One word - hormones. The high male hormonal level of studs drives them to be more naturally dominant, especially, when a mare in heat comes in sight. That also adds short attention span to any external circumstances (human interaction, for example) and often high sensitivity. Their behavior is not neccesarily aggressive - it's just very dominant, and a dominant horse needs a really high motivation to listen to a human - thus, the handler needs to be experienced in horse psychology and body language to treat a stud successfully.
A well mannered, calm stud is a pleasure to work with, though - just not for anyone. If a hore owner is not a professional breeder, one doesn't really need a stud. Also, many myths about the crazy studs come from the tendency to keep them stalled or seperately paddocked away from other horses since early age - such studs don't get to learn normal horsey social interactions and often don't get enough movements, so are more prone to being high strung, inadequate and dangerous. I used to work in a barn where most of the studs were turned out with small groups of geldings daily - they were perfectly calm and easy to handle guys.
I have come a long way, to surrender my shadow to the shadow of my horse.
Last edited by Saranda; 11-27-2012 at 01:56 AM.