We have a horse that we've had on trial for about a month and have an option to lease him for six months. He's a 16 hh, 10 year old, Appy/TB cross. He has experience in hunter equitation and has evented for the past three years. My daughter loves to ride him, but he is so mouthy! He bites and reaches out constantly. Eben when you try to bring him in from his turnout, he won't move and if you give him a tug he will bite. He has already bitten me and my daughter and several people at the barn.
Biting is one of those behaviors that some people think is trivial, but it can be truly dangerous. Although you haven't said whether the horse is nipping (pinching the skin with his teeth) or really biting (breaking the skin, leaving sizable bruises, etc.), biting often starts as nipping and can then escalate.
Nipping often starts in young horses who are exploring the world with their mouth. It seems to be more common in colts, especially those who are not yet gelded, but fillies may also nip. Some people ignore the behavior, thinking it'll go away on its own. Others even think it is cute when a young horse nibbles their shirt, hair or skin and pet them, talk to them, or otherwise give them positive attention when they do it. This encourages the horse to continue nibbling and then the owner or handler is surprised when one day the horse bites them, breaking the skin. The horse is surprised when the human yells or scolds them. In his mind, he was just doing what he had been encouraged to do in the past.
In my barn, if a horse nibbles or nips, he is immediately reprimanded. If he's wearing a halter and leadrope, the reprimand is normally a loud NO followed by a jerk on the leadrope or making the horse back up. If the horse is loose, I give a loud no and walk away and ignore the horse. If the horse repeats the behavior, I will smack him or hit him in the chest, neck or shoulder in additional to giving a loud NO.
Some people think it is cruel to smack or hit a horse. I do not advocate hitting a horse with a whip or other "tool/implement", repeatedly hitting a horse, hitting a horse for no reason, punching a horse or hitting a horse in the head. However a firm smack or hit on the neck, shoulder, or chest is similar to the punishment horses give each other for inappropriate behavior. Watch a mare with her older foal or a group of horses in the pasture: if the foal bites his mother, his mother may bite him back, gently push him with her hoof or even kick. If a grown horse bites or nips at another, the punishment is often more stern: a hard bite or kick from the horse who was bitten. A single smack from a human is a pretty mild punishment compared to a strong bite or kick from another horse.
If a horse in my barn bites, he is immediately reprimanded with a loud no and either a smack/hit to the chest, neck or shoulder. I'll follow that up by backing him out of my space. Since bites can do a lot of damage, I make sure to make it very clear that biting is not an acceptable behavior.
If you discipline a horse this way, you need to keep a few things in mind:
- The punishment must be immediate. If the horse was loose and runs away, you cannot chase him down, catch him and then smack him. By the time you've done that, he doesn't understand what the smack is. Likewise, you can't walk off, grab a whip, and smack him with the whip because by the time you get back and smack him with a whip, too much time has passed and he's not making the connection between biting and getting smacked.
- If the horse is loose, smacking or hitting him may not be safe as he may whirl around and kick you. If he is loose, then make a loud noise, shoo him away and then walk away and ignore him.
- Learn the signs that your horse is about to bite (pinned ears, swishing tail, tightness in his mouth) and move away from him when he displays those signs. Don't give him a chance to bite.
- Rarely, disciplining a horse for biting makes him more aggressive. If your horse reacts this way, get professional help.
I've known some people who have carried a stiff bristle brush, a tack or a nail in their hands and when the horse goes to bite, the person thrusts the brush, nail or tack towards the horse so that the horse hits the sharp edge(s) with his muzzle. For some horses, after a few times of hitting the sharp edge when they go to bite, they decide that biting is painful and they stop.
Another thing to keep in mind: if you have a biter or nipper, do not hand-feed him/her treats. Some horses can eat hand-fed treats with no problems, but I've found that some horses become pushy, look for treats constantly, and bite your hands, clothing, arms, etc. while trying to find them.
You also mentioned that your horse is constantly reaching out towards you. Don't let him. Set a space around yourself that's your personal bubble. When your horse wants to intrude on that space, push him out with your hand or make him back up (if he's haltered). You need to be consistent - any time he invades your space even if only part of his body (like his muzzle) invades your space, make him get out. Don't give him that opportunity to get close to you and then bite.
When dealing with a horse who nips or bites, you must be consistent. Any time he nips or bites you (or even at you), you must discipline him. You can't ignore the biting sometimes because you are tired or it was cute or it was minor or he really didn't mean it. You must stay on top of this behavior if you want it to stop.
If your horse continues biting after you discipline him, then you'll need to seek professional help. And until you do, don't let your daughter handle the horse and consider putting a muzzle on him so he can't bite you (or anyone else).