A beaver tale.

Two beaver skulls. The smaller one is the North American beaver (Castor canadensis) and the larger one the extinct giant beaver Castoroides ohioensis which also lived in North America, but during the Pleistocene the fossils being about 130,000 years old.

This is what Aberdeen University's Bestiary, written and illuminated in England around the year 1200 AD, has to say about the beaver.

Of the beaver. There is an animal called the beaver, which is extremely gentle; its testicles are are highly suitable for medicine. Physiologus says of it that, when it knows that a hunter is pursuing it, it bites off its testicles and throws them in the hunter's face and, taking flight, escapes. But if, once again, another hunter is in pursuit, the beaver rears up and displays its sexual organs. When the hunter sees that it lacks testicles, he leaves it alone. Thus every man who heeds God's commandment and wishes to live chastely should cut off all his vices and shameless acts, and cast them from him into the face of the devil. Then the devil, seeing that the man has nothing belonging to him, retires in disorder. That man, however, lives in God and is not taken by the devil, who says: 'I will pursue, I will overtake them...'(Exodus, 15:9) The name castor comes from castrando, 'castrate'. 


A different mediaeval bestiary in the  British Library collections contains a most graphic illumination showing the beaver biting off its bits and pieces.

Beavers really were hunted for their testicles and also for castoreum, a brownish, unctuous substance with a strong, musky, penetrating odour, contained in the anal sacs of male and female beavers,  for use in traditional medicine. Yupik medicine used dried beaver testicles like willow bark to relieve pain. Dried beaver testicles were also used as contraception. Beaver testicles were used as medicine in Iraq and Iran during the tenth to nineteenth century.The story of beavers chewing off their testicles to preserve themselves from hunters, probably came about because the beaver's testicles are hidden inside its body. European beavers (Castor fiber) were hunted to extinction in Britain, and to near extinction on the Continent because of the demand for castoreum, which was used as an analgesic, anti-inflammatory, and antipyretic. Castoreum was described in the 1911 British Pharmaceutical Codex for use in dysmenorrhea and hysterical conditions (i.e. pertaining to the womb), for raising blood pressure and increasing cardiac output. Castoreum is still used in perfume production and as a natural flavouring because it can be manipulated to taste like vanilla and strawberry.