Mountain lions and black bears are among the more common enemies of horses. The large size of horses makes them less appealing to other predators, and they rely on their running speed and herding mentality to flee from danger. Predators typically seek out sick or wounded horses in the herd.
Despite the close relationship between humans and horses, some people also consider humans an enemy to the horse. Development of land and the destruction of natural habitats contribute to limitations on the size of horse populations. The use of horses in war and sport racing contributes to shortened lives for many horses.