Eastern gorilla

The eastern gorilla (Gorilla beringei) is a critically endangered species of the genus Gorilla and the largest living primate. At present, the species is subdivided into two subspecies. The eastern lowland gorilla or Grauer’s gorilla (G. b. graueri) is more populous, at about 3,800 individuals.[3] The mountain gorilla (G. b. beringei) has only about 1,000 individuals.[4] The International Union for the Conservation of Nature mentioned illegal hunting in its assessment of threats to the species.[5][6]

Eastern gorilla[1]
Temporal range: Pleistocene to recent
Male
Female with infant
Both are mountain gorillas, photographed in the Virunga Mountains
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Primates
Suborder: Haplorhini
Infraorder: Simiiformes
Family: Hominidae
Subfamily: Homininae
Genus: Gorilla
Species:
G. beringei
Binomial name
Gorilla beringei
Matschie, 1903
Subspecies

G. b. beringei
G. b. graueri

Eastern gorilla range

Taxonomy and phylogeny
Mountain gorilla and eastern lowland gorilla

There are two recognised subspecies of eastern gorilla: the mountain gorilla (Gorilla beringei beringei) of the volcanic slopes of Rwanda, Uganda and eastern Democratic Republic of Congo; and the eastern lowland gorilla or Grauer's gorilla (Gorilla beringei graueri) in eastern Democratic Republic of Congo.

The eastern lowland gorillas and mountain gorillas were previously thought to be two of the three subspecies of one single species, the gorilla (Gorilla gorilla). However, genetic research has shown that the two eastern subspecies are far more closely related than the western subspecies: the western lowland gorilla (G. gorilla gorilla), which justified the separate classification.[7] The two eastern subspecies are now classified as G. beringei.

Physical description

The eastern gorilla is a large hominid with a large head, broad chest, and long arms. It has a flat nose with large nostrils. The face, hands, feet and breast are bald. The fur is mainly black, but adult males have a silvery "saddle" on their back. When the gorilla gets older, the hair on the saddle of the back becomes white, much like the gray hair of elderly people. This is why the older males are called silverbacks. Grauer's gorilla has a shorter, thicker, deep black fur, while the mountain gorilla has a more bluish color. The mountain gorilla is slightly smaller and lighter than Grauer's gorilla, but still larger and heavier than the western lowland gorilla and the Cross River gorilla. Males are much larger than females. A full-grown male eastern gorilla typically weighs 140–205.5 kg (309–453 lb) and stands 1.7 m (5.6 ft) upright and a female typically weighs 90–100 kg (200–220 lb) and stands 1.5 m (4.9 ft) tall.[8][9] The tallest silverback recorded was a 1.95-metre (6.4 ft) individual shot in Alimbongo, northern Kivu in May 1938.[10] The heaviest gorilla recorded was a 1.83-metre (6.0 ft) silverback shot in Ambam, Cameroon, which weighed 267 kilograms (589 lb),[10] although the latter area is within the range of the western gorilla, far outside that of the eastern gorilla.

Distribution and ecology

Mountain gorillas are restricted to the mountain rainforest and subalpine forest of eastern Democratic Republic of the Congo, southwestern Uganda and Rwanda. Grauer's gorilla occur across the forests of the Albertine Rift in eastern DRC.

Eastern gorillas are herbivorous, with a heavily foliage based diet, due to lack of available fruit in their habitats. They have smaller home ranges than western gorillas as foliage is more abundant than fruit. They are diurnal but the majority of foraging occurs in the morning and late afternoon. At night, they build nests by folding over vegetation, usually on the ground.

Behavior

Eastern gorillas live in stable, cohesive family groups, led by a dominant silverback male. Eastern gorillas tend to have larger group sizes than their western relatives, numbering up to 35 individuals. There is no distinct breeding season and females give birth only once every 3–4 years due to the long period of parental care and a gestation period of 8.5 months. Newborn gorillas have greyish-pink skin and can crawl after 9 weeks; they are not fully weaned until 3.5 years. Males defend their females and offspring using their large size in intimidating displays involving charging and chest-beating.

