Gorillas are the largest and most powerful of all primates. Gorillas are one of our closest living relatives, with a genetic makeup almost 98% similar to humans.
There are three species of Gorilla: Western Lowland (20,000 + in the wild), Eastern Lowland (about 5000 in the wild) and the critically endangered Mountain Gorillas of Uganda/Rwanda (about 500 only in the wild).
Gorillas have been re-classified. We now say there are two species of Gorilla the Eastern and the Western Gorillas. The Western Gorillas includes the Western Lowland Gorillas (species held at Taronga) and the Cross River Gorillas. The Eastern Gorillas includes the Eastern Lowland Gorillas and the Mountain Gorillas.
The female adult gorilla averages 1.5m in height and weighs 90kg, while an adult male averages 1.7m and weighs 160kg or more.
The gorilla is a gentle, social animal that lives in close family groups of five to 10 animals. These groups provide safety, protection and opportunities for young gorillas to learn.
The group is led by a dominant male called a “silverback.” The Silverback has grey hair on its back which develops with sexual maturity at the age of 11. The Silverback is responsible for leading, protecting and defending the group.
Adult males are called “Blackbacks” and are often driven away from the group by the Silverback when they reach maturity. They then join bachelor groups or start their own families with low ranking females. Ranking is part of the gorilla family's hierarchy. If a low ranking female has an infant her rank may change as she now plays the important role of mother.
Adult females rear the young. The Silverback may have a favourite female among this group. Young females stay with the family until they reach breeding age. They then leave the group to form families with unrelated males.
Along with the other species of gorillas, the Western Lowland Gorilla is classified as an endangered species and is facing extinction.
The greatest threat to their wild existence is the bush meat trade. Although Africa's great apes are protected by national wildlife laws, it is estimated that over 600 adult gorillas are killed as bush meat every year. This also leads to thousands of young gorillas becoming orphans.
Adult gorillas are often hunted for trophies and infant gorillas are stolen for the pet trade. To obtain a young gorilla, poachers often kill all defensive family members. Other threats include mining, forest clearance for timber and farming.
There are approx. 690 gorillas in zoos and wildlife parks around the world, contributing to world breeding programs. These are nearly all Western Lowland Gorillas. These zoos work together to share potential breeding animals and data in the effort to build a healthier, genetically varied population and to increase reproductive rates.
There are no Mountain Gorillas in zoos but conservation efforts for this species are in place in the wild.
Distribution & Habitat
The Western Lowland Gorilla is found in Cameroon, Central African Republic (CAR), mainland Equatorial Guinea (Rio Muni), Gabon, Nigeria, Republic of Congo (RoC), Cabinda (Angola), and possibly in the Democratic Republic of Congo (DRC).
They are found primarily in lowland tropical forest, particularly where there is dense ground-level herbaceous growth, and in swamp forests with plenty of new growth where it is hot and humid with year round rainfall.
Gorillas live in groups averaging 10 and occasionally over 20 individuals, composed of at least one adult male, several adult females and their offspring. Each group’s home range may be as large as 20 km² and group ranges overlap extensively.
Western Lowland Gorillas breed throughout the year. Females usually begin to breed when they are 10 to 11 years old while males rarely mate successfully before they are 15. The female is pregnant for eight to nine months, giving birth to a single young or occasionally twins. During the early weeks, a newborn gorilla is clutched belly to belly for close contact until it develops the strength and coordination to cling onto its mother’s hair at about two months. The young gorilla is suckled for about a year (weaned at about three years of age) and will stay with its mother until it is three to four years old.
Gorillas life expectancy is up to 50 years in zoos but usually considerably less, approx. 35 years, in the wild.
Gorillas eat for most of the day with the Silverback leading the family in search of food and travelling around 400m each day. Gorillas are mostly vegetarian. Western Lowland Gorillas eat over 200 different types of plants and will also feed on flowers and fungus. Favourite foods include bamboo, thistles and wild celery. They never strip a site bare - this means the forest will regenerate.
Soft chest beating is commonly used for family communication in the dense forest. More threatening chest beating and roaring is used by the Silverback to protect the group and his position. Young gorillas are often seen practising this behaviour.
Gorillas sleep about 13 hours each night and rest for several hours during the middle of the day. Each gorilla builds two nests every day - one for the midday sleep and one for the night. A nest is never used twice. The nests are made by bending plants, leaves and branches into a springy platform, usually on the ground or in low trees