Scientific Name: Gorilla gorilla gorilla
An adult male gorilla, aged 10 to 12 years, begins to develop silver hair on his back, signaling his maturation and strength.
Gorillas are the strongest and largest of the great apes, a primate group that also includes chimpanzees, bonobos, and orangutans. The western lowland gorilla is a subspecies of western gorilla (Gorilla gorilla). All gorillas in U.S. zoos are western lowland gorillas.
STATUS: The western lowland gorilla is classified as critically endangered due to exceptionally high levels of hunting and disease (primarily Ebola), which combined are estimated to have caused its population to decline by more than 60 percent in the last 20 to 25 years.
HABITAT: Western lowland gorillas live in lowlands and swamp forests of subtropical and tropical Africa in Cameroon, Central African Republic, Equatorial Guinea, the Democratic Republic of the Congo, Gabon, and Angola (Cabinda).
DIET: Gorillas are herbivores, eating various parts of plants including leaves, bark, vines, and stalks. They enjoy bamboo, thistles, and wild celery. Lowland gorillas also eat fruit.
PHYSICAL CHARACTERISTICS: Males are twice as large as females, often weighing over 350 pounds, and have longer canine teeth. On two feet they may stand up to six feet tall. Because their substantial weight is not well-supported by branches, gorillas travel on the ground rather than swinging from tree to tree. They typically walk on all fours with hind feet plantigrade (in which the entire sole of the foot is planted on the ground), similar to bears, and supporting their weight on the backs of their fingers’ mid-sections. This is called “knuckle-walking,” and gorillas possess knuckle pads to protect their hands. Like other apes, gorillas’ thumbs and big toes are opposable, so they can manipulate food and other objects easily. They have large teeth and jaws for eating tough vegetation, and have developed strong jaw and neck muscles. Gorilla lifespan in the wild is unknown. However, in captivity, one gorilla lived 53 years.
Being in the “Band”
Gorilla group structure is well-established. A silverback male leads his “band” of several females with infants, younger males, and juveniles. Mature females leave their natal groups for other bands or single silverbacks. Juvenile males may live alone until they meet females and form their own bands. Within the band, gorillas are usually calm and quiet. However, rival males can display aggressively when bands meet. Males may express agitation or excitement by beating their chests.
Females typically give birth to one infant after a gestation period of nine to ten months. At three months, the infant rides on mom’s back; at six to seven months it walks and climbs independently.
During the day, band members forage for food. Each night, they sleep in either new nests built on the ground (larger males) or in trees (juveniles and lighter females). Wild gorillas have been observed to use rocks and sticks as rudimentary tools.