Grey squirrels introduced to Ireland in 1911 could wipe out the local reds unless urgent measures are taken, writes Dick Ahlstrom.
Efforts are under way to halt the spread of a small furry invader, the grey squirrel. A non-native species introduced here almost 100 years ago, it now threatens to kill off the native red squirrel and could wipe out whole plantations of broadleaf trees.
People all over Ireland are being asked to register sightings of both red and grey squirrels in a Government-funded initiative to curtail the spread of the grey. A website has been opened and information from the public will deliver the first national survey of these animals for a decade, says forestry and management consultant Dr Michael Carey.
Dr Carey is project manager forCombined Research and Investigation of Squirrels in Irish Silviculture (Crisis), a Forest Service-funded effort to protect the endangered red squirrel and to discover ways to control the spread of the greys.
Dr Carey is also overseeing the national squirrel survey with funding from Coford, the National Council for Forest Research and Development.
There are two main reasons why the grey is being targeted, he says. "They are threatening the existence and survival of the red squirrel. They can also cause damage to broadleaf trees."
The grey, Sciurus carolinensis, was introduced at Castleforbes, Co Longford, in 1911 and has spread like wildfire since. It has pushed out its habitat from Co Longford at a rate equivalent to three kilometres a year and is now present in at least 23 counties, says Carey.
As it advanced, so the native red, Sciurus vulgaris, retreated. The assumption is the grey is able to out-compete the red for habitat and so the red is simply pushed out of any woodlands the greys occupy. The greys are only a problem in Ireland, Britain and in northern Italy where they threaten tree nut production.
Part of the Crisis programme involves changing people's views of the grey, from cute furry acrobat that can break into any suburban bird feeder, to arch villain that is bullying the reds out of existence. The grey squirrel has picked up the nickname "tree rat" in the process.
"The public need to be educated," Carey suggests. "We are working with schools down in Co Meath. The kids love the red squirrel but once they are told what the grey squirrels can do in terms of destroying the reds and forestry, they are for controlling the greys."
It is also about efforts by the Government to increase the planting of more valuable broadleaf tree species to replace the familiar lower value conifers, he adds.
The greys are a particular threat given their inclination to gnaw off the bark all the way around the main trunk of a tree. This kills the tree, and broadleaf species including beech and sycamore are a particular attraction for the greys.
"If these fellows are still around in 10 to 15 years they have the potential to wipe these trees out," he says. "We are surprised at the extent that oak are being attacked."
The last national squirrel survey took place 10 years ago, so the data is very out of date, says Dr Carey. "What we are trying to do is confirm where they are," and the public can help with this initiative, he adds.
The more information that comes in from the public on the presence of either the reds or greys the better. The website established to receive public information includes a simple questionnaire asking about the squirrels but also about the presence of pine martens.
The thinking is the pine marten may be a natural predator of the squirrel, says Carey. There are suggestions that the numbers of grey squirrels in counties Longford, Cavan and Monaghan may be in decline. "We have information this population has gone down while the pine marten numbers have gone up."
Crisis has a broader mission, to protect the red squirrel while finding ways to reduce the grey squirrel population. Trapping and shooting in forestry plantations helps but there may be a more humane method based on "immunocontraception" (IMC), he says.
A UK study last year showed IMC has potential. It involves vaccinating the squirrels to raise antibodies against gonadotrophin, an essential hormone needed for egg and sperm production. If a method could be found to inoculate the squirrels they would remain unharmed but would become sterile.The EU is being lobbied to provide funding for more research into IMC, Carey says.
Register sightings squirrels at www.Irishsquirrelsurvey.com