Mountain Gorilla trekking with Alan Tours

About Gorillas and Chimpanzees

The chimpanzee is the mammal most like a human. Noisy and curious, intelligent and social, Chimpanzees fascinate humans and are favorites both in zoos and the wild.

There are three subspecies of gorillas living in different parts of Africa. The differences between them are very slight.
• Western Lowland Gorilla (gorilla gorilla)
• Eastern Lowland Gorilla (gorilla graueri)
• Mountain Gorilla (gorilla berengei)

Western – Approximately 10,000-35,000 free-living, 550 in captivity worldwide. Found in Nigeria, Cameroon, Gabon, Congo, Central African Republic and Zaire.

Eastern – Approximately 4,000 free-living. Less than 24 in captivity. Found in eastern Zaire.

Mountain – Approximately 620 free-living. Zero in captivity. Found in 285 square miles in the rain forests of Rwanda, Uganda and Zaire.

Physical characteristics
Height: Male’s 1.7 metre upright, 1.35 metres normal stance. Females’ 1.5 metre’ upright, 1.06 metres normal stance.

Weight: Adult Males 220 kgs. Females 115 kgs. Babies from one to three years weigh between +- 13 Kgs.

Arm Span: Up to 2.80 metres’ (one male specimen).

Colour: Black or brown-grey fur with black skin on chests palms and faces. Red heads are common in Cameroon gorillas especially. Males develop a silver back as they mature.

Stance: Gorillas are quadruped. They walk on all fours with the soles of their feet flat on the ground and the knuckles of the hands curled and planted on the ground.

Recognition: Gorillas recognize each other by their faces and body shapes. Each gorilla has a unique nose print. The differences between mountain gorillas and lowland gorillas are slight and result mainly from adaptation to high altitudes. Mountain gorillas have longer body hair, higher foreheads, longer palates, larger nostrils, broader chests, shorter arms, shorter, wider hands and feet.

Gestation is 8-1/2 months. There are typically 3-4 years between births. Infants stay with their mothers for 3-4 years. Females mature at 10-12 years (earlier in captivity); males 11-13 years, sometimes sooner if they assume leadership early. Lifespan is between 30-50 years.

Gorillas eat some 200 types of leaves, tubers, flowers, fruit, fungus and some insects. Favourite foods include bamboo, thistles and wild celery. Gorillas do not drink water. They obtain all the moisture they need from the vast amounts of foliage they consume. Males consume approximately 50 lbs. a day.

Daily Routine
6am-8am: Wake-up
8am-10am: Eat
10am-2pm: Eat, play, relax, sleep
2pm-5pm: Travel 100metres to 5 kms – foraging on the way
5pm-6pm: Build nest
6pm-6am: Sleep

Social Structure
Gorillas live in groups of 3-30 individuals. A typical group consists of one silverback, one immature silverback, one immature male, three to four adult females and three to six youngsters under eight years old. A female will usually transfer to another group, particularly if the silverback is her father and there are no other suitable males to mate with. Adult males usually leave after sexual maturity and start their own group or join other “bachelors.”

Gorillas learn from their mothers and other adults what to eat, social and sexual behaviour and how to rear their young. They care for their babies with great affection, patience and playfulness. Energetic, mischievous youngsters are disciplined with stern vocalizations (pig-like grunts), body posturing and strong looks. Gorillas also chuckle, smile and purr to show their emotions. They are gentle and intelligent. Gorillas feel deeply and remember for years. Groups are not territorial and generally avoid each other, but when they do meet, sometimes threats and fighting occur, with the silverback remaining to challenge the attacker while the rest of the group flees. To intimidate his opponent, the silverback stands upright to appear larger, beats on his chest, roars, and waves his arms, tears branches and charges. This is all done to frighten off, not harm, other males. Distress behaviour includes diarrhoea and strong, pungent body odour.

Man is the Gorilla’s only enemy. Because of the actions of male Gorillas protecting their groups with such determination from hunters, humans developed folklore about the ferocity of Gorillas. Gorillas defence of standing and chest-beating make them a perfect target for unscrupulous hunters. Like all tightly knit social groups, Gorillas will defend their young tyo the death.

Gorillas are generally quiet. They are not physically capable of making the same sounds as humans. They generate about 25 distinct noises, however. Hooting can carry a mile through the forest and is usually exchanged between rival silverbacks. Other vocalizations include screams, grunts (indicating contentment) and high-pitched barks (indicating curiosity).

An hour visit in Africa with Gorillas with a group of eight tourists is permitted to visit each habituated Gorilla group per day. It can take several hours to reach the Gorillas through the dense, mountainous jungle. Tourism generates a great deal of money for Uganda and helps protect other species as well as the Gorilla.

