# Gorilla
Gorillas (genus *Gorilla*) are the largest living primates, ground-dwelling plant-eating great apes native to the forests of equatorial Africa. Two species are currently recognized on the basis of morphology and geographic distribution: the western gorilla (*Gorilla gorilla*) in the tropical forests north of the [Congo River](https://www.edgepedia.org/congo-river), and the eastern gorilla (*Gorilla beringei*) roughly 1,000 km to the east, extending to the slopes of the central African mountains[1](https://pmc.ncbi.nlm.nih.gov/articles/PMC3672199/). Each species is divided into two subspecies: western lowland gorillas (*G. g. gorilla*) and Cross River gorillas (*G. g. diehli*) in the west, and mountain gorillas (*G. b. beringei*) and Grauer's gorillas (*G. b. graueri*) in the east[2](https://animals.sandiegozoo.org/animals/gorilla).
| Key fact | Detail |
|---|---|
| Species and subspecies | Western gorilla (*G. gorilla*: western lowland, Cross River) and eastern gorilla (*G. beringei*: mountain, Grauer's), separated by a gap of several hundred kilometers[1](https://pmc.ncbi.nlm.nih.gov/articles/PMC3672199/) • [2](https://animals.sandiegozoo.org/animals/gorilla) |
| Size | Males up to 5.7 ft (1.75 m) and 300 to 400 lb (136 to 181 kg); females up to 5 ft (1.5 m) and 159 to 216 lb (72 to 98 kg)[2](https://animals.sandiegozoo.org/animals/gorilla) |
| Divergence | Average sequence divergence between the western and eastern species about 1.75 million years ago, with evidence of more recent genetic exchange and a population bottleneck in the eastern species[3](https://www.nature.com/articles/nature10842.pdf) |
| Genetic diversity | Western gorillas are more diverse genome-wide; eastern lowland gorillas appear to be the most inbred gorilla population, with both recent and ancient inbreeding[4](https://www.nature.com/articles/nature12228.pdf) |
| Conservation | Eastern gorilla listed as Critically Endangered in 2016; mountain gorilla downlisted to Endangered in November 2018 after its population exceeded 1,000[5](https://iucn.org/news/species/201609/four-out-six-great-apes-one-step-away-extinction-%E2%80%93-iucn-red-list) • [6](https://iucn.org/news/species/201811/fin-whale-mountain-gorilla-recovering-thanks-conservation-action-iucn-red-list) |
| Numbers | The western lowland subspecies may number up to 200,000 individuals; the eastern population as a whole is around ten times smaller[3](https://www.nature.com/articles/nature10842.pdf) |
| Reproduction | A female gives birth to one baby every four to six years and only three or four over her lifetime[7](https://www.worldwildlife.org/species/gorilla) |
## Taxonomy and distribution
The two-species classification is a recent development. Until recently the eastern and western populations were considered subspecies of a single species, and the first detailed study of gorilla taxonomy, published by Groves in 1970, recognized one species with three subspecies[8](https://eazawebsite-prod.s3.nl-ams.scw.cloud/uploads/202406_EAZA_Western_lowland_gorilla_Best_Practice_Guidelines_3rd_edition_V2_954baec722.pdf). Studies of geographic variation in DNA, skulls, and teeth led to the recognition of two species, and the 2021 IUCN Red List distinguishes four subspecies[9](https://pubmed.ncbi.nlm.nih.gov/27260175/) • [8](https://eazawebsite-prod.s3.nl-ams.scw.cloud/uploads/202406_EAZA_Western_lowland_gorilla_Best_Practice_Guidelines_3rd_edition_V2_954baec722.pdf).
The contemporary distribution features a pronounced gap of several hundred kilometers between the two species, which nonetheless retain behavioral and morphological similarities[10](https://pmc.ncbi.nlm.nih.gov/articles/PMC3078889/). [Western gorilla](https://www.edgepedia.org/western-gorilla) populations reside primarily in Cameroon, Equatorial Guinea, Gabon, Congo, and the [Central African Republic](https://www.edgepedia.org/central-african-republic), while eastern gorilla populations occur in lowlands and highlands in the Democratic Republic of Congo, Uganda, and Rwanda[11](https://pmc.ncbi.nlm.nih.gov/articles/PMC4327160/). The northwestern limit of the western lowland subspecies is the Sanaga River in Cameroon[12](https://storre.stir.ac.uk/bitstream/1893/26838/1/Gorilla%2010.2305_IUCN.UK.2016-2.RLTS.T9404A17963949.en.pdf).
