The beaver and renunciation: an ancient legend turned sermon
Why in the bestiaries the beaver mutilates itself to escape hunters: from Aesop and Pliny to Isidore, and on to the moral lesson about shedding vices.
Few images in the bestiaries are as stark as that of the beaver pursued by hunters. In the miniatures it is shown turning towards the armed man and carrying out a drastic act, which the text describes without any reticence. The story, much older than Christianity, was taken into the bestiaries because it lent itself to an effective moral lesson that was easy to remember, and its long life says a great deal about how the Middle Ages handled the reports it received from the ancients.
A belief of the ancient world
The legend springs from a real product. Castoreum, a strong-smelling substance secreted by the animal, was much sought after in antiquity and used in pharmacy and perfumery. It was wrongly believed to come from the beaver’s testicles, and from this the story developed: knowing it was hunted for that part of its body, the animal would bite it off and throw it to the hunter, thereby saving its life.
The story appears in a fable attributed to Aesop, is reported by Pliny the Elder and even finds a place in Latin satire: Juvenal, in his twelfth satire, compares a merchant throwing his cargo overboard during a storm to the beaver that sacrifices part of itself to survive. Isidore of Seville, finally, drew from it an etymology destined for a long career: castor would be so called a castrando.
The lesson of the Physiologus
The Physiologus and the bestiaries add a detail. If the beaver, already mutilated, is chased a second time by another hunter, it rises on its hind legs and shows that it no longer has what the man is after, and the hunter lets it go. At this point comes the interpretation. The hunter is the devil, and what he desires are the vices of man: lust, greed, pride, the works of the flesh.
Whoever wishes to live chastely and escape the enemy must therefore cut those vices away and throw them to the devil, who will then have nothing left to claim. The moral is severe but clear, perfectly suited to sermons on penance and renunciation. It is not a literal invitation to mutilation: the animal’s act is a figure, as always in the bestiaries, of the inner detachment from sin.
What we know today
Modern zoology has cleared up the misunderstanding. Castoreum is produced by specific glands, distinct from the reproductive organs, and in beavers these glands are not even visible from outside. The animal, of course, does nothing like the act described in the legend. Some ancient authors had already voiced doubts about the story, but the prestige of the sources and the force of the moral example kept it alive for centuries.
In the bestiaries the chapter on the beaver is often accompanied by a lively miniature, with the hunter, the dogs and the animal caught at the moment of sacrifice. Other details complete its portrait, such as its skill in building dams and lodges along rivers, which medieval readers admired without necessarily giving it a spiritual meaning.
The beaver’s story shows the method of the bestiaries with particular clarity: a mistaken report, born from a real trade and handed down by classical authors, is accepted as fact and turned into teaching. What mattered was not natural truth, but the image’s power to stick in the mind and to guide conduct.