The survival of horses depends upon sufficient time and safety to consume enough grass and the ability to detect a hunter in time to escape. In other words, man and dogs are looking for lunch while horses are intent upon not becoming lunch. Horses are rewarded by quiet, safety, and freedom from the hunter. Further, both man and dogs hunt in packs. They hide themselves from their prey.
Horses graze in view of each other.
They focus upon body language for communication. They must be quiet so as to not attract hunters. If one detects a hunter, he signals the herd and dashes to safety. The herd follows. Typically, it is a dominant member or leader of the herd who selects the grazing site and who watches for the hunter.