Gorilla
Gorillas owe their name to the voyage of a Carthaginian explorer who sailed around 500 BC, and nobody can say for certain what he saw. Hanno the Navigator led an expedition down the west African coast, toward the area that later became Sierra Leone. His party reported meeting "savage people, the greater part of whom were women, whose bodies were hairy, and whom our interpreters called Gorillae". It is unknown whether those beings were gorillas, another ape, monkeys, or even humans. Skins of the Gorillae women, brought home by Hanno, were reputed to have been kept at Carthage until Rome destroyed the city in 146 BC, 350 years later, at the end of the Punic Wars.
The animals that carry the name today live in the tropical forests of equatorial Africa, and they are the largest living primates. How big do they really grow? How close are they to us on the family tree? What holds a troop together, what do these apes know, and what stands between them and extinction?
A wild adult male gorilla weighs between 136 and 227 kilograms, while an adult female weighs between 68 and 113. Males stand 1.4 to 1.8 metres tall, and their arm spans stretch from 2.3 to 2.6 metres. Females are shorter, at 1.25 to 1.5 metres, with smaller spans. Averages depend on who does the weighing. In 1970 Colin Groves calculated a mean of 144 kilograms for 42 wild adult males. In 1997 Smith and Jungers found a mean of 169 kilograms across 19 wild adult males.
Silver hair reaching down to the hips gives adult males their name, silverbacks. The tallest wild gorilla on record was a silverback shot in Alimbongo, northern Kivu, in May 1938. He stood 1.95 metres, had an arm span of 2.7 metres and a chest of 1.98 metres, and weighed 219 kilograms. The heaviest wild gorilla on record was a silverback of 1.83 metres, shot in Ambam, Cameroon, who weighed 267 kilograms. In captivity, Gust was taken as a baby from Belgian Congo and spent his life at Antwerp Zoo. This western lowland gorilla reached 2.20 metres. Captive males can grow overweight, with weights up to 310 kilograms.
The eastern gorilla has darker fur than the western gorilla, and the mountain gorilla is the darkest of all, with the thickest hair. The western lowland gorilla can be brown or greyish, with a reddish forehead. Lowland gorillas are more slender and agile than their bulky mountain cousins. The eastern gorilla also has a longer face and a broader chest than the western one.
Like humans, gorillas have individual fingerprints. Their eyes are dark brown, each framed by a black ring around the iris. The lower jaw protrudes farther than the upper jaw, a trait called mandibular prognathism. Adult males also carry a prominent sagittal crest, a ridge of bone along the top of the skull.
A 2018 study at Bwindi Impenetrable National Park examined the hand posture of 77 mountain gorillas, about 8% of the population. Knuckle-walking turned up only 60% of the time. The apes also bore their weight on fists, on the backs of their hands and feet, and on flexed palms and soles. Scientists had previously linked that range of postures only to orangutans. Gorillas sometimes rise and walk upright for short distances, usually while carrying food or facing a threat.
A gorilla normally lives 35 to 40 years in the wild. Zoo gorillas may reach 50 or more in rare cases. The oldest male on record, Ozoum, lived to 61 years and 24 days. Gorilla blood adds one more oddity. It does not react to anti-A and anti-B antibodies, which would signal type O in a human. Novel sequences make it different enough that it fails to fit the human ABO system, which the other great apes do fit.
About 7 million years ago, a common ancestor gave rise to the three lines leading to gorillas, chimpanzees and humans. Gorillas are the next closest living relatives of humans after bonobos and chimpanzees. Human gene sequences differ by only 1.6% on average from the matching gorilla genes. The number of copies of each gene differs as well. Depending on what is counted, overall DNA similarity runs from 96 to 99%.
Kamilah, a female western lowland gorilla, supplied the DNA for the first gorilla genome. Researchers used short-read and Sanger sequencing. Only one great ape genus had been sequenced before the gorilla. Chimpanzees are the closest living relatives of humans, yet 15% of the human genome proved closer to the gorilla's. Another 30% of the gorilla genome is closer to human or chimpanzee than those two are to each other. This is rarer around coding genes, which suggests that selection acted widely during great ape evolution. Hearing genes also evolved rapidly in gorillas, which casts doubt on the idea that such change gave rise to human language.
SIVgor is a simian immunodeficiency virus that infects western lowland gorillas. It resembles a certain strain of HIV-1. For that reason, Gorilla gorilla gorilla is believed to be one of the zoonotic origins of HIV/AIDS.
For a long time, gorillas counted as a single species with three subspecies: the western lowland, the eastern lowland and the mountain gorilla. Scientists now agree on two species, the eastern gorilla and the western gorilla, each with two subspecies. During the Ice Age their forest habitats shrank and became isolated from one another. That isolation produced the separate species and subspecies. Population genetics suggest the western and eastern lowland populations diverged around 261 thousand years ago. Primatologists still explore how the populations relate. A third subspecies of Gorilla beringei has been proposed. It is the Bwindi population of the mountain gorilla, sometimes called the Bwindi gorilla, and it has no formal three-part name yet.
