Gorilla

The largest of the world’s primates, it is thought that the gorilla lineage split from that of the chimpanzee and humans about seven million years ago.

In spite of their fearsome appearance, gorillas are not aggressive by nature. They live in small family groups, moving through their territory and making fresh beds (nests) of grass where they sleep each night. They will climb trees on occasion, particularly the younger, more agile members of the group, to reach fruit. There are fears that, aside from poaching, the Ebola virus may be decimating populations of these great apes.

Distribution: Western Africa, occurring in the forests of Gabon, Equatorial Guinea, Cameroon and south as far as Angola.

Weight: 60 - 275 kg (132 - 606 lb); males are larger.

Length: 140 - 180 cm (55 - 71 in).

Maturity: Females 10 years; males 15 years.

Gestation Period: 251 - 289 days.

Breeding: 1, very rarely twins; weaning occurs at 3 - 4 years.

Diet: Feeds mainly on leaves, also fruit, flowers, roots and invertebrates; will eat clay to detoxify plant matter.

Lifespan: Up to 50 years.

Head colouration

The reddish area on the head is a distinctive feature of lowland gorillas.

Feet

These are very broad, facilitating walking, but the toes are relatively short and the big toe is widely spaced.

Forearms

These are strong, and gorillas walk on their knuckles rather than their palms.

FEEDING

These gorillas may venture into wet areas, feeding on aquatic vegetation. They have also been known to use primitive tools.

Male gorillas appear especially formidable when they stand up on their hind legs.

Mountain Gorilla

Although there is doubt as to whether mountain gorillas constitute a separate subspecies, genetic analysis has shown that they are more closely related to the eastern-lowland gorillas than to the western-lowland gorillas. Mountain gorillas tend to be larger, and have much longer and silkier fur, especially on their arms, than their lowland cousins. They also occupy a very different habitat, and are found almost exclusively in cold mountain rainforests of bamboo, at altitudes over 2,000 m (6,560 ft).

Scientists George Schaller and Dian Fossey, who spent many years living in close contact with mountain gorillas, studied these enigmatic animals in detail. They found that they live in relatively large groups of up to 30 individuals, and that they communicate with a wide range of calls.

Gorillas travel up to 1 km (0.6 miles) in search of food each day, and build crude nests out of leafy branches, usually on the ground, where they sleep at night. They number little more than 600 animals in the wild. Mountain gorillas have suffered heavily from accidental trapping.

The long, silky fur of the mountain gorilla helps to protect it from the freezing conditions sometimes found in its mountain habitat.

Distribution: The Virunga volcanoes lying between Congo, Rwanda and Uganda.

Habitat: Montane forest and bamboo forest.

Food: Leaves and shoots.

Size: 1.5 - 1.8 m (5 - 6 ft); females 110 - 140 kg (240 - 300 lb); males 200 - 275 kg (440 - 605 lb).

Maturity: Females 7 years; males 15 years.

Breeding: Single young, or occasionally twins, born after 9 months' gestation. Females usually give birth to only 2 - 3 surviving young in a lifetime.

Life span: 50 years.

Status: Critically endangered.

Western-lowland Gorilla

Western-lowland gorillas live in relatively small groups of only about six animals. Each group is led by dominant males, or silverbacks - so called because of the grey-white fur only found on the backs of older males.

Although gorillas are large and extremely powerful, they are gentler than chimpanzees. Gorilla groups tend to avoid one another although, on occasion, groups will meet amicably for a short time. Sometimes meetings are not peaceful, and a dominant silverback may respond to intruders by standing up, hooting and beating his chest with cupped hands, followed by a display of strength by breaking branches. This display may lead to an all-out fight between the large males.

The armspan of a gorilla is greater than its height - up to a huge 2.75 m (9 ft). This illustration shows a male silverback.

Distribution: South-eastern Nigeria, west-central and southern Cameroon, southwestern Central African Republic, Guinea, Gabon and the Congo.

Habitat: Lowland tropical forests.

Food: Leaves and shoots.

Size: 1.25 - 1.75 m (4 - 5.5 ft); females 70 - 140 kg (154.25 - 308.75 lb); males 135 - 275 kg (297.5 - 606.25 lb).

Maturity: Females 7 years; males 15 years.

Breeding: Single young, or occasionally twins.

Life span: 50 years. Status: Endangered.