Gorilla

Facts
Conservation
SSP Status

The western lowland gorilla has blue-black to brownish gray hair. Their bare skin is black. Mature males have a silver or gray saddle on their back, thus they are called “silverbacks”. Male gorillas that are not of breeding age are called “blackbacks”. Gorillas have a robust build with a big stomach, long thick arms, and short legs. Their hands and feet are wide with thick digits. The hands are dexterous and can pick up amazingly small, delicate objects. Their feet, like their hands, have opposable thumbs. Gorillas walk on all fours with their fingers carried under, this develops calluses on their knuckles and preserves the <image> sensitivity of their fingers. They have large teeth with sharp canines which they are used for defense as well as breaking tough vegetation. They have an exceptional sense of smell and can see and hear very well. There are 16 to 25 vocalizations that have been identified as well as various body postures. Facial expressions help them also to communicate to others in the family group. Adult females weigh 68.1–113.5 kg. (150–250 lb.), while males weigh 158.9–204.3 kg. (350–450 lb.) The largest primate, they are 1.5–1.8 m. (5–6 ft.) tall.

Gorilla Facts

Range

Cameroon, Zaire, Gabon

Diet

Gorillas eat over 200 distinct species of plants, mainly leaves, buds, shoots, roots, bark and fruit. Banana and sugar cane plantations are usually sought out. They also eat termites and ants.

Behavior

Gorillas have very well developed social behavior. Their troop, or group, is a non-territorial harem that consists of 2 – 30 members. In general, the dominant male, or silver back, changes only with births or deaths however sometimes it may occur as a result of the addition of a solitary male. The home range, depending on habitat and size of the troop, is 7 – 9 square meters (8.4–10.8 sq. yd.) Their day range is 1 – 2 kilometers (.6–1.2 mi.) daily, and is not territorial. Diurnal, they are most active during the day, and wander casually, changing sleeping quarters daily and building new nests every night. When troops meet, they either disregard or greet each other, fighting is uncommon. The intimidating chest beating of a male gorilla is usually a bluff to scare off intruders, while the rest of his troop disappears into the forest. Staring is a sign of hostility to a gorilla. A direct gaze signals a challenge to the gorilla and may be stressful.

Reproduction

The female becomes sexually mature at approximately 8 years of age, the male at approximately 11. The hierarchy within a troop is based on size and seniority and it determines mating. After 8 to 9 months, the mother gives birth to one baby, weighing 1.8–2.5 kilograms (4–6 lb.) Twins are rare. The young live with the mother for three years, with weaning commences at 1.5 years.

Conservation Status

Listed by USFWS (United States Fish and Wildlife Service) as endangered and protected by CITES. Gorillas are endangered due to increases in human population and the need to cultivate more land for farming and cattle. The natural habitat of the gorilla is shrinking. Poaching is also a problem for gorillas.

Lifespan

In captivity they live 40 – 50 years. In the wild, 30 – 40 years.

Gorilla Conservation Issues

General statement

There are two species and four species of gorillas found in Africa. Western gorillas, found in the countries of Nigeria, Cameroon, Gabon, Equatorial Guinea, Republic of Congo, Angola, and Central African Republic, are divided into the Cross River and western lowland subspecies. Both are considered critically endangered. Eastern gorillas, found in the countries of Democratic Republic of Congo, Uganda and Rwanda, are divided into the mountain gorilla and Grauer’s gorilla subspecies. Mountain gorillas are classified as critically endangered and Grauer’s gorillas as endangered. Threats to gorillas vary geographically. Western gorillas are primarily threatened by disease and the bushmeat trade. Threats to eastern gorillas include habitat loss and poaching.

Bushmeat

Though habitat loss is often cited as the primary threat to wildlife, commercial hunting for the meat of wild animals (bushmeat) such as gorillas has become the most significant threat to the future of wildlife in Africa and around the world. Poaching of western gorillas in for food occurs despite the fact that they are protected under both national and international laws in all range states.

For thousands of years, bushmeat has been part of the subsistence of rural populations in Africa. But as the population of Central Africa has become increasingly urbanized, bushmeat has become a commercial trade, with meat fetching a high price on the black market, consumed by the rich and middle class and sold in the US and Europe as well.

Deforestation

Areas surrounding eastern gorilla habitat have some of the highest human population densities in the world. As a result, habitat has been destroyed to create farms and extract firewood or water. In western Africa, commercial logging is damaging large tracts of pristine forest and facilitates the bushmeat trade. In addition to loosing their homes and food, fragmented forests leave gorillas vulnerable to poachers, hunters and human disease transmission.

Poaching/Pet trade

Historically, gorillas were poached for their hands, feet, and heads and infant gorillas were captured for zoos or private collections. Whereas the trade in body parts has decline in the last few decades, gorillas infants are still captured for the pet trade. Because a group of gorillas will protect their young, the capture of an infant involves the death of its mother and often its father. Many of these animals do not survive or suffer severe physical and psychological damage.

Political unrest

Political unrest can create serious problems for wildlife. Political instability can make it difficult for wildlife authorities to protect endangered species and their habitats. Often people displaced from war will rely on hunting as a means of support for their families.

Diseases

The Ebola virus has had a devastating impact on western populations and may be responsible for a 50–90% decline in western gorilla populations in many parts of Gabon and Congo over recent years. Disease risks posed by humans pose an additional danger. Gorillas have already been shown to be vulnerable to human pathogens, mainly those associated with respiratory, intestinal and skin diseases. The eastern species of gorillas, which lives in areas of high human density and has several well-developed ecotourism programs, is particularly vulnerable to human-induced diseases.

Online resources

AZA Gorilla SSP Status

The Gorilla Species Survival Plan (SSP) guides the management of over 360 gorillas in 52 zoos across the United States. Although the SSP’s primary roles are population management and promoting optimal care in zoos, the members are also committed to addressing critical issues facing apes. Critically endangered in their native Africa, gorilla populations are perilously low due to several factors including deforestation, disease and the bushmeat crisis. The SSP supports in situ activities that address these issues. To learn more, visit the Gorilla SSP at: www.gorillassp.org.

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