The lifestyle of the gorilla

Gorillas live in family groups of 2 to 20 for Western gorillas but larger groups, up to 35 for Eastern gorillas (including Mountain gorillas), consisting of a single mature male and several females with their young. Other males usually wander alone, sometimes joining a group for a while. They have no defended territory and groups of gorillas which live within the same area co-exist peacefully, sometimes mingling for a while or simply ignoring one another. Aggression in gorillas is extremely rare and serious fights occur only when a group leader meets another group leader.

They are very social animals and communication between them is important involving a variety of grunts, howls, hoots and barks. There are nearly twenty different vocalisations, each having a different meaning. Gorillas also communicate by beating on their chests, or on the ground. For the silverback male (so called because they develop light grey hair on their back at about 11-13 years of age), chestbeating is a show of power, designed to intimidate. They are also very intelligent and show a full range of emotions including love, hate, grief, fear, joy, pride, shame and jealousy and even laughter.

Gorillas may live for thirty-five to forty years, reaching sexual maturity between the ages of eight and eleven. Females begin breeding at about 10 years of age, but males do not breed until they are at least 15 years old since he usually leaves his parental group when his "silver back" begins developing at twelve or thirteen, to wander alone, or with other males, for a few years before managing to attract females from other groups to join him, thus forming his own family. The gestation period is about 8.5 months, and usually only a single young is born weighing 1.8-3.2 kg, about half the normal weight of a human baby. However, the baby gorilla develops twice as fast as its human counterpart crawling at about nine weeks and walking from 30-40 weeks. Females successfully produce offspring which survive to maturity only once every four to eight years, since 40-60% of gorillas die in their first year of life.