Mountain Gorillas

Few animals have sparked the imagination of man as much as the gorilla, the largest of the living primates. Most gorillas live in inaccessible regions in various dense forests in tropical Africa, and one subspecies, the mountain gorilla (Gorilla beringei beringei), was not even known to science until 1902.

A chain of eight volcanoes known as the Virungas runs through a western section of the Rift Valley, forming part of the border between Uganda, Democratic Republic of Congo (formerly Zaire) and Rwanda. These spectacular mountains and the nearby Bwindi Impenetrable National Park in Uganda are the last refuges of the most endangered of the gorilla subspecies, the mountain gorilla. Only about 700 of these wondrous creatures remain.

Physical Characteristics

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. It is the hairiest race of gorillas; its long, thick black hair insulates it from the cold of living at high elevations. Gorillas have large heads – especially males, who’s sculls have a prominent crest. Facial features like wrinkles around the nose – called nose prints - are unique for each individual and are often used by human researchers for identification.

Habitat

Mountain gorillas are confined to four national parks, separated into two forest blocks no more than 45 kilometers (28 miles) apart and comprising approximately 590 sq km (228 sq mi) of afromontane and medium altitude forest. One population of mountain gorillas inhabits the Bwindi Impenetrable National Park in Uganda. A census in 2002 recorded between 310-315 individuals here. The second population of mountain gorillas is found in the habitat shared by Mgahinga Gorilla National Park (Uganda), Volcano National Park (Rwanda) and Virunga National Park -Southern Sector (DRC). The Virunga population numbers at least 358 individuals and has grown by 11% in the past 12 years.

Behaviour

Mountain gorillas are not the ferocious beasts depicted in imaginative movies. Although strong and powerful, gorillas are generally gentle and shy. Gorillas have strong attachments to members of their own group. They live in groups of 2-30 individuals, on average 11. Groups are led by a dominant male, the silverback, named for the silvery gray hairs that grow when the male matures. The silverback serves as the chief protector and defender of the group. All members of the group defer to the silverback. He leads, deciding when and where to forage, rest and sleep. He arbitrates disputes among his family members and protects them from rival silverbacks or human predators.

Gorillas continually wander through their home ranges of 1.5 to 3 square miles, feeding and resting throughout the day. Mountain gorillas roughly spend 30% of their day feeding, 30% traveling or moving, and 40% resting. At dusk, they settle down for the night and sleep in nests. These nests are made of vegetation that the gorillas shove under and around them, forming rimmed cushioned platforms.

Gorillas, especially males, have a wide range of vocal and physical communications. Silverbacks can roar, scream and bark to deter predators or competitors. They stand on their legs and beat their massive chests, which contain airsacks, to produce an intimidating thudding sound. They may even charge at people or gorillas they see as threatening, striking the ground with their fists in a display of aggression.

Diet

It is perhaps surprising that mammals as large and strong as mountain gorillas are primarily herbivores (vegetarians), which eat a variety of plants and leaves. They eat a staggering 142 different species of plants, including bamboo, wild celery, thistles, stinging nettles, bedstraw and certain fruit. They rarely need to drink since their diet is so rich in succulent herbs, from which they get enough water. They will occasionally eat their feces, possibly to prevent the loss of minerals through digestion, although the exact reason has not yet been determined.

Caring for the young

Mountain gorillas have a slow rate of reproduction. This slow reproduction makes this species even more threatened. In a 40-50 year lifetime, a female might have only 2-6 living offspring. Females give birth for the first time at about age 10 and will have offspring every four years or more. A male reaches sexual maturity between 10 and 12 years. Able to conceive for only about three days each month, the female produces a single young and in rare cases twins.

Newborn gorillas are weak and tiny, weighing about 4 pounds. Their movements are as awkward as those of human infants, but their development is roughly twice as fast. At 3 or 4 months, the gorilla infant can sit upright and can stand with support soon after. It suckles regularly for about a year and is gradually weaned at about 3.5 years, when it becomes more independent.

Predators

The mountain gorilla's true threat is man. The primary threat to mountain gorillas comes from forest clearance and degradation, as the region's growing human population struggles to eke out a living. Conversion of land for agriculture and competition for limited natural resources such as firewood lead to varying degrees of deforestation of gorilla’s natural habitat. The only way to maintain gorilla habitat is to develop alternative economic activities that allow people to meet their daily needs, so that they see gorillas not as competitors, but as a means of improving their own situation.

Poachers have also killed entire family groups in their attempts to capture infant gorillas for zoos, while others are killed to sell their heads and hands as trophies.

Gorillas are closely related to humans, with similar anatomical and physiological features. This makes them vulnerable to many of the same diseases. Because the gorillas have not developed the necessary immunities, first time exposure to an illness or virus that is relatively innocuous to humans may devastate an entire population.

AWF, in collaboration with WWF and FFI, established the International Gorilla Conservation Program (IGCP) to safeguard the last remaining mountain gorillas. This coalition has been a tremendous success. Although mountain gorilla numbers are slowly increasing, much more help is needed.

Visit AWF to find out how you can help Save the Last Mountain Gorillas

Did you know...

• Humans and gorillas are 98% genetically identical.
• Male silverback gorillas can weigh 50-100 pounds more - and are about 10 times stronger - than the biggest American football players.
• When the group is attacked by humans, leopards, or other gorillas, the silverback will protect them even at the cost of his own life.