Stoat (Ermine)

Stoat (Ermine) - Mustela Erminea

Stoat (Ermine) – Mustela Erminea

The stoat (Mustela erminea), also known as the short-tailed weasel, is a species of Mustelidae native to Eurasia and North America, distinguished from the least weasel by its larger size and longer tail with a prominent black tip. The name ermine is often, but not always, used for the animal in its pure white winter coat, or the fur thereof.[2] In the late 19th century, stoats were introduced into New Zealand to control rabbits. The stoats have had a devastating effect on native bird populations (see stoats in New Zealand).

It is classed by the IUCN as least concern, due to its wide circumpolar distribution, and because it does not face any significant threat to its survival.[1] It was nominated as one of the world’s top 100 “worst invaders”.[3]

Ermine luxury fur is often used by Catholic monarchs, pontiffs and cardinals, who sometimes use it as the mozetta cape. It is also used in capes on devotional images such as the Infant Jesus of Prague. The parliamentary and coronation robes of British peers of the realm are also made from ermine.[citation needed]

Etymology

The root word for “stoat” is likely either the Belgic and Dutch word stout (“bold”)[4] or the Gothic word stautan (“to push”).[5] 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,[4] though other authors have linked it to the Norman French from the Teutonic harmin (Anglo-Saxon hearma). This seems to come from the Lithuanian word šarmu.[5] In Ireland (where the least weasel does not occur), the stoat is referred to as weasel, while in North America it is called short-tailed weasel. A male stoat is called a doghob, or jack, while a female is called a bitch or jill. The collective noun for stoats is either gang or pack.[6]

Evolution

Skulls of a long-tailed weasel (top), a stoat (bottom left) and least weasel(bottom right), as illustrated in Merriam‘s Synopsis of the Weasels of North America

The stoat’s direct ancestor was Mustela palerminea, a common carnivore in central and eastern Europe during the Middle Pleistocene,[7] that spread to North America during the late Blancan or early Irvingtonian.[8] The stoat is the product of a process begun 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 to exploit the new food source. The stoat first arose in Eurasia, shortly after the long-tailed weasel 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 half a million years ago, when falling sea levels exposed the Bering land bridge.[9]

Combined phylogenetic analyses indicate the stoat’s closest living relative is the mountain weasel (Mustela altaica), though it is also closely related to the least weasel (Mustela nivalis) and long-tailed weasel (Mustela frenata). Its next closest relatives are the New WorldColombian weasel (Mustela felipei) and the Amazon weasel (Mustela africana).[10]

Subspecies

As of 2005,[11] 37 subspecies are recognised.

Physical description

Build

The stoat is entirely 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,[21] 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.[22] 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.[23] 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.[24] 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.[24]

The dimensions of the stoat are variable, but not as variable as the least weasel.[25] Unusual among the Carnivora, the size of stoats tends to decrease proportionally with latitude, in contradiction to Bergmann’s rule.[7] Sexual dimorphism in size is pronounced, with males being 1.5-2.0 times the weight of females.[17] On average, males measure 187–325 mm (7.4–12.8 in) in body length, while females measure 170–270 mm (6.7–10.6 in). The tail measures 75–120 mm (3.0–4.7 in) in males and 65–106 mm (2.6–4.2 in) in females. In males, the hind foot measures 40.0–48.2 mm (1.57–1.90 in), while in females it is 37.0–47.6 mm (1.46–1.87 in). The height of the ear measures 18.0–23.2 mm (0.71–0.91 in) in males and 14.0–23.3 mm (0.55–0.92 in). The skulls of males measure 39.3–52.2 mm (1.55–2.06 in) in length, while those of females measure 35.7–45.8 mm (1.41–1.80 in). Males weigh 258 grams (9.1 oz), while females weigh less than 180 grams (6.3 oz).[25]

The stoat has large anal scent glands measuring 8.5 mm × 5 mm (0.33 in × 0.20 in) in males and smaller in females. Scent glands are also present on the cheeks, belly and flanks.[24] 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.[26]

Fur

The winter fur is very dense and silky, but quite closely lying and short, while the summer fur is rougher, shorter and sparse.[21] 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.[24] Differences in the winter and summer coats are less apparent in southern forms of the species.[27] In the species’ southern range, the coat remains brown, but is denser and sometimes paler than in summer.[24]

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