Horses are herd animals. How well do they tolerate a lack of other horse companionship. I know some other herd animals easily bond with other species including humans. Some don't though and are completely miserable unless the owners spend a great deal of time filling that gap so to speak and even then it can be inadequate.

Sometimes it depends on the actual horse and how they have been raised and trained. I've only come across a couple horses that were so bonded to their companions that they couldn't be left alone. Its normally not a problem unless they've been kept with only one other horse for long periods and allowed to act up when separated.

That's why I always make sure to have a companion animal in the pasture with them. They seem happier with a friend. Also, I find a lot of people have two horses for that reasin.

My horse now had 5 other horses she ran with. At first she was very lonely but then she made friends with the goat we have. It is like they are family, they follow each other around all day long.

My old horse, Jenny, was like that. She HAD to have a buddy. When we were keeping her on our own land, she was our only large animal. She was acting up quite a lot until she befriended one of our cats, who I think she believed was her baby!