Gorilla
Gorillas are large, primarily herbivorous, great apes that live in the tropical forests of equatorial Africa. The genus Gorilla is divided into two species: the eastern gorilla and the western gorilla, and either four or five subspecies. The DNA of gorillas is highly similar to that of humans, from 96 to 99% depending on what is included, and they are the next closest living relatives to humans after the bonobos and chimpanzees.
Gorillas are the largest living primates, reaching heights between, weights between, and arm spans up to, depending on species and sex. They tend to live in troops, with the leader being called a silverback. The eastern gorilla is distinguished from the western by darker fur colour and some other minor morphological differences. Gorillas tend to live 35–40 years in the wild.
Gorillas' natural habitats cover tropical or subtropical forests in Sub-Saharan Africa. Although their range covers a small percentage of Sub-Saharan Africa, gorillas cover a wide range of elevations. The mountain gorilla inhabits the Albertine Rift montane cloud forests of the Virunga Volcanoes, ranging in altitude from. Lowland gorillas live in dense forests and lowland swamps and marshes as low as sea level, with western lowland gorillas living in Central West African countries and eastern lowland gorillas living in the Democratic Republic of the Congo near its border with Rwanda.
There are thought to be around 316,000 western gorillas in the wild, and 5,000 eastern gorillas. Both species are classified as Critically Endangered by the IUCN; all subspecies are classified as Critically Endangered with the exception of the mountain gorilla, which is classified as Endangered. There are many threats to their survival, such as poaching, habitat destruction, and disease, which threaten the survival of the species. However, conservation efforts have been successful in some areas where they live.
History and etymology
The word gorilla comes from the history of Hanno the Navigator, a Carthaginian explorer on an expedition to the west African coast to the area that later became Sierra Leone. Members of the expedition encountered "savage people, the greater part of whom were women, whose bodies were hairy, and whom our interpreters called Gorillae". It is unknown whether what the explorers encountered were what we now call gorillas, another species of ape or monkeys, or humans. Skins of gorillai women, brought back by Hanno, are reputed to have been kept at Carthage until Rome destroyed the city 350 years later at the end of the Punic Wars, 146 BC.In 1625 Andrew Battel mentioned the existence of the animal, under the name Pongo:
A century and a half after Battel's story was published, one writer called Radermacher wrote that "the large species, described by Buffon and other authors as of the size of a man, is held by many to be a Chimera."
The American physician and missionary Thomas Staughton Savage and naturalist Jeffries Wyman first described the western gorilla in 1847 from specimens obtained in Liberia. They called it Troglodytes gorilla, using the then-current name of the chimpanzee genus. The species name was derived, as described by Hanno.
Evolution and classification
The closest relatives of gorillas are the other two Homininae genera, chimpanzees and humans, all of them having diverged from a common ancestor about 7 million years ago. Human gene sequences differ only 1.6% on average from the sequences of corresponding gorilla genes, but there is further difference in how many copies each gene has.| Phylogeny of superfamily Hominoidea |
Until recently, gorillas were considered to be a single species, with three subspecies: the western lowland gorilla, the eastern lowland gorilla and the mountain gorilla. There is now agreement that there are two species, each with two subspecies. More recently, a third subspecies has been claimed to exist in one of the species. The separate species and subspecies developed from a single type of gorilla during the Ice Age, when their forest habitats shrank and became isolated from each other. Primatologists continue to explore the relationships between various gorilla populations. The species and subspecies listed here are the ones upon which most scientists agree.
The proposed third subspecies of Gorilla beringei, which has not yet received a trinomen, is the Bwindi population of the mountain gorilla, sometimes called the Bwindi gorilla.
Some variations that distinguish the classifications of gorilla include varying density, size, hair colour, length, culture, and facial widths. Population genetics of the lowland gorillas suggest that the western and eastern lowland populations diverged around 261 thousand years ago.
Characteristics
Wild male gorillas weigh, while adult females weigh. Adult males are tall, with an arm span that stretches from. Female gorillas are shorter at, with smaller arm spans. Colin Groves calculated the average weight of 42 wild adult male gorillas at 144 kg, while Smith and Jungers found the average weight of 19 wild adult male gorillas to be 169 kg. Adult male gorillas are known as silverbacks for the characteristic silver hair on their backs, reaching to the hips. The tallest wild gorilla recorded was a silverback with an arm span of, a chest of, and a weight of, shot in Alimbongo, northern Kivu in May 1938. The heaviest wild gorilla recorded was a silverback shot in Ambam, Cameroon, which weighed. The tallest gorilla in captivity was Gust, a western lowland gorilla that was captured as a baby in Belgian Congo and spent his life at Antwerp Zoo. He was tall. Males in captivity can be overweight and reach weights up to.File:Gorilla gorilla & Gorilla beringei.jpg|thumb |right |Western gorilla and eastern gorilla
The eastern gorilla is more darkly coloured than the western gorilla, with the mountain gorilla being the darkest of all. The mountain gorilla also has the thickest hair. The western lowland gorilla can be brown or greyish with a reddish forehead. In addition, gorillas that live in lowland forest are more slender and agile than the more bulky mountain gorillas. The eastern gorilla also has a longer face and broader chest than the western gorilla. Like humans, gorillas have individual fingerprints.
