Gorilla

The word gorilla comes from the history of Hanno the Navigator ( 500 BC), 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. 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. 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.{{cite journal |doi=10.1093/molbev/msu394 |pmid=25534031 |pmc=4327160 |title=Inference of gorilla demographic and selective history from whole-genome sequence data |journal=Molecular Biology and Evolution |volume=32 |issue=3 |pages=600–612 |year=2015 |last1=McManus |first1=K. F. |last2=Kelley |first2=J. L. |last3=Song |first3=S. ==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. 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 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 . 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 (8% of the population) 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 (with the digits flexed). 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 activities 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 . 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. Nesting Gorillas construct nests for daytime and night use. Nests tend to be simple aggregations of branches and leaves about in diameter and are constructed by individuals. Gorillas, unlike chimpanzees or orangutans, tend to sleep in nests on the ground. The young nest with their mothers, but construct nests after three years of age, initially close to those of their mothers. Gorilla nests are distributed arbitrarily and use of tree species for site and construction appears to be opportunistic. Nest-building by great apes is now considered to be not just animal architecture, but as an important instance of tool use. Interspecies interactions One possible predator of gorillas is the leopard. Gorilla remains have been found in leopard scat, but this may be the result of scavenging. When the group is attacked by humans, leopards, or other gorillas, an individual silverback will protect the group, even at the cost of his own life. Gorillas do not appear to directly compete with chimpanzees in areas where they overlap. When fruit is abundant, gorilla and chimpanzee diets converge, but when fruit is scarce gorillas resort to vegetation. The two apes may also feed on different species, whether fruit or insects. Gorillas and chimpanzees may ignore or avoid each other when feeding on the same tree, but they have also been documented to form social bonds. Conversely, coalitions of chimpanzees have been observed attacking families of gorillas including silverbacks and killing infants. ==Behaviour==

Social structure Gorillas live in groups called troops. Troops tend to be made of one adult male or silverback, with a harem of multiple adult females and their offspring. However, multiple-male troops also exist. Without a silverback to protect them, the infants will likely fall victim to infanticide. Joining a new group is likely to be a tactic against this. However, while gorilla troops usually disband after the silverback dies, female eastern lowlands gorillas and their offspring have been recorded staying together until a new silverback transfers into the group. This likely serves as protection from leopards. The silverback is the centre of the troop's attention, making all the decisions, mediating conflicts, determining the movements of the group, leading the others to feeding sites, and taking responsibility for the safety and well-being of the troop. Younger males subordinate to the silverback, known as blackbacks, may serve as backup protection. Blackbacks are aged between 8 and 12 years and lack the silverback hair. The bond that a silverback has with his females forms the core of gorilla social life. Bonds between them are maintained by grooming and staying close together. Females form strong relationships with males to gain mating opportunities and protection from predators and infanticidal outside males. In multi-male groups, a female's relationship with the silverback can give her dominance over the other males, even though they are twice their size. Aggressive behaviours between males and females do occur, but rarely lead to serious injury. Relationships between females may vary. Maternally related females in a troop tend to be friendly towards each other and associate closely. Otherwise, females have few friendly encounters and commonly act aggressively towards each other. Females may fight for social access to males and a male may intervene. Severe aggression is rare in stable groups, but when two mountain gorilla groups meet the two silverbacks can sometimes engage in a fight to the death, using their canines to cause deep, gaping injuries. Females will purse their lips and slowly approach a male while making eye contact. This serves to urge the male to mount her. If the male does not respond, then she will try to attract his attention by reaching towards him or slapping the ground. In multiple-male groups, solicitation indicates female preference, but females can be forced to mate with multiple males. Males incite copulation by approaching a female and displaying at her or touching her and giving a "train grunt". Recently, gorillas have been observed engaging in face-to-face sex, a trait once considered unique to humans and bonobos. Gorilla infants are vulnerable and dependent, thus mothers, their primary caregivers, are important to their survival. Infants begin to break contact with their mothers after five months, but only for a brief period each time. By 12 months old, infants move up to from their mothers. At around 18–21 months, the distance between mother and offspring increases and they regularly spend time away from each other. In addition, nursing decreases to once every two hours. They may also be used during social interactions when discipline is required. Screams and roars signal alarm or warning, and are produced most often by silverbacks. Deep, rumbling belches suggest contentment and are heard frequently during feeding and resting periods. They are the most common form of intragroup communication. For this reason, conflicts are most often resolved by displays and other threat behaviours that are intended to intimidate without becoming physical. As a result, fights do not occur very frequently. The ritualized charge display is unique to gorillas. The entire sequence has nine steps: (1) progressively quickening hooting, (2) symbolic feeding, (3) rising bipedally, (4) throwing vegetation, (5) chest-beating with cupped hands, (6) one leg kick, (7) sideways running, two-legged to four-legged, (8) slapping and tearing vegetation, and (9) thumping the ground with palms to end display. A gorilla's chest-beat may vary in frequency depending on its size. Smaller ones tend to have higher frequencies, while larger ones tend to be lower. They also do it the most when females are ready to mate. ==Intelligence==

