There are two species of gorilla found in Africa: the Western Gorilla (Gorilla gorilla) and the Eastern Gorilla (Gorilla beringei). The Eastern Gorilla consists of two subspecies: the well-known Mountain Gorilla (G. b. beringei) of Bwindi and Virunga Forests of Uganda and Rwanda and the Democratic Republic of Congo, and the Eastern Lowland Gorilla (G. b. graueri) of the eastern parts of the Democratic Republic of Congo.
Both of these subspecies are considered Endangered. The Western Gorilla also consists of two subspecies: the Western Lowland Gorilla (G. g. gorilla) principally of Congo (Brazzaville) and Gabon, and the little known Cross River Gorilla (G. g. diehli) of the border region between Cameroon and Nigeria.
Both of these subspecies are considered Endangered as a result of commercial bushmeat hunting, disease epidemics and habitat loss. The very slow rate of reproduction exacerbates this situation.
It is the Western Lowland Gorilla that occurs in Odzala and is found here at the highest densities so far recorded for the species. In the area of Ngaga Camp, Western Lowland Gorillas live in groups ranging in size from 10 to 25 individuals (average 16-17 animals), usually with one silverback, 5-7 adult females and a collection of subadults, babies and sometimes subordinate males.
In this high-density area, home range size is between just less than 4 km2 and just over 8 km2 (average 5-6 km2 or 2 square miles). Their movements within the home range depend on finding food. Staple foods for example include leaves, shoots and plant material, but the seasonal availability of fruit is crucial in the diet and influences group foraging movements. Born at 2 kg (4.5 lb), female Western Lowland Gorillas can weigh around 70 kg (150lb), while the much larger males may reach 180 kg (390lb) and stand 1.8m (6 feet) in height.
The Western Lowland Gorilla plays a fundamental ecological role in forest regeneration through seed dispersal. It also stands as a flagship species for tropical forest conservation initiatives across Central Africa.
However, its continued existence depends on coordinated international action, law enforcement, and local community engagement.
Scientific institutions, national parks, and wildlife authorities have recognised the urgency.
Ongoing interventions involve habitat protection, anti-poaching patrols, and gorilla habituation for conservation tourism.
Yet even with these, the species’ survival remains uncertain without long-term funding and political will.
Taxonomy And Physical Description
| Taxonomic Rank | Classification |
| Kingdom | Animalia |
| Phylum | Chordata |
| Class | Mammalia |
| Order | Primates |
| Family | Hominidae |
| Genus | Gorilla |
| Species | Gorilla gorilla |
| Subspecies | Gorilla gorilla gorilla (Western Lowland Gorilla) |
The Western Lowland Gorilla is the smallest among the four gorilla subspecies, although describing any of them as small would be misleading.
Adult males weigh between 140 and 180 kilograms and can reach up to 1.75 meters when standing upright. Females average between 70 and 90 kilograms.
Sexual dimorphism is marked. Mature males develop a silvery-white saddle of hair on the back, hence the term “silverback.”
Their sagittal crest is prominent, providing an anchor point for large jaw muscles. The face, ears, hands, and feet are hairless, revealing dark skin.
Fur coloration is lighter than in other subspecies, with a brownish or grayish hue often accompanied by a reddish crown.
This subtle coloration helps camouflage them in the filtered light of the forest understory.
Compared to mountain gorillas, they exhibit more slender limbs, longer hands and feet, and smaller jaws.
Their cranial capacity is significant, yet lower than that of Gorilla beringei. The nostril pattern used in photographic identification is unique to each individual and functions similarly to a fingerprint.
This subspecies is adapted to life in dense lowland forests.
Their physical build supports terrestrial quadrupedalism (knuckle-walking), but they also climb trees to access fruiting canopies.
Infant gorillas often display semi-arboreal behavior during the first few years of life.
Quick Facts About the Western Lowland Gorilla
Behavior and Social Structure
Western Lowland Gorillas live in cohesive groups averaging 4 to 8 individuals, although larger assemblies occur.
Each group is led by a dominant silverback who directs movement, selects nesting sites, resolves conflict, and provides protection.
Adult females maintain loose bonds with each other but exhibit substantial maternal investment.
Subordinate males, known as blackbacks, may remain temporarily within the group before dispersing to form their own unit or live solitarily.
Juveniles engage in social play, which facilitates the formation of hierarchies and the development of coordination skills.
