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)
High levels of poaching, disease transmission, and habitat degradation continue to threaten population of western lowland and Cross River gorillas. Western lowland gorillas are the most populated of the sub-species, with one assessment estimating over 300,000 remaining individuals (Strindberg et al., 2018). 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 their declining numbers and 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.
Eastern Species (Gorilla beringei)
ENDANGERED & CRITICALLY ENDANGERED
Grauer's gorillas (formerly known as eastern lowland gorillas) are listed as Critically Endangered by the IUCN, and their populations are continuing to decrease. It was believed that the population suffered declines during the civil war in the Democratic Republic of Congo, and it was estimated that between 5,500 and 28,000 individuals remain (Mehlman, 2007). Due to amazing conservation efforts, the mountain gorilla population has been increasing. Previous census work found populations of 380 Virunga and 320 Bwindi mountain gorillas (Gray et al., 2005), and the most recent assessment indicates that the total number of mountain gorillas in over 1000 individuals. In 2018, the IUCN upgraded this sub-species' status from Critically Endangered to Endangered.
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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.
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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.
Strindberg, S., Maisels, F., Williamson, E. A., Blake, S., Stokes, E. J., Aba’a, R., ... & Wilkie, D. S. (2018). Guns, germs, and trees determine density and distribution of gorillas and chimpanzees in Western Equatorial Africa. Science advances, 4(4), eaar2964.