Grey squirrels may be given contraceptives to prevent them breeding and wiping out the last remaining 40,000 red squirrels in the 32 counties.
The immuno-contraception idea has been proposed in a draft All-Ireland Species Action Plan launched yesterday by the National Parks and Wildlife Service (NPWS).
The new conservation plan said the red squirrel is one of the most threatened mammals in the country and is declining at a rate of approximately 1 per cent per annum because of competition from grey squirrels.
A recent all-Ireland survey of the greys found that they are now in 16 of the 26 counties in the Republic and in all six Northern counties, and are expanding at the rate of 1.9km per annum.
In the North the greys have replaced reds in all the counties and the only remaining ones there are to be found in northwest Antrim and western Fermanagh.
However, while the greys have found their way into all but 10 counties in the Republic, they have yet to cross the Shannon.
The plan, a collaborative effort between the NPWS and the Environment and Heritage Service in Northern Ireland, has suggested a wide range of options including supporting research into using contraceptives to prevent the spread of greys. Other methods include shooting and trapping and poisoning them by using warfarin, which is banned in the North.
Future actions identified in the plan included translocation projects, where red squirrels are moved to areas in which they face less competition from greys. Other measures identified included promoting certain types of forestry which suit red squirrels better than greys, and the construction of rope bridges in red squirrel areas.
The plan proposed the establishment of local squirrel groups to survey and monitor red squirrel and setting up a red squirrel action plan steering group to direct research funding between the bodies in Ireland.
Minister for the Environment John Gormley highlighted the importance of all-Ireland co-operation on species-conservation matters. "The red squirrel is declining North and South for pretty much the same reasons and a co-ordinated approach to its conservation is necessary to ensure that this beautiful animal remains a viable part of our biodiversity."