So I have two really close friends with a similar problem... they both own mares that tend to be a little....hmmm.... scanky, shall we say (during their heat cycle) and both of their mares are stabled with geldings who are in denial about their "gelded" status and therefor feel the compulsive need to over compensate for what they are lacking by demonstrating, more than once or twice a day, just how much of a stud they are!!
We are talking about two separate barns in the same town... (must be somethin' in the water! Which would explain a little about the people too! ) One of the gelding was in a herd of 3 mares and 1 gelding and the other was with 3 mares and 3 geldings.)
So what is with these geldings gone wild!!??
Some say they act "studdy" because they were gelded late.
Others say it is because they were not gelding properly (completely).
Some claim that these horses are just plain ol' studdy for no good reason at all besides the fact that they are, (despite a lack of testicles) simple male.... Boys will be boys, and all that...
Both of these geldings ended up having to be separated from the general herd because they were mounting and (excuse me) actually entering the mares!!!
Both geldings tend to be studdy outside of the herd as well... they can be aggressive to handle, difficult, nippy, pushy, and hard headed. Both will drive off other geldings from "their" mares and one of them actually charged (but deeked at the last second) a person coming to get her mare from the field.
Unfortunately both geldings are owned by "newbies" (go figure!) and I fear that both of them do not appreciate that this kind of behavior, IMHO, is a big flashing DANGER sign!
I think that if a horse acts like a stud, it should be treated with the same extra care and caution that you would if he actually were a stallion.
What is your experience with geldings who act like studs?