I recently brought a horse to my trainer’s barn on a month trial. He is a 16 year old ISH gelding. He was previously stalled and turned out in small paddocks with one or two horses (geldings and mares) where he was reported to have no issues. Our barn has a large 10 acre pasture that a herd of 11 horses (five mares + six geldings) go out in 9am-5pm before being brought in at night and stalled.
The first five days on the property we turned him out in one of the smaller paddocks with a couple members of the herd to start slowly acclimating him. He was so relaxed and taking everything in stride. He could be brought in the barn by himself and worked without an issue. Then on day six we turned him out to pasture. The herd got a bit excited by his presence, but nothing out of the ordinary. My horse, however latched on to one mare in particular and became like velcro to her. He almost started acting studdish, which I know geldings can do. However, now he has become a nightmare to handle by himself when the herd is turned out. If he is taken away from his buddies, he whinnies, grunts, paces, constantly looks around for his friends, and loses all focus. If everyone is in their stalls he is not like this and can be brought out, tacked up, and ridden in the arena away from the barn without an issue. It is only when everyone is turned out that he gets so stressed.
This has been going on now for four days. I try to bring him out of the pasture for short periods to graze or lunge him until he settles and focuses on me instead of looking for the herd. Will this go away as he acclimates? I have not seen such sudden change in behavior in any of my previous horses. Part of me wonders if he is overwhelmed being in a herd of this size for the first time in his life. Should I try to keep separating him or maybe bring a horse friend along? Or should I just keep handling him only when everyone is in their stalls and leave him be to figure out the herd dynamic?