The Congo River and its tributaries separate the ranges of the two species. The western gorilla lives in west central Africa and the eastern gorilla in east central Africa. Mountain gorillas inhabit the Albertine Rift montane cloud forests of the Virunga Volcanoes. Eastern lowland gorillas live in the Democratic Republic of the Congo, near its border with Rwanda. Eastern gorillas as a whole occupy montane and submontane forests between 650 and 4000 metres above sea level. Western gorillas live from sea level up to 1600 metres, in swamp forests and montane forests. Cross River gorillas occupy low-lying and submontane forests between 150 and 1600 metres.
Mountain gorillas eat mostly leaves, stems, pith and shoots, and fruit is a very small part of their diet. Their food is so widely spread that neither individuals nor groups compete for it. On an average day they move 500 metres or less. Eastern lowland gorillas eat more varied diets that shift with the seasons. Fruit can make up as much as 25% of what they eat, and they favour ants when they take insects. Western lowland gorillas depend on fruit more than the others, and they travel 1105 metres per day on average. They also eat termites and ants, and in some areas they reach aquatic herbs.
A 2025 study challenged the picture of gorillas as strictly ground-dwelling apes. Gorillas at Bwindi and at Loango National Park spent more time climbing trees than those at Virunga. Much of their foraging in the trees went to leaves and other non-fruit foods, not to fruit. At Loango, close to half of the fruit eating still happened on the ground. In all three areas, adult females were more arboreal than males.
Gorillas rarely drink. The succulent plants they eat are almost half water, and morning dew adds more, though both mountain and lowland gorillas have been seen drinking.
One possible predator is the leopard, since gorilla remains have turned up in leopard scat. That may reflect scavenging. Gorillas and chimpanzees do not seem to compete directly where they overlap. When fruit is plentiful their diets converge, and when it is scarce gorillas turn to leafy vegetation. Chimpanzees and gorillas may ignore each other at a shared tree, and they have been documented forming social bonds. Coalitions of chimpanzees have also been seen attacking gorilla families, including silverbacks, and killing infants.
Every day a gorilla builds a new nest, usually about an hour before dusk, and it never reuses an old one even when staying put. Nests are simple piles of branches and leaves roughly 2 to 5 feet across, and each is built by one individual. Unlike chimpanzees or orangutans, gorillas tend to sleep on the ground. Young gorillas share their mothers' nests until they are three, then build their own nearby. Gorillas sleep an average of 12 hours a day, longer than humans. Researchers now treat great ape nest-building as an important instance of tool use, not merely animal architecture.
A troop of gorillas usually centres on one silverback, several adult females and their offspring, though multiple-male troops exist. A silverback is typically more than 12 years old, and maturity brings large canine teeth. He makes the decisions, settles disputes, sets the route, leads the group to feeding sites and answers for its safety. Blackbacks, subordinate males aged 8 to 12 who lack the silver hair, may serve as backup protection. When humans, leopards or rival gorillas attack, a silverback defends the group even at the cost of his own life.
Both males and females tend to leave the group they were born into. Among mountain gorillas, females leave more often than males, and both mountain and western lowland gorillas often move on to a second new group. Mature males usually leave to found their own troops by attracting departing females. Some male mountain gorillas stay in their birth troop under the silverback. If he dies, these males may become dominant or mate with the females, a pattern not seen in eastern lowland gorillas.
In a single-male troop, the silverback's death usually sends the females and their young off to find a new group. Infants without a protector are likely to fall victim to infanticide, and joining a new group is probably a defence against that. Female eastern lowland gorillas have been recorded staying together with their offspring until a new silverback transfers in, which likely protects them from leopards.
The bond between a silverback and his females forms the core of gorilla society. They keep it up by grooming and staying close. Females gain mating opportunities and protection from predators and from infanticidal outsider males. In multi-male groups, a female's tie to the silverback can give her dominance over other males, even though they are twice her size. Females related through their mothers tend to be friendly, while other females commonly treat one another aggressively within stable dominance hierarchies. Males in all-male groups usually get along, socialising through play, grooming and staying together. When two mountain gorilla groups meet, the two silverbacks can sometimes fight to the death, using their canines to open deep wounds.
Female gorillas mature at 10 to 12 years, and males at 11 to 13. A female's first ovulatory cycle comes at age six, followed by two years of adolescent infertility. The estrous cycle lasts 30 to 33 days, and the gestation period lasts 8.5 months. Female mountain gorillas first give birth at 10 and then wait four years between births. Gorillas mate year round. A female may purse her lips and approach a male slowly while holding eye contact, or slap the ground to win his attention. Males start courtship by displaying or touching, and by giving a "train grunt". Copulation typically lasts 1 to 2 minutes and can last as long as 20.
