By Ella Daly
After years of indecision surrounding how to tackle the UK’s grey squirrel problem, pine martens are an increasingly popular ecologically-based solution to manage the invasive species. Pine martens, whose British populations have long suffered, are currently being considered for re-introduction in more locations in the UK following recent releases in mid-Wales. The mustelid has been courted by the media and conservationists as a ‘perfect predator’ that preferentially hunts grey squirrels and leaves the beloved red squirrel alone.
This optimism stems from research in Scotland and Ireland which has shown that the presence of pine martens is associated with population declines for grey squirrels and rises for reds. Unfortunately, findings in ecology and conservation are rarely so simple or universal. Further research on pine martens in Scotland and other parts of Europe has shown that the red squirrel can be up to 53% of the pine marten’s diet. Further compounding the uncertainty, it’s also not fully known why grey squirrel populations decline in the presence of pine martens or if this phenomenon is geographically universal. The actual efficacy of releasing pine martens for grey squirrel control isn’t the only concern here.
As with any intentional species introduction or eradication, unintended consequences are a near certainty. Pine martens have been an issue to the point of lethal intervention because of their predation on ecologically important seabirds. They also interfere with poultry and game birds, which may cause economic losses and lead some farmers or gamekeepers to deal with pine martens by any means necessary. Their presence may also interfere with the conservation or re-introduction of other struggling species they prey upon. No re-introduction is guaranteed to have all desired effects, but the effects of this one are especially uncertain given the anthropogenic simplification of many ecosystems in the UK. As Bangor University’s Craig Shuttleworth discusses in a recent article published on The Conversation, pine martens will need to be adaptively managed as they inevitably spread throughout the UK and shouldn’t be depended on as the only hope for red squirrel conservation