Weasel
A small, carnivorous mammal of the Northern hemisphere, the weasel is renowned for its cunning (from which comes the old expression, "cunning as a sack full of weasels") and its savagery, often killing prey several times its own size.
There are several types of weasel, mainly separated by geographic range, and a number of similar small animals, such as the mink, the polecat and the stoat.
The Old Testament declares weasels to be unclean:
These also shall be unclean unto you among the creeping things that creep upon the earth; the weasel, and the mouse, and the tortoise after his kind, Leviticus 11:29 (KJV)