On a hillside so assiduously nibbled by sheep, only waysides have room for the surge of summer growth. The boreen is suddenly flanked with buttercups that, having crept through the winter, now rear up in thigh-high waves of gold. Strung among them are garlands of climbing vetch, glinting with blue and amethyst, and carmine puffs of clover.
In the tiger years of bungalow building, this billowing growth along the boreen used to hide, eventually, rubbish tossed casually out of van windows: cigarette packets, fizzy drink cans, sandwich boxes. I could have carried a bag on my morning walk and brought it all home to the bin, but mostly I just gave off to the birds.
What the leaves hide now are notches in the grassy rim of the ditches, worn by paws and furry bellies of hares, squeezing under the fence to cross the boreen, their paths more familiar than anyone would guess. I used to meet them often early in the spring, frozen in mid-pothole or spaced out, three or four in a meadow, a female daring all from the corner of her eye.
At least I could be sure they were the Irish hare, Lepus timidus hibernicus, a subspecies of the Arctic mountain hare, and not need to peer at their ears for hints of alien genes. Up in central Ulster a second look often finds larger hares, with the long, black-tipped ears of Lepus europaeus, the brown hare of Britain and the Continent. Even then one might not be sure. "I am convinced," wrote James Fairley, long an authority on Ireland's furry animals, "that the number of people who can be depended upon to distinguish brown and Irish hares in Ireland in the field is extremely few."
Fairley was not infallible. The brown hare, in some parts called the English hare or "thrush", was introduced by Irish landlords for coursing in the later 19th century (to Powerscourt, for example, in 1865). Their frantic sprinting, up to 70km/h, was supposedly more exciting than that of the Irish animal. Most of them did seem to die out over time without breeding with each other or the natives, but Fairley was premature in wondering, as he did in his 2001 book A Basket of Weasels, "whether there have, in fact, been any brown hares in Ireland at all for many years".
In the last island-wide survey of hares, of 2006, the Republic lacked any certain presence of L europaeus, though "a number of anecdotal reports suggest that a small population of brown hares may exist between Julianstown, Co Meath, and Balbriggan, Co Dublin, and may extend as far north as Co Louth". Irish hunters have since added sightings, and occasional bodies, from Leitrim and Donegal.
Things are very different in the North, where zoologists at Quercus, Queen's University Belfast's ecological research unit, are deeply concerned about the spread of the brown hare and its threat to Lepus hibernicus. Aiming spotlights from pickup trucks, they judged that more than half the hares of mid-Ulster were of the European species, numbering perhaps 2,000. Now they have shown a trebling of the animals' range since 2005, with an advance of almost a kilometre a year.
The modern population was introduced surprisingly recently, about 1970, so that this rapid expansion seems especially dramatic. A new study of their "invasion ecology" by QUB's Anthony Caravaggi, Prof Ian Montgomery and Dr Neil Reid found brown hares sharing perilous intimacy with Lepus hibernicus. Irish hares may prefer good quality, sugar-rich grass, and the Europeans eat more widely and make more use of hedgerows, but as both have been seen on the same grassland at the same time, and even boxing in typical mating behaviour, hybridisation joins competition in the threats to our native lagomorph.
Given the brown hare's inroads elsewhere on Europe's surviving mountain hare populations, a deliberate culling of L europaeus may be in prospect. Meanwhile, the Quercus team has been trying to find out more about the brown hare in the Republic. "I have strong suspicions," says Reid, "that the species is widespread." Brown hares, he insists, "look quite different to Irish hares."
They are also big enough to cull selectively, which is more than can be said of Ireland’s smallest invading mammals, the greater white-toothed shrew and the bank vole. Both are extinguishing the native pygmy shrew and field mouse across widening areas of the midlands. If the spread continues at its present rate, Montgomery has warned, our small native mammals will die out in at least 80 per cent of their available habitat.
The gathering pace and variety of such introductions to Ireland, on land, in rivers and lakes and coastal waters, are turning much of the island’s conservation into a rearguard battle.
Given all the unknowns of climate change, even optimists of restoration ecology will be pressed to hold their nerve.