from Sunday Herald, 16 February 2014
It’s not often that an animal that eats you turns out to be your saviour, but that’s exactly what scientists say pine martens are for red squirrels.
According to a new study, pine martens prefer to eat grey squirrels, the red’s great rival. So much so, that populations of the greys crash, while their red cousins thrive.
Grey squirrels are fatter and slower than the nimble reds, so make a more attractive and easier meal for the martens, which are known to be opportunistic predators.
Greys, an invasive species introduced from North America in the 19th century, have squeezed out the native reds by eating their food and giving them a fatal pox. As a result, reds are now at risk of extinction, with only 121,000 left in Scotland.
Wildlife groups have banded together to try and save the reds by trapping, killing and shooting thousands of the greys. But now they say they have a new friend in the pine marten.
Martens were persecuted to the verge of extinction, but under legal protection have been recovering in recent decades. They are now established in large parts of Scotland north of the central belt, with an adult population of around 3,000.
A major study published in the scientific journal, Biodiversity and Conservation, has concluded that the spread of pine martens could be a “critical factor” in the success or failure of grey squirrels. A survey over 9,000 square kilometres in central Ireland found that red squirrels had become common and greys had suffered a “population crash” in areas where pine martens were active.
The study’s authors, Emma Sheehy and Colin Lawton from the National University of Ireland, suggest that their findings apply to Scotland. This is the first evidence of a grey squirrel retreat, they say, and “could prove highly significant in terms of red squirrel conservation.”
The Scottish Wildlife Trust (SWT), one of the groups working to protect red squirrels, was delighted that pine martens were making a comeback. “Evidence from Ireland that pine marten predation on grey squirrels can significantly reduce their numbers and thereby help the expansion of red squirrels is increasingly compelling,” said the trust’s conservation director, Jonny Hughes.
“It appears the Scottish Wildlife Trust has a new natural ally in our efforts to protect the red squirrels from extinction in Scotland.”
Hughes pointed out that pine martens and red squirrels had evolved together, so the squirrels could have worked out how to avoid getting caught. “Reds are far more agile whereas the heavier and less agile greys can’t escape so easy,” he said.
Roy Dennis, a leading highland wildlife expert, agreed. He pointed out that red squirrels could escape martens by keeping to thin branches high in trees.
“It does make sense,” he told the Sunday Herald. “I think that if you are a marten chasing after a meal, it’s the slower and bigger animals that you would go for.”
The response of the government’s wildlife agency, Scottish Natural Heritage (SNH), was more cautious. “We’re aware of this interesting study and have also heard the suggestion that a similar effect could be taking place in some parts of Scotland,” said SNH’s mammal expert, Rob Raynor.
“The Irish evidence shows there may be a link, albeit a strong link, between pine marten expansion and grey squirrel abundance - but we’re not aware of any evidence that shows a clear cause and effect,” he added.
“Without this, we feel it would be premature to draw firm conclusions on the practical applications in Scotland and elsewhere. But we will keep a close eye on any future research.”
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