So to win this game, establish authority, and also acquire a useful skill for other purposes, fixing the biter is simply a matter of backing the horse up. In this video below, you will see me teaching a horse to back up. He already knows the skill pretty well and so does not need a lot of reinforcement. However, the principles are the same for a horse that has never learned it, and can be applied universally.
The cue to back up in this case is a simple lifting, and shaking of the lead rope. The motivation to back up is more vigorous shaking or tapping the lead rope with a dressage whip. The following are key elements to remember:
1. Leave a lot of slack in the rope so that you can shake it.
2. Raise the rope BEFORE shaking. Shake the rope BEFORE tapping with the whip.
3. If the Horse so much as moves a single foot back, Stop all movement and drop your hand. If you want three steps ask three times.
4. Do not allow your horse to come back to you without an invitation. Make him stand apart from you until you are ready to invite him back.
5. If he is not learning this skill within about 5 minutes, then something is not right and you should contact me for troubleshooting.