IT seemed a simple plan and was designed to eradicate an alien predator from an internationally important archipelago for wildlife.

But police are now involved in a £6 million scheme to eradicate stoats from Orkney after a sustained attack by vandals and thieves following other species of animals, including cats, being killed by traps.

The traps that are designed to wipe out the stoat population have inadvertently caught and killed cats as well as hundreds of other animals.

Pet owners are now concerned after the dead cats were found and another was  found injured by the traps.

Other wildlife casualties included 242 rabbits, 48 mice, 18 hedgehogs, 10 voles and nine frogs and toads since the scheme launch in 2017, said cull coordinators the Orkney Native Wildlife Project.

Scottish SPCA chief superintendent Mike Flynn said at the time it hoped that planned alterations to the size of the entrance would prevent any further incidents happening.

But Police Scotland has now confirmed that it is investigating a number of incidents involving damage to and the theft of traps.

A spokesman said there had been a number of incidents throughout last year and they are still happening.

The traps were placed at numerous locations throughout Orkney including at Stromness, South Ronaldsay, Deerness and Evie throughout 2020.

In total around 6,500 traps have been laid for the stoat eradication project.

It is the world’s largest clearance programme of the animal and so far more than 780 have been killed.

More than 700 landowners have given permission for the internationally important conservation project.

The scheme is run by NatureScot and the RSPB and intends to wipe out all the stoats on Orkney to conserve native wildlife.

The five-year ONWP has caused controversy, not least within the RSPB’s membership, with a section opposed to the killing of animals.

But it has the overwhelming support of islanders.

Stoats are native to the UK mainland, but not to Orkney – where they were first reported in 2010 and now pose a very serious threat to the local wildlife.

The stoat project mirrors similar eradication schemes of non-native species from other Scottish islands, including mink, rats, rabbits, and hedgehogs – which together have cost more than £8m.

Orkney is home to internationally important populations of wildlife.

Despite the combined land area of Orkney’s 70 islands accounting for less than one per cent of the UK, the islands are home to more than one-fifth of the UK’s breeding hen harriers, important numbers of seabirds and are one of the few places in the UK in which waders such as curlews are still a common breeding species.

Stoats are very accomplished predators and feed on small birds, eggs and small mammals.

The presence of stoats in Orkney threatens the Orkney vole, which is found nowhere else in the world, and many birds including hen harriers, short-eared owls, red-throated divers, waders and seabirds, many of which support Orkney’s thriving wildlife tourism industry.

Despite their small size, stoats are also capable of swimming significant distances over open water.

How they arrived on Orkney is unclear. Some people believe they hid among imported farmers’ hay, others that they were deliberately introduced. Their numbers have since soared.

A spokesman for ONWP said it was “inappropriate to comment on an ongoing police investigation”.

But he added: “While we cannot promise that we will never catch anything that isn’t a stoat, we can promise that we will do everything we can to minimise the chances.

“We can also promise that we will continue to learn from each incident. Orkney has quite a lot of feral cats and we’ve been unable to confirm if any of the cats killed were pets despite searching lost pet pages on social media. So, we’ve purchased a microchip scanner and will knock on doors or contact folk living nearby to help us discover if there is a missing cat.

“These measures will be used as part of a strict protocol to ensure the project is being open and transparent.

“Not eradicating stoats will cause irreparable change to Orkney’s natural environment and have devastating impacts on Orkney’s native wildlife with internationally and nationally important populations of ground-nesting birds. Given the importance of wildlife for our individual wellbeing, our culture and our economy, the cost of not eradicating stoats would be too great.”