NOBODY is quite sure how stoats managed to make their way to Orkney.

But whether they were illegally released or arrived as fugitives on a boat, over the past decade the species has established itself on the mainland, posing a significant threat to the islands’ native wildlife.

“The stoat isn’t a native species to Orkney and there aren’t any land-based predators to keep their numbers under control,” said Lianne Sinclair, project manager at the Orkney Native Wildlife Project.

In a place like Orkney, which hosts internationally important populations of seabirds, the introduction of a non-native predator could spell disaster for both ecology and economy.

As such, in 2019 – nearly ten years on from the first reports of stoats on Orkney in 2010 – one of the most ambitious species eradication projects in the world got underway.

While some criticism has been levelled at the project for not getting going sooner, Sinclair said that in comparison to other islands where non-native predators had been introduced, Orkney was in a good position.

The National: An Orkney Native Wildlife Project staff member gets ready to deploy a trap An Orkney Native Wildlife Project staff member gets ready to deploy a trap (Image: Orkney Native Wildlife Project)

“In the beginning we were guided a lot by similar projects in New Zealand,” she told The National.

“However, by the time they started their eradication projects many species had already been lost – and in some cases even extinct.”

In the 19th century stoats were introduced into New Zealand in a bid to control rabbits.

However, they ultimately contributed to the extinction of bird species such as the laughing owl and the South Island kokako. Today, they still threaten the country’s national bird: the kiwi.

“We’re now 14 years on from the first stoat being reported on Orkney and some projects in New Zealand didn’t get started until 30 or 40 years after the first predator was seen,” added Sinclair. “In that sense, we’re ahead of the game.”

The Orkney vole and the scale of the threat

In many places stoats thrive as a healthy part of complex ecosystems.

However, Orkney’s geography, history and habitat mean it has acted as a unique haven for wildlife. As well as being as a crucial stop off point for more than 150 species of migratory birds, it also hosts one in five of the UK’s hen harriers and a significant population of short-eared owls.

These birds of prey rely upon the Orkney vole – a distinct sub-species of the common vole found nowhere else in the world – for their food.

Unfortunately, stoats are also partial to an Orkney vole and have a habit of killing large amounts of prey to “cache” for later consumption, decimating populations in the process. Caches containing more than 100 Orkney voles have been found in the past.

Add to that the threat they pose to seabirds and ground-nesting birds such as curlews and the need for their eradication becomes obvious.

“This is the biggest eradication of a species in a populated place in the Northern Hemisphere,” said Sinclair.

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“It’s an absolutely huge undertaking, which is why all the data we’re collecting is so important.”

The project sees upwards of 90 staff and volunteers checking nearly 8000 lethal, humane traps across 38,000 hectares.

As of yet, the stoats remain confined to the mainland of Orkney despite their ability to swim more than three kilometres.

But biosecurity networks ensure that any reported sighting is investigated, with a team of trained dogs being used to confirm the presence of stoats.

Since 2019, 5827 stoats have been removed from Orkney.

“So far, it’s all pointing in the right direction,” said Sinclair.

“We’re looking to extend our current funding plan with the aim of having stoats eradicated by 2028, which is what our data suggests is possible”.

Giving up?

The scheme has already cost £8 million to fund, with bosses saying last year that they’ll need another £8m to complete it.

A recent article in The Times noted the dissatisfaction of one anonymous Orkney Native Wildlife Project staff member with the costs and results of the eradication project.

They claimed not enough stoats were being killed to make a difference and that the project should be scrapped.

But Sinclair said that there was too much lose by giving up now.

“If this project were to stop it would be heart-breaking,” said Sinclair.

“We’re obviously trying to protect the native wildlife here, with Orkney being an invaluable place for many species.

“But, if we don’t keep going, it also creates much bigger problems for people living here.

The National: A specially trained dog attempts to sniff out a stoatA specially trained dog attempts to sniff out a stoat (Image: Orkney Native Wildlife Project)

“If stoats are allowed to decimate seabird populations or rob birds of prey of their food source, it ultimately impacts upon the amount of money coming into the islands.

“Our wildlife is a huge draw for tourists. If that disappears, we can’t expect the local economy to benefit from it as much as it does just now.”

According to a survey commissioned by Orkney Islands Council in partnership with VisitScotland, visitors to the islands in 2019-20 spent £70m.

Nearly half of them (46%) engaged in wildlife watching activities.

Sinclair continued: “It would also have a knock-on effect for local farmers, who receive subsidies for maintaining habitat for wildlife on their properties.

“Without wildlife to protect, those payments are at risk”.

Indeed, farmers in Orkney received £2.35m in Agri-Environment Climate Scheme payments in 2019. If hen harriers and curlews disappear, so do many of those subsidies.

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A peer-reviewed paper on the Orkney scheme notes that eradication projects are “typically large and expensive”.

However, mustelid biologist Dr Tim Hofmeester said they can be successful and even provide scientists with data which helps them conserve stoats in other places.

“Eradicating stoats is very difficult, as we know from the enormous efforts that have been taken in New Zealand,” he told The National.

“But it is not impossible, as we know from several islands off the coast of New Zealand.

“Capturing the last stoats will be a tremendous effort, as getting to the last few is really difficult.

“But the combination of methods being used to track and kill stoats on Orkney has been proven to be successful in the past.”

The National: Stoat traps are checked regularly by staff and volunteersStoat traps are checked regularly by staff and volunteers (Image: Orkney Native Wildlife Project)

He added: “To date, most of our knowledge about this species comes from studies in New Zealand.

“They’ve improved our understanding of its natural history and even been used in several European countries where stoats are declining.

“Whether or not the effort is good value for money is a political question I cannot answer.

“But I am convinced that the effort is evidence-based and supervised by some of the top scientists on small mustelids”.

In straitened economic times it’s correct that multi-million-pound projects are scrutinised, particularly those in island communities already facing challenges.

Ultimately, however, the eradication of stoats could prove pivotal for Orkney’s future as a destination for both wildlife and people.