Almost the last word.

David Marlin Equine exercise physiologist, Cambridge, UK Horses are herd animals. When a horse finds itself surrounded by other horses all intent on running in one direction, its simple instinct is to respond to the "danger" pursuing them and to strive not to be that final doomed straggler. "Wild horses are herd animals whose main defence against attack by predators is to run. [Extracted from the article]