Pine Martens confirmed as key to reversing grey squirrel invasion

Dr Emma Sheehy, Professor Xavier Lambin and colleagues have just published some fabulous and quite ground breaking research that reveals that pine martens can help in the conservation of red squirrels.

It builds upon earlier field work from Ireland which was widely reported in 2014. However, unlike the Irish work, the latest research  from Scotland used DNA forensics and computer analyses in addition to field observation to work out how changing presence of martens affect grey squirrels and crucially – also red squirrels that were present in the woodlands.

The results show that pine martens reduce grey squirrels but not red squirrels. That where grey squirrels decline, red squirrels return and that this pattern occurs in the presence of a favourite pine marten food, the field vole. This vole species is absent from Ireland and thus there had been some uncertainty as to whether pine martens would impact greys in other parts of the British Isles in the way that had been seen in the Irish Midlands.

Pine martens eat a variety of foods and prey on a range of animals. The authors have been quite open that there may be some negative impacts on rare species as the predator returns. Further research is required. We should also be careful not to assume that pine martens will never adversely affect red squirrels, there may be some local landscapes where other factors could contribute to this e.g. in fragmented forest habitats where red squirrel populations are low and declining anyway. That said, Sheehy & Lambin have produced a powerful piece of research with an unambiguous headline that red squirrel nationally will benefit from pine marten and grey squirrel will decline.

‘The enemy of my enemy is my friend: native pine marten recovery reverses the decline of the red squirrel by suppressing grey squirrel populations’, is published in the journal Proceedings of The Royal Society – B.