Western Lowland Gorilla Facts

Western lowland gorilla (Gorilla gorilla gorilla), Bayanga, Central African Republic
Western lowland gorilla (Gorilla gorilla gorilla), Bayanga, Central African Republic. David Schenfeld / Getty Images

The western lowland gorilla (Gorilla gorilla gorilla) is one of two subspecies of western gorillas The other subspecies is the Cross River gorilla. Of the two subspecies, the western lowland gorilla is more numerous. It's also the only subspecies of gorilla kept in zoos, with few exceptions.

Fast Facts: Western Lowland Gorilla

  • Scientific Name: Gorilla gorilla gorilla
  • Distinguishing Features: Relatively small gorilla with dark brownish black hair and large skull. Mature males have white hair on their backs.
  • Average Size: 68 to 227 kg (150 to 500 lb); males about twice the size of females
  • Diet: Herbivorous
  • Life Span: 35 years
  • Habitat: Western sub-Saharan Africa
  • Conservation Status: Critically Endangered
  • Kingdom: Animalia
  • Phylum: Chordata
  • Class: Mammalia
  • Order: Primates
  • Family: Hominidae
  • Fun Fact: The western lowland gorilla is the only subspecies kept in zoos, with very rare exceptions.

Description

Gorillas are the largest apes, but western lowland gorillas are the smallest gorillas. Males are considerably larger than females. An adult male weighs between 136 and 227 kg (300 to 500 lbs) and stands up to 1.8 m (6 ft) tall. Females weigh between 68 and 90 kg (150 to 200 lb) and stand around 1.4 m (4.5 ft) tall.

The western lowland gorilla has a larger, wider skull than a mountain gorilla and dark brownish black hair. Young gorillas have a small white rump patch until they are about four years old. Mature males are called "silverback" males because they have a saddle of white hair across their backs and extending onto the rump and thighs. Western lowland gorillas, like other primates, have unique fingerprints and nose prints.

Distribution

As their common name suggests, western lowland gorillas live in western Africa at low elevations ranging from sea level to 1300 meters. They inhabit rain forests and forested areas of swamps, rivers, and fields. Most of the population lives in the Republic of the Congo. The gorillas also occur in Cameroon, Angola, Congo, Gabon, Central African Republic, and Equatorial Guinea.

Gorilla species distribution
Gorilla species distribution. Fobos92

Diet and Predators

Western lowland gorillas are herbivores. They preferentially select fruit that is high in sugar and fiber. However, when fruit is scarce, they eat leaves, shoots, herbs, and bark. An adult gorilla eats about 18 kg (40 lb) of food per day.

The gorilla's only natural predator is the leopard. Otherwise, only humans hunt gorillas.

Social Structure

The gorillas live in groups of one to 30 gorillas, usually averaging between 4 and 8 members. One or more adult males lead the group. A group stays within a home range of 8 to 45 square kilometers. Western lowland gorillas are not territorial and their ranges overlap. The lead silverback organizes eating, resting, and traveling. While a male may make an aggressive display when challenged, gorillas are generally nonaggressive. Females engage in sexual behavior even when they are non-fertile to compete with other females. Young gorillas spend their time playing, much like human children.

Reproduction and Life Cycle

The reproductive rate of western lowland gorillas is very low. In part, this is because females don't reach sexual maturity until age 8 or 9 and don't reproduce when caring for young. As in humans, gorilla gestation lasts about nine months. A female gives birth to one infant. An infant rides on its mother's back and depends on her until it is about five years old. Occasionally, a male commits infanticide to gain a opportunity to mate with its mother. In the wild, a western lowland gorilla may live 35 years.

Females care for young until they are around five years of age.
Females care for young until they are around five years of age. Willis Chung / Getty Images

Conservation Status and Threats

The International Union for Conservation of Nature (IUCN) lists the western gorilla as critically endangered, which is the last category before global extinction in the wild. Only about 250 to 300 of the Cross River gorilla species are believed to remain, while estimates place the number of western lowland gorillas around 300,000 in 2018. While this may seem like a relatively large number of gorillas, the population size continues to dwindle and the animals face serious threats.

Challenges facing the western lowland gorilla include deforestation; loss of habitat to human encroachment for settlements, farming, and grazing; climate change; slow reproductive rate coupled with infertility; and poaching for trophies, folk medicine, and bushmeat.

Disease may pose an even greater threat to gorillas than other factors. Western lowland gorillas are one of the zoonotic origin of HIV/AIDs, which infects gorillas in a similar fashion as it does humans. Gorillas suffered over 90% mortality from an Ebola epizootic in 2003 to 2004 that killed two-thirds of the species' population. Gorillas are also infected with malaria.

While the outlook for wild western lowland gorillas appears grim, the species acts as a seed disperser, making it key to the survival of many other species in its habitat. Worldwide, zoos maintain a population of about 550 western lowland gorillas.

Sources

  • D'arc, Mirela; Ayouba, Ahidjo; Esteban, Amandine; Learn, Gerald H.; Boué, Vanina; Liegeois, Florian; Etienne, Lucie; Tagg, Nikki; Leendertz, Fabian H. (2015). "Origin of the HIV-1 group O epidemic in western lowland gorillas". Proceedings of the National Academy of Sciences. 112 (11): E1343–E1352. doi:10.1073/pnas.1502022112
  • Haurez, B.; Petre, C. & Doucet, J. (2013). "Impacts of logging and hunting on western lowland gorilla (Gorilla gorilla gorilla) populations and consequences for forest regeneration. A review". Biotechnologie, Agronomie, Société et Environnement. 17 (2): 364–372.
  • Mace, G.M. (1990). "Birth Sex Ratio and Infant Mortality Rates in Captive Western Lowland Gorillas". Folia Primatologica. 55 (3–4): 156. doi:10.1159/000156511
  • Maisels, F., Strindberg, S., Breuer, T., Greer, D., Jeffery, K. & Stokes, E. (2018). Gorilla gorilla ssp. gorilla (amended version of 2016 assessment). The IUCN Red List of Threatened Species 2018: e.T9406A136251508. doi:10.2305/IUCN.UK.2016-2.RLTS.T9406A136251508.en
  • Rogers, M. Elizabeth; Abernethy, Kate; Bermejo, Magdalena; Cipolletta, Chloe; Doran, Diane; Mcfarland, Kelley; Nishihara, Tomoaki; Remis, Melissa; Tutin, Caroline E.G. (2004). "Western gorilla diet: A synthesis from six sites". American Journal of Primatology. 64 (2): 173–192. doi:10.1002/ajp.20071