The stoat (Mustela erminea), also known as the Eurasian ermine or ermine, is a species of mustelid native to Eurasia and the northern regions of North America. Because of its wide circumpolar distribution, it is listed as Least Concern on the IUCN Red List. The name ermine () is used especially in its pure white winter coat of the stoat or its fur. Ermine fur was used in the 15th century by Catholic monarchs, who sometimes used it as the mozzetta cape. It has long been used on the ceremonial robes of members of the United Kingdom House of Lords. It was also used in capes on images such as the Infant Jesus of Prague.
The stoat was introduced into New Zealand in the late 19th century to control rabbits. However, they have had a devastating effect on native bird populations; as such, the species was nominated as one of the world's top 100 "worst invaders".
Etymology The root word for "stoat" is likely either the Dutch word ("bold") or the Gothic word (, "to push"). According to John Guillim, in his Display of Heraldrie, the word "ermine" is likely derived from Armenia, the nation where it was thought the species originated, though other authors have linked it to the Norman French from the Teutonic (Anglo-Saxon ). This seems to come from the Lithuanian word . In North America it is called a short-tailed weasel. A male stoat is called a dog, hob, or jack, while a female is called a jill. The collective noun for stoats is either gang or pack.
Taxonomy Formerly considered a single species with a very wide circumpolar range, a 2021 study split M. erminea into three species: M. erminea sensu stricto (Eurasia and Alaska), M. richardsonii (most of North America), and M. haidarum (several islands off the Pacific Northwest coast).
Subspecies , 21 subspecies are recognized.
ImageSubspeciesCommon nameDescriptionRangeSynonymsM. e. erminea Linnaeus, 1758 (Nominate subspecies)Northern stoatSmall-to-medium-sized with a relatively short and broad facial regionThe Kola Peninsula, Scandinaviahyberna (Kerr, 1792) maculata (Billberg, 1827)M. e. aestiva Kerr, 1792Middle Russian stoatModerately sized with dark, tawny or chestnut summer furEuropean Russia (except for the Kola Peninsula), Central and Western Europealgiricus (Thomas, 1895) alpestris (Burg, 1920) giganteus (Burg, 1920) major (Nilsson, 1820)M. e. arctica Merriam, 1826Tundra stoatLarge, with a dark yellowish-brown summer coat, a deep yellow underbelly and a massive skull; it resembles the Eurasian stoat subspecies more closely than any other American stoat subspeciesAlaska, northwestern Canada, and the Arctic Archipelago (except for Baffin Island)audax (Barrett-Hamilton, 1904) kadiacensis (Merriam, 1896) kadiacensis (Osgood, 1901) richardsonii (Bonaparte, 1838)M. e. augustidens Brown, 1908M. e. ferghanae Thomas, 1895Fergana stoatSmall; very light, straw-brownish or greyish coat, which is short and soft. Light spots on the neck, sometimes forming a collar. It does not turn white in winter.Tien Shan and Pamir-Alay mountains, Afghanistan, India, western Tibet and the adjacent parts of the Tien Shan in Chinashnitnikovi (Ognev, 1935) whiteheadi (Wroughton, 1908)M. e. hibernica Thomas and Barrett-Hamilton, 1895Irish stoatLarger than aestiva, but smaller than stabilis. Distinguished by the irregular pattern on the dividing line between the dark and pale fur on the flanks, though 13.5% of Irish stoats exhibit the more typical straight dividing line. They do not turn white in winter.Ireland and Isle of ManM. e. kadiacensis Merriam, 1896Kodiak stoatKodiak IslandM. e. kaneii Baird, 1857East Siberian stoat (known locally as Ezo stoat in Japan)Moderately sized, it is smaller than M. e. tobolica, with close similarities to M. e. arctica. The summer coat is relatively light coloured, with varying intensities of browning-yellow tinges.Eastern Siberia and the Russian Far East including Kamchatka, except the Amur Oblast and Ussuriland, Transbaikalia and the Sayan Mountains. Also in Hokkaidō.baturini (Ognev, 1929) digna (Hall, 1944) kamtschatica (Dybowski, 1922) kanei (G. Allen, 1914) naumovi (Jurgenson, 1938) orientalis (Ognev, 1928) transbaikalica (Ognev, 1928)M. e. karaginensis Jurgenson, 1936Karaginsky stoatVery small, with a light chestnut-coloured summer coatKaraginsky Island, along the eastern coast of KamchatkaM. e. lymani Hollister, 1912Altai stoatModerately sized with less dense fur than M. e. tobolica. The summer coat consists of weakly developed reddish-brown tones. The skull is similar to that of M. e. aestiva.The mountains of southern Siberia eastwards to Baikal and the contiguous parts of MongoliaM. e. martinoi Ellerman and Morrison-Scott, 1951birulai (Martino and Martino, 1930)M. e. minima Cavazza, 1912Swiss stoatSwitzerlandM. e. mongolica Ognev, 1928Gobi stoatThe Govi-Altai ProvinceM. e. nippon Cabrera, 1913Japanese stoatnorthern HonshūM. e. ognevi
Jurgenson, 1932M. e. polaris Barrett-Hamilton, 1904Polar stoatGreenlandM. e. ricinae Miller, 1907Hebrides stoatThe HebridesM. e. salva Hall, 1944M. e. stabilis Barrett-Hamilton, 1904British stoatLarger than mainland European stoatsGreat Britain; introduced to New ZealandM. e. teberdina Korneev, 1941Caucasian stoatSmall, with a coffee to reddish-tawny summer coatThe northern slope of the middle part of the main Caucasus rangebalkarica (Basiev, 1962)M. e. tobolica Ognev, 1923Tobolsk stoatLarge; it is somewhat larger than aestiva, with long and dense fur.Western Siberia, eastwards to the Yenisei and Altai Mountains and in Kazakhstan
Evolution The stoat's direct ancestor was Mustela palerminea, a common carnivore in central and eastern Europe during the Middle Pleistocene, that spread to North America during the late Blancan or early Irvingtonian. The stoat is the product of a process that began 5–7 million years ago, when northern forests were replaced by open grassland, thus prompting an explosive evolution of small, burrowing rodents. The stoat's ancestors were larger than the current form, and underwent a reduction in size as they exploited the new food source. The stoat first arose in Eurasia, shortly after the long-tailed weasel, which is in a different genus (Neogale), arose as its mirror image in North America 2 million years ago. The stoat thrived during the Ice Age, as its small size and long body allowed it to easily operate beneath snow, as well as hunt in burrows. The stoat and the long-tailed weasel remained separated until 500,000 years ago, when falling sea levels exposed the Bering land bridge.
