Postures, gestures, and facial expressions communicate many messages and emotions within a group.
 | When greeting a dominant individual after an absence or in response to an aggressive gesture, nervous subordinates may approach with submissive signals—crouching, presenting the rump, hold the hand out—accompanied by pant-grunts or squeaks. In response, the dominant individual is likely to make gestures of reassurance, such as touching, kissing, or embracing the subordinate. Friendly physical contact is crucial in maintaining good relationships among chimpanzees. For this reason, social grooming is probably the most important social behaviour, serving to sustain or improve friendships within the community and to calm nervous or tense individuals. The grin of fear seen in frightened chimpanzees may be similar to the nervous smiles given by humans when tense or in stressful situations. |
When angry, chimpanzees may stand upright, swagger, wave their arms, throw branches or rocks—all with bristling hair and screaming or with lips bunched in ferocious scowls. Male chimpanzees proclaim their dominance with spectacular charging displays during which they slap their hands, stamp with their feet, drag branches as they run, or hurl rocks. In doing so, they make themselves look as big and dangerous as they possibly can and indeed may eventually intimidate a higher-ranking individual without having to fight. | Watch chimp displays:  |