Mothers are the main caregivers of gorilla infants, and males take little part in direct care. For the first five months infants stay in contact with their mothers, who in turn stay near the silverback. Infants suckle at least once an hour and share their mothers' nests. By 12 months they range up to 5 metres away. At 18 to 21 months nursing slows to once every two hours, and by 30 months infants spend only half their time with their mothers. The juvenile period runs from the third year to the sixth, when weaning happens and the young sleep in their own nests. The silverback has a largely supportive relationship with the infants, shielding them from aggression and acting as a play partner. Play partners ease conflict over weaning. Once the young are weaned, females begin to ovulate and soon become pregnant again.
Researchers recognise 25 distinct gorilla vocalisations, many used mainly for group communication in dense vegetation. Grunts and barks are heard most often while the troop travels, and they reveal where each member is. They can also enforce discipline in social encounters. Screams and roars signal alarm or warning, and silverbacks produce them most often. Deep, rumbling belches suggest contentment and are the most common form of communication within a group.
Conflicts are mostly settled through displays meant to intimidate without any fighting, which is why real fights are uncommon. The ritualized charge display is unique to gorillas. It runs through nine steps: faster and faster hooting, symbolic feeding, rising on two legs, throwing vegetation, chest-beating with cupped hands, a one-leg kick, sideways running, slapping and tearing vegetation, and finally thumping the ground with the palms. The pitch of a chest-beat varies with body size, with smaller gorillas beating at higher frequencies. Chest-beating is most frequent when females are ready to mate.
Koko is one of a few captive gorillas taught a subset of sign language. Like the other great apes, gorillas can laugh, grieve and form strong family bonds. They also make and use tools and think about the past and future. Some researchers believe gorillas have spiritual feelings or religious sentiments. Different areas have developed distinct cultures around methods of food preparation, and individuals show colour preferences.
In September 2005, a team led by Thomas Breuer of the Wildlife Conservation Society reported tool use among wild gorillas. In Nouabalé-Ndoki National Park in the Republic of Congo, a female used a stick as though gauging water depth while crossing a swamp. A second female used a tree stump as a bridge, and also as a support while fishing in the swamp. Those sightings meant all the great apes were now known to use tools. That same month, a two-and-a-half-year-old gorilla in a game sanctuary in the Republic of Congo was found smashing open palm nuts with rocks. It was the first such observation for a gorilla, though chimpanzees had been seen fishing for termites with tools over 40 years earlier. Nonhuman great apes have semiprecision grips, and they can use simple tools and even improvise a club from a fallen branch.
In 1625, Andrew Battel described an animal he called Pongo. He wrote that it was like a man in proportion but "more like a Giant in stature". His report added that "Those Pongos are neuer taken aliue, because they are so strong, that ten men cannot hold one of them". A century and a half after Battel's story was published, a writer called Radermacher noted that many held the man-sized ape described by Buffon and others to be "a Chimera".
Thomas Staughton Savage, an American physician and missionary, obtained the first specimens, a skull and other bones, during his time in Liberia. In 1847 he and the naturalist Jeffries Wyman published the first scientific description in the Proceedings of the Boston Society of Natural History. They named the animal Troglodytes gorilla, borrowing the then-current name of the chimpanzee genus. We now know it as the western gorilla. Paul Du Chaillu became the first westerner to see a live gorilla, during travels through western equatorial Africa from 1856 to 1859. He brought dead specimens to the UK in 1861.
Carl Akeley of the American Museum of Natural History travelled to Africa in the 1920s to hunt an animal to be shot and stuffed. His party included the mystery writer Mary Bradley, her husband and their young daughter Alice, who later wrote science fiction as James Tiptree Jr. Mary Bradley wrote On the Gorilla Trail afterward and became an advocate for gorilla conservation. In the late 1920s and early 1930s, Robert Yerkes and his wife Ava furthered the study of gorillas by sending Harold Bigham to Africa. Yerkes also wrote a book in 1929 about the great apes.
After World War II, George Schaller was among the first researchers to study primates in the field. In 1959 he conducted a systematic study of wild mountain gorillas and published it. Dian Fossey, at the behest of Louis Leakey and the National Geographic, later carried out a much longer and more comprehensive study. Her work disproved many myths about gorillas, including the idea that they are violent.
Western zoos prized gorillas from the 19th century, but the earliest attempts to keep them ended in early deaths. Care improved significantly in the late 1920s. Colo of the Columbus Zoo and Aquarium, born on the 22nd of December 1956, was the first gorilla born in captivity. She died on the 17th of January 2017. Captive gorillas can show stereotypic behaviours, among them pacing, rocking, overgrooming and regurgitation. Bachelor groups containing young silverbacks show more aggression and wounding than groups of mixed ages and sexes.