## Evolutionary history
Genomic studies have reconstructed a complex split between the two species. One analysis of neutral autosomal loci proposed a scenario in which a single ancestral gorilla population persisted until 0.9 to 1.6 million years ago, followed by reduced, possibly male-mediated gene flow until a population split around 77,700 years ago[13](https://academic.oup.com/mbe/article/24/1/146/1075518). The gorilla genome paper estimated an average sequence divergence time of 1.75 million years between the species but found evidence of more recent genetic exchange[3](https://www.nature.com/articles/nature10842.pdf). A later comparative analysis of 53 resequenced genomes, using a mutation rate of 1.8 × 10−9 per generation and a 20-year generation time, estimated that gene flow between the two species stopped circa 150,000 to 180,000 years ago[14](https://pmc.ncbi.nlm.nih.gov/articles/PMC10811819/).
**Gene flow was a recurring theme.** A Y-chromosome study genotyping 257 wild male gorillas from all four subspecies found 102 unique Y-haplotypes and concluded that male-mediated gene flow may have been important in the past[15](https://onlinelibrary.wiley.com/doi/10.1002/ajp.23363). A 2023 analysis reported admixture from a possible unsampled "ghost" population in eastern gorillas, and the comparative genome study detected multiple signals of introgression between subspecies, suggesting gene flow was likely common throughout gorilla evolution[16](https://www.nature.com/articles/s41559-023-02145-2) • [14](https://pmc.ncbi.nlm.nih.gov/articles/PMC10811819/).
[Genetic diversity](https://www.edgepedia.org/genetic-diversity) is unevenly distributed. Western lowland gorillas show the highest variation, best explained by larger present and past effective population sizes and higher rates of gene flow through largely continuous habitat[17](https://pubmed.ncbi.nlm.nih.gov/25975353/). Eastern lowland gorillas appear to represent the most inbred population, with evidence of both recent and ancient inbreeding[4](https://www.nature.com/articles/nature12228.pdf). Despite population decline, gorillas maintain an overall level of genetic diversity equal to or greater than that of humans[1](https://pmc.ncbi.nlm.nih.gov/articles/PMC3672199/).
## Physical characteristics, diet, and ecology
With their heavily built bodies, wide chests and shoulders, big hands resembling those of humans, and small eyes in faces lacking hair, gorillas have a distinctive appearance.[7](https://www.worldwildlife.org/species/gorilla) They can stand upright but prefer to walk on all fours using the backs of their fingers, a gait called knuckle walking, and their arms are much longer than their legs[2](https://animals.sandiegozoo.org/animals/gorilla). Captive life-span averages 33 years for males and 39 years for females[2](https://animals.sandiegozoo.org/animals/gorilla).
Almost everything a gorilla eats is plant material: leaves, stems, fruits, seeds, and roots, supplemented with ants and termites[2](https://animals.sandiegozoo.org/animals/gorilla). An adult male eats up to 40 pounds (18 kilograms) of food each day[2](https://animals.sandiegozoo.org/animals/gorilla). Field studies indicate the western gorilla diet comprises as many as 230 plant parts from 180 plant species[11](https://pmc.ncbi.nlm.nih.gov/articles/PMC4327160/). Gorillas play a key role in their forests: their fibrous scat acts as rich fertilizer and seedlings sprout from it rapidly, and by spreading seeds and opening gaps in the canopy they help sun-loving plants grow[2](https://animals.sandiegozoo.org/animals/gorilla) • [7](https://www.worldwildlife.org/species/gorilla).
## Social organization and life history
A group of gorillas is called a troop, typically of 5 to 30 animals, led by a dominant adult male known as a silverback for the silver hair he develops with age[2](https://animals.sandiegozoo.org/animals/gorilla) • [18](https://www.axios.com/local/san-diego/2026/09/09/kitoko-matumaini-western-lowland-gorillas-new-troops). The silverback makes decisions about daily travel, feeding, and resting sites, and builds each night's nest; gorillas never use the same nest twice[2](https://animals.sandiegozoo.org/animals/gorilla).
