Fantastically Wrong: Why People Used to Think Beavers Bit Off Their Own Testicles
“Ah, the thrill of the hunt. The trusty hounds at your side, howling and panting and dragging you toward your quarry: a lumbering beaver not accustomed to moving on land. You close in. You raise your spear. The beaver suddenly stops, looks over its shoulder at you, and lifts a back leg. It bears its teeth, stares you right in the eye, and proceeds to chew off its own testicles. Then it throws them at you.
Perhaps a bit taken aback by this gesture, you let it scurry away sans gonads, because a medieval hunter like you is only after the precious oil, known as castoreum, those organs bear. The beaver has quite cleverly just saved its own life.
Or at least according to any number of medieval bestiaries, often gorgeously illustrated tomes that cataloged nature’s critters—the real, the totally imagined, or the slightly embellished.”