I'm not sure. It looks like he's trying to get out in front of the horse. The general rule is not to approach the animals closer than 50 feet, but sometimes the horses move closer to you. Depending on the situation you may or may not be able to back away easily. I've had them wander in from all directions making it difficult to back-off from one without moving too close to another. You do have to try to be a bit extra careful this year. There were a lot of incidents with tourist types trying to feed, pet, ride etc. the horses so the park service is being perhaps a bit overzealous in issuing tickets at the moment.