PINE MARTEN have emerged as conservation heroes, with a new study suggesting that the species is particularly good at thinning out invasive grey squirrels.

New research by Queen’s University Belfast has highlighted the role that the native predator, now recovering from a slump in its own population, is playing in rebalancing the UK ecosystem – and in so doing, has re-opened the discussion about what positive effects other predatory species might have.

Introduced from the Americas, the invasive grey squirrel has replaced the native red squirrel across much of its former range in the UK and Ireland, but as pine marten numbers rise, they are hitting the grey populations while positively affecting their native cousins.

The Queens researchers exposed both red and grey squirrels to pine marten scent at twenty feeding sites across Northern Ireland, and recorded how the different species responded to their shared predator. What they found was that native red squirrels showed clear behavioural responses when they caught a whiff of pine marten, visiting those feeders less often and increasing their vigilance, whilst the grey squirrels did not change their behaviour.

This is likely as a result of red squirrels having shared the British Isles with pine marten over a long period of time, while grey squirrels, being relative newcomers, are less sensitive to the threat that the marten poses to them, making them much more vulnerable to predation. This explains why grey squirrel populations are declining wherever the pine marten recovers.

Lead author and PhD student at Queen's Uni's School of Biological Sciences, Joshua Twining, said: “Grey squirrels, introduced to the UK from North America, have only shared the landscape for a mere blink of the eye on an evolutionary timescale, and thus currently appear to be naïve to the threat of predation by this native predator.

“In a modern world that is daunted by environmental crisis and ecological collapse, it is more important than ever to recognise the potential of nature, its resilience and ability to provide solutions to our mistakes. This is especially pertinent in the UK and Ireland where we currently live in a highly managed, unnaturally predator free world.

"Historic human activities have led to the loss of predators at the top of the food chain including the wolf and the lynx. The UK government currently spends £1.7 billion a year to control invasive species in a bid to balance the ecosystem. More research is required, but our initial findings add to the evidence suggesting that an alternative measure could involve restoring our native predators to naturally rebalance the ecosystem.”

Co-author and research coordinator at National Museums NI, Dr David Tosh, said: “The benefits of native predator populations are slowly being realised in Britain and Ireland. While this study began with a focus on identifying what was behind the observed relationship between squirrels and pine martens, it has shown us the potential benefits predators may have in rebalancing the ecosystem. We believe this discovery will demonstrate to the wider public the benefits that native predators can bring to our countryside.”