Communication and Displays
Gorillas use a wide range of vocalisations, body postures, and facial expressions.
Over 20 distinct vocal sounds have been catalogued, ranging from low grunts to alarm barks and belch vocalisations during relaxed feeding.
Chest-beating, often misunderstood as a sign of aggression, serves various functions, including display, spacing regulation, and mate advertisement.
Silverbacks most often perform it, but can also be observed in juveniles. Facial expressions, such as the play face (a relaxed, open mouth), are used during non-aggressive interactions.
Nesting and Daily Movement
Groups construct fresh nests each evening from foliage, either on the ground or in trees. Nesting location often reflects predation risk, rainfall, and undergrowth density. While tree nests are more common in juveniles and females, males generally nest on the ground.
The daily range varies between 0.5 and 2.5 kilometres, depending on food availability. The group moves in a loosely coordinated fashion, led by the silverback, with feeding punctuated by resting periods.
Feeding Behaviour and Seasonal Diet
The diet is predominantly frugivorous, though seasonal fruit scarcity prompts a shift to leaves, shoots, and bark. Major fruit genera consumed include Dialium, Ficus, and Annonaceae species.
Feeding peaks during the early morning and late afternoon. Gorillas spend up to 60 percent of daylight hours foraging. Their digestive system, particularly the enlarged hindgut, allows fermentation of fibrous plant matter.
During dry seasons, feeding becomes opportunistic and includes swamp vegetation rich in sodium. This dietary plasticity is a key ecological adaptation.
Tool Use and Cognitive Evidence
Western Lowland Gorillas have demonstrated tool use in the wild. One well-documented example occurred in Mbeli Bai, Republic of Congo, where individuals used sticks to test water depth and support themselves while crossing swampy areas (Breuer et al., 2005).
They also exhibit behaviours associated with advanced cognition, such as memory-based foraging, social learning, and delayed gratification.
These findings continue to reshape assumptions about great ape intelligence and support the case for strong ethical frameworks in gorilla tourism.
Reproduction and Lifecycle
Reproductive activity in Western Lowland Gorillas is non-seasonal. The female typically initiates courtship through postures, eye contact, and vocalisations.
The silverback may respond by approaching, vocalising, or ignoring the advance.
Dominant silverbacks monopolise mating access, but females retain some agency. Polyandry within a group is rare but not absent.
Female choice plays a role in mate selection, with preferences sometimes given to males who show tolerance toward infants.
Inter-birth intervals average 4 to 6 years due to prolonged offspring dependency. Female reproductive output is among the lowest of any mammal species.
Gestation and Birth
Gestation lasts approximately 255 days. Births typically occur at night, often in nests prepared by the mother.
Only one infant is born per pregnancy, weighing around 1.8 to 2 kilograms.
Neonates are altricial. They depend entirely on maternal care for thermoregulation, protection, and nutrition. Twins are extremely rare and usually do not survive due to maternal resource limitations.
Infant Development
During the first six months, the infant clings to the mother’s ventral side and feeds exclusively on breast milk. Locomotor skills begin to develop in month four.
At around eight months, the infant starts riding dorsally and experimenting with solid foods.
Weaning occurs between 3 and 4 years of age. However, mother-infant bonds persist far beyond the weaning period. Social integration into the group intensifies once mobility and feeding independence are established.
Infanticide, illness, accidents, and silverback displacement influence infant mortality. Yet where stable silverbacks are present, survival rates improve significantly.
Juvenile and Adolescent Stage
Juveniles are individuals aged 4 to 8 years. They play extensively, interact across group boundaries, and exhibit trial behaviours such as mock chest-beating.
Puberty begins at around 8 years. Males enter a blackback phase, with increased size and strength but without a silver saddle.
Females may experience swelling of the external genitalia and begin ovulating.
Adulthood and Maturation
Silverback development occurs between ages 12 and 15. The back hair turns silvery-white, and the sagittal crest becomes pronounced.
Dominance contests can emerge between blackbacks and the resident male, particularly in multi-male groups.
Females become sexually mature at 10 to 12 years and may emigrate to other groups.
Reproductive success depends on access to resources, male stability, and freedom from external disturbance.
Lifespan in the wild averages 35 to 40 years. In captivity, Western Lowland Gorillas can live beyond 50 years, though stress-related illnesses are common.