AAt first, the stoat looks like a faint speck from a distance. But as it gets closer, its sleek body is recognized by a heat-detecting camera, and with it an alert is sent to Orkney stoat hunters.
With the help of an artificial intelligence program trained to detect the shape and sinuous movement of the stoat, trapping teams are sent out with the express goal of finding and killing it. It is the most advanced technology used in one of the world’s largest mammal eradication projects, which aims to discover the few remaining in Orkney.
Conservationists on the islands, located in the far north of Scotland, have already used a pack of 9,000 lethal traps and eight specially trained tracking and detection dogs to dispatch nearly 8,000 stoats over the past six years. At least 30 of these digital cameras will soon be deployed across the marshes and coasts of the Orkney mainland, building a network linking camera strikes to computers and mobile apps used by trapping teams.
The stoat represents an existential threat to the native ground-nesting birds for which Orkney is famous – it is home to 11% of all the UK’s breeding seabirds and around 25% of the hens, as well as the most valuable native rodent, the Orkney vole.
The Royal Society for the Protection of Birds in Scotland, which runs the Orkney Native Wildlife Project, believes stoats arrived from the Scottish mainland in around 2011. Since then, their numbers have exploded, colonizing the Orkney mainland, the nearby Burray and South Ronaldsay Islands and the Deerness Peninsula – stoats can swim many kilometers – with devastating effects.
Sarah Sankey, area operations manager at RSPB Scotland, says the biggest advantage stoats have is the lack of predators in Orkney. “They have nothing to control: we have no foxes, and very few hawks,” she says, holding up a map of Orkney with thousands of red dots marking the trap network. “We have seen this all over the world. This population of stoats could have kept moving until they cleared everything away.”
“We saw it before we started eliminating them. There were stoats running between people’s legs, there were stoats in the kitchen cabinets, there were stoats in people’s attics.”
In less than a decade, it had spread over 58,000 hectares (143,260 acres). A feasibility study said that if it spread to all of the Orkney Islands, it would be impossible to control financially and logistically. So the project, which will run for at least 10 years, was given a budget of £16 million and 46 staff.
The stoat burrows into vole burrows, forages for eggs and chicks in thousands of curlew, lapwing and hen nests, and also hunts along Orkney’s extensive coastline for seafood, feeding on starfish and sea urchins.
“Here we have a complete disaster where we have large amounts of food year-round,” Sankey says. “There’s nothing to control stoats and a lot of native wildlife to lose, and the tourism economy is kind of dependent on it.
“Why did we start all this? The Orkney Islands make up less than 1% of the land area of the UK, but we have about a quarter of all the Arctic terns and hens, and about a third of the Arctic croakers, and we’re the only place with the Orkney vole. So there was a lot to lose, basically.”
The latest survey data indicates the project is a success. Since it began in 2019, there has been a 1,267% increase in the chance of curlews hatching, a 218% increase in vole activity, and a 64% increase in chickadee numbers. Orkney is heavily persecuted by gamekeepers on the UK mainland and is now home to 160 hens.
“On the back of massive population declines, particularly of curlews and bobwings, we have successfully stabilized the population in Orkney,” says Sankey.
The AI system, sourced from New Zealand, where conservationists face an uphill battle to remove millions of non-native predatory mammals, is being supplemented with thermal scopes and drones, says the project’s lead technology expert, James Gillock, a New Zealander who worked on an eradication project near Wellington.
He says thermal detectors are more sensitive to movement than the surveillance cameras typically used by conservationists. It works perfectly in the dark and sends live alerts in real time after uploading the video footage to a cloud server. Artificial intelligence has learned to distinguish between stoats, otters and voles.
“It’s a much more accurate monitoring tool than a typical trail camera,” Gillock says.
After six years of coordinated trapping efforts, including interruptions to lockdowns during the Covid crisis when stoat numbers rose again, the RSPCA hopes to begin a “purge” phase in December – a threshold that will be reached after 95% of stoats have been eradicated.
They estimate that there are only about 100 pregnant stoats left in Orkney. “We are all conservationists who work here,” Sankey says. “None of us are here because we want to kill an animal. We are here because we want to protect Orkney’s nature.”