels didn’t avoid the feeders but red squirrels did. This is most likely thanks to red squirrels and pine martens evolving together in the UK for millennia. This has given red squirrels the instinct to avoid pine martens — an instinct completely lacking in grey squirrels. 

However, the effect of pine martens on red squirrel populations is only significant in areas with an established pine marten population. Hence, recovery for the native red squirrel populations is still a long way off. Introductions like the one done by the Devon Wildlife Trust are steps in the right direction. Even though there currently isn’t a population of red squirrels in the South West, the establishment of pine martens across the country will set the stage for the return of red squirrels in the not-so-distant future. The classic phrase ‘the enemy of my enemy is my friend’ has been proven true once again.

Words by Caitlin Hughes

References:

1. Devon Wildlife Trust 2024. Wild once more: pine martens return to the South West of England after 100-year absence. Devonwildlifetrust.org. [Online]. [Accessed 18 November 2024]. Available from: https://www.devonwildlifetrust.org/news/wild-once-more-pine-martens-return-south-west-england-after-100-year-absence.
2. Sheehy, E., Sutherland, C., O’Reilly, C. and 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. Proceedings. Biological sciences. 285(1874), p.20172603.
3. Slade, A., White, A., Lurz, P.W.W., Shuttleworth, C., Tosh, D.G. and Twining, J.P. 2023. Indirect effects of pine marten recovery result in benefits to native prey through suppression of an invasive species and a shared pathogen. Ecological modelling. 476(110216), p.110216.Twining, J.P., Ian Montgomery, W., Price, L., Kunc, H.P. and Tosh, D.G. 2020. Native and invasive squirrels show different behavioural responses to scent of a shared native predator. Royal Society open science. 7(2), p.191841.