• Mink, which have been blamed for a drop in seabird populations, have made a surprise return to North Uist. Picture: Complimentary
Six intrepid trappers are in the midst of trying to track down and kill the creatures, which are targeting the Western Isles' celebrated seabirds, causing an initial decline in species such as corncrakes and Arctic terns.
The mammals, a legacy of when Lewis housed two mink farms in the 1960s, were thought to have been eradicated during a programme that began a decade ago, but have survived with dire consequences for the bird population.
The American mink were initially bred for their fur, but they escaped and then bred in the wild, first on Lewis, then on Harris, and they were found to have reached North Uist in the early 1990s.
Since 2001, a project has been under way to trap and kill the mink on the islands, but David MacLennan, SNH area manager for the Western Isles, said they could prove difficult to trap.
The project is in its final year, but a small number of mink have returned to part of North Uist. So far, 1,232 mink have been killed across the islands, but the recent project in North Uist has captured ten, including two yesterday.
The six-man team visited the island in November and returned there a couple of weeks ago.
Bob Chaffer, who is in charge of trapping on Uist, insisted they were succeeding. "We had been told to check an area we thought was clear and so discovered them, but we are making a difference," he said.
The creatures are trapped using small steel cages – 2ft long and 6in wide – baited with an extract of mink scent imported from North America.
As soon as a creature steps on a pressure pad, the cage is closed. As it can trap any small animal, the traps are checked every 24 hours to free anything that is not a mink. The captured mink, however, is shot dead with an airgun.
"It is difficult to tell how many mink are still on the islands," said Mr MacLennan. "We currently have 8,000 traps on the ground in Lewis and Harris, but only a certain number of them are open at any one time so we can check them each day.
"Once the captured mink is killed, we conduct an autopsy on each one to learn what we can. With females, we can discover their breeding rates, which helps us try to calculate how many there still might be."
Leaving them at large could have drastic consequences for seabirds, such as the Arctic tern, common tern, black-throated diver and corncrakes, which had declined, but SNH said some had since recovered.
RSPB Scotland supports the eradication programme. Its Western Isles conservation officer, Martin Scott, said: "The rediscovery of mink on the Uists demonstrates the importance of seeing such projects through to completion.
"We believe that, with the right support and management, this can be achieved in the Western Isles, benefiting wildlife, creating jobs and supporting poultry, angling and fish-farm businesses."