The gestation period for a baby gorilla is about 250-285 days. The huge silverback is a patient father who takes care of the baby while the mother forages for food. Gorillas form small, non-territorial harems usually dominated by a single, mature male. There is no defense of the home range and the ranges of neighboring groups overlap. The groups tend to avoid each other.
Mutual evasion is accomplished by frequent calls from dominant males.
On rare occasions of encounters, the dominant males display chest beating, charging, and plant beating. Sometimes these incidences culminate in fighting. The same displays are used to greet humans, predators, and herbivores such as bushpigs. In contrast, the females are usually docile in nature. In the Spring of 2000, primatologists reclassified gorillas into two species and five subspecies.