Fossilised stoat remains have been recovered from Denisova Cave. Combined phylogenetic analyses indicate the stoat's closest living relatives are the American ermine (M. richardsonii) and Haida ermine (M. haidarum), the latter of which partially descends from M. erminea. It is basal to most other members of Mustela, with only the yellow-bellied (M. kathia), Malayan (M. katiah), and back-striped (M. strigidorsa) weasels being more basal. The mountain weasel (Mustela altaica) was formerly considered its closest relative although more recent analyses have found it to be significantly more derived. It was also previously thought to be allied with members of the genus Neogale such as the long-tailed weasel, but as those species have since been separated into a new genus, this is likely not the case.
Description Build
The stoat is similar to the least weasel in general proportions, manner of posture, and movement, though the tail is relatively longer, always exceeding a third of the body length, though it is shorter than that of the long-tailed weasel. The stoat has an elongated neck, the head being set exceptionally far in front of the shoulders. The trunk is nearly cylindrical, and does not bulge at the abdomen. The greatest circumference of body is little more than half its length. The skull, although very similar to that of the least weasel, is relatively longer, with a narrower braincase. The projections of the skull and teeth are weakly developed, but stronger than those of the least weasel. The eyes are round, black and protrude slightly. The whiskers are brown or white in colour, and very long. The ears are short, rounded and lie almost flattened against the skull. The claws are not retractable, and are large in proportion to the digits. Each foot has five toes. The male stoat has a curved baculum with a proximal knob that increases in weight as it ages. Fat is deposited primarily along the spine and kidneys, then on gut mesenteries, under the limbs and around the shoulders. The stoat has four pairs of nipples, though they are visible only in females.
The dimensions of the stoat are variable, but not as significantly as the least weasel's. Unusual among the Carnivora, the size of stoats tends to decrease proportionally with latitude, in contradiction to Bergmann's rule. Sexual dimorphism in size is pronounced, with males being roughly 25% larger than females and 1.5–2.0 times their weight. On average, males measure in body length, while females measure . The tail measures in males and in females. In males, the hind foot measures , while in females it is . The height of the ear measures in males and . The skulls of males measure in length, while those of females measure . Males average in weight, while females weigh less than .
The stoat has large anal scent glands measuring in males and smaller in females. Scent glands are also present on the cheeks, belly and flanks. Epidermal secretions, which are deposited during body rubbing, are chemically distinct from the products of the anal scent glands, which contain a higher proportion of volatile chemicals. When attacked or being aggressive, the stoat secretes the contents of its anal glands, giving rise to a strong, musky odour produced by several sulphuric compounds. The odour is distinct from that of least weasels.
Fur
The winter fur is very dense and silky, but quite closely lying and short, while the summer fur is rougher, shorter and sparse. In summer, the fur is sandy-brown on the back and head and a white below. The division between the dark back and the light belly is usually straight, though this trait is only present in 13.5% of Irish stoats. The stoat moults twice a year. In spring, the moult is slow, starting from the forehead, across the back, toward the belly. In autumn, the moult is quicker, progressing in the reverse direction. The moult, initiated by photoperiod, starts earlier in autumn and later in spring at higher latitudes. In the stoat's northern range, it adopts a completely white coat (save for the black tail-tip) during the winter period. Differences in the winter and summer coats are less apparent in southern forms of the species. In the species' southern range, the coat remains brown, but is denser and sometimes paler than in summer.
Distribution and habitat The stoat has a circumboreal range throughout North America, Europe, and Asia. The stoat in Europe is found as far south as 41ºN in Portugal, and inhabits most islands with the exception of Iceland, Svalbard, the Mediterranean islands and some small North Atlantic islands. In Japan, it is present in central mountains (northern and central Japanese Alps) to northern part of Honshu (primarily above 1,200 m) and Hokkaido. Its vertical range is from sea level to . In North America, it is found throughout Alaska and western Yukon to most of Arctic Canada east to Greenland. Throughout the rest of North America, as well as parts of Nunavut, including Baffin Island and some islands in southeast Alaska, it is replaced by M. richardsonii.