Most countries have passed laws protecting the gorillas, but enforcement is difficult in remote jungles where the people exist by hunting. Most zoos around the world have agreed not to purchase gorillas from the wild and participate in a worldwide captive breeding program designed to expand the existing captive population while maintaining a viable gene pool.

The greatest threat to the long-term survival of gorillas is habitat encroachment. The human population explosion in Africa continues to create a need for more land to grow food and house people. Gorillas have no place else to go. They can adapt to no new way of life. Tourism has contributed greatly to saving gorillas, but the future is not at all certain.


Fact file:
Swahili Name: Sokwe Mtu
Scientific Name: Pan troglodytes
Size: 900mm to 1.4 metre tall when standing.
Weight: 25kgs. To 50 kg
Lifespan: 50 years
Habitat: Forest
Diet: Omnivorous forager
Gestation: 8 months
Predators: Humans, Leopards

Noisy and curious, intelligent and social, the chimpanzee is the mammal most like a human. Chimpanzees fascinate humans and are favorites both in zoos and the wild.
Three subspecies of common chimpanzees are distributed across the forest zone of Africa from Guinea to western Tanzania and Uganda. Another species of chimpanzees, the bonobo (Pan paniscus), is found exclusively in central Democratic Republic of Congo. In East Africa the chimpanzee is found in the wild in Tanzania and Uganda, but only in captivity in Kenya. Gombe National Park in Tanzania is the first park in Africa specifically created for chimpanzees.

Physical Characteristics

The Chimpanzee has a thickset body with long arms, short legs and no tail. Much of the body is covered with long black hair, but the face, ears, fingers and toes are bare. They have hands that can grip firmly, allowing them to pick up objects. The discovery that they used “tools” for certain purposes surprised the world.


Chimps are mainly found in rain forests and wet savannas. While they spend equal time on land and in trees, they do most of their feeding and sleeping in trees.


Chimps live in groups called troops, of some 30 to 80 individuals. These large groups are made up of smaller, very flexible groups of just a few animals, perhaps all females, all males or a mixed group. Chimps sometimes chew leaves to make them absorbent and then use them as a sponge, dipping them in water and sucking out the moisture. They also use grass stems or twigs as tools, poking them into termite or ant nests and eating the insects that cling to them. They are able to wedge nuts between the roots of a tree and break the shells open with a stone. They are both arboreal and terrestrial, spending much of their daytime hours on the ground. They are quadruped, walking quickly on all fours with the fingers half-flexed to support the weight of the forequarters on the knuckles. They occasionally walk erect for short distances. Agile climbers, building nests high up in trees to rest in during midday and sleep in at night. They construct new nests in minutes by bending branches, intertwining them to form a platform and lining the edges with twigs. Some groups have learnt to make nests on the ground.

Caring for the Young

The female chimp has an estrus cycle of about 34 to 35 days. While in heat, the bare skin on her bottom becomes pink and swollen, and she may mate with several males. She normally gives birth to just one baby, which clings tightly to her breast and, like a human baby, develops rather slowly. An infant can sit up at 5 months and stand with support at 6 months. It is still suckled and sleeps with its mother until about 3 years of age, finally becoming independent and separating from her at about 4 years. Sexual maturity is reached between 8 and 10 years.


Chimps are diurnal (but often active on moonlit nights) and begin their activities at dawn. After descending from their night nests they hungrily feed on fruits, their principal diet, and on leaves, buds and blossoms. After a while their feeding becomes more selective, and they will choose only the ripest fruit. They usually pick fruit with their hands, but they eat berries and seeds directly off the stem with their lips. Their diet consists of up to 80 different plant foods.

In keeping with their close Human relatives Chimps are among the noisiest of all wild animals and use a complicated system of sounds to communicate with each other. A loud “wraaa” call, which can be heard, more than a mile away, warns of something unusual or disturbing. They hoot “hoo-hoo-hoo,” scream, grunt and drum on hollow trees with the flat of their hands, sometimes for hours.

Chimps touch each other a great deal and may kiss when they meet. They also hold hands and groom each other. An adult chimp often has a special “friend” or companion with which it spends a lot of time. Female chimps give their young a great deal of attention and help each other with babysitting chores. Older chimps in the group are usually quite patient with energetic youngsters.


The number of chimps in the wild is steadily decreasing. The wilderness areas necessary to their survival are disappearing at an alarming rate as more forests are cut down for farming and other activities. As the human’s closest relative the chimp is vulnerable to many of the same diseases, and their capture for medical research contributes to their decline, especially in West Africa, as more forests are cut down for farming activities.

Did you know?

Chimpanzees use large sticks and branches as clubs or throw them at enemies like leopards and humans.

Chimps supplement their diets with meat, such as young antelopes or goats. Their most frequent victims, however, are other primates such as young baboons, Colobus monkeys and Blue monkeys.


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