My stallion, in the one breeding we did while I had him, clamped on her neck and hung on... but not hard, we thought it was sortof sweet ;~D
I think most stallions have been so isolated since adulthood that their pasture manners are atrocious.... faced with the excitement of finally coming into contact with another horse in the pasture, especially a she-type-horse in heat, is just more than they'd know how to behave about. Hormone overload.
I've seen Rocky get hold of a mares neck, he's never left a mark tho. I've thought he did it more to help stay on:)...Poor guy is so short.
Becky