Stoat cull credited with rise in Orkney vole activity

Efforts to remove invasive stoats from Orkney have given a boost to the islands' native voles and birds of prey, according to a new report.

The Orkney Native Wildlife Project report shows vole activity in spring 2025 was the highest since 2019 when a project to protect native wildlife from not-native stoats began.

It also revealed the number of breeding attempts by rare hen harriers and short-eared owls - which rely on the voles as a food source - were high compared with six years ago.

Conservationists said it was "fantastic" to see the impact of removing the invasive stoats from Orkney, where they posed a serious risk to native wildlife.

The stoat eradication is being carried out by the Orkney Native Wildlife Project - a partnership between RSPB Scotland, NatureScot and Orkney Islands Council.

Stoats, which are native to mainland Britain but not to Orkney, were first found on the islands in 2010.

Conservationists have warned that stoats could devastate populations of wildlife including the Orkney voles, which are unique to the islands.

Individual stoat food stores containing about 100 Orkney voles have been discovered on the islands.

Since 2019 more than 8,500 stoats have been removed using humane lethal traps and Europe's first stoat detection dogs.

The new monitoring report surveyed Orkney voles by looking for signs such as droppings and grass clippings.

Across 22 sites surveyed on the mainland and the islands, signs of voles were found in a third of the 1,082 small survey squares searched.

Monitoring also found autumn activity by the voles was high.

Hen harriers, one of the UK's rarest birds of prey and a species which has a strong breeding presence of the islands, have also benefited from the stoat removal scheme, the team said.

In 2025 volunteers from the Orkney Raptor Study Group (ORSG) found hen harriers breeding in 74 locations on islands with stoats, making it the best year for the birds since 2012.

Wet weather resulted in a high number of chick deaths but it is thought about 60 chicks fledged from monitored nests.

Short-eared owls were confirmed at 55 sites on islands with stoats during the breeding season, with 16 places where they definitely bred and nests found at a further six places.

The conservation team said the results showed a continued increase in breeding sites for short-eared owls since 2019, when the stoat removal began.

Both hen harriers and short-eared owls rely on Orkney voles to feed themselves and their chicks and good vole numbers are strongly linked to breeding attempts and success for the birds.

Matt Marsh, monitoring officer for the Orkney Native Wildlife Project, said: "It's fantastic to see the continued positive impact that removing stoats from Orkney is having on our native wildlife.

"Hen harriers are one of the most fascinating species we monitor, as well as being one of the rarest birds of prey in the UK, so it's excellent to see that their numbers are increasing.

"Orkney voles are found nowhere else in the world and are the species that is probably most threatened by the arrival of stoats, so to see historically high rates of vole activity is very encouraging."

Anne McCall, director of RSPB Scotland, said: "The Orkney Native Wildlife Project is showing that we can halt and reverse species declines if we take action to address the threats wildlife is facing.

"Invasive non-native predators are a significant threat to much of the iconic wildlife found on Scotland's islands.

"However to give species like the Orkney vole their best chance, removing invasive non-native species like stoats from islands is essential."