Since I was little a lot of people said that the mares are the boss. (in a herd)
But I rarely see it. Of friends, family or just random peoples houses I've been to, the stud or (a) gelding is the 'boss' of the herd. Even my own. The girls are always the bottom of the pecking order.
Either the horses around here are weird.. Or that's not true. Kinda wondering where it came from, too.