Terns, waders, divers and ducks were among wildlife “devastated” on the islands due to the invasive American species that escaped from fur farms and preyed on ground-nesting birds and fish.
Scottish Natural Heritage (SNH) led a “complex and challenging” 17-year scheme to remove the predators and protect the native wildlife.
The success of the Hebridean Mink Project (HMP) in catching nearly 2,200 of the animals, and its positive effect on native species, has also resulted in a boost in tourism.
SNH chairman Mike Cantlay said: “Mink, an invasive non-native species, prey on ground-nesting birds and fish. With major funding from the EU Life programme, at the project’s height a team of just 12 core Scottish Natural Heritage staff worked as teams of trappers to remove mink, and help bring back native birds to one of the remotest, wildest landscapes anywhere in Scotland.”
Hundreds of islands contribute to a coastline of approximately 2,500km – 15 per cent of Scotland’s total. More than 7,500 freshwater lochs – around 24 per cent of Scotland’s total – helped invasive mink grow to dense populations rarely reached in their native North America.
SNH area manager for Argyll and the Outer Hebrides David Maclennan said: “Invasive species are one of the greatest threats to the beauty and variety of our nature. But the Hebridean Mink Project shows that we can take on invasive species and win. It is fantastic to start welcoming back our native species.
“A range of factors are likely to be at play, but local people are telling us that a mink-free Outer Hebrides is having a hugely positive effect on wildlife and the economy.”
Murray Macleod, an operator with tourist boat provider SeaTrek, added: “Boat operators are already starting to see the results of the mink project.
“We have changed our tourist routes this year because. in places where there used to be no bird populations to view. Now we are seeing colonies of terns with chicks.
“It’s been an incredible boost to local tourism.”
The introduction of mink in Scotland has been directly connected to the fur farming industry established in the 1950s.
In the Outer Hebrides fur farms on the Isle of Lewis went out of business in the 1960s and feral populations quickly became established.
Small-scale control operations carried out by sporting estates and an attempt by SNH to prevent the mink population spreading south had limited effect.
By 1999 breeding populations of mink had become established on North Uist and Benbecula.
The HMP was set up in 2001 by SNH and partners as a five-year conservation initiative with the aim of removing mink from the islands of North Uist, Benbecula, South Uist and the Sound of Harris, with funding from EU Life.
The HMP used so-called “mink police”, small waterproof units attached to live catch cage traps which are activated when a mink is trapped inside.
To date, 2,198 mink have been caught, with only two non-breeding females and associated males caught in Lewis and Harris in the last 18 months.