Out of curiousity, I went and looked up "torture" on Wikipedia. I then scrolled through the different methods to see if there was any I'd never heard of (there were of course many).
I then happened upon one called "rat torture". This had several variations including putting people into pits with rats. Outcome is obvious.
Another involved placing rats in an upturned bowl on the prisoner's stomach, then heating up the bowl. The rats, in an effort to escape the heat, chew their way into the victim.

So it has to follow (to me anyway) that animals such as rats must have been used to mutilate/devour a male's penis. It just strikes me as obvious somehow.

I'm sure other animals have been used in this way as well, but I have never been able to find any reference to it.

Just commenting is all.

Rebecca