The gorilla is shy and retiring rather than ferocious and treacherous. It usually seeks no trouble unless harassed but will valiantly defend its family group if threatened. Family groups are close-knit and may have up to 30 members, but even if smaller, the group usually consists of at least one older male, one or more females and a few juveniles. Gorillas have strong attachments to members of their own group and even when groups meet and mingle and then subsequently part, each animal tends to remain with its respective unit. An adult male called a silverback named for the silvery gray hairs on its back normally leads each group, serving as its chief protector and defender. Gorillas continually wander through their home ranges of 10 to 15 square miles, feeding and resting throughout the day. Because gorillas are nomadic, they build new nests each day at dusk, constructing them of bent branches in a tree or of grasses on the ground.
A group’s hierarchy, ritualized behavior and bluff charges between males prevents conflict among and between groups. Gorillas scream, grab foliage and stuff it in their mouths, stand erect on their hind legs, tear up and throw plants, drum on the chest with hands or fists, stamp their feet, strike the ground with the palms of their hands and gallop in a mock attack on all fours.