My gelding has been acting like a stud since I brought two mares home... He has been nipping at their knees and flanks and even mating them... The other day I brought a paint gelding home and then put them together today. He won't let him near the mares and was chasing him around the pasture for awhile. So I separated my paint from him. He used to be best buddies with my 25 year old gelding that recently passed away, but that was before I bought my 2 other mares. Any advice is appreciated.