FOREST FRIENDS IN HIGH PLACES
CAN PINE MARTENS REVERSE THE DECLINE OF RED SQUIRRELS? A STUDY IN SCOTLAND REVEALS ITS RESULTS.
Encouraging the spread of pine martens into their former range across the UK might prove a godsend for another beloved native mammal. New research shows that red squirrels are able to recolonise in their wake.
The story of the retreat of red squirrels in the face of the advance of North American greys introduced to Britain little more than a century ago is a familiar one. But in 2014, biologists working in Ireland documented a grey squirrel population crash – and a red squirrel recovery – in a region recently recolonised by pine martens.
The suspicion that martens suppress grey squirrel populations has now been confirmed by a more thorough study of the three species’ interactions in the Scottish Highlands.
“The results were clear – the higher the exposure to martens, the less likely grey squirrels were to be present,” says Emma Sheehy of the University of Aberdeen, who was involved in both the Irish and Scottish work. “Red squirrels actually outcompete grey squirrels where pine marten activity is medium to high.”
The team found evidence that reds avoid feeding stations frequented by martens, but that greys aren’t deterred, which could make them more vulnerable to attack. Such naivety could be the result of the introduced greys’ lack of familiarity or shared evolutionary history with European martens, which wouldn’t have been a problem until martens started recolonising former haunts.
Encouraging the expansion of pine martens could reduce the need to cull greys. “Where pine martens are established and living in healthy numbers, they eliminate the need for grey squirrel control locally,” Sheehy explains.
Martens remain rare in, or absent from, most of England and Wales. “What portion of the UK may eventually be recolonised by pine martens is yet unknown,” says Sheehy. “And successful recolonisation – to reach healthy enough numbers to suppress grey squirrels – will take many decades.”