The River Shannon might be the only thing to tame the march of a recently discovered shrew threatening to make one of its closest relatives extinct.
Invasive miniature mammal the greater white-toothed shrew - three times the size of its rival, the pygmy shrew - is on course to be in every corner of the island by 2050 if it can cross the natural barrier.
Researchers from University College Dublin (UCD) warned that in the seven years since the furry creature was discovered, it has colonised 7,600 km2 in seven counties.
Dr Allan McDevitt, UCD School of Biology and Environmental Science and lead author of the study, said the speed it has progressed is a sign it may kill off the native Irish species.
"Species can live together after invasions occur, but in this case there may not be sufficient landscape complexity in Ireland to allow niche partitioning between these two species of shrew," he said.
The study, published in the journal PLOS ONE, found the greater white-toothed shrew now has a habitat stretching across Tipperary, Limerick, Cork, Waterford, Kilkenny, Offaly and Laois, and in parts of Cork city and Mullingar.
The fight for food and habitat has seen the pygmy shrew become extinct in parts of Tipperary after living here for thousands of years.
Its competitor was first discovered in Ireland in the pellets of barn owls and kestrels in 2007 and it has now been recorded spreading at a rate of more than five kilometres a year.
Dr Jon Yearsley, also of UCD and a co-author of the study, said the pygmy is facing total extinction unless its rival's march is halted.
"The displacement of the pygmy shrew will continue in Ireland as the greater white-toothed shrew carries on spreading rapidly, with the invader only being temporarily hindered by rivers and other barriers," he said.
The researchers have called for authorities north and south to address the issue of invasive species causing severe ecological impacts across the island.
Professor Ian Montgomery of Queen's University Belfast, who has studied the phenomenon, said ensuring bigger hedgerows and more deciduous woodland may enable the protection of species against invaders.
The pygmy shrew is one of the world's smallest mammals, weighing in at 3g-6g. They have iron deposits at the tip of their teeth which give them a red colour.
Their rival, the greater white-toothed shrew, weighs in at 8g-14g, and as their name suggests, they have distinctive teeth and have become a popular meal for birds of prey.