The stoat was introduced into New Zealand in the late 19th century to control rabbits, but had a devastating effect on native bird populations and was nominated as one of the world's top 100 "worst invaders".

[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).

[6] 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 northern North America), M. richardsonii (most of North America), and M. haidarum (several islands off the Pacific Northwest coast).

The stoat's direct ancestor was Mustela palerminea, a common carnivore in central and eastern Europe during the Middle Pleistocene,[18] that spread to North America during the late Blancan or early Irvingtonian.

[19] 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 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.

[22] The mountain weasel (Mustela altaica) was formerly considered its closest relative although more recent analyses have found it to be significantly more derived.

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.

In the stoat's northern range, it adopts a completely white coat (save for the black tail-tip) during the winter period.

[7] Stoats were introduced into New Zealand during the late 19th century to control rabbits and hares, but are now a major threat to native bird populations.

The warnings were ignored and stoats began to be introduced from Britain in the 1880s, resulting in a noticeable decline in bird populations within six years.

Stoats undergo embryonic diapause, meaning that the embryo does not immediately implant in the uterus after fertilization, but rather lies dormant for a period of nine to ten months.

[37] The gestation period is therefore variable but typically around 300 days, and after mating in the summer, the offspring will not be born until the following spring – adult female stoats spend almost all their lives either pregnant or in heat.

[38] Males play no part in rearing the young, which are born blind, deaf, toothless and covered in fine white or pinkish down.

In Russia, its prey includes rodents and lagomorphs such as European water voles, common hamsters, pikas and others, which it overpowers in their burrows.

Prey species of secondary importance include small birds, fish, and shrews and, more rarely, amphibians, lizards, and insects.

[43] In Great Britain, European rabbits are an important food source, with the frequency in which stoats prey on them having increased between the 1960s and mid 1990s since the end of the myxomatosis epidemic.

Typically, male stoats prey on rabbits more frequently than females do, which depend to a greater extent on smaller rodent species.

In continental Europe, 26 flea species are recorded to infest stoats, including Rhadinospylla pentacantha, Megabothris rectangulatus, Orchopeas howardi, Spilopsyllus ciniculus, Ctenophthalamus nobilis, Dasypsyllus gallinulae, Nosopsyllus fasciatus, Leptospylla segnis, Ceratophyllus gallinae, Parapsyllus n. nestoris, Amphipsylla kuznetzovi and Ctenopsyllus bidentatus.

Mite species known to infest stoats include Neotrombicula autumnalis, Demodex erminae, Eulaelaps stabulans, Gymnolaelaps annectans, Hypoaspis nidicorva, and Listrophorus mustelae.

[50] The nematode Skrjabingylus nasicola is particularly threatening to stoats, as it erodes the bones of the nasal sinuses and decreases fertility.

[53] In the Zoroastrian religion, the stoat is considered a sacred animal, as its white winter coat represented purity.

Similarly, Mary Magdalene was depicted as wearing a white stoat pelt as a sign of her reformed character.

Gilles Servat's song La Blanche Hermine ("The White Ermine") became an anthem for Bretons (and is popular among French people in general).

The fur from the winter coat is referred to as ermine and is the traditional ancient symbol of the Duchy of Brittany, forming its earliest flag.

The ceremonial robes of members of the United Kingdom House of Lords and the academic hoods of the universities of Oxford and Cambridge are traditionally trimmed with ermine.

Prelates of the Catholic Church still wear ecclesiastical garments featuring ermine (a sign of their status equal to that of the nobility).

Henry Peacham's Emblem 75, which depicts an ermine being pursued by a hunter and two hounds, is entitled "Cui candor morte redemptus" ("Purity Bought with His Own Death").

[57] The stoat was a fundamental item in the fur trade of the Soviet Union, with no less than half the global catch coming from within its borders.