Predation is considered one of the most important selective pressures on animals. Evidence of predation on primates is particularly rare; however, it is thought that it has been a major selective force for many species in the primate order. This can be seen through the occurrence and application of vigilance and alarm calling in many primate species. Studies of vigilance have shown that animals have a tendency to decrease individual vigilance as group size increases. However, it has been found that primates do not fit this model, and either maintain or increase their individual vigilance as group size increases. A likely reason for the maintenance of individual vigilance is that primates utilise this behaviour as both a form of antipredation behaviour and social monitoring; thus it largely depends on the social structure of the species and the environmental conditions of the ecosystem being occupied by a primate group. Another antipredator behaviour that occurs in primates is alarm calling, which may be to deter predators. The studies presented here show that primates have the ability to distinguish between predators, between and within predator classes and also predator hunting styles. It is believed that the development of these behaviours in the primate order shows that these animals have evolved in environments where predation is a threat.