ABSTRACT
African apes differ from orangutans in having long, narrow heads, large brow ridges, flat foreheads, and dark hair. Gorillas are the largest primates and among the most sexually dimorphic. The descriptions of primate behavior are arranged under: ecology, sociality, life cycle, and cognition. Dependence on terrestrial herbaceous vegetation (THV) leads gorillas to favor open canopy forest with dense ground cover. Gorillas live in stable cohesive social units. Group members congregate near the leader, a silverback, during rest periods. Chest beating is a unique signal in which cupped hands are slapped against the chest in rapid alternation. Young females experience their first labial swellings, estrus behavior, and completed copulations. However, this is the time of adolescent sterility. Females reach adult size after age eight and usually give birth for the first time at ten years. Infanticide is much more common among mountain gorillas than western gorillas. Evidence is slowly accumulating that gorilla cognitive skills are greater than has long been assumed.
