The American Ermine (Mustela richardsonii), also known as the American stoat, short-tailed weasel, or simply as stoat, or ermine, is a species of mustelid native to most of North America. It is a member of the genus Mustela of the family Mustelidae, distinguished from the least weasel by its larger size and longer tail with a prominent black tip. Once considered to be the same species as the Eurasian ermine (M. erminea), the American ermine was recognized as distinct in 2021, along with the Haid