Mustela erminea

The ermine, or short-tailed weasel, is a circumpolar species that is native to the northern temperate regions of North America, Europe and Asia, and it is one of three species of weasels that occur in North America. Ermine are small, quick and extremely efficient predators that specialize in rodents and rabbits. As with other weasels, they are well-known for their curiousity, boldness and courage. These animals prefer cooler climates, and their recovery from Late Pleistocene deposits south of their current range serves as a good indicator of cooler conditions during this time period. 

Short-tailed weasel

Ermine, or short-tailed weasel (Mustela erminea). Credit: U.S. Fish and Wildlife Service, By Steve Hillebrand. 

Carnivora (Dogs, Cats, Bears, etc.)
Mustelidae (Weasels)

Length: males 19-33 cm (7.5-13.0 in) body, 7.5-10 cm (3.0-3.9 in) tail; females 17-27 cm (6.7-10.6 in) body, 6.5-10.5 cm (2.6-4.1 in) tail

Weight: 56-206 g (2.0-7.3 oz)