Conservation status

The eastern gorilla has become increasingly endangered since the 1990s, and the species was listed as critically endangered in September 2016 as its population continued to decrease. Primary threats to the eastern gorilla include habitat destruction for residential, commercial, and agricultural purposes, habitat fragmentation caused by transportation corridors and resource extraction, as well as disease.[11] Between 1996 and 2016, the eastern gorilla lost more than 70 percent of its population, and by 2016 the total population was estimated to be less than 6,000.[6] An exception to this declining trend is the mountain gorilla. According to the most recent estimates, there are approximately 1,004 mountain gorillas, and their numbers continue to grow.[12]

In some national parks, viewing mountain gorillas is a popular tourist attraction. These national parks include Volcanoes National Park in Rwanda, Virunga National Park in the Democratic Republic of the Congo, and Mgahinga Gorilla National Park and Bwindi Impenetrable National Park in Uganda. While ecotourism can benefit gorilla populations by generating revenue for conservation efforts,[13] there is concern that increased exposure to humans will place gorillas at greater risk of contracting zoonotic diseases.[14] Studies have shown that habituated eastern gorillas, that is, those that leave protected areas to forage in surrounding communities, have higher diseases rates than their unhabituated counterparts, with nearby humans and livestock as the likely sources of transmission.[15]

Unlike the western gorilla, there are few eastern gorillas in zoos. The Antwerp Zoo is the only zoo outside the native range of the species that has eastern gorillas. Outside the native range, the mountain gorilla is not held in captivity at all.[16] Small groups consisting of animals confiscated from poachers are kept in the Democratic Republic of Congo: Grauer's gorillas at the Gorilla Rehabilitation and Conservation Education (GRACE) center in Tayna Nature Reserve,[17] and mountain gorillas at the Senkwekwe Center in Virunga National Park.[18]

References
  1. Groves, C. P. (2005). Wilson, D. E.; Reeder, D. M. (eds.). Mammal Species of the World: A Taxonomic and Geographic Reference (3rd ed.). Baltimore: Johns Hopkins University Press. pp. 181–182. ISBN 0-801-88221-4. OCLC 62265494.
  2. Plumptre, A.; Robbins, M.; Williamson, E. A. (2016). "Gorilla beringei". IUCN Red List of Threatened Species. 2016: e.T39994A17964126.
  3. "Gorillas on Thin Ice". United Nations Environment Programme. 15 January 2009. Archived from the original on 18 May 2016. Retrieved 19 May 2010.: "The Eastern Lowland Gorilla population in the DRC has plummeted dramatically over the last 10 years, with probably only about 5,000 of the formerly 17,000 animals remaining."
  4. "The most recent surveys of Mountain Gorillas estimated that there are now at least 1,004 individuals – IUCN Red List". IUCN Red List of Threatened Species. 31 July 2018. 31 July 2018.
  5. "The Eastern Gorilla listed on Red List of Endangered Species by IUCN". CBSnews. AP. September 4, 2016. Retrieved September 4, 2016.
  6. "Four out of six great apes one step away from extinction – IUCN Red List". 4 September 2016. Archived from the original on 8 September 2016. Retrieved 4 September 2016.
  7. Taylor, Andrea Beth; Goldsmith, Michele Lynn (2003). Gorilla biology: a multidisciplinary perspective. Cambridge University Press. p. 13. ISBN 978-0-521-79281-3.
  8. Williamson, E.A. and Butynski, T.M. (2013) Gorilla gorilla. In: Butynski, T.M. (Ed) The Mammals of Africa. Volume 6. Elsevier Press. ISBN 1408122561
  9. Burnie D and Wilson DE (Eds.), Animal: The Definitive Visual Guide to the World's Wildlife. DK Adult (2005), ISBN 0789477645
  10. Wood, Gerald L. (1983) The Guinness Book of Animal Facts and Feats. Sterling Pub Co Inc. ISBN 978-0-85112-235-9
  11. Plumptre, A., Robbins, M.M. & Williamson, E.A. "The IUCN Red List of Threatened Species". IUCN Red List of Threatened Species. Archived from the original on 2018-10-28. Retrieved 2019-11-22.CS1 maint: multiple names: authors list (link)
  12. Hickey, J.R., Basabose, A., Gilardi, K.V., Greer, D., Nampindo, S., Robbins, M.M. & Stoinski, T.S. "The IUCN Red List of Threatened Species". IUCN Red List of Threatened Species. Archived from the original on 2018-10-28. Retrieved 2019-11-22.CS1 maint: multiple names: authors list (link)
  13. Okello, M.M. & Marina Novelli. (January 1, 2014). "Tourism in the East African Community (EAC): Challenges, opportunities, and ways forward". Sage. 14: 53–66 – via SAGE journals.
  14. Shackley, Myra (1995-01-01). "The future of gorilla tourism in Rwanda". Journal of Sustainable Tourism. 3 