THE GREY squirrel, Ireland’s most notorious invasive species, is here to stay and wiping them out is not a viable option, a conference on biodiversity has been told.
The entire population of grey squirrels in Ireland originated from their presentation as a gift at a wedding in Co Longford in 1911.
Since then they have outbred the native red squirrel to the extent that they now outnumber them by a possible factor of 10 to one.
It is estimated that there are between 300,000 and 400,000 grey squirrels in Ireland, but only 40,000 red squirrels.
Grey squirrels have wiped out their red equivalent in a large swathe of the north midlands from Longford to Louth and in south Leinster.
The two species do not attack each other but instead compete for limited resources, and the larger, more adaptable grey squirrel has proven to be more adept at survival.
Grey squirrels can also do serious damage to timber and are regarded as a pest by foresters.
Dr Colin Lawton, a lecturer in mammal ecology at NUI Galway, said grey squirrels were too prevalent and the traditional “knee-jerk” response which is to wipe them out was not a feasible option unless millions of euro and thousands of hours were spent achieving it.
Instead, he told a two-day seminar on Irish biodiversity in the National Museum, it would be better to concentrate on saving the red squirrel.
The river Shannon had always proved to be a barrier to the grey squirrel, and the animal was not found in large parts of the west of Ireland. Scientists believe this may have to do with the habitats of the west of Ireland where there are fewer networks of smaller forests for them to breed in.
Dr Lawton said there had been a highly successful introduction of red squirrels into wildlife parks in Co Mayo and Co Galway in recent years and there was no threat to the species there from grey squirrels.
Dr Lawton also revealed that grey squirrels were facing a threat of their own and their population was declining in Laois and Offaly and in parts of Cavan and Monaghan.
He speculated that this may be down to the pine marten as a predator, or to changing farming practices.
The Heritage Council’s wildlife officer, Cliona O’Brien, said the new EU habitats and birds directive would contain a provision for a risk assessment of every potential invasive species brought into Ireland.
She cited the example of the South African pondweed, which is suspected to have come from a local ornamental garden and is now threatening a valuable trout fishery in upper Lough Corrib.
“It is an example of something very simple that is costing potentially millions to eradicate,” she said.
The manager of the national invasive species database, Colette O’Flynn, confirmed that restrictions would be placed on invasive species. She said the public should carefully dispose of all unwanted aquatic plants or pets.
