Stoats have the typical long slender body of a Mustelid with short legs and a medium-short tail with a black tip. Fur is reddish brown to ginger above and white to cream below. In winter in Scotland and the north of England the stoat can turn all white with the exception of the black tail tip (known as ermine); it can also partially turn, giving a piebald animal (Flintoff, 1935). The author’s first ever encounter with a Stoat in ermine was in the late 1970s at Warden Law, Sunderland; since then they have been seen in most winters. A request for ermine sightings by Northumberland Wildlife Trust produced a total of 70 records in the winter of 2010/11, mainly in January and February and well distributed across the county.
Sexual dimorphism is pronounced in Stoats with males much bigger than females. Body length varies around 350 mm and weight around 300 g. Most Stoats die before their second birthday but they can occasionally live up to eight years (King, 1989).
Stoats, like Weasels Mustela nivalis, are systematic if opportunistic hunters, mostly of small mammals with occasional birds and eggs (Harris and Yalden, 2008). Rabbit Oryctolagus cuniculus is the chief prey and will be hunted both below and above ground, even being pursued doggedly in the open over some distance before capture. Stoats are said to dance in order to mesmerise their prey, thus gaining a distance advantage before rushing the quarry. The author has only ever seen this once at a large Rabbit warren in Allendale. They are good swimmers and often hunt along watercourses; Terry Coult, (pers. comm., 2012) reports watching a Stoat hunt a Water Vole Arvicola amphibius by scent, not sight, holding the line even when the vole crossed the river.
Stoats are indigenous and may well have remained in the UK throughout the last ice age, living on the fringe of the ice sheets in southern England (Harris and Yalden, 2008). This would have given it an advantage over the Weasel when re-colonising the country and may explain its presence in Ireland. Stoat bones were recorded by Simms (1974) along with those of Wolf Canis lupus and Brown Bear Ursus arctos when excavating the Teesdale Cave.
The Stoat occurs throughout Britain and Ireland, living in a wide variety of habitats including urban areas and at any altitude with sufficient ground cover and food. Their larger size allows them to survive better than the Weasel in upland and cooler locations (Harris and Yalden, 2008). Mennell and Perkins (1864), commenting on the relationship with the Weasel, state “in the uplands probably more abundant” and this is reflected in our current distribution maps. There are UK populations on many of the offshore islands, where they may have been introduced (Harris and Yalden, 2008), and they have been recorded on Lindisfarne (Perry, 1946).
Stoat home ranges vary depending on the distribution and density of prey. They have a typical mustelid pattern, male territories encompassing smaller overlapping female territories; resident animals may defend their ranges when numbers are high but in the spring the system breaks down as males prospect widely for females (Powell, 1979).
There may be several dens within a range and these are usually made in the nest of prey species although natal nests can also be in stone walls or wood piles and, as Stoats are good climbers, can be at height in trees, buildings and roof voids, and are generally lined with the fur of their prey (Harris and Yalden, 2008). Their ability to climb sometimes leads to confusion with the Pine Marten Martes martes. One Stoat on the Cragside estate lived in the warmth and security of the rafters of the heated out-buildings during the winter of 2010/11, coming down to scavenge anything it could from the nearby homesteads including deer hung in larders.
Stoats have an unusual breeding strategy: rather than mating solely with mature females a male may mate with all female age classes, including kits in the nest, which may be only two to three weeks old. They do not give birth however until the following spring because implantation is delayed for 9-10 months, by which time females may have dispersed a considerable distance from where they were actually mated. This strategy contributes widely to the Stoat’s success and widespread distribution (McDonald and Harris, 1998).
To compensate for high mortality rates large litters of between six to nine young are born. The female feeds them for up to 12 weeks by which time they are efficient self-supporting hunters (Harris and Yalden, 2008).
Food shortage is the main killer of young Stoats and although they are widely trapped as a predator of game birds, this appears to have little effect on overall numbers. The species occasionally falls prey to larger birds of prey, foxes and even cats (Harris and Yalden, 2008). There is little competition between Weasels and Stoats, as the bigger and more powerful Stoat is able to take larger prey.
From the author’s experience notable hot spots for seeing Stoats include Allendale where they are often seen hunting along water courses for Water Vole. Druridge Bay in Northumberland has some highly visible Stoats responsible for periodically removing the Rabbits from the little islands at Hauxley nature reserve.
Like many Mustelids they are very inquisitive and they can often be enticed close to an observer by squeaking like a frightened Rabbit or rodent. The author once squeaked a whole family to his and his son’s feet in Teesdale, the kits half climbing up our legs. The author’s last encounter with a Stoat was on Prestwick Carr in March 2012. It was up in a willow tree where a broken bough contained a natal den.
The estimated pre-breeding population in Great Britain is around 462,000; however this varies greatly each year due to variable recruitment, fluctuating food supply and mortality (Harris and Yalden, 2008).
Written by Kevin O’Hara (Last updated Nov 12)