Gorilla
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| 200px Eastern Lowland Gorilla | ||||||||||||
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| Troglodytes gorilla Savage, 1847 | ||||||||||||
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Gorilla gorilla |
The gorilla, the largest of the living primates, is a ground-dwelling herbivore that inhabits the forests of Africa. Gorillas are apes in the family Hominidae and superfamily Hominoidea. Members of the Hominidae family, which include the gorillas, chimpanzees, orangutans, and humans, are known as the "great apes" while all other apes belong to the family Hylobatidae and are known as the "lesser apes" (gibbons).
Gorillas are divided into two species and (under debate as of 2006) either four or five subspecies. Their DNA is 98% identical to that of humans, making them the second closest living relative to humans after the two chimpanzee species (Chen 2001).
Name
The American physician and missionary Thomas Staughton Savage first described the Western Gorilla (he called it Troglodytes gorilla) in 1847 from specimens obtained in Liberia. The name derived from the Gorillai, a "tribe of hairy women," described by Hanno the Navigator, a Carthaginian navigator and possible visitor (circa 480 B.C.E.) to the area that later became Sierra Leone (Müller 1979).
Physical characteristics
Gorillas move around by knuckle-walking. Adult males range in height from 165 to 175 centimeters (5 feet 5 inches to 5 feet 9 inches), and in weight from 140 to 165 kilograms (310 to 365 pounds). Females are about half the weight of males. Gorillas' facial structure is described as prognathous; that is, their mandible, or lower jaw, protrudes further out than the maxilla, upper jaw.
Gestation (the carrying of the embryo or fetus inside the female prior to birth) is eight and a half months. Infants stay with their mothers for three to four years, and females typically do not have more offspring during that time. Females mature when they are 10 to 12 years old (earlier in captivity); males mature between the ages of 11 and 13. Gorillas live to be 30 to 50 years old. The oldest gorilla on record is the Philadelphia Zoo's Massa, who lived to be 54.
Gorillas are mainly vegetarian, eating fruits, leaves, and shoots, but they also eat insects. Due to their diet of plant life, gorillas often have bloated stomachs.
Almost all gorillas share the same blood type, B, and, as seen in the photo, above have individual finger prints, like humans.
Classification
Scientists for decades thought there were three species of gorilla, The Western Lowland, The Eastern Lowland, and the Mountain Gorilla. Primatologists now agree that the gorilla is divided into two species of at least two subspecies each. More recently it has been claimed that a third subspecies exists in one of these groups.
Primatologists continue to explore the relationships between various gorilla populations (Groves 2002). The species and subspecies listed below are the ones most scientists agree upon (Groves 2005).
- Genus Gorilla
- Western Gorilla (Gorilla gorilla)
- Western Lowland Gorilla (Gorilla gorilla gorilla)
- Cross River Gorilla (Gorilla gorilla diehli)
- Eastern Gorilla (Gorilla beringei)
- Mountain Gorilla (Gorilla beringei beringei)
- Eastern Lowland Gorilla (Gorilla beringei graueri)
- Western Gorilla (Gorilla gorilla)
The proposed third subspecies of Gorilla beringei, which has not received a full latin designation, is the Bwindi population of the Mountain Gorilla, sometimes called Bwindi Gorilla.
Endangerment
Both species of gorilla are endangered, and have been subject to intense poaching. Threats to gorilla survival include habitat destruction and the bushmeat trade. A population of several hundred gorillas in the Odzala National Park, Republic of Congo was essentially wiped in 2004 out by the Ebola virus (Caillaud 2006).
Behavior
A silverback is an adult male gorilla, typically more than 12 years old and named for the distinctive patch of silver hair on his back. Silverbacks have large canines that come with maturity. Blackbacks are sexually mature males of up to 11 years of age.
Silverbacks are the strong, dominant troop leaders. Each typically leads a troop of five to 30 gorillas and is the center 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.
Males slowly begin to leave their original troop when they are about 11 years old, travelling alone or with a group of other males for two to five years before they attract females to form a new group and start breeding. While infant gorillas normally stay with their mother for three to four years, silverbacks will care for weaned young orphans, though never to the extent of carrying the little gorillas.
If challenged by a younger male or even by an outsider male, a silverback will scream, beat his chest, break branches, bare his teeth, then charge forward. Sometimes a younger male in the group can take over leadership from an old male. If the leader is killed by disease, accident, fighting or poachers, the group will split up and individuals will look for a new protective male. Though extremely rare, a group might be taken over in its entirety by another male. In this case, the new leader may kill the infants of the dead silverback.
