Western gorilla [1] | |
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Male at the San Francisco Zoo | |
Female with infant at the Bronx Zoo | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Mammalia |
Order: | Primates |
Suborder: | Haplorhini |
Infraorder: | Simiiformes |
Family: | Hominidae |
Subfamily: | Homininae |
Genus: | Gorilla |
Species: | G. gorilla |
Binomial name | |
Gorilla gorilla (Savage, 1847) | |
Subspecies | |
Western lowland gorilla (Gorilla gorilla gorilla) | |
Western gorilla range. Each of the two subspecies is confined to two separate regions. |
The western gorilla (Gorilla gorilla) is a great ape found in Africa, one of two species of the hominid genus Gorilla . Large and robust with males weighing around 168 kilograms (370 lb), the species is found in a region of midwest Africa, geographically isolated from the eastern gorilla (Gorilla beringei). The hair of the western species is significantly lighter in color.
The western gorilla is the second largest living primate after the eastern gorilla. Two subspecies are recognised: the western lowland gorilla (Gorilla gorilla gorilla) is found in most of West Africa; while the Cross River gorilla (Gorilla gorilla diehli) is limited to a smaller range in the north at the border of Cameroon and Nigeria. Both subspecies are listed Critically Endangered.
A formal description of the species was provided by Thomas Savage in 1847, allying the new species to an earlier description of the chimpanzee as Troglodytes gorilla in a group of eastern simians he referred to as "orangs". The author selected the specific epithet for the name given by Hanno to "wild men" he had noted on the east coast of Africa, presumed by Savage to be a species of orang. [4] The population is recognised as two subspecies:
Image | Subspecies | Population | Distribution |
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Western lowland gorilla (Gorilla gorilla gorilla) | 276,000 [2] | Angola, Cameroon, Central African Republic, Republic of the Congo, Democratic Republic of the Congo, Equatorial Guinea and Gabon. | |
Cross River gorilla (Gorilla gorilla diehli) | 250 to 300 [5] [6] | Cameroon-Nigeria border region. | |
Nearly all of the individuals of this taxon belong to the western lowland gorilla subspecies, whose population is approximately 276,000 individuals. Only 250 to 300 of the only other western gorilla subspecies, the Cross River gorilla, are thought to remain.
Western gorillas are generally lighter colored than eastern gorillas. Western gorillas have black, dark grey or dark brown-grey hair with a brownish forehead. Males average 167 cm (5 ft 5.7 in) although reaching a height up to 176 cm (5 ft 9.3 in), with males having an average weight of 168 kilograms (370 lb) and females weighing 58 to 72 kilograms (128 to 159 lb). [7] Captive western gorillas average 157 kg (346 lb) in males and 80 kg (176 lb) in females. [8] Another source[ which? ] describes the weight of wild male western lowland gorillas as 146 kg (322 lb). [9] The Cross River gorilla differs from the western lowland gorilla in both skull and tooth dimensions.
Western gorillas live in groups that vary in size from two to twenty individuals. Such groups are composed of at least one male, several females and their offspring. A dominant male silverback heads the group, with younger males usually leaving the group when they reach maturity. Females transfer to another group before breeding, which begins at eight to nine years old; they care for their young infants for the first three to four years of their lives. The interval between births, therefore, is long, which partly explains the slow population growth rates that make the western gorilla so vulnerable to poaching. Due to the long gestation time, long period of parental care, and infant mortality, a female gorilla will only give birth to an offspring that survives to maturity every six to eight years. Western gorillas are long-lived and may survive for as long as 40 years in the wild. A group's home range may be as large as 30 km2 (12 sq mi), but is not actively defended. Wild western gorillas are known to use tools. [10]
Western gorillas' diets are high in fiber, including leaves, stems, fruit, piths, flowers, bark, invertebrates, and soil. The frequency of when each of these are consumed depends on the particular western gorilla group and the season. Furthermore, different groups of western gorillas eat differing numbers and species of plants and invertebrates, suggesting they have a food culture. Fruit comprises most of the western lowland gorillas' diets when it is abundant, directly influencing their foraging and ranging patterns. There is a correlation between the amount of time a western gorilla travels and the season in which fruits are available. Western gorillas spend more time traveling and feeding during the seasons when fruits are abundant compared to when there is less fruits available. [11] Fruits of the genera Tetrapleura, Chrysophyllum , Dialium , and Landolphia are favored by the western gorillas. Low-quality herbs, such as leaves and woody vegetation, are only eaten when fruit is scarce. In the dry season from January to March, when fleshy fruits are few and far between, more fibrous vegetation such as the leaves and bark of the low-quality herbs Palisota and Aframomum are consumed. Of the invertebrates consumed by the western gorillas, termites and ants make up the majority. Caterpillars, grubs, and larvae are also consumed in rarity.
