Welcome to the latest news and updates from the Orkney Native Wildlife Project.
New to our blog and want to find out more about the project, how to volunteer with us or have a question? Visit our Facebook page, our website or email stoatsightings@rspb.org.uk
Trap network nearly complete!
We are delighted to report that we have almost finished deploying trap boxes across West Mainland to complete our initial eradication network! Our network currently covers 76% of the land in Orkney Mainland and the linked isles – 78% coverage in East Mainland, 73% coverage in South Ronaldsay and the linked isles and 76% coverage in West Mainland.
Finishing deployment on the hills
We are so grateful to all the landowners who are supporting the project by giving access for trapping on their land and it’s not too late to join them. If you are a landowner now able to grant permission for trap boxes to be placed on your land, please do get in touch by emailing us at stoatsightings@rspb.org.uk
The total number of stoats caught so far is 780 stoats.
Why can’t we translocate stoats from Orkney?
This is a great question and one that recently came up on the letters page in The Orcadian.
Stoats in Orkney are an invasive non-native species and were first recorded in Orkney in 2010. With no natural predators here, they pose a serious threat to our native wildlife particularly the Orkney vole, hen harriers, short-eared owls and other ground-nesting birds including red-throated divers, Arctic terns and curlews. More information about the impact of stoats in Orkney can be found in this NatureScot commissioned report. The only way to protect our native wildlife (and its contribution to our economy) is to remove stoats from Orkney.
Stoat with vole
Translocations are not always the most suitable action for the welfare of the animals or other wildlife in the release area, the logistics are difficult and costly and any translocations are strictly regulated with a Scottish Code for Translocations. Translocating stoats from Orkney would likely be cruel and inhumane to both them and the wildlife already present in release areas. Live captures are stressful on animals and the stoats would need to be kept in prolonged captivity before being transported by ferry across to the Scottish mainland. Some stoats would not survive this.
Finding suitable translocation release sites on the British mainland would also be problematic. Legal killing of stoats is routinely undertaken in many areas and stoats from Orkney would need to compete with locally established stoat populations for territory and food sources and they would not be familiar with predators such as foxes and badgers, increasing chances of mortality. In addition to this the live traps would need to be checked daily – not logistically possible with the huge area covered by 6000 trap boxes across the county.
Fox by Ben Andrew (rspb-images.com)
Using legal lethal humane traps to kill stoats is not an easy decision to have made but it is a necessary one – the risk to Orkney’s native wildlife is severe if we do nothing and by not acting now, we can expect irreparable changes to Orkney’s natural heritage. Eradication of stoats is the only way to protect Orkney’s internationally important native wildlife.
Curlew chicks on South Ronaldsay, June 2020, by Julio Merayo
Back to stoat school
We are often sharing information about why and how we are eradicating stoats in Orkney but not so much about what they are and how they work! So, it’s time to go back to school and find out a few facts about their biology and ecology.
Stoat by Steve Sankey
The stoat (Mustela erminea) is a relatively common species in the UK and is native to the Scottish mainland but not in Orkney. Stoats are sexually dimorphic which means male stoats are generally bigger than females. However, stoats have a large variation in body size and their body length can range from 250mm to 310mm and weight can range from 140g to 440g and we often find large females and small males – not confusing at all!
Age is trickier to work out, but a look at the sharpness of the teeth may help identify a juvenile or older animal – the sharper the teeth, the younger the animal. Stoats can live over five years, but usually only survive 1-2 years in the wild.
Big eaters
They are incredibly active with a high metabolic rate, travelling up to 2 km in a few hours to hunt at speeds of up to 20 mph! That’s the hundred metres in 11.1 seconds. They have ferocious appetites, needing to eat 12-30% of their body weight daily (about one vole) and up to 200% for females feeding young. How much would you have to eat to match this?!
Stoat with rabbit by Jemma Ward
Like many carnivores, stoats also engage in surplus killing – killing more than they need to eat – and storing food which is one of the reasons we are so worried about their impact on Orkney’s native wildlife. Stoats in Orkney feed on Orkney voles, rabbits, mice and the eggs and chicks of ground-nesting birds. We are also often asked about rats. There is no evidence that stoats could control Orkney’s rat population. A UK study of the diet of stoats analysed stomach contents and found that rat was found only twice in 570 stoat stomachs. The stoat is an opportunistic predator and seeks much easier prey in Orkney.
It is also unlikely stoats would be naturally controlled by predators such as short-eared owls and kestrels as they mainly feed on smaller mammals. A hen harrier may take an occasional stoat, but this would not have a significant impact on stoat populations. Quite the opposite in fact as hen harriers are one of the species highlighted as most at risk from stoats, mostly due to competition for food (voles) but a brave stoat could also take their eggs or chicks.
Prolific breeders
Stoats are highly fertile with very young sexual maturity and pregnant females can delay implantation to ensure offspring are born in the spring when there are good food supplies. Studies have shown that young females (or kits) can be sexually mature at 20 days, while males mature at around a year. Virtually all female stoats (juveniles and adults) are already pregnant by the time they leave the den as males will visit to mate them and the adult female during the breeding season. Litter sizes vary but up to 14 kits can be born to a single female each year, so stoat populations can multiply quickly, particularly on islands such as Orkney where they have no natural predators. Other than in the breeding season, male and female stoats tend to be solitary animals living in separate territories, hence the large network of traps covering the whole county to ensure we can catch each individual.
Skull science
Stoat skull side view (credit www.ecologycenter.us)
Stoat skulls tell us a lot about the animal and a few of the team have been collecting skulls as a resource to show at community events, talks and school sessions when we are able to do these again. Stoats have large jaws and necks for such a small mammal and their skull contains big spaces for these features to give them a strong grip and bite. The teeth are designed for meat eating, with sharp front canines for catching prey and dispatching it instantly with a crunching bite through the neck and skull. They have back teeth used for chewing on bones, but no grinding teeth so will instead slice through their food and swallow it in lumps.
Stoat skull (credit Klaus Rassinger und Gerhard Cammerer, Museum Wiesbaden)
The project is keeping the stoats we catch to help scientists and conservationists understand more about the stoat population in Orkney, providing projects for UK Universities to study stoat biology and behaviour. Studying the weight, length, skull size, teeth and sex of the stoats we catch will help us measure the success of the eradication, make any adaptations in the efficiency of the traps and trial different trapping locations and baits used. We will keep genetic samples for using to determine if the stoat population in Orkney is more closely related to populations in Aberdeenshire or Caithness which will help us focus our biosecurity work to prevent a spread of stoats happening again in the future. We will keep you posted on our findings as the project progresses.
Covid and stoats
One other question that has been coming up is about stoats and Covid. As the world continues to discover more about SARS-CoV-2 – the virus that causes Covid-19 – it is now known that several types of animals can be infected and a question we have been asked recently is could stoats infect people. Across the world small numbers of pet cats and dogs have tested positive, several lions and tigers at New York Zoo and mink on fur farms in the Netherlands, Spain, Italy, Sweden, Denmark and the United States. In all these cases, it is believed likely that people passed the virus to these animals initially.
As both ferrets and mink can be infected, it is reasonable to assume that other mustelids such as stoats might be too. However, it is also reasonable to assume the probability of human to stoat transfer is significantly lower outside of a fur farm or domestic setting – there have been no recorded cases of Covid-19 in wild mustelids.
Biosecurity trap deployment in Flotta
As our project staff do handle dead stoats, we have always been working to strict safety and hygiene protocols including wearing gloves and regularly washing hands. We will continue to review and amend these to ensure the safety of our staff and our community.