The weasel is a dirty animal that must not be eaten. It conceives at the mouth and gives birth through the ear (though some say it is the other way around). If the birth takes place through the right ear, the offspring will be male; if it is through the left ear, a female will be born. There are two types of weasel; one lives in the woods and the other in houses. Weasels chase mice and snakes. The cleverness of weasels is shown by the way they move their young from place to place. They are also skilled in medicine and can revive their young if they are killed.

Pliny the Elder [1st century CE] (Natural History, Book 8, 33): A weasel's hole can be easily found because of the foulness of the ground around it. If a basilisk is thrown into a weasel's hole, the stench of the weasel will kill the basilisk, though the weasel will also die. (Book 8, 41): If a weasel is injured in a fight with mice while hunting them, it cures itself with the herb rue. Isidore of Seville [7th century CE] (Etymologies, Book 12, 3:3): The weasel (mustella) is called the "long mouse" from its length (telum). Weasels attack snakes and mice. There are two kinds of weasel: a large one that lives in the forest, and another that lives in the houses of men. Some say that the weasel conceives through the mouth and gives birth through the ear, but this, says Isidore, is false. Gerald of Wales [12th century CE] (The Journey Through Wales, book 1, chapter 12): In our time, a person residing at the castle of Penbroch, found a brood of young weasels concealed within a fleece in his dwelling house, which he carefully removed and hid. The mother, irritated at the loss of her young, which she had searched for in vain, went to a vessel of milk that had been set aside for the use of the master's son, and raising herself up, polluted it with her deadly poison; thus revenging, as it were, the loss of her young, by the destruction of the child. The man, observing what passed, carried the fleece back to its former place; when the weasel, agitated by maternal solicitude, between hope and fear, on finding again her young, began to testify her joy by her cries and actions, and returning quickly to the vessel, overthrew it; thus, in gratitude for the recovery of her own offspring, saving that of her host from danger. In another place, an animal of the same species had brought out her young into a plain for the enjoyment of the sun and air; when an insidious kite carried off one of them. Concealing herself with the remainder behind some shrubs, grief suggested to her a stratagem of exquisite revenge; she extended herself on a heap of earth, as if dead, within sight of the plunderer, and (as success always increases avidity) the bird immediately seized her and flew away, but soon fell down dead by the bite of the poisonous animal. (from the Everyman edition) Bartholomaeus Anglicus [13th century CE] (De proprietatibus rerum, book 18): But he [basilisk/cockatrice] is overcome of the weasel; and men bring the weasel to the cockatrice's den, where he lurketh and is hid. For the father and maker of everything left nothing without remedy. ... the weasel taketh and overcometh him, for the biting of the weasel is death to the cockatrice. And nevertheless the biting of the cockatrice is death to the weasel. And that is sooth, but if the weasel eat rue before. ( Steele edition of 1905)

