The stoat (Mustela erminea), also known as the short-tailed weasel, is a mammal of the genus Mustela of the family Mustelidae native to Eurasia and North America, distinguished from the least weasel by its larger size and longer tail with a prominent black tip. Originally from Eurasia, it crossed into North America some half million years ago, where it naturalized and joined the notably larger closely related native long-tailed weasel.

The name ermine is often, but not always, used for the stoat in its pure white winter coat, or the fur thereof. In the late 19th century, stoats were introduced into New Zealand to control rabbits, where they have had a devastating effect on native bird populations. (source)