Gorillas are divided into 2 recognised species and 4 sub species. The Western Gorilla comprises of the Western Lowland Gorilla and the Cross River Gorilla. The Eastern Gorilla comprises of the Mountain Gorilla and the Eastern Lowland Gorilla. It is being debated that the Bwindi Gorilla is a proposed third separate species of Gorilla.
The Virunga Volcanoes, a chain of eight volcanoes runs through a western section of the Great Rift Valley, forming part of the border between Uganda, Congo and Rwanda.
These magnificent mountains and the nearby Bwindi Impenetrable National Park in Uganda are the last safe havens of the most endangered of the gorilla subspecies, the mountain gorilla. Only about 660 of these individuals remain.
Most of the gorillas reside on the slopes of the three dormant volcanoes in the upper region(Karisimbi, Mikeno, and Visoke),while the rest inhabit the other three dormant volcanoes in the lower region (Sabinyo, Mgahinga, and Muhavura). Apparently, the gorillas never climb above about 3,965 m (13,000 ft) and are rarely seen in the low area between the two groups of dormant volcanoes.
The gorillas also seem to avoid open meadow areas - they will rather go around a meadow than cross it. The gorillas are located most often in the Hagenia forests, in the bamboo forests (depending on the season), and now and then in the subalpine vegetation zone.
The gorilla population is fairly small and still on the decline. Currently, there are about 50,000 western lowland gorillas living in West Central Africa. This gorilla is also the type most often seen in zoos. The eastern lowland gorilla population, on the other hand, has dramatically declined in recent years.
In the 1960's an estimated 5,000-15,000 lived in the eastern Congolese rainforest. Today only about 2,500 remain in the wild, and only a few dozen can be spotted in the world's zoos. The mountain gorillas are the rarest of all and are on the brink of extinction.
Only about 600 mountain gorillas are left in the wild. Hunting and poaching reduced their numbers to about 250 by 1981, when the protection efforts of the late Dian Fossey and others brought the decline to a halt.
Today, about 320 inhabit the Virunga Mountains and another 300 in the Bwindi Impenetrable Forest National Park in Uganda, but their long-term survival continues to be threatened by natural changes and disasters, hunters and poachers and the chronic political instability. None are found in captivity.
The gorilla is enormous! Mature males average around 400 pounds in the wild and the females around 200 pounds. Standing upright, males can sometimes measure up to six feet tall. The separate subspecies of gorilla differ slightly in appearance:
Eastern gorillas tend to be darker in color, with longer hair, jaws and teeth. They also have shorter arms than their western gorilla relatives. The mountain gorilla has a robust build with long, muscular arms and short legs, a massive chest, and broad hands and feet with thick digits.
Gorillas have large heads - especially males, who's sculls have a prominent crest. Adult males grow a crown of muscle and hair that makes the head look even longer. The fully grown adult male mountain gorilla is twice as large as the female.
Gorillas have a unusually large head with a bulging forehead, a ridge on top, tiny ears, and small, dark-brown eyes. They have no tail. Adult gorillas have 32 teeth, with large molars for chewing food and large canines used for biting, The canines are especially large in the male gorillas. Gorillas each have a unique nose print.
Hands and Feet
Gorillas' hands are very similar to humans'hands: they have five fingers, including an opposable thumb. Their feet have five toes, including an opposable big toe. Gorillas can grasp things with their hands as well as their feet.
Gorillas have senses very similar to the human being, including hearing, sight (colour vision), smell, taste, and touch.
Newborn gorillas are small, covered with thick black hair, and weigh about 2.3 kg (5 lbs). Until the age of 2, they must be cared for at all times. When they reach the age of 2, they are able to reach and chew on vines and branches. According to research, they develop almost twice as fast as human babies.
Male and female gorillas between the ages of about 3 and 6 are classed as juvenile. During this stage, both sexes have thick black hair and black skin. Both sexes of juveniles increase in size and weight at similar tempos for the first 6years. Around age 6 they are about 1.2 m (4 ft) tall and weigh about 68 kg (150 lbs).
Female gorillas mature at about age 6 and don't seem to grow taller, although they continue to gain weight gradually until they reach weights of 113-136 kg (250-300 lbs) at ages of 10 to 11 years. Males, on the other hand continue to grow both in size and weight past the age of 6. They only start maturing until they are about 10years old. Between the ages of about 6 and 10years, males maintain the black hair colour of their youth and are called 'blackbacks'.
As the male mountain gorilla mature, they develop a patch of grayish or silver-coloured hair on their backs. Hence, mature males are called silverbacks. Males do not grow in size or weight after maturity, but at typical heights of 1.5-1.8 m (5-6 ft) and weights of 204-227 kg (450-500 lbs), they are strikingly large animals. It is quite difficult to estimate the maximum life span of mountain gorillas in the wild, but it has been estimated at around 25 - 30 years.
The gestation period for gorillas is about nine months- the same as humans. Gorilla mothers with an infant is not capable of having another for up to 4 years. In addition,there is no evident breeding season, since births of baby gorillas take place throughout the year. However, many baby gorillas die in the first year of their life, and almosthalf of all gorillas die before reaching adulthood. This is due to factors such as mishaps and disease.
