WESTERN LOWLAND GORILLA

Gorilla gorilla gorilla

Distribution

Western lowland gorillas are endemic to Central Africa. They can be found in Cameroon, the Central African Republic, the Republic of the Congo, the DRC, Equitorial Guinea, Angola and Gabon.

Western lowland gorillas are a tailless member of the great apes family. They are the smallest of the gorilla subspecies, and also the most numerous. The skin is jet-black and short, dark, coarse hair covers the whole body, except for the face, ears, hands and feet. The hair on the back and rump of males take on a silver-grey colour as they get older, which led to the “Silverback” nickname. These gorillas have a wide skull, with a pronounced brow ridge, big nostrils and small eyes and ears. The arms are very long, well suited to quadrupedal movement. Males are usually larger than females and can weigh up to 275kg, whereas females will only weigh about half of that.

Western lowland gorillas prefer rainforests or dense jungle swamps. Gorillas are good climbers, but can mostly be found on the ground. They make themselves “nests” from twigs and leaves to sleep in. Young gorillas often make their nests in trees, and older gorillas make their nests on the ground.

These gorillas are mainly frugivorous (fruit eaters), but they also supplement their diet with leaves, pith, berries, shoots, bark, nuts, lizards, rodents, termites and ants. They can climb trees up to 15m in height in search of food, and won’t strip one food source completely.

Western lowland gorillas live in groups (called troops) of about 5-15 individuals. These gorillas are polygynous (males will have more than one female mate at a time). A troop typically consists of a dominant (silverback) male, with a group of adult females and their offspring.

Sometimes a group of smaller, less-dominant males will live on the fringes of the troop. The silverback will remain dominant until he is displaced, and will typically roam solitary after displacement from his dominant position.

Gorillas are generally peaceful, shy, and amiable unless threatened. Males, if threatened, will attempt to intimidate the threat by standing upright and beating their chests. They also growl and charge at perceived threats. Males may hoot to alert members to danger. Unlike other primates, mutual grooming is not very common.

Western lowland gorillas have a large home range of about 8-47 square km, but don’t display territorial behaviour. Neighbouring groups’ home ranges may overlap. These gorillas will move around within the home range according to seasonal availability of fruit. They can travel up to about 3 km per day!

The dominant male will father all the offspring in his troop. After a gestation period of nine months, a single offspring is born. Females will take on all the parental responsibility for the infant and males will rarely interact with them. The infant will cling to its mother’s fur and when it reaches about four months, it will start riding on its mother’s back. Babies are weaned at 36-48 months and will become independent at about 3-4 years. Both males and females leave their natal groups, but females will move to another breeding group, rarely found alone, whereas males may go through a “bachelor” stage, living in solitary or a non-breeding group. Females reach sexual maturity at about 10 years of age, and males at about 15 years. Gorillas can live up to 50 years in captivity.

Because of their large size, these gorillas don’t have a lot of natural predators.

The threats faced by western lowland gorillas include habitat loss due to farming and human development and hunting. Because gorillas are close relations to humans, human diseases also affect them.

Did you know?

• Gorillas choose fruit that is high in sugar for energy, as well as fiber
• They are able to use tools
• They have the ability to comprehend simple sign language
• Younger males are known as black backs
• Their arms are longer than their legs for quadrupedal walking