Gorillas

Gorilla Facts

Classification:

• Kingdom: Animalia
• Subkingdom: Bilateria
• Phylum: Chordata
• Subphylum: Vertebrata
• Class: Mammalia
• Order: Primates (apes, monkeys, and humans)
• Family: Hominidae
• Genus and species:Gorilla gorilla (western gorilla),Gorilla beringei (eastern gorilla)
• Geographical location: Equatorial West Africa
• Habitat: Lowland and highland forests
• Gestational period: Nine months
• Life span: Thirty to forty years in the wild, up to fifty years in captivity
• Special anatomy: Long arms used to walk on all fours

Gorillas, the largest and strongest apes, look the most human of all other primates. They live in equatorial West African forests, from lowlands near the Cameroon Coast to highland altitudes of 10,000 feet in Rwanda, the Democratic Republic of the Congo, and Uganda. All gorillas are believed to belong to one species, Gorilla gorilla.

Physical Characteristics of Gorillas

Males are 5.75 feet tall when on all fours, over six feet when standing erect, and thus are taller than the average man. They are much heavier, weighing three hundred to six hundred pounds. Unsurprisingly, their bone structure is heavier than that of humans. Females, a foot shorter than males, weigh half as much. Gorilla skin is dark and, except for the face and hands, covered with long, coarse, dark brown to black hair. This hair turns gray on the backs of older males, who are then called silverbacks.

Gorillas, especially males, look fierce, although they are timid unless mating, cornered, or threatened. Their fierce looks are due to hulking bodies and somber faces, with dark, hairless, strong jaws and long, powerful teeth. In addition, gorillas have brutish brow ridges that jut out above small eyes. Finally, the face of the male is dominated by a large, flat nose with coarse nostrils. Combined, these features produce what humans perceive as a somber and threatening expression.

Gorilla brain cases and brain sizes are smaller than in humans, promising lower intelligence. As to skeletal structure, the gorilla is similar to humans, but its bones are thicker. Its arms are much longer and its legs are much shorter. Gorilla spines lack the structures needed for a continual erect posture. Therefore, while gorillas can stand upright and walk erect, most often they walk on all fours, using the knuckles of their hands as supports.

Life and Sexual Cycles of Gorillas

Contrary to their legendary savagery, reinforced by their appearance, gorillas are shy, friendly creatures. Once they become used to unthreatening intruders, as Dian Fossey discovered, these individuals are accepted. Initially, males of gorilla groups charge intruders, growling and beating their chests. Intruders who run are often killed. Those who stand their ground and behave in an unthreatening manner are not harmed.

Gorillas live in families and extended families (bands) of five to twenty individuals. A band has a silverback leader, up to three subordinate males who help protect it, several mature females, and numerous young. The silverback drives most young gorilla males away at maturity. At these times all males are fierce and use their strength to attain and maintain supremacy. Males that are driven off form bachelor groups or join other bands. Silverbacks, challenged and defeated, live alone.

Gorilla bands each have a territory they allow others to enter. A band lacks permanent dwellings. Rather, its members build temporary shelters each night after a long day of travel to forage for the honey, eggs, plants, berries, bark, and leaves that make up the gorilla diet. In the wild or in captivity gorillas will eat meat, but do not seek it or kill other animals, except in self defense. When the terrain permits, females and young sleep on tree platforms of branches and leaves. Mature males nest at the bases of trees occupied by other band members.

Female gorillas, like women, menstruate monthly and mate successfully at any time. Pregnancy lasts 9.5 months and yields one or two young. Baby gorillas are suckled for a year. They are adults ten to eleven years later. Wild gorillas live for thirty to forty years. A few captive gorillas have attained more than fifty years.

Gorilla Language and Intelligence

Gorilla language is composed of several sounds. Hooting signals alarm or indicates unusual events. Hooting by a silverback gains immediate attention from all band members. Other language sounds include sharp grunts that discipline young gorillas and low growls signifying pleasure. All gorillas beat their chests. In males, this is a symbol of power and intimidates other creatures.

The mental capacity of gorillas was long thought inferior to chimpanzees. Their intelligence is still being explored and testing is changing experimenters’ opinions. Different techniques are needed to train gorillas, who are not as curious as chimpanzees. Trained correctly, gorillas have better memories and problem-solving skills than chimpanzees. They also discriminate between geometric shapes better. In addition, it is reported that they are most likely to perform tasks associated with intelligence out of interest, not for rewards. In exploration of communication via American Sign Language (ASL), some gorillas have mastered over one hundred words.

Gorillas’ Endangered Status

Gorillas are close to extinction because of intrusion on their habitat of farmers, animal herders, and hunters. In the early 1970s, the estimated gorilla population was one thousand. About 25 percent were in Zaire’s Kahuzi-Biega National Park (KBP) and 40 percent in its Mount Virunga area (MVA). The rest were scattered but relatively numerous in Rwanda’s Parc des Volcans and Uganda’s Gorilla Game Reserve.

In 1980, the number of gorillas in KBP was unchanged and those in MVA had dropped 40 percent. The implied decline, which may be continuing, is explained by increased farming and cattle herding in gorilla habitats. Also, killing and poaching of elephants and buffalo causes these animals to move into gorilla habitats, cutting down food sources for the great apes. Estimates based on surveys that began in the mid-2000s have noted a population of about 150,000 to 250,000 for the G. g. gorilla, the largest subspecies remaining. However, between 2005 and 2013, this population declined by almost 19 percent. As of 2016, the IUCN Red List of Threatened Species listed the western gorilla as "critically endangered." The eastern gorilla has an estimated population of less than five thousand. This subspecies is also listed as critically endangered.

Principal Terms

band: A gorilla group of five to twenty apes, including males, females, and young

silverback: An older, male band leader, whose back hair has turned gray

Bibliography

Dixson, A. F. The Natural History of the Gorilla. New York: Columbia UP, 1981. Print.

Maisels, F., R. A. Bergl, and E. A. Williamson. "Gorilla gorilla." IUCN Red List of Threatened Species 2016. International Union for Conservation of Nature and Natural Resources, 2016. Web. 4 Oct. 2016.

Mowat, Farley. Woman in the Mists: The Story of Dian Fossey and the Mountain Gorillas of Africa. New York: Warner, 1987. Print.

Nichols, Farley. The Great Apes: Between Two Worlds. Washington: National Geographic Society, 1993. Print.

Plumptre, A., M. Robbins, and E.A. Williamson. "Gorilla beringei." IUCN Red List of Threatened Species 2016. International Union for Conservation of Nature and Natural Resources, 2016. Web. 4 Oct. 2016.

Verrengia, Joe. Cenzoo: The Story of a Baby Gorilla. Boulder: Roberts Rinehart, 1997. Print.