Gorillas are known to live in small family groups made up of altering numbers of males, females, infants, and juveniles. Each group is led by a dominant male gorilla. It is the dominant silverback's responsibility to protect his group and lead in the search for food.
Typically, the females stay with the family, while the males leave their groups at adolescence. As a result, mothers, daughters, sisters, and grandmothers stick together in family groups. However, a different social structure is emerging among gorillas i.e. females leave their family and join other groups.
Another behavioural trait the gorillas display, is that they try to defend one another when faced with danger. The death of a one gorilla also has a tremendous effect on the others, especially when the dominant silverback dies the family group may be severely disrupted.
The group may split into two or more smaller groups. When a new silverback takes over a family group, he may kill all of the infants of the dead silverback. This is considered as an effective reproductive strategy since the new male conceives offspring that carry on his genes. In most harmonious groups, there is no clear evidence of infanticide.
Gorillas have strong attachments to members of their own group. Even when groups meet and mingle and then go their separate ways again, each gorilla tends to remain with its social group. Gorillas continually stroll through their habitat ranges of about 12 square miles, feeding and resting throughout the day. They build new nests each day at sunset, creating them of branches in a tree or of grasses on the ground.
A group's hierarchy, ritualized behavior and bluff charges between males prevents conflict among and between groups. Gorillas scream, grab foliage and stuff it in their mouths, stand erect on their hind legs, tear up and throw plants, drum on the chest with hands or fists, stamp their feet, strike the ground with the palms of their hands and gallop in a mock attack on all fours.
Communication is used to teach the young many skills in order for them to survive, and for other gorillas to communicate about food, distress, mating, etc. Gorillas communicate with each other through sound and body language. Many of their actions symbolises the hierarchy of the group. A silverback may make a 'threat gesture' by turning sideways to show how big he is or by 'yawning' to boast his large canine teeth.
Gorillas are known to make many sounds. Over 25 distinct sounds have been documented. Some of them include:
- Hooting, plant slapping, and beating of the chest, sometimes accompanied by prancing
- Sharp grunting: a sign of disapproval
- Chuckling: a sign of playfulness
- Screaming: a sign of alarm or warning
- High-pitched barking: a sign of curiosity
- Roaring: a sign of aggression
- Belching: a sign of contentment
Gorillas are very intelligent and can learn tremendously complex tasks. Some gorillas have even been taught sign language by people and others have learned how to form simple sentences and communicate with people.
Gorillas knuckle-walk using both their legs and their long arms with the fingers rolled into the hand. Gorillas never walk using only their legs. They can climb trees, but do so very rarely. Gorillas cannot swim.
Mountain gorillas are primarily vegetarians. They eat various types of plants, including the roots and stems of some plants, the leaves and flowers of other plants, and even the bark of certain trees. They also eat the fruit of several types of trees and vines, wild celery, thistles, the tender shoots of bamboo plants, and certain vines in their entirety.
These plants seem to supply the gorillas with sufficient moisture. Therefore, water is not really necessary.Bamboo shoots are available only a few months of the year usually between August and December. The gorillas also eat the soft centers of the giant senecio trees, which can be found in the subalpine zone. Gallium vines, are also a favorite. Gorillas often take naps after eating a meal in the middle of the day. An average adult male eats more or less 50 pounds of food a day.
The only real enemies of gorillas are leopards and humans. Although, crocodiles are potentially dangerous to lowland gorillas. In western Africa, gorillas are frequently hunted for meat, but in eastern Africa they have been the victims of traps set for other animals like antelope. Poachers have also abolished entire family groups in their attempts to capture infant gorillas for zoos, while others have been killed to sell their heads and hands as trophies.
Life for mountain gorillas isn't all harmonious. They are endangered and threatened by civil war in the small area of Africa where they live. Many devoted scientists, park rangers, and other concerned people are working hard to protect mountain gorillas and their forests.
Where to visit
The two main areas to visit gorillas are Bwindi Impenetrable Forest and Mgahinga National Park. Gorilla tracking is strictly controlled to ensure that the gorillas do not get disturbed. Only 6 visitors are allowed each day. Visitors should book with a tour operator beforehand or directly with Uganda National Parks in Kampala. 3 months notice is recommended.
Gorilla Tracking in Bwindi
There are two gorilla groups available for viewing in Bwindi. Mubare Group consists of 16 members with 1 silverback and has been habituated since 1993. Habinyanya Group consists of 23 gorillas with 2 silverbacks and a third group consisting of 17 members and 2 silverbacks is currently being habituated and may be ready by 2002.
Gorillas in Mgahinga NP
There is currently one group habituated to receive visitors. Known as The Tourist group (or Nyakagezi group) it consists of 9 members: 2 silverbacks, 3 adult females, 2 juveniles and 2 infants. A second group is currently being habituated and may be ready for visitors in 2002.
Gorilla Safari treks
Read more on Gorilla Safari treks and tours in Uganda and Rwanda.