Some ethnographic and pharmacological studies have suggested a possible medicinal value in particular foods consumed by the western gorilla. The fruit and seeds of multiple Cola species are consumed. Given the low protein content, the main reason for their consumption may be the stimulating effect of the caffeine in them. Western gorillas inhabiting Gabon have been observed consuming the fruit, stems, and roots of Tabernanthe iboga, which, due to the compound ibogaine in it, acts on the central nervous system, producing hallucinogenic effects. It also has effects comparable to caffeine. [12] There is also evidence for medicinal value for the seed pods of Aframomum melegueta in western gorillas' diets, which seem to have some sort of cardiovascular health benefit for western lowland gorillas, and are a known part of the natural diets for many wild populations. [13]
A study published in 2007 announced the discovery of this species fighting back against possible threats from humans. [14] They "found several instances of gorillas throwing sticks and clumps of grass". [15] This is unusual, because western gorillas usually flee and rarely charge when they encounter humans.
One mirror test in Gabon shows that western gorilla silverbacks react aggressively when faced with a mirror, although refusing to look fully at their reflection. [16]
The World Conservation Union lists the western gorilla as critically endangered, the most severe denomination next to global extinction, on its 2007 Red List of Threatened Species. The Ebola virus might be depleting western gorilla populations to a point where their recovery might become impossible, and the virus reduced populations in protected areas by 33% from 1992 to 2007, which may be equal to a decline of 45% for a period of just 20 years spanning 1992 to 2011. [2] [17] Poaching, commercial logging and civil wars in the countries that compose the western gorillas' habitat are also threats. [17] Furthermore, reproductive rates are very low, with a maximum intrinsic rate of increase of about 3% and the high levels of decline from hunting and disease-induced mortality have caused declines in population of more than 60% over the last 20 to 25 years. Rather, under the optimistic estimate scenarios, population recovery would require almost 75 years. Yet within the next thirty years, habitat loss and degradation from agriculture, timber extraction, mining and climate change will become increasingly larger threats. Thus, a population reduction of more than 80% over three generations (i.e., 66 years from 1980 to 2046) seems likely.[ citation needed ] In the 1980s, a census taken of the gorilla populations in equatorial Africa was thought to be 100,000. Researchers adjusted the figure in 2008 after years of poaching and deforestation had reduced the population to approximately 50,000. [18]
Surveys conducted by the Wildlife Conservation Society in 2006 and 2007 found around 125,000 previously unreported gorillas have been living in the swamp forests of Lake Tele Community Reserve and in neighbouring Marantaceae (dryland) forests in the Republic of the Congo. This discovery could more than double the known population of the animals, though the effect that the discovery will have on the gorillas' conservation status is currently unknown. [18] [19] With the new discovery, the current population of western lowland gorillas could be around 150,000–200,000. However, the gorilla remains vulnerable to Ebola, deforestation, and poaching. [18]
Estimates on the number of Cross River gorillas remaining is 250–300 in the wild, concentrated in approximately 9-11 locations. [5] Recent genetic research [20] and field surveys suggest that there is occasional migration of individual gorillas between locations. The nearest population of western lowland gorilla is some 250 km (160 mi) away. Both loss of habitat and intense hunting for bushmeat have contributed to the decline of this subspecies. In 2007, a conservation plan for the Cross River gorilla was published, outlining the most important actions necessary to preserve this subspecies. [21] The government of Cameroon has created the Takamanda National Park on the border with Nigeria, as an attempt to protect these gorillas. [22] The park now forms part of an important trans-boundary protected area with Nigeria's Cross River National Park, safeguarding an estimated 115 gorillas—a third of the Cross River gorilla population—along with other rare species. [23] The hope is that these gorillas will be able to move between the Takamanda reserve in Cameroon over the border to Nigeria's Cross River National Park.
The names of individuals of the species includes:[ citation needed ]
The chimpanzee, also simply known as the chimp, is a species of great ape native to the forests and savannahs of tropical Africa. It has four confirmed subspecies and a fifth proposed one. When its close relative the bonobo was more commonly known as the pygmy chimpanzee, this species was often called the common chimpanzee or the robust chimpanzee. The chimpanzee and the bonobo are the only species in the genus Pan. Evidence from fossils and DNA sequencing shows that Pan is a sister taxon to the human lineage and is thus humans' closest living relative. The chimpanzee is covered in coarse black hair, but has a bare face, fingers, toes, palms of the hands, and soles of the feet. It is larger and more robust than the bonobo, weighing 40–70 kg (88–154 lb) for males and 27–50 kg (60–110 lb) for females and standing 150 cm.
