Research
David S. Jachowski et al. (2024) Non-invasive methods for monitoring weasels: emerging technologies and priorities for future research
Species Stoat
Facts about stoats
- English name: Stoat
- Scientific Name: Mustela erminea
- Number of young: 6-12 kits, born March to April
- Diet: Small mammals, especially rabbits and voles.
- Habitat: Grassland, farmland, woodland, riparian, marshland, coastal and urban habitats.
Identification
Females:
length 24.2-29.2cm weight 140-220gMales:
length 27.5-31.2cm weight 200-445g- The stoat's fur is brown on its back and creamy white on its belly.
- Stoats always have a black tip to their tail
- In areas of regular sitting snow, stoats can turn white as a camouflage but still retain the black tip
Distribution and status
The stoat lives throughout Britain and Ireland and is well established on some of the outer British Isles.
The stoat is not legally protected in the Britain, but it is across the island of Ireland where a different sub-species of stoat lives — the Irish stoat Mustela erminea hibernica.
The stoat is listed on the Red List as Least Concern in Great Britain.
The stoat has a long slender body and short legs, with sandy brown fur on the back and head, and a creamy white belly.
The division between the brown back and the lighter underbelly fur is always straight on stoats (but not for the Irish stoat), which distinguishes it from the similar but smaller weasel, which generally has an irregular division between back and belly fur colours.
Another distinctive feature of the stoat is its black-tipped tail.
The stoat can live in a wide variety of habitats and at any altitude where there is sufficient prey and cover for hunting.
The presence of stoats on small islands depends on prey availability. It uses dense cover and linear features like hedgerows and walls for hunting.
The stoat is territorial, with male territories overlapping smaller female territories. Territory size depends on habitat type, quality and food availability. They will have several den sites around their territory, usually using the nests of their former prey.
Stoats are primarily nocturnal and are very elusive.
The stoat is a specialist predator of small and medium-sized mammals, especially rabbits and voles. Rabbits are a particularly important food source in spring.
A small proportion of their diet consists of birds and birds’ eggs, and fruit and invertebrates including earthworms comprise the smaller proportion. Stoats can kill and carry much larger prey than themselves.
Stoats hunt opportunistically, systematically checking all available burrows, holes and crevices for food, and they may enter burrows to pursue prey. They are able to hunt beneath snow in winter and are very capable tree climbers when necessary.
Mating takes place between April – July but females delay implantation until the following year, giving birth in the spring.
The delayed implantation lasts around 9–10 months, followed by brief active pregnancy that lasts just 4 weeks. Stoats have large litters of 6–9 kits that are born blind and deaf and are dependent on their mother.
Solid food is taken from 4 weeks old, and their black tipped tail develops at 6–7 weeks. At 10–12 weeks, kits begin to hunt, and the family group breaks up after 12 weeks.
Unusually, female kits can be mated when they are just 2–3 weeks old and still in the nest. Males don’t become sexually mature until 10–11 months old.
Threats include persecution (control by gamekeepers), habitat loss, and road casualties.
Traditionally, gamebag data collected by gamekeepers have been used to record the distribution and abundance of stoats, although the accuracy of these data has been questioned. There is therefore a need to develop a more effective survey methodology to monitor population trends in the species.
Populations of stoats can experience local extinctions, but they are good at recolonising when conditions improve.
VWT's work
We have been recently trialing methods to study stoats and weasels and have worked in collaboration with the Dutch Small Mustelid Foundation to trial the ‘Mostela’. The Mostela is a box with a tube and a trail camera and is based on the idea that stoats and weasels are curious and like to investigate tunnels and holes looking for prey.
It was designed by a member of the Dutch Small Mustelid Foundation and is one of the tools we use to try and find out more about the current status of stoats and weasels. Watch the video of a stoat in a Mostela.
FAQs about stoats
During times of high food availability and abundance, stoats may kill all available prey. This is an adaptive response to ensure survival at times when food may be scarce. Poultry, if vulnerable to predation, may therefore be at risk from predation, however stoats are small carnivores and are specialised hunters of rabbits and rodents primarily.
Stoats in groups are most likely to be a family group — a mother and kits, but they split up at 9-12 weeks. Groups of stoats do not work together to take larger prey items.
The stoat’s natural predators include domestic cats, foxes, owls, and birds of prey.
Yes, stoats in some regions turn white in winter, when they may be called ‘ermine’. This physiological change occurs in response to changes in daylight length and temperature, and is meant to provide the stoat camouflage in areas with sitting snow — for example at higher altitudes where they are capable of inhabiting. Conversely, the Irish stoat in Ireland does not turn white in winter.
Further reading
Research
Croose, E. & Carter, S.P. (2019). A pilot study of a novel method to monitor weasels (Mustela nivalis) and stoats (M. erminea) in Britain
Information leaflet
A Guide to Identifying the Small Mustelids of Britain and Ireland
Information chart
A quick-start guide to the identification of small mustelids