Privacy screens on exhibit windows eased the stress of dense crowds and reduced stereotypic behaviour. Naturalistic sounds reduced stress behaviour, compared with classical music, rock music or no added sound. Scattering clover-hay on the exhibit floor lowered stereotypic activity and encouraged positive food-related behaviour. Recent research on welfare urges individual assessments instead of one approach for every group, because age, sex, personality and personal history change how each gorilla reacts to stress.
In Cameroon's Lebialem highlands, folk stories link people and gorillas through totems, and a gorilla's death means the connected person will die too. That belief creates a local conservation ethic. The Baka have words to distinguish at least ten types of gorilla individuals, by sex, age and relationships. In 1861, Paul Du Chaillu reported a Cameroonian story that a pregnant woman who sees a gorilla will give birth to one. In 1911, the anthropologist Albert Jenks noted the Bulu people's knowledge of gorilla behaviour and their stories, including "The Gorilla and the Child". The Fang name for gorilla is ngi, a root meaning fire and denoting positive energy, and the Bulu name is njamong.
Since the apes gained international attention, popular culture has usually cast them as aggressive. Emmanuel Frémiet's sculpture Gorilla Carrying off a Woman inspired a run of stories in which gorillas kidnap women, including the film Ingagi in 1930 and, most notably, King Kong in 1933. The comic play The Gorilla debuted in 1925 with an escaped gorilla carrying a woman out of her house. Gorilla Grodd is a DC Comics supervillain and an enemy of the Flash. More sympathetic portrayals include Son of Kong in 1933, Mighty Joe Young in 1949, Gorillas in the Mist in 1988 and the 1992 novel Ishmael.
Around 316,000 western gorillas are thought to live in the wild, against about 5,000 eastern gorillas. The IUCN classifies both species as Critically Endangered. All subspecies are Critically Endangered except the mountain gorilla, which is Endangered. In 2016, about 4,000 western lowland gorillas lived in zoos. The eastern lowland gorilla population was under 5,000 in the wild and 24 in zoos. Mountain gorillas are the most severely endangered, at an estimated 880 in the wild and none in zoos.
In 2004, Ebola essentially wiped out a population of several hundred gorillas in Odzala National Park, Republic of Congo. A 2006 study in Science concluded that more than 5,000 gorillas may have died in recent Ebola outbreaks in central Africa. Together with commercial hunting, the researchers wrote, the virus creates "a recipe for rapid ecological extinction". Habitat destruction and poaching for the bushmeat trade add to the danger, and captive gorillas have been infected with COVID-19.
All gorillas are listed in Appendix I of the Convention on International Trade in Endangered Species, which regulates international trade in the animals and their parts. The Great Apes Survival Project is a partnership between the United Nations Environment Programme and UNESCO. The Agreement on the Conservation of Gorillas and Their Habitats, concluded under the Convention on Migratory Species, took effect in June 2008. It is the first legally binding instrument exclusively targeting gorilla conservation. Governments of gorilla countries have banned killing and trading, yet weak enforcement lets poachers, traders and consumers go largely unchallenged. Efforts have still succeeded in some areas, but the mountain gorilla, with about 880 left and none in zoos, has no backup population outside its forests.
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Updated
Common questions
How big do gorillas get?
Wild adult male gorillas weigh 136 to 227 kilograms and stand 1.4 to 1.8 metres tall, with arm spans of 2.3 to 2.6 metres. Adult females weigh 68 to 113 kilograms and stand 1.25 to 1.5 metres tall.
How closely are gorillas related to humans?
Gorillas are the next closest living relatives of humans after bonobos and chimpanzees, and the lines diverged from a common ancestor about 7 million years ago. Human gene sequences differ by only 1.6% on average from corresponding gorilla genes.
Where does the word gorilla come from?
The word gorilla comes from the account of Hanno the Navigator, a Carthaginian explorer who sailed the west African coast around 500 BC. His interpreters called the hairy people the expedition met Gorillae.
How many gorillas are left in the wild?
About 316,000 western gorillas and about 5,000 eastern gorillas are thought to live in the wild. Mountain gorillas are the most severely endangered, with an estimated 880 left and none in zoos.
What is a silverback gorilla?
A silverback is an adult male gorilla named for the silver hair on his back, which reaches to the hips. He typically leads a troop, makes its decisions and takes responsibility for its safety.
What threatens gorillas the most?
Habitat destruction, poaching for the bushmeat trade and disease threaten gorillas. In 2004, Ebola essentially wiped out a population of several hundred gorillas in Odzala National Park in the Republic of Congo.
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