SOCIAL PLAY. This “conga line” is typical of the games young gorillas create to amuse themselves.
of its opponent with a stiff-legged, exaggerated gait. It holds its upper body erect, keeps its arms bowed out at the elbows, and tilts its head to one side, averting its eyes and glancing up only occasionally. As the aggressive mood develops, the gorilla may push forward the corners of its mouth and retract its lips to display its toothy arsenal in the aggressive bared-teeth threat.
The chest beating for which gorillas are known occurs in many different contexts, including play, sexual excitement, frustration, and alarm at the sight of intruders (including zoogoers). It is often part of a longer display (see the three charges described below), but it can also occur all by itself. The loud pockpock sound that you hear occurs because the gorilla cups its hands as it beats, trapping air against the naked skin of its chest. A dilated sac in the larynx acts as a resonator. Females may thump their thighs instead of their chest.
When used in a threat situation, chest beating is a brandishing of the fist, so to speak; it allows the gorilla to advertise his or her strength and size while avoiding an actual attack. Within groups, the dominant male may use chest beating to rally the troops to move on, to get the female’s attention, or to stop squabbles that arise among members. The display sometimes spreads contagiously throughout the group, as if members are communicating their positions to one another. In a wild population, chest beating may help to space groups apart so they don’t compete for food sources.
THREAT CHARGES If gestures alone don’t do the trick, the gorilla may resort to one of three threat charges: the diagonal bluff charge, the rush charge, or the slam charge. The gorilla begins all three from a standing position or from a stiff, elbows-out, four-legged stance. Listen for a soft hooting, which gets faster and less distinct toward the peak of the display. During the display, the gorilla may kick out one leg, roar, throw a handful of vegetation or rocks into the air, or beat its chest. In the diagonal charge, the gorilla runs sideways on two or four legs past the adversary for up to 66 feet. In the rush charge, the gorilla rushes directly toward the adversary, stopping just short of a collision. In the slam charge, the most intense of the displays, the gorilla makes contact, shouldering the adversary or slamming an exhibit wall as it charges by.
CHEST BEATING. A gorilla cups its hand against its chest to make a loud pockpock sound when alarmed, excited, frustrated, or angry.
STRUTTING WALK. To remind other gorillas of his dominance, the silverback stands and strides in a stiff, exaggerated gait.
FIGHTING Typically, the only contact occurring during threat displays is the shouldering or smacking during the charge sequence. All-out fights between gorillas are extremely rare, usually occurring only between resident males and their male challengers. You know a fight is in the making when both parties are displaying their teeth, screaming, and roaring in fury.
SUBMISSION AND FEAR Gorillas that want to keep out of this kind of trouble have a variety of humble-pie displays. To show submission to a dominant, a gorilla will cower on the ground with its abdomen protected and only its broad back exposed. Sometimes it may use its arms to cover its head.
When a gorilla wants to interact, but is uncertain, it folds its lips in against its teeth and averts its gaze. This lip tucking is an expression similar to human lip biting. Another telltale mark of nervousness is repeated yawning.
Gorillas use several sounds to express alarm or outright terror. The question bark (sounds like “who are you?” because the middle note is higher) and the aptly named hiccup are signs of mild alarm or curiosity, often heard in response to a sharp sound in the distance. A really fearful troop of gorillas will fall absolutely silent, as if paralyzed with listening. When faced with extreme danger, a gorilla may also open its mouth wide, throw back its head, and scream.
Another form of alarm is not as shrill as a scream or deep as a roar but sounds like its name—wraagh. Listen for this abrupt outburst at the zoo when a sudden noise surprises the gorillas.
SEXUAL BEHAVIOR
Another myth about gorillas is their insatiable sexual appetite, often the subject of grisly tales about women being dragged away from jungle camps by lustful beasts. In reality, male gorillas have rather lackluster libidos, probably because they have no need to woo or fight for females that are already securely bonded with them. In fact, females often wind up playing the role of initiator, soliciting the male when they are receptive. Once females are pregnant, they become even more sexually active than when they are in estrus, but not with the silverback.
Gentle, leisurely homosexual pairings (among females) may occur, along with masturbation and dalliances with the younger males in the group. The silverback tolerates these extracurricular activities as long as the offspring of the pregnant females are sure to be his.
PRESENTATION. The friskier female gorilla blatantly solicits the male’s sexual attentions.