Originally Posted by smrobs
There is really not much that you can do when they are in the pasture by themselves. It sounds like to me that he is either the lowest in the pecking order but has not yet learned his place or he annoys them to the point that they chase him off. Either way, I think it is best that you leave him where he is at because it sounds like the mares are trying to teach him some manners. He is still a kid, almost like a teenager, and it would be good for him to learn from some older horses how to properly behave in a herd environment. He will either learn how to act or he will continue to be reprimanded by them, either way is good for him IMO.
He's still a kid in your mares' eyes. The mares will put him in his place, and give him some manners too. You said, you've offered him toys to play with out there? Eventually he'll learn to stop pestering the girls, and go play with his toys. He's young, and he's going to act like that for a least a year or two more. Once he's older I bet he'll appreciate having a herd of mares, but for now he just has to tough it out.