http://www.abdn.ac.uk/bestiary/translat/11r.hti
"Of the beaver There is an animal called the beaver, which is extremely gentle; its testicles are highly suitable for medicine. Physiologus says of it that, when it (The Beaver) 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."
Nuff Said...
The beaver in the photo had been trapped when the tree it was attempting to fall landed on it's foot, pinning it to the ground. The photographer was able to release it, and it swam away shortly thereafter... without even saying thank you!
Why doesn't that surprise me?
(USA Today Sports)