[Social organization](https://www.edgepedia.org/social-organization) varies markedly between the species. Western gorilla groups are almost exclusively one-male, yet approximately 40% of mountain gorilla groups are multimale. A review by Martha M. Robbins and colleagues at the Max Planck Institute for Evolutionary Anthropology identified five ultimate causes for this variability: human disturbance, ecological constraints on group size, risk of infanticide, life history patterns, and population density, with the most evidence for the ecological constraints and life history hypotheses[19](https://onlinelibrary.wiley.com/doi/abs/10.1002/evan.21721).
Reproduction is slow. Females become sexually mature around seven or eight years old but do not begin breeding until a couple of years later; once breeding, a female gives birth to one baby every four to six years and only three or four in her lifetime[7](https://www.worldwildlife.org/species/gorilla). Gestation lasts 8 to 9 months, newborns weigh 4 to 5 pounds (1.8 to 2.3 kg), and females reach maturity at about 8 years, males at about 13[2](https://animals.sandiegozoo.org/animals/gorilla). This low reproductive rate makes it difficult for gorilla populations to recover from declines[7](https://www.worldwildlife.org/species/gorilla).
## Conservation
Both gorilla species are listed as endangered or critically endangered. The eastern gorilla, the largest living primate, was listed as [Critically Endangered](https://www.edgepedia.org/critically-endangered) in 2016 due to illegal hunting[5](https://iucn.org/news/species/201609/four-out-six-great-apes-one-step-away-extinction-%E2%80%93-iucn-red-list). Grauer's gorilla lost 77% of its population since 1994, declining from 16,900 individuals to just 3,800 in 2015[5](https://iucn.org/news/species/201609/four-out-six-great-apes-one-step-away-extinction-%E2%80%93-iucn-red-list). The western gorilla is also listed as Critically Endangered[20](https://portals.iucn.org/library/sites/library/files/documents/2024-034-En.pdf).
**Mountain gorillas are the exception.** A 2018 survey put the global mountain gorilla population above 1,000, a significant recovery for a subspecies that once faced possible extinction, and the IUCN downlisted it from Critically Endangered to Endangered in November 2018[21](https://apnews.com/article/9ad0cdc5b5eca2884d083b3038c4abcb) • [6](https://iucn.org/news/species/201811/fin-whale-mountain-gorilla-recovering-thanks-conservation-action-iucn-red-list). [Mountain gorilla](https://www.edgepedia.org/mountain-gorilla) habitat remains restricted to protected areas covering approximately 792 km2 in two locations, the Virunga Massif and Bwindi-Sarambwe[6](https://iucn.org/news/species/201811/fin-whale-mountain-gorilla-recovering-thanks-conservation-action-iucn-red-list).
Threats include poaching, habitat destruction and fragmentation, civil unrest, and disease. Scientists in 2003 estimated that a third of the wild gorilla population had been killed by the Ebola virus, which is deadly to both gorillas and humans[7](https://www.worldwildlife.org/species/gorilla). Because of their genetic similarity to people, gorillas are susceptible to human pathogens, and almost 60% of the remaining mountain gorillas are habituated to humans, coming into close contact with people daily[22](https://doi.org/10.2305/IUCN.UK.2018-2.RLTS.T39999A17989719.en). Only about 22% of western lowland gorillas live in protected areas, leaving most of the subspecies vulnerable to poachers[7](https://www.worldwildlife.org/species/gorilla). Unselective hunting with snares set for other wildlife, such as antelopes and bush pigs, often kills or injures gorillas[23](https://www.worldwildlife.org/resources/facts/what-do-gorillas-eat-and-other-gorilla-facts/).
Conservation responses include gorilla tourism, which has turned poachers into conservationists in Uganda while generating economic benefits for local communities, and reforestation around Bwindi, where communities have planted trees for medicine, firewood, and crafts to reduce pressure on the park[24](https://apnews.com/article/916d874dd7babcfbf04c25b9a39d1961) • [21](https://apnews.com/article/9ad0cdc5b5eca2884d083b3038c4abcb). The International Gorilla Conservation Programme, a coalition of WWF, Conservation International, and Fauna & Flora, has contributed to the mountain gorilla recovery[7](https://www.worldwildlife.org/species/gorilla).
