A Stoat in winter coat, then called Ermine. Just as tough on Grouse and Rabbits as mice and other rodents. Interesting to watch and unusually pretty in the wild. Though I have never seen it, they apparently do a dance bounce and flopping to fool rabbits into thinking that they are not a threat while getting closer and closer until they charge in for the kill. I believe they have a very musky gland to defend against animals and birds of prey...sort of like a skunk.