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
Well done Charlotte and Ella for questionning the re-introduction. This is a good article which goes part of the way to identifying flaws and gaping holes in the the highly damaging Scottish report of 2018. Although that report took almost two years to publish, it was based on a survey between Jan-May 2016. It compared the strike rate of pine martens in areas thick with grey squirrels compared to areas thinly populated with red squirrels. Reds being more territorial with each other, naturally form less dense populations than greys. Not surprisingly, over the incredibly short survey, the PM strike rate against greys was significantly higher than it was on red squirrels. Absolutely no surprise there to anyone who knows anything about squirrels. But where the Scottish Report goes completely off piste, is by extrapolating the strike rate trends continuing unchanged, indefinitely, concluding that it’s only a matter of time before the PM’s wipe out grey squirrels for good leaving the reds and rest of woodland in blissful harmony. Only Walt Disney could ensure those outcomes! The Scottish report fails to factor in what the PM’s will look for to eat, once grey numbers are reduced. It also overlooks the increasing PM population, after it becomes established, or how all of the other prey species, red squirrels, nesting birds, dormice etc will manage under the cosh of a top predator which not only roams the woodland floor but is also an expert tree climber.
Sadly too many ecologists across the country, have taken the Scottish Report at face value and use it as a platform to justify ploughing ahead with re-introduction of the pine marten, regardless of many knowledgeable objectors. Here in Gloucestershire, where of course we have no red squirrels, GWT ecologists are planning re-introduction of the PM imminently, promising that it will pave the way for re-introduction of red squirrels, one day. These are the same ecologists who pressed for re-introduction of wild boar into the Forest of Dean, promising that it would be controlled, closely monitored and any problems arising would be dealt with. Once they got their way, the boar were released. Subsequently, the boar population has increased many fold and the boar have spread into farms, small holdings, gardens and all number of areas, causing extensive property damage. Many residents in the area are at their wits end, meanwhile GWT have washed their hands of the mayhem and moved on to new projects including pine martens.