Weasel. The weasel is a highly active predator found throughout the United Kingdom and often confused with its close relative, the stoat. However, it is significantly smaller than the stoat, being the smallest European carnivore, and it never has a black tip to its tail.Weasels eat mainly mice, voles and shrews, but will probably kill and eat any other prey that they can master, including young rabbits, small birds and eggs.