Gorillas are herbivorous, predominantly ground-dwelling great apes that inhabit 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 95 to 99% depending on what is included, and they are the next closest living relatives to humans after chimpanzees and bonobos.
Orangutans are great apes native to the rainforests of Indonesia and Malaysia. They are now found only in parts of Borneo and Sumatra, but during the Pleistocene they ranged throughout Southeast Asia and South China. Classified in the genus Pongo, orangutans were originally considered to be one species. From 1996, they were divided into two species: the Bornean orangutan and the Sumatran orangutan. A third species, the Tapanuli orangutan, was identified definitively in 2017. The orangutans are the only surviving species of the subfamily Ponginae, which diverged genetically from the other hominids between 19.3 and 15.7 million years ago.
Primates are the members of a diverse order of mammals. They are divided into the strepsirrhines, which include the lemurs, galagos, and lorisids, and the haplorhines, which include the tarsiers and the simians. Primates arose 85–55 million years ago first from small terrestrial mammals, which adapted to living in the trees of tropical forests: many primate characteristics represent adaptations to life in this challenging environment, including large brains, visual acuity, color vision, a shoulder girdle allowing a large degree of movement in the shoulder joint, and dexterous hands. Primates range in size from Madame Berthe's mouse lemur, which weighs 30 g (1 oz), to the eastern gorilla, weighing over 200 kg (440 lb). There are 376–524 species of living primates, depending on which classification is used. New primate species continue to be discovered: over 25 species were described in the 2000s, 36 in the 2010s, and six in the 2020s.
The mountain gorilla is one of the two subspecies of the eastern gorilla. It is listed as endangered by the IUCN as of 2018.
The purple-faced langur, also known as the purple-faced leaf monkey, is a species of Old World monkey that is endemic to Sri Lanka. The animal is a long-tailed arboreal species, identified by a mostly brown appearance, dark face and a very shy nature. The species was once highly prevalent, found in suburban Colombo and the "wet zone" villages, but rapid urbanization has led to a significant decrease in the population level of the monkeys. It had traditionally been classified within the genus Trachypithecus but was moved to the genus Semnopithecus based on DNA evidence indicating that is it more closely related to the gray langurs.
The Bili apes, or Bondo mystery apes, were names given in 2003 in sensational reports in the popular media to a purportedly new species of highly aggressive, giant ape supposedly inhabiting the wetlands and savannah around of the village of Bili in the Democratic Republic of the Congo. "The apes nest on the ground like gorillas, but they have a diet and features characteristic of chimpanzees", according to a 2003 National Geographic article.
The hoolock gibbons are three primate species of genus Hoolock in the gibbon family, Hylobatidae, native to eastern Bangladesh, Northeast India, Myanmar, and Southwest China.
The western lowland gorilla is one of two Critically Endangered subspecies of the western gorilla that lives in montane, primary and secondary forest and lowland swampland in central Africa in Angola, Cameroon, Central African Republic, Republic of the Congo, Democratic Republic of the Congo, Equatorial Guinea and Gabon. It is the nominate subspecies of the western gorilla, and the smallest of the four gorilla subspecies.
The Cross River gorilla is a critically endangered subspecies of the western gorilla. It was named a new species in 1904 by Paul Matschie, a mammalian taxonomist working at the Humboldt University Zoological Museum in Berlin, but its populations were not systematically surveyed until 1987.
The eastern lowland gorilla or Grauer's gorilla is a Critically Endangered subspecies of eastern gorilla endemic to the mountainous forests of eastern Democratic Republic of the Congo. Important populations of this gorilla live in the Kahuzi-Biega and Maiko National Parks and their adjacent forests, the Tayna Gorilla Reserve, the Usala forest and on the Itombwe Massif.
The Sumatran orangutan is one of the three species of orangutans. Critically endangered, and found only in the north of the Indonesian island of Sumatra, it is rarer than the Bornean orangutan but more common than the recently identified Tapanuli orangutan, also found in Sumatra. Its common name is based on two separate local words, "orang" and "hutan" ("forest"), derived from Malay, and translates as 'person of the forest'.
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The eastern gorilla is a critically endangered species of the genus Gorilla and the largest living primate. At present, the species is subdivided into two subspecies. There are 6,800 eastern lowland gorillas or Grauer's gorillas and 1,000 mountain gorillas. Illegal hunting threatens the species.
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