This is either a Short-tailed Weasel (Mustela erminae) or a Long-tailed Weasel (Mustela frenata)…They are nearly identical in appearance. Short-tails are called Ermine in winter when they turn white [February; Sax-Zim Bog, St. Louis County, Minnesota] This is either a Short-tailed Weasel (Mustela erminae) or a Long-tailed Weasel (Mustela frenata)…They are nearly identical in appearance. Short-tails are called Ermine in winter when they turn white [February; Sax-Zim Bog, St. Louis County, Minnesota]