In bullfighting, the movement of the matador's cape, and not the color, provokes a reaction in the bull.
It's true, bu I have being fucked by dog very roughly..
The penis is quite rigid when not erect, and becomes even more rigid during erection.
Protrusion is not affected much by erection, but more by relaxation of the retractor penis muscle and straightening of the sigmoid flexure.
A wild, young, unmarked bull is known as a micky in Australia.
In some countries, an incompletely castrated male is known also as a rig or ridgling.