Western lowland gorillas use a wide variety of methods to communicate. Their vocal repertoire includes at least 17 vocalizations, which can be divided into two categories: short- and long-distance calls. 

Short-distance calls are used for within-troop communication in close quarters and include calls produced in specific contexts. Examples include cough grunts signifying aggression, copulatory pants when mating, rumbling belches when content, whoop barks when curious, sharp grunts when disciplining youngsters, and chuckles when playing. Close calls can also involve multiple calls used in sequence in many contexts, including whinnies, grunts, grumbles, and variations of these sounds. Short-distance calls represent the majority of the western lowland gorilla vocal repertoire for all age-sex classes. Among those, grunts and grumbles together constitute more than 80% of adult vocalizations and are emitted during many activities. 

Long calls, meanwhile, are used in communication between males of different troops, and in some cases, within-troop communication. They are composed of a series of hoots with or without chest beats, screams, roars, “wraaghs”, and barks. Roars, barks, and “wraaghs” may signify aggression, fear, or mild alarm calls. Most long calls are used only by males during encounters between different gorilla troops. Excluding screams, commonly emitted by females and juveniles during internal fights or sudden danger, the only long-range call type used by both sexes in western lowland gorillas is the series of hoots. Ongoing and future research will eventually determine the context and function of hoots and other gorilla calls. Finally, infants use three distress calls, similar to the cries of human babies. Mom immediately responds upon hearing these.

Now, that was A LOT regarding vocalizations, but there’s still more!

The famous chest beats of gorillas, while predominantly performed by males, aren’t limited to them. Females will chest-beat infrequently and will more typically beat their hands against the insides of their thighs. Chest-beating can also indicate playful behavior, especially in juveniles. Young gorillas engage in play much like human children do, playing tag and doing somersaults.

A silverback protecting his troop may attempt to intimidate his aggressor by standing tall and slapping his chest with cupped or flat hands. That’s right – despite what is popularly depicted, gorillas do NOT beat their fists against their chest. If this elaborate display is unsuccessful and the intruder persists, the silverback may rear back his head several times.

He may also drop on all fours and charge toward the intruder. Generally, the intent is not to hit the intruder. Instead, he merely rushes past the intruder, turns, and rushes again until the rival gives up. This display of aggression maintains order among separate troops and reduces the possibility of injury. It is thought that size plays an important role in determining the outcome of these interactions, with the larger male typically winning.

Gorillas also interact using grooming behaviors, although less than most other primates. Associating with one another may also be shown through simple physical proximity. Young gorillas play often, and are more arboreal than the large adults. Adults, even the silverback, tolerate infant play behavior. The silverback also tolerates and often participates in the play of older juveniles and blackback males. The secretive nature and sheer variability of gorillas as a whole prevent scientists from fully understanding these behaviors. 

Finally, silverbacks also have a distinctive odor that they use to communicate with other troops and to maintain contact with their own troop.