Gorillas are one of the five types of great apes along with chimpanzees, orangutans, bonobos, and humans. They are well-known for their intelligence and complex social behavior patterns. All gorilla subspecies are endangered or critically endangered.
Two species of gorilla are currently recognized: a western species (Gorilla gorilla) and an eastern species (Gorilla beringei) (Groves, 2001; Grubb et al., 2003). The western gorilla species is divided into two subspecies: the western lowland gorilla (Gorilla gorilla gorilla) and the Cross River gorilla (Gorilla gorilla diehli) (Sarmiento and Oates 2000; Groves 2001; Grubb et al., 2003). Eastern gorillas are divided into two subspecies, mountain gorillas (Gorilla beringei beringei) and Grauer's gorillas (Gorilla beringei graueri), with the mountain gorillas further divided into two distinct subpopulations (Virunga and Bwindi).
- G.b. beringei: Bwindi, mountain, or Virunga gorilla
- G.b. graueri: eastern lowland gorilla or Grauer's gorilla
- G.g. diehli: Cross River gorilla
- G.g. Gorilla: western lowland gorilla
Western Species (Gorilla Gorilla)
Precise estimates of the numbers of western lowland and Cross River gorillas are not available. In the late 1990s it was estimated that there were as many as 110,000 western gorillas in Central Africa (Harcourt 1996; Butynski 2001). However, high levels of hunting and recent outbreaks of Ebola mean that the number of animals is likely considerably less today. Though tens of thousands of western lowland gorillas still remain, the number of Cross River gorillas is orders of magnitude less. Current estimates suggest that fewer than 300 individuals of this subspecies are left (Oates et al., 2007).
Due to the extreme threat of extinction faced by Cross River gorillas and western lowland gorillas, The World Conservation Union (IUCN)
classifies both species as Critically Endangered. The Cross River gorillas are the most endangered ape in Africa.
- Text by Richard Bergl, Ph.D.
Eastern Species (Gorilla beringei)
Both subpopulations of mountain gorillas are classified as Critically Endangered by The World Conservation Union (IUCN). Recent census work found populations of 380 Virunga and 320 Bwindi mountain gorillas (Gray et al., 2005). Grauer's gorillas (formerly known as eastern lowland gorillas) are listed as Endangered by the IUCN but their current numbers are unknown. It is thought that the population has suffered declines during the recent civil war in the Democratic Republic of Congo, and it is estimated that between 5,500 and 28,000 remain (Mehlman, 2007).
- Text by Tara S. Stoinski, Ph.D.
Butynski, T.M. 2001. Africa's great apes. In: Beck, B.B., Stoinski, T.S., Hutchins, M., Maple, T.L., Norton, B., Rowan, A., Stevens, E.F., Arluke, A., eds. Great Apes and Humans: The Ethics of Coexistence. Smithsonian Institution Press, Washington, DC. pp. 3-56.
Gray, M., McNeilage, A., Fawcett, K., Robbins, M.M., Ssebide, B., Mbula, D. & Uwingeli, P. 2005. Virunga Volcano Range mountain gorilla census, 2003. Joint organiser's report (unpublished), International Gorilla Conservation Programme, Institute of Tropical Forest Conservation, The Dian Fossey Gorilla Fund, International & Europe, Berggorilla und Regenwald Directhilfe, Mountain Gorilla Veterinary Project, the Max Planck Institute for Evolutionay Anthropology, Wildlife Conservation Society.
Groves, C.P. 2001. Primate Taxonomy. Smithsonian Institution Press, Washington, D.C.
Grubb, P., Butynski, TM, Oates, J.F., Bearder, S.K., Disotell, T.R., Groves, C.P. & Struhsaker, T.T. 2003. Assessment of the diversity of African primates. International Journal of Primatology 24: 1301-1357.
Harcourt, A.H. 1996. Is the gorilla a threatened species? How should we judge? Biological Conservation 75: 165-176.
Mehlman, P.T. 2007. Current status of wild gorilla populations and strategies for their conservation. In Stoinski, T.S., Steklis, H.D. & Mehlman, PT, eds. Conservation in the 21st Century: Gorillas as a Case Study. New York: Springer, pp. 3-54.
Oates, J., Sunderland-Groves, J., Bergl, R., Dunn, A., Nicholas, A., Takang, E., Omeni, F., Imong, I., Fotso, R., Nkembi, L. and Williamson, L. 2007. Regional Action Plan for the Conservation of the Cross River Gorilla (Gorilla gorilla diehli). IUCN/SSC Primate Specialist Group and Conservation International, Arlington, VA, USA.
Sarmiento, E.E. & Oates, J.F. 2000. The Cross River gorilla: a distinct subspecies Gorilla gorilla diehli Matschie 1904. American Museum Novitates 3304: 1-55.