Stoats painted heraldry white—and wrecked New Zealand birds
Mustela erminea, the Eurasian ermine, ranges circumpolar across Eurasia and northern North America as an IUCN Least Concern mustelid whose winter white coat named aristocratic ermine. Released in late-nineteenth-century New Zealand to kill rabbits, it became a top-100 worst invader for native birds.
The white fur that trimmed royal robes is a seasonal disguise. Stoats moult twice a year, prompted by day length: slowly in spring, from forehead to back to belly, and quickly in autumn in the reverse direction, starting earlier in autumn in the far north. The summer coat is sandy brown above and white below, usually divided by a straight line, though only 13.5 percent of Irish stoats show it. Winter fur is dense and silky. Ermine capes were worn by Catholic monarchs in the fifteenth century and still adorn the ceremonial robes of the House of Lords.
Built long and narrow, the stoat has its head set far forward on an elongated neck, a nearly cylindrical trunk, short flattened ears and large non-retractable claws. Its tail always exceeds a third of its body length. Unusually for carnivores, stoats get smaller toward the poles, the opposite of Bergmann's rule, and males are about a quarter longer and up to twice as heavy as females. Anal glands release a musky blend of sulphur compounds when the animal is attacked.
Its lineage traces to Mustela palerminea of Middle Pleistocene Europe, whose ancestors shrank as grasslands replacing forest 5 to 7 million years ago spread small burrowing rodents. Stoat fossils have turned up in Denisova Cave, and a 2021 study split the species into three, separating the American and Haida ermines. The name may come from Dutch for bold or a Gothic word for push; males are jacks, females jills, and a group is a gang.
Stoats range from Portugal to Arctic Canada and up to 3,000 metres. Introduced to New Zealand in the late nineteenth century, they devastated native birds, and on Orkney a project spent £7.9 million trapping over 6,300 stoats by 2024.
Source: Stoat