## References
1. [A Genome-Wide Survey of Genetic Variation in Gorillas Using Reduced Representation Sequencing, PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC3672199/)
2. [Gorilla, San Diego Zoo Animals & Plants](https://animals.sandiegozoo.org/animals/gorilla)
3. [Insights into hominid evolution from the gorilla genome sequence, Nature](https://www.nature.com/articles/nature10842.pdf)
4. [Great ape genetic diversity and population history, Nature](https://www.nature.com/articles/nature12228.pdf)
5. [Four out of six great apes one step away from extinction, IUCN Red List (2016)](https://iucn.org/news/species/201609/four-out-six-great-apes-one-step-away-extinction-%E2%80%93-iucn-red-list)
6. [Fin Whale, Mountain Gorilla recovering thanks to conservation action, IUCN Red List (2018)](https://iucn.org/news/species/201811/fin-whale-mountain-gorilla-recovering-thanks-conservation-action-iucn-red-list)
7. [Gorillas, WWF](https://www.worldwildlife.org/species/gorilla)
8. [EAZA Best Practice Guidelines for the Western Lowland Gorilla](https://eazawebsite-prod.s3.nl-ams.scw.cloud/uploads/202406_EAZA_Western_lowland_gorilla_Best_Practice_Guidelines_3rd_edition_V2_954baec722.pdf)
9. [Geographic variation in gorilla limb bones, PubMed](https://pubmed.ncbi.nlm.nih.gov/27260175/)
10. [Historical sampling reveals dramatic demographic changes in western gorilla populations, PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC3078889/)
11. [Inference of Gorilla Demographic and Selective History from Whole-Genome Sequence Data, PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC4327160/)
12. [The IUCN Red List of Threatened Species: Gorilla gorilla](https://storre.stir.ac.uk/bitstream/1893/26838/1/Gorilla%2010.2305_IUCN.UK.2016-2.RLTS.T9404A17963949.en.pdf)
13. [The Complex Evolutionary History of Gorillas: Insights from Genomic Data, Molecular Biology and Evolution](https://academic.oup.com/mbe/article/24/1/146/1075518)
14. [Comparative genomic analyses provide new insights into evolutionary history and conservation genomics of gorillas, PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC10811819/)
15. [Complex evolutionary history of gorillas: Y-chromosomal perspectives, American Journal of Primatology](https://onlinelibrary.wiley.com/doi/10.1002/ajp.23363)
16. [Ghost admixture in eastern gorillas, Nature Ecology & Evolution](https://www.nature.com/articles/s41559-023-02145-2)
17. [The geographic distribution of genetic diversity within gorillas, PubMed](https://pubmed.ncbi.nlm.nih.gov/25975353/)
18. [Two new gorillas join San Diego Zoo and Safari Park, Axios](https://www.axios.com/local/san-diego/2026/09/09/kitoko-matumaini-western-lowland-gorillas-new-troops)
19. [Variation in the social organization of gorillas: Life history and socioecological perspectives, Evolutionary Anthropology](https://onlinelibrary.wiley.com/doi/abs/10.1002/evan.21721)
20. [Species Threat Abatement and Restoration in the Central African Republic, IUCN](https://portals.iucn.org/library/sites/library/files/documents/2024-034-En.pdf)
21. [Ugandans plant trees near national park to keep people out of gorillas' habitat, AP News](https://apnews.com/article/9ad0cdc5b5eca2884d083b3038c4abcb)
22. [Gorilla beringei ssp. beringei (Mountain Gorilla), IUCN Red List](https://doi.org/10.2305/IUCN.UK.2018-2.RLTS.T39999A17989719.en)
23. [Gorilla Facts: Behavior, Diet, & Conservation, WWF](https://www.worldwildlife.org/resources/facts/what-do-gorillas-eat-and-other-gorilla-facts/)
24. [Tourism is helping Uganda's endangered mountain gorillas make a comeback, AP News](https://apnews.com/article/916d874dd7babcfbf04c25b9a39d1961)
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*Topic: Encyclopedia › Life and health › Animals › Vertebrates › Mammals › Primates*
*Initially written Sep 17, 2026 · Reviewed: Oct 21, 2026 · Edited: Oct 15, 2026; Oct 21, 2026 · Last review: Oct 21, 2026*
*Copyright 2026 EdgeChat AI, a subsidiary of Biostate AI.*
License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license