Orkney vole thriving as invasive stoat numbers reduced

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• About the Orkney Native Wildlife Project

  • The Orkney Native Wildlife Project is a partnership between RSPB Scotland, NatureScot and Orkney Islands Council. It has the generous support of the National Lottery Heritage Fund, EU Life and the Scottish Government’s Nature Restoration Fund, managed by NatureScot, as well as financial and in-kind contributions from partners.

  • The project is the world’s largest and most ambitious stoat eradication to date. It employs more than 40 people and involves the use of Europe’s first conservation detection dog team. Being the first of its kind at this size and scope means lessons learned are of international interest and consequence.

  • The project began trapping in 2019, after a consultation period which indicated extensive support for Orkney’s wildlife: 92% believe we have a duty to protect Orkney’s wildlife for future generations; 88% are worried about the decline in native wildlife if stoats are not removed from the islands; 84% thought it was important to eradicate stoats from Orkney. The project has worked with more than 1190 landowners, received the equivalent of twelve working years in volunteer hours and conducted more than 701,000 individual trap checks.

  • The project has removed more than 8,500 stoats from Orkney using humane lethal traps which comply with the Spring Trap Approval Order. There are 8,813 trap boxes (including network, response, and biosecurity) deployed as of 20 March 2026, most of which contain two DOC-200 spring traps. The majority of the traps are ‘network traps’. These remain in the field permanently and are checked on a regular schedule. ‘Response traps’ are deployed in response to public sightings or detection dog indications, while ‘biosecurity traps’ are deployed on the islands which are believed to be free from stoats.

  • The project is following international best practice for conducting an invasive species eradication. The methodology was initially to significantly reduce (technically known as ‘knock-down’) stoat numbers with network traps and ‘mop-up’ the remaining stoats once there were few enough to respond to all public sightings. The two-year monitoring period which follows the eradication before it can be declared successful is also international best practice. If a stoat is found within this period, it will be removed, and the clock reset.

  • The project is split between eradication and biosecurity. The eradication effort focuses on removing stoats from the Orkney Mainland and Linked South Isles where the invasive population is established. The biosecurity programme is intended to prevent stoats from colonising the stoat-free Orkney islands.

  • The project’s stoat detection dogs, which were Europe’s first, were initially used for checking whether stoats had established on other islands. They are now used for following up public sightings and conducting area searches to help the project target its trapping effectively. Most of these detection dogs indicate when they locate stoat scat (poo). Others indicate when they scent the recent presence of an actual stoat. All the project’s detection dogs are trained not to interact with the stoats themselves.

  • More information available on the website, www.orkneynativewildlife.org.uk, Facebook page www.facebook.com/OrkneyNativeWildlifeProject

• The importance of Orkney’s native wildlife  
  • Despite being less than 1% of the UK landmass, it is home to 15% of its hen harriers, 6% of its breeding seabirds, very high densities of breeding curlews, and important populations of lapwing, oystercatcher, and the Orkney vole, a subspecies found nowhere else in the world. Many of these species are struggling to adapt to the pace of change on the UK mainland, meaning that their survival in Orkney has national and sometimes international significance.

  • Situated on the East Atlantic Flyway, a migration route used by over 155 species, Orkney is also a crucial stopping off point for huge numbers of migratory birds.

  • This abundance of wildlife has major benefits for the local economy. Orkney has a thriving wildlife tourism industry. Visitors spent £70 million in 2019-20, with 46% of visitors engaging in wildlife watching activities (Island visitor survey commissioned by Orkney Islands Council in partnership with VisitScotland).

  • In 2019, farmers in Orkney received £2.35 million in Agri-Environment Climate Scheme payments (9% of all Scottish payments despite being just 1.3% of its land area). These payments are at risk if wildlife like curlews and hen harriers decline in Orkney.

  • Since 2019, when trapping started, the number of successful curlew nests has increased on the Orkney Mainland (the area under eradication) and in 2022-2023, almost 83% of oystercatcher nests survived until hatching.

• Stoats and their impact on native wildlife
  • Stoats (Mustela erminea) are native to the UK Mainland but not to Orkney, where they were first recorded in 2010. Since then, the population has increased and has spread throughout Mainland Orkney, and the linked isles including Burray and South Ronaldsay.

  • Stoats are very skilled hunters. They are fast and agile and good climbers with very good eyesight, hearing and sense of smell. They typically feed on small mammals, birds and eggs but can kill prey much larger than themselves. They also tend to kill more than they need and hide (cache) the rest to eat later. In Orkney, caches containing as many as 100 Orkney voles have been found. With no natural predators in Orkney, they pose a very serious threat to Orkney's native wildlife.

  • Stoats have played a critical role in the extinction of several species elsewhere in the world. They were introduced to New Zealand in the 19th century in an attempt to control invasive rabbits. Instead, they contributed to the extinction of the laughing owl, South Island kōkako, and mātuhituhi, all ground-nesting birds. To this day, they continue to threaten the iconic kiwi.

  • Although common throughout mainland Britain where they are native, stoats are usually shy and elusive creatures. In Orkney, their unusually bold behaviour is likely due to the abundance of food (in the form of ground-nesting birds and Orkney voles) and a scarcity of natural predators.

  • In 2014, NatureScot commissioned a report: Stoat on the Orkney Islands – assessing the risks stoats posed to native species (SNH Commissioned Report No. 871). The report concluded that stoats threaten several species both directly and indirectly, including: the Orkney vole, hen harrier, short-eared owl, and many ground-nesting birds. The report recommended that removal of stoats is the best option to safeguard Orkney’s wildlife and prevent knock-on-effects to Orkney's wildlife tourism industry as well as other activities such as poultry rearing.

• The costs of invasive species 
  • According to the United Nations, invasive non-native species cost the global economy £338 billion every single year. From Asian hornets to giant hogweed and even stoats, invasive species are having a colossal impact on ecosystems, economies, infrastructure, and more in the UK.

  • Invasive species are responsible for 40% of extinctions worldwide in the past 400 years. Despite making up less than 6% of the world’s surface, 60% of extinctions in this period have taken place on islands.