Gorillas produce more than 15 recognized vocalizations. Some sounds are used mainly for group communication because gorillas are nearly invisible to each other while feeding and traveling in the vegetation. Deep belches are common during feeding and suggest contentment. Primate researcher Dian Fossey, trained observers in the field to mimic this sound when approaching feeding bands. Silverbacks vocalize the most.
Infants whine, cry, and chuckle.
B. Visual communication. The ritualized charge display is unique to gorillas and includes demonstrative body language. Other aggressive behaviors are stares, head jerks, lunges, grabbing, and biting.