I am not sure where to put this as there doesn't seem to be a "horse behaviour forum". Anyways, I have two geldings and a mare, all living together at home. For the last year, we just had my Arab gelding and the mare. In June, we brought our old friend Sam, a 20 year old gelding home. All three horses seem to get along very well. They eat together, scratch each other, etc. The last month or so, however, the geldings have developed this evening ritual of "sparring". They bite at each other, chase each other around, rear at each other and carry on for quite some time. There is no squealing and appears to be very minimal contact, but my Arab is getting more an more small nicks and bite marks all over his body. It doesn't appear that one horse consistently starts it, and there never appears to be a "winner". After about half an hour or an hour or so, they go back to munching grass side by side peacefully.
I will say that both of these geldings seem quite "attached" to me. The Arab is my horse, and my usual mount, so I have spent and do spend a lot of time with him. We became very close last year when I nursed him back to health after a serious injury. Sam is a horse I owned for many years and have always had a very strong connection with him. I just recently found him again after about a 4 year absence and he clearly remembers me. When I ride one, the other seems visibly jealous, following me around and even sometimes trying to knock me off the other horse.
So what is this behaviour about? Are they trying to establish who is dominant after being together for 3 months? Are they just being silly boys, fooling around for some fun and exercise? Are they trying to impress the mare? Are they jealous (or can they experience jealousy)?
Does anyone have any insights? Should I be concerned about the "sparring" escalating to full blown fighting?