Their eye colour is dark brown, framed by a black ring around the iris. Gorilla facial structure is described as mandibular prognathism, that is, the mandible protrudes farther out than the maxilla. Adult males also have a prominent sagittal crest.
Gorillas move around by knuckle-walking, although they sometimes walk upright for short distances, typically while carrying food or in defensive situations. A 2018 study investigating the hand posture of 77 mountain gorillas at Bwindi Impenetrable National Park found that knuckle walking was done only 60% of the time, and they also supported their weight on their fists, the backs of their hands/feet, and on their palms/soles. Such a range of hand postures was previously thought to have been used by only orangutans. Studies of gorilla handedness have yielded varying results, with some arguing for no preference for either hand, and others right-hand dominance for the general population.
Studies have shown gorilla blood is not reactive to anti-A and anti-B monoclonal antibodies, which would, in humans, indicate type O blood. Due to novel sequences, though, it is different enough to not conform with the human ABO blood group system, into which the other great apes fit.
A gorilla's lifespan is normally between 35 and 40 years, although zoo gorillas may live for 50 years or more in rare circumstances. At, Fatou is both the oldest living gorilla and oldest living female gorilla. The oldest male gorilla ever was Ozoum, who reached the final age of 61 years, 24 days. The oldest living male gorilla is Guhonda, aged.
Distribution and habitat
Gorillas have a patchy distribution. The range of the two species is separated by the Congo River and its tributaries. The western gorilla lives in west central Africa, while the eastern gorilla lives in east central Africa. Between the species, and even within the species, gorillas live in a variety of habitats and elevations. Gorilla habitat ranges from montane forest to swampland. Eastern gorillas inhabit montane and submontane forests between above sea level.Mountain gorillas live in montane forests at the higher end of the elevation range, while eastern lowland gorillas live in submontane forests at the lower end. In addition, eastern lowland gorillas live in montane bamboo forests, as well as lowland forests ranging from in elevation. Western gorillas live in both lowland swamp forests and montane forests, at elevations ranging from sea level to. Western lowland gorillas live in swamp and lowland forests ranging up to, and Cross River gorillas live in low-lying and submontane forests ranging from.
Ecology
Diet and activites
A gorilla's day is divided between rest periods and travel or feeding periods. Diets differ between and within species. Mountain gorillas mostly eat foliage, such as leaves, stems, pith, and shoots, while fruit makes up a very small part of their diets. Mountain gorilla food is widely distributed and neither individuals nor groups have to compete with one another. Their home ranges vary from, and their movements range around or less on an average day. Despite eating a few species in each habitat, mountain gorillas have flexible diets and can live in a variety of habitats.Eastern lowland gorillas have more diverse diets, which vary seasonally. Leaves and pith are commonly eaten, but fruits can make up as much as 25% of their diets. Since fruit is less available, lowland gorillas must travel farther each day, and their home ranges vary from, with day ranges. Eastern lowland gorillas will also eat insects, preferably ants. Western lowland gorillas depend on fruits more than the others and they are more dispersed across their range. They travel even farther than the other gorilla subspecies, at per day on average, and have larger home ranges of. Western lowland gorillas have less access to terrestrial herbs, although they can access aquatic herbs in some areas. Termites and ants are also eaten.
While traditionally thought of as ground-dwelling apes, a 2025 study found that gorillas can spend significant amounts of time in trees, depending on the area. In both Bwindi Impenetrable National Park and Loango National Park, gorillas spend more time climbing trees than those at Virunga. Such behaviours were not necessarily driven by foraging for fruit, which was consumed close to half of the time terrestrially in Loango gorillas and in both Bwindi and Loango they spend a majority of their foraging time in the trees feeding on leaves and other non-fruits. In all three areas, adult females were more arboreal than males. Gorillas rarely drink water "because they consume succulent vegetation that is almost half water as well as morning dew", although both mountain and lowland gorillas have been observed drinking.