Studies
- Nineteenth century: The first known study of gorillas was in 1867. The French researcher heading the project read legends about gorillas, then wrote tall tales. He portrayed them as dangerous animals that would raid villages and rape women.
- Early twentieth century: The next systematic study was not conducted until the 1920s, when Carl Akely 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 famous mystery writer, and her husband. 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, mostly childrens books. 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.
- Mid-twentieth century: After WWII, 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. It was not until she published her work that many misconceptions and myths about gorillas were finally disproved, including the myth that gorillas are violent.
Intelligence
Gorillas are closely related to humans and are considered highly intelligent. A few individuals in captivity, such as Koko, have been taught a subset of sign language (see animal language for a discussion).
Natural tool use by all the "great apes"
In September 2005 Thomas Breuer, a conservation biologist with the Wildlife Conservation Society, led a team of TKs to TK to observe gorillas. During the expedition they saw several examples of gorillas using tools in the wild. A female gorilla in the Nouabalé-Ndoki National Park in the Republic of Congo was recorded using a stick as if to gauge the depth of water whilst crossing a swamp. A second female was seen using a tree stump as a bridge and also as a support whilst fishing in the swamp. From these observations, reserachers have concluded that all great apes are now known to use tools (Breuer 2005).
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. While this was the first such observation for a gorilla, over 40 years previously chimpanzees had been seen using tools in the wild, famously 'fishing' for termites. Other animals also use tools; sea otters, for example, place rocks on their chests to break sea urchins. Gorillas use sticks and rocks to thwart predators (Beck 1980). Great apes are endowed with a semi-precision grip, and certainly have been able to use both simple tools and even weapons, by improvising a club from a convenient fallen branch. With training, in twentieth-century carnival and circus acts, chimpanzees have been taught to operate simple motorbikes.
Gorillas in pop culture
Giant gorillas have been a recurring theme in film since the 1930s. Following their popularity in the 1930s and 1940s, most notably in the films King Kong, Tarzan, and Mighty Joe Young, gorillas came to be heavily featured in comic books. Short contrived gorilla plots were often included so that they could appear on the cover to boost sales.
Gorilla suits are a perennially popular gag costume, appearing in large numbers of TV shows since the 1950s. A number of sports teams have a gorilla as a mascot, usually personified by an actor in a gorilla suit.
See also
- List of apes — notable individual apes
ReferencesISBN links support NWE through referral fees
- Beck, B. B. 1980. Animal tool behavior: The use and manufacture of tools by animals. New York: Garland Press.
- Breuer, T., M. Ndoundou-Hockemba, and V. Fishlock. 2005. First Observation of Tool Use in Wild Gorillas. PLoS biology. 3: 380.
- Caillaud, D., et al. 2006. Gorilla susceptibility to Ebola virus: the cost of sociality. Current Biology. 16: R489-91.
- Cawthon Lang KA. 2006. January 23. Primate Factsheets: Gorilla (Gorilla) Taxonomy, Morphology, & Ecology.
- Chen, F. C., and W. H. Li. 2001. Genomic divergences between humans and other hominoids and the effective population size of the common ancestor of humans and chimpanzees. American Journal of Human Genetics. 68: 444-56.
- Groves, C. 2005. Mammal Species of the World, 3rd edition. D. E. Wilson, and D. M. Reeder (editors). Johns Hopkins University Press
- Groves, C. 2002. A history of gorilla taxonomy. Gorilla Biology: A Mulidisciplinary Perspective. A. B. Taylor and M. L. Goldsmith (editors).
- Müller, C. 1979. Geographici Graeci Minores (1855-61). ed. J. Blomqvist.
- Primate Info Net, Primate Factsheets: Gorilla, <http://pin.primate.wisc.edu/factsheets/entry/gorilla> (accessed August 10, 2006).
External links
- ARKive - images and movies of the western gorilla (Gorilla gorilla)
- ARKive - images and movies of the eastern gorilla (Gorilla beringei)
- Bagheera An educational website about Earth's Endangered Animals.
- Gorilla Haven - information about gorillas
- Gorillas Online - natural history, genetics, conservation and photos
- The Gorilla Foundation, home of Koko the gorilla famous for her sign language skills
- Tim Knight's Gorilla Gallery - gorilla pictures
- Primate Info Net Gorilla Factsheet - taxonomy, ecology, behavior and conservation
- San Diego Zoo Gorilla Factsheet - features a video and photos
- World Wildlife Fund: Gorillas - conservation, facts and photos
- Mountain Gorilla - many facts about gorillas
- Gorillas at Prague Zoo - hit reality-tv show (24/7) of live gorillas at the Prague Zoo
- Gorilla quick facts
- The Dian Fossey Gorilla Fund International
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