Western Lowland Gorilla

The western lowland gorilla is the smallest gorilla subspecies, scattered mostly around Central Africa. Even though their approximate population remains unknown, according to a rough estimate, 100,000 western lowland gorillas are left in the wild. Diseases and poaching are prime factors behind their fast-dwindling population. 

Like most gorillas, these land-dwelling apes are generally peaceful and play a pivotal role in maintaining an ecological balance by acting as an “umbrella species” and helping other species.

Description

Length: Male – 5 to 6 ft (1.5 to 1.8 m); Female – 4 to 4.5 ft (1.21 to 1.4 m)

Weight:   Male – 400 to 500 lbs (181 to 227 kgs); Female – 150 to 200 lbs (68 to 90 kgs)

Body and Coloration: Their coat is usually black or gray, although western lowland gorillas tend to be brownish.

Infants have a small tuft of white hair on their rumps. As they mature, males often develop a patch of graying hair or a silver patch of receding hair on their backs that can extend up to their thighs, signifying them becoming silverbacks. Graying fur below the ears and around the neck indicates aging in females.

They have lighter colored fur than eastern lowland gorillas, wider skulls than mountain gorillas, and prominent brow ridges and ears that are smaller with respect to their face and head.

Range and Distribution

Western lowland gorillas remain widely distributed throughout the Congo Basin and the Republic Of Congo. They are also sparsely spread in parts of Gabon, the Central African Republic, Cameroon, Nigeria,  Angola, and  Equatorial Guinea.

A single gorilla’s territory ranges between 8 and 14 square miles (20.7 to 36.2 square kilometers). The  distance traversed in a single day is often less than a mile (1.6 kilometers), but if more food is available, they often travel further.

Habitat

These gorillas inhabit thick tropical rainforests, lowland areas, foothills of mountains, and dense primary or undisturbed secondary forests. They often visit open swampy or marshy areas (“bais”) full of aquatic and semi-aquatic sedges, in search of food .

Diet

In the wild, they mostly eat grass, roots, shoots, stems, fruit, seeds, leaves, wild celery, sedges, tree bark, herbs, shrubs, and pulp.

Although herbivorous, they are also known to have a strong appetite for invertebrates like termites and ants. Gorillas in captivity also consume meat.

Behavior

• Western lowland gorillas are diurnal and spend most of their waking hours searching for food. 
• Infants have an intense feeding period in the morning that lasts for about 2 hours and a less intense one  in the afternoon.
• Due to their large size, these gorillas primarily live on the ground but may also nest in trees.Infant gorillas sleep in their mother’s nest until they are four.
• Gorillas communicate using auditory signals, visual signals, and odors. They have over 20 vocalizations, including roars, screams, grunts, belches, whistles, chuckles, and barks.

• They live in social groups, called troops, led by a dominant silverback male. These troops comprise females, their offspring, and a few younger males who have yet to mature. Troops can vary in size from as few as five individuals to as many as 30. They occasionally interact with other western lowland gorilla troops, but it happens rarely.
• When threatened, they may beat their chests to establish their formidability, mark their territory, or as a protective reflex. 

Lifespan

The western lowland gorillas live in the wild for 30 to 40 years. In captivity, they live into their 50s or 60s but sometimes living in captivity can also lower their lifespan.

A western lowland gorilla named Fatou recently celebrated her 66th birthday at the Berlin Zoo, making her the longest-living gorilla ever.

Adaptations

• They typically move around by “knuckle-walking” on all fours.
• Their opposable thumbs and big toes facilitate climbing, grasping, maneuvering objects, and using tools.Some western lowland gorillas can even use buckets as a tool to collect water.
•  Like all gorillas, they have a sagittal crest atop their heads that is essential for grinding vegetation, and their enlarged intestines help digest their massive diet.

Mating and Reproduction

Western lowland gorillas do not have a specific breeding season. They are known to be polygamous, and the males mate with multiple females. This behavior allows for genetic diversity within the population and helps ensure the species’ survival. However, this polygamous behavior also pressures the males to compete for breeding opportunities, leading to violent confrontations. A male gorilla often kills infants to mate with the mother when she refuses him due to the burden of childcare and nursing. In such cases, there is no biological relationship between the killer and the infant.Males start to copulate by age 9 to 10 but encounter few mating opportunities until they become silverbacks.

Female gorillas deliver their firstborn at 9 to 11 years and thereon once every four years. The gestation period lasts for 8 to 9 months. Like humans, just one gorilla is produced, though twins and triplets might be rarely born.  The female gorilla gives birth in a supine position and cuts off the umbilical cord herself. The mother ape takes care of the infants till they are at least four years old.

Predators

They don’t have too many predators but leopards prey on non-human primates such as monkeys and apes, even the western lowland gorilla. A study published in the Journal of Human Evolution has revealed that African primates are at significant risk from leopards, with predation rates ranging from 8% to 80% across different populations.

Conservation Status

The western lowland gorillas have been classified as “Critically Endangered”  by the IUCN since 2007. 

Sadly, their habitat is being destroyed by forest loss, which opens them up to being hunted for bushmeat and more vulnerable to poaching.

 Infectious diseases have also taken a significant toll on them, with the Ebola virus alone believed to have killed up to a third of the western lowland gorilla population in the early 2000s.

Interesting Facts

• One female western lowland gorilla, Koko, could communicate through sign language and had a vocabulary of over 1000 words, equivalent to that of a three-year-old human child. Koko even had a pet kitten. Koko passed away at 46 while under the care of the San Francisco Zoo.
• “Snowflake,” a western lowland gorilla, was the singular known albino gorilla worldwide. Regrettably, he passed away while under the care of the Barcelona Zoo in 2003.
• In human care, certain western lowland gorillas may display uncommon behaviors such as regurgitation, reingestion, urophagia (urine consumption), and coprophagy (feces consumption), although the explanations for these actions remain uncertain. 
• Some of these gorillas have been observed utilizing buckets to collect water. 
• Interestingly, western lowland gorillas are believed to be one of the zoonotic sources of the HIV/AIDS virus. This highlights the intricate and complex relationship between humans and animals, down to the microscopic level.