The American ermine or American stoat (Mustela richardsonii) is a species of mustelid native to most of North America.
It was long considered conspecific with the stoat (M. erminea), but a 2021 study found it to be a distinct species, forming distinct genetic clades from erminea.[1] [2] [3] The finding has been accepted by the American Society of Mammalogists.[4] The Haida ermine (M. haidarum) is thought to be a hybrid species originating from ancient hybridization between M. erminea and M. richardsonii.
The specific epithet refers to Arctic explorer and naturalist John Richardson.
The species is found throughout most of North America aside from most of Alaska (although it is found on some islands in southeastern Alaska), eastern Yukon, most of Arctic Canada, and Greenland, where it is replaced by M. erminea. It reaches the northern extent of its range in Ellesmere Island and a portion of eastern mainland Nunavut and ranges from here to cover almost all of western North America south to northern New Mexico, and eastern North America south to northern Virginia. It is absent from most of the Southeastern United States and the Great Plains.
In North America, where the ecological niche for rat- and rabbit-sized prey is taken by the larger long-tailed weasel (Neogale frenata), the American ermine preys on mice, voles, shrews, young cottontails, chipmunks, deer mice, jumping mice, and house mice. Usually the ermine kills by biting at base of skull. Small birds, frogs, small fish, and earthworms are other types of prey for ermines.[5]
Ermines live and find cover from predators in hollow spaces from logs, burrows and man made structures. Ermines sometimes den within their prey's nest and use their skin and fur as a lining for their den.
They breed in dense parts of the forest. The season for breeding is late springtime to the summer from July to August. The males mature in a year while the females only take three to four weeks to mature. The females carry a litter of four to seven babies for 255 days then gives birth.
Some of the larger wild predators of ermines are minks, martens, fishers, bobcats, coyotes, and large owls and hawks. Occasionally a domesticated cat or dog may kill an ermine. Their small agile bodies help them evade these predators, while also allow them to compete with their predators for food in more barren months.
About 13 subspecies are known:
| Subspecies | Trinomial authority | Description | Range | Synonyms | |
|---|---|---|---|---|---|
| Junean stoatM. r. alascensis. | Merriam, 1896 | Similar to M. r. richardsonii, but with a broader skull and more extensive white tips on the limbs | Juneau, Alaska | ||
| Vancouver Island stoatM. r. anguinae | Hall, 1932 | Vancouver Island | |||
| Western Great Lakes stoatM. r. bangsi | Hall, 1945 | The region west of the Great Lakes | cicognani (Mearns, 1891)pusillus (Aughey, 1880) | ||
| Bonaparte's stoatM. r. cigognanii | Bonaparte, 1838 | A small subspecies with a dark brown summer coat; its skull is more lightly built than that of richardsonii. | The region north and east of the Great Lakes | pusilla (DeKay, 1842)vulgaris (Griffith, 1827) | |
| M. r. fallenda | Hall, 1945 | ||||
| M. r. gulosa | Hall, 1945 | ||||
| M. r. initis | Hall, 1945 | ||||
| M. r. invicta | Hall, 1945 | ||||
| Southwestern stoatM. r. muricus | Bangs, 1899 | The southwestern extremity of the species' American range (Nevada, Utah, Colorado and other states) | leptus (Merriam, 1903) | ||
| Olympic stoatM. r. olympica | Hall, 1945 | The Olympic Peninsula, Washington | |||
| Richardson's stoatM. r. richardsonii | Bonaparte, 1838 | Similar to M. r. cigognanii, but larger, with a dull chocolate brown summer coat | Newfoundland, Labrador and nearly all of Canada (save for the ranges of other American stoat subspecies) | imperii (Barrett-Hamilton, 1904)microtis (J. A. Allen, 1903) mortigena (Bangs, 1913) | |
| Baffin Island stoatM. r. semplei | Sutton and Hamilton, 1932 | Baffin Island and the adjacent parts of the mainland | labiata (Degerbøl, 1935) | ||
| M. r. stratori | Merriam, 1896 |
The fur of ermine was valued by the Tlingit and other indigenous peoples of the Pacific Northwest Coast. They could be attached to traditional regalia and cedar bark hats as status symbols or made into shirts.[6]