Coypu discovered in Irish rivers: Sadly, this pest must be eradicated

LORD POWERSCOURT introduced Japanese Sika deer — just one stag and three hinds — to Ireland in 1860, for “ornamental purposes”. 

Half a century later, in 1911, grey squirrels from England — six pairs only — were released at Castle Forbes, in Longford, for “aesthetic reasons”. The deer have spread across the island and have interbred with red deer, diminishing the genetic integrity of our magnificent native deer. The grey squirrel has largely displaced the native red squirrel, which is just a memory in former strongholds. The negative impact of just 16 animals was unforeseen and, even at this remove, unimaginable.

Zebra mussels, a native of the Caspian and Black Seas, reached Ireland through ballast water dumped in the Shannon Estuary in the 1990s. The female mussel can produce up to one million eggs each year. Zebra mussels remove a great proportion of the plankton on which juvenile fish rely, so the mussels have an unwelcome impact on threatened fish stocks.

When plantsman, Conrad Loddiges, brought the rhododendron to England, in 1763, he could not have imagined it would, more than 200 years later, represent a threat to one of Ireland’s remaining native oak woods, in Killarney National Park. As the never-ending battle to remove the aggressive, dominant plant continues, those who undertake the back-breaking work can look down on the Lakes of Killarney — if their view is not impaired by another gorse fire — which are struggling to cope with the choking, oxygen-depleting impact of non-native pond weeds imported to beautify fish ponds.

The populations of waterfowl and smaller mammals, once abundant around those lakes, have been greatly reduced by the descendants of the American mink, introduced to Ireland by fur farmers in the 1950s. Some mink escaped, others were released by deluded activists, and their progeny continues to have an unprecedented impact on waterfowl and ground-nesting birds across the country.

Just as fur farmers brought the American mink to these shores, English fur farmers imported the coypu, a large rodent, from Argentina to East Anglia in 1929. Inevitably, there were escapes. The rodents are voracious herbivores. Like most animals in that category, their primary survival tactic is to out-breed predators. They mature after eight months and can breed five times in two years, with up to nine young in each litter. That rate suggests that the two or three coypu released into the Curraheen River, a tributary of the Lee, in Cork, two years ago, might already have scores of descendants — more than enough to, in time, cause the kind of damage seen on the Norfolk Broads. That destruction led to a multi-million pound, half-a-century-long campaign to eradicate the pest, because the problem was not nipped in the bud. Though some coypu, around 10, have been captured by the National Parks and Wildlife Service (NWPS), it is likely that more than enough remain at large to create real problems. Unfortunately, it is necessary to eradicate this animal, which has already been so misused by man.

The scale of that challenge should not be underestimated, but we must recognise it as an obligation to the future. There are precedents. New Zealand has, just in recent weeks, announced a far more ambitious programme. The Kiwis plan to eradicate rats, stoats, and opposums, another fur industry import, to protect vulnerable native birds. The scale of that ambition is impressive, but the prize, no matter how long it takes to realise, will be priceless. Norway has spent tens of millions removing gyrodactylus salaris — the salmon fluke — from its rivers, because it is fatal to Atlantic salmon. Efforts continue to remove hedgehogs from Scotland’s Western Isles to try to protect nesting seabirds.

Of course, it would be far better if these countermeasures were not needed, but human stupidity, and indifference to unintended consequences, make them obligatory. The impact of just one imported species, the American mink, on our wildlife shows what can happen if a problem is not tackled as soon as it is understood. Every humane method, including offering a bounty, should be used to remove coypu from this island. The NWPS should be encouraged to take the lead in achieving that aim. Those measures should be matched by strengthened legislation to make the importation of non-native species, animal or plant, utterly unattractive.


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