The Gorilla is a highly social primate and lives in a relatively stable, cohesive group, which is held together by long-term bonds between adult males and females. 61% of groups are composed of one adult male and a number of females and 36% contain more than one adult male.
The remaining Gorillas are either lone males or exclusively male groups, usually made up of one mature male and a few younger males. Group sizes vary from five to thirty, with an average of ten individuals. A typical group contains: one dominant silverback, who is the group’s undisputed leader; another subordinate silverback (usually a younger brother, half-brother, or even an adult son of the dominant silverback); one or two blackbacks, who act as sentries; three to four sexually mature females, who are ordinarily bonded to the dominant silverback for life; and from three to six juveniles and infants.
Most males, and about 60% of females, leave their natal group. Males leave when they are about 11 years old, and often the separation process is slow: they spend more and more time on the edge of the group until they leave altogether. They may travel alone or with an all-male group for 2–5 years before they can attract females to join them and form a new group. Females typically emigrate when they are about 8 years old, either transferring directly to an established group or beginning a new one with a lone male.
Females often transfer to a new group several times before they settle down with a certain silverback male.
Gorillas use a wide range of facial expressions, body gestures and sounds to communicate. They are active by day feeding on fruits, leaves, shoots, stems, seeds, soft bark and some small creatures such as grubs and termites. Living in stable social groups of 3 – 20 with a dominant male (silverback), at night they bend tree twigs and branches to form a sleeping NEST.
Strong and powerful, with no natural predators, these magnificent, peaceful, primarily vegan, animals are threatened by the slash-and-burn clearance of their habitat, illegal hunting for the bushmeat trade, and trophy poaching. This has resulted in gorillas becoming a critically endangered species. Reintroduction of captive-bred individuals (from zoos and parks) into the wild are rarely attempted, partly due to the gorilla’s complex, close-knit social life; but some excellent work has been done by the UK based Aspinall Foundation in this respect. Nevertheless, government protection and habitat conservation must remain a long-term priority if they are to survive.