Horses need companions. They are herd animals and feel safer if they have their own kind to live with. In the wild, horses live in small herds or bands. There are leaders and followers and each horse has a place on the social ladder within the herd. Horses that are kept with other horses are less bored and less likely to indulge in destructive habits like stall walking, wood chewing, and other abnormal repetitive behaviors. It's better physically and emotionally for your horse if he can be part of a herd, even if your horse spends part of its time in a stable. Owning other horses can be costly if you’ve only budgeted for one. Just owning two horses means twice the hay and feed costs, vaccination, vet, and farrier expenses, and taking care of multiple horses takes more time. But when you can't afford to buy another horse, want other animals and perhaps won’t have space for them all, or just don’t want another horse, what can you do? Here are a few ideas.
If you have space and time to take care of another horse, you can offer some sort of board. That way your pasture might make a little money to support your own horse while providing a buddy. Because not all horses get along with other horses, choose carefully if you are just boarding to provide your horse with companionship. Have boarders sign clear contracts and make sure everyone knows what the expectations are.
Look For a Free Companion Horse
A companion horse may be just what you need. Contact a horse rescue, search online horse classifieds, or ask around for a free companion horse. Many people are glad to find good homes for unsound or older horses that can't be ridden for some reason. This will solve two problems; give your horse company and provide a loving home for a horse that may be running out of options. Be aware that you may be getting a horse that needs extra care, so be sure you're able to look after a horse with special needs. Just because the initial price of a horse is low or zero doesn’t mean its upkeep will be free or cheap.
If you don't have the room for an average-sized horse, why not consider a miniature horse? Small but very personable, miniature horses can make excellent companions, with smaller upkeep demands.
Try to Find a Non-equine Friend
A companion for your horse doesn’t necessarily have to be another horse. A goat, donkey, alpaca/llama or some other four-legged creature (like a pot-bellied pig!) could be a buddy for your horse. Some horses are perfectly happy living with other livestock. Others can be a menace; it depends on the species and your horse's personality.
Behavioral Problems of Horses. Merck Manual Veterinary Manual.