Gorillas are considered highly intelligent. A few individuals in captivity, such as Koko, have been taught a subset of sign language. Like the other great apes, gorillas can laugh, grieve, have "rich emotional lives", develop strong family bonds, make and use tools, and think about the past and future. Some researchers believe gorillas have spiritual feelings or religious sentiments. In September 2005, a two-and-a-half-year-old gorilla in the Republic of Congo was discovered using rocks to smash open palm nuts inside a game sanctuary. While this was the first such observation for a gorilla, over 40 years previously, chimpanzees had been seen using tools in the wild 'fishing' for termites. Nonhuman great apes are endowed with semiprecision grips, and have been able to use both simple tools and even weapons, such as improvising a club from a convenient fallen branch. ==Scientific study==

American physician and missionary Thomas Staughton Savage obtained the first specimens (the skull and other bones) during his time in Liberia. where Troglodytes gorilla is described, now known as the western gorilla. Other species of gorilla were described in the next few years. The first systematic study was not conducted until the 1920s, when Carl Akeley of the American Museum of Natural History traveled to Africa to hunt for an animal to be shot and stuffed. On his first trip, he was accompanied by his friends Mary Bradley, a mystery writer, her husband, and their young daughter Alice, who would later write science fiction under the pseudonym James Tiptree Jr. After their trip, Mary Bradley wrote On the Gorilla Trail. She later became an advocate for the conservation of gorillas, and wrote several more books (mainly for children). In the late 1920s and early 1930s, Robert Yerkes and his wife Ava helped further the study of gorillas when they sent Harold Bigham to Africa. Yerkes also wrote a book in 1929 about the great apes. After World War II, George Schaller was one of the first researchers to go into the field and study primates. In 1959, he conducted a systematic study of the mountain gorilla in the wild and published his work. Years later, at the behest of Louis Leakey and the National Geographic, Dian Fossey conducted a much longer and more comprehensive study of the mountain gorilla. When she published her work, many misconceptions and myths about gorillas were finally disproved, including the myth that gorillas are violent. Western lowland gorillas (G. g. gorilla) are believed to be one of the zoonotic origins of HIV/AIDS. The SIVgor Simian immunodeficiency virus that infects them is similar to a certain strain of HIV-1. Genome sequencing The gorilla became the next-to-last great ape genus to have its genome sequenced. The first gorilla genome was generated with short read and Sanger sequencing with DNA from a female western lowland gorilla named Kamilah. This gave scientists further insight into the evolution and origin of humans. Although chimpanzees being the closest extant relatives of humans, 15% of the human genome was found to be more similar to that of the gorilla. In addition, 30% of the gorilla genome "is closer to human or chimpanzee than the latter are to each other; this is rarer around coding genes, indicating pervasive selection throughout great ape evolution, and has functional consequences in gene expression." Analysis of the gorilla genome has cast doubt on the idea that the rapid evolution of hearing genes gave rise to language in humans, as it also occurred in gorillas. , 2009 ==Captivity==

Gorillas became highly prized by western zoos since the 19th century, though the earliest attempts to keep them in captive facilities ended in their early death. In the late 1920s, the care of captive gorillas significantly improved. Colo (22 December 1956 – 17 January 2017) of the Columbus Zoo and Aquarium was the first gorilla to be born in captivity. Captive gorillas exhibit stereotypic behaviors, including eating such as regurgitation, reingestion and self-injurious or conspecific aggression, pacing, rocking, sucking of fingers or lip smacking, and overgrooming. Negative vigilance of visitor behaviors have been identified as starting, posturing and charging at visitors. Groups of bachelor gorillas containing young silverbacks have significantly higher levels of aggression and wounding rates than mixed age and sex groups. The use of both internal and external privacy screens on exhibit windows has been shown to alleviate stresses from visual effects of high crowd densities, leading to decreased stereotypic behaviors in the gorillas. Enrichment modifications to feed and foraging, where clover-hay is added to an exhibit floor, decrease stereotypic activities while simultaneously increasing positive food-related behaviors. Recent research on captive gorilla welfare emphasizes a need to shift to individual assessments instead of a one-size-fits-all group approach to understanding how welfare increases or decreases based on a variety of factors. Individual characteristics such as age, sex, personality and individual histories are essential in understanding that stressors will affect each individual gorilla and their welfare differently. ==Conservation status==

, Democratic Republic of the Congo All species (and subspecies) of gorilla are listed as endangered or critically endangered on the IUCN Red List. All gorillas are listed in Appendix I of the Convention on International Trade in Endangered Species (CITES), meaning that international export/import of the species, including in parts and derivatives, is regulated. In 2016, around 316,000 western lowland gorillas were thought to exist in the wild, Threats to gorilla survival include habitat destruction and poaching for the bushmeat trade. Gorillas are closely related to humans, and are susceptible to diseases that humans also get infected by. In 2004, a population of several hundred gorillas in the Odzala National Park, Republic of Congo was essentially wiped out by the Ebola virus. A 2006 study published in Science concluded more than 5,000 gorillas may have died in recent outbreaks of the Ebola virus in central Africa. The researchers indicated in conjunction with commercial hunting of these apes, the virus creates "a recipe for rapid ecological extinction". In captivity, it has also been observed that gorillas can also be infected with COVID-19. Conservation efforts include the Great Apes Survival Project, a partnership between the United Nations Environment Programme and the UNESCO, and also an international treaty, the Agreement on the Conservation of Gorillas and Their Habitats, concluded under UNEP-administered Convention on Migratory Species. The Gorilla Agreement is the first legally binding instrument exclusively targeting gorilla conservation; it came into effect in June 2008. Governments of countries where gorillas live placed a ban on their killing and trading, but weak law enforcement still poses a threat to them, since the governments rarely apprehend poachers, traders and consumers that rely on gorillas for profit. ==Cultural significance==

In Cameroon's Lebialem highlands, folk stories connect people and gorillas via totems; a gorilla's death means the connected person will die also. This creates a local conservation ethic. Many different indigenous peoples interact with wild gorillas. In 1911, the anthropologist Albert Jenks noted the Bulu people's knowledge of gorilla behaviour and ecology, and their gorilla stories. In one such story, "The Gorilla and the Child", a gorilla speaks to people, seeking help and trust, and stealing a baby; a man accidentally kills the baby while attacking the gorilla. Some beliefs are widespread among indigenous peoples. The Fang name for gorilla is ngi while the Bulu name is njamong; the root ngi means fire, denoting a positive energy. From the Central African Republic to Cameroon and Gabon, stories of reincarnations as gorillas, totems, and transformations similar to those recorded by Du Chaillu are still told in the 21st century. Since gaining international attention, gorillas have been a recurring element of many aspects of popular culture and media. They were usually portrayed as murderous and aggressive. Inspired by Emmanuel Frémiet's Gorilla Carrying off a Woman, gorillas have been depicted kidnapping human women. This theme was used in films such as Ingagi (1930) and most notably King Kong (1933). The comedic play The Gorilla, which debuted in 1925, featured an escaped gorilla taking a woman from her house. Several films used the "escaped gorilla" trope including The Strange Case of Doctor Rx (1942), The Gorilla Man (1943), Gorilla at Large (1954) and the Disney cartoons The Gorilla Mystery (1930) and Donald Duck and the Gorilla (1944). Gorillas have been used as opponents to jungle-themed heroes such as Tarzan and Sheena, Queen of the Jungle, as well as superheroes. The DC Comics supervillain Gorilla Grodd is an enemy of the Flash. Gorillas also serve as antagonists in the 1968 film Planet of the Apes. More positive and sympathetic portrayals of gorillas include the films Son of Kong (1933), Mighty Joe Young (1949), Gorillas in the Mist (1988) and Instinct (1999) and the 1992 novel Ishmael. Gorillas have been featured in video games as well, notably Donkey Kong. ==See also==