Northern Ireland's red squirrels have suffered hard times in recent years, after being ousted from their native homeland by their invasive grey counterparts.
But the beleaguered reds now appear to be mounting a fightback with help from an unlikely ally — the predatory pine marten.
Experts have noticed a changing trend in the midlands of Ireland that could signal a reversal of fortune for our squirrel population.
An upsurge in the number of pine martens could be ousting the alien grey squirrels from a number of counties. This marks a change which could in turn benefit native red squirrels that have been steadily losing ground to greys, giving them a chance to bounce back.
Scientists in NUI Galway investigating the mysterious decline of the American grey squirrel in the midlands believe a surge in the number of pine martens could be responsible.
The woodland predator was eradicated in many parts of Ireland by gamekeepers but is now spreading back into areas where it once thrived.
This could be good news for red squirrels, who for years have been outcompeted by the advancing greys. Grey squirrels are also carriers for a pox virus which is lethal to reds. Squirrel expert Dr Colin Lawton of NUI Galway said the results show that the grey squirrel population in the midland counties of Laois and Offaly has undergone a substantial decline.
“The red squirrel, despite being considered absent from this area for about 30 years, is once again widespread and common,” he said.
Reports of disappearing grey squirrels in the midlands coinciding with a pine marten comeback have been boosted by studies by Emma Sheehy, a PhD candidate in Lawton’s group in NUI Galway, who predicts greys will continue to decline.
“We expected them to have disappeared from a few woodlands. But it seems to be quite a large area,” Dr Lawton said.
Dr Lawton suggests pine martens prey more often on grey squirrels than reds, but this may not be the full story.
“Pine martens would find it harder to hunt and capture a red. The time they spend in the (forest) canopy and their light size means they go out on to finer branches,” he said.
“I would be leaning toward a more stress-induced factor, where (pine martens) are causing the greys to breed less or causing them not to settle in woodlands when they detect a pine marten population.”
Dr Neil Reid of Quercus, a centre at Queen’s which carries out wildlife research, said pine martens had undergone huge declines across Ireland but lingered in refuges in the west and in Crom estate in Co Fermanagh.
“They had been eradicated in many areas by gamekeepers who were protecting birds’ eggs and poultry. But gamekeeping has now gone into decline and more lately they are being found throughout Northern Ireland,” he said.
“Pine martens are known to prey on squirrels, and given the high density of greys in some areas it makes logical sense that they would prey on them.
“But I don’t know whether this is good news for red squirrels as I suspect they will eat red squirrels as easily as grey squirrels. Although red squirrels and pine martens have been co-evolving in Europe as predator and prey for a long time, there might have been a certain naivete among grey squirrels.”
And Dr Lawton cautioned against over-optimism.
“Their long-term prospects are not as good as we thought. But we are trying to find the cause and figure out whether this retraction is permanent or temporary. The one worry I have is that this is a temporary blip. A change to the habitat conditions in the areas could see the greys bounce back,” he said.
The grey squirrel
It is a native of the deciduous forests of North America. In 1911 a handful of grey squirrels were released at Castle Forbes, Co Longford, and have since colonised much of Ireland in less than 100 years. It has short front legs and a long bushy tail. It is similar to the red squirrel, but larger and sturdier.
The Pine marten
The pine marten is the size of an ordinary domestic cat with a long body, small head, pointed muzzle, round ears and eyes that are usually dark brown. A pine marten's fur is brown and during the summer the hue of the coat turns lighter. It has a cream/yellow ‘bib’ marking on its chest. Its feet are furred, with claws to enable it to climb. The pine marten is an omnivore. It’s a protected species.