>Those searches miss images of a stallion's rear end where a mare also happens to be in the frame.
What do you mean, as itn a mare could still be in the picture or it will not have mares in picture? I clearly said stallion butt only, relating to your original post. The "-mare" tag would exclude all inages tagged with mares if you want stallion ass (fucking faggot), and the "solo" tag means there won't be any other character than the stallion himself.