There is a progressive set of behaviors in horses in which lipping behavior (when the horse puts his lips on you and nuzzles) leads to nipping (a small quick pinch with the teeth) leads to biting. These are all progressive signs of dominance leading to aggression.
If the lipping behavior goes unchecked, the horse begins to nip and if the nipping goes unchecked, he begins to bite. As the horse goes through this progressive behavior, he is simply testing his boundaries to see if he can gain dominance over you. It sounds like your colt is still in the nipping stage and you need to "nip it in the bud" so to speak.
It has been my experience that people bring these behaviors on themselves by allowing horses to be in their space and by nuzzling, smooching and playing with the horseís muzzle all the time. Another common action that leads to nipping/biting is when you hand feed treats to horses. In the herd setting, there is a "linear hierarchy" which means that each and every individual of the herd is either dominant over or subordinate to each and every other individual. This means that between you and your horse, one of you will be the dominant leader and one of you will be the subordinate follower.
It sounds like you haven't quite got this settled between you and your horse yet. If you were dominant in his mind, he would not dare move into your space or put his lips or teeth on you.
Horses establish dominance in the herd by controlling the resources of the herd (food and water) and by controlling the space of the subordinate members (running them off, pushing them around). If you allow your horse to move into your space at all, it confuses the dominant-subordinate relationship. Horses are much more aware of spatial issues than humans are. When we get horses in training here at my barn, whether youngsters or older horses, one of the first rules of behavior they will learn is to never move into our space with any part of their body, including the nose. Most people constantly allow their horses to move into their space especially with its nose. In fact, it is often encouraged by feeding treats or by playing with the horse's nose. All of these actions confuse the horse and make him think he is dominant.
For your colt, you need to establish a more respectful distance between you and him. Do not stand close to his face or pet him on the face and do not allow him to move his nose toward you at all while you are working around him. Every time he moves his nose toward you, correct it by poking a finger in his cheek or just pointing at his nose until he puts it back in its proper place, in front of his chest. If you establish this basic rule (your nose must stay in front of your chest at all times that I am working around you) and you correct him 100% of the time he makes an infraction, he will learn this important ground manner quickly. Also, any time any other part of his body moves toward you, vigorously back him out of your space. This will help him to learn a respectful distance and to be respectful of your space as the dominant herd member.
When the colt reaches out to nip or bite, you should instantly poke him with a pointed finger or back him aggresively out of your space. This correction must come instantly without any pause at all on your part. The optimal time for a correction is one-half second after the behavior, in order for a strong association between the behavior and the correction to be made by the horse. There is a 3 second window of opportunity within which to reward or correct a horse, but the sooner in that 3 seconds the correction or reward occurs, the more meaningful it is to the horse, and the optimal time is one half second.
Your colt already knows that he is doing something wrong, that is why he is backing up after he nips. If you feel you cannot poke him in a timely fashion, go ahead and jerk on the lead rope and back him up vigorously for a far stretch and yell or growl at him like you are angry.
John Lyons has an interesting theory about correcting horses that bite. He says that you should pick up whatever is handy and act like you are going to kill the horse with it, but only for three seconds. Of course, he would never actually advocate beating the horse with something, but by the time you have picked it up, swung it over your head and lunged at the horse, at least 3 seconds has gone by so you would never actually have time to hit the horse. This puts the "fear of god" into the horse and makes him very leery of putting his mouth on you again (donít ever try something like this with a tied horse because it will lead to a pull-back problem).
If you are leery of poking the horse in the cheek, then you can give him a pinch on his neck, to simulate the alpha horse biting him. Take your thumb and index finger and give him a hard squeeze at the base of his neck muscle. Wrap your fingers around several inches of the big strapping muscle that defines the bottom line of his neck and then give a quick sharp squeeze. This will give him quite a shock and simulates biting. It gives him a taste of his own medicine, so to speak.
One more time, I want to reinforce the fact that as likely as not, the human is the one that has made the horse nippy by crowding his space, playing with his mouth, feeding treats and allowing the horse to push him around. So make sure that you correct your behavior too, if necessary, so as not to encourage the horse to be disrespectful.
Clinician and Trainer
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