Stoat, or short-tailed weasels (Mustela erminea)

Three species of weasels swap their warm summer browns for icy whites: the least weasel (Mustela nivalis), the long-tailed weasel (M. frenata), and the short-tailed weasel, or stoat (M. erminea). The latter species is perhaps best known as the ermine, also the name of its winter fur, which is white except for the black tip of the tail. The uniquely patterned fur was once used to trim the robes of royalty and clergy. Weasels of the same species that live in more southerly climates usually don’t change color, though their more northerly relatives do. In transition zones, some weasels only partially change color, resulting in patchy white-and-brown fur. Interestingly, color-changing weasels have been shown to change color regardless of temperature or location, suggesting that they too rely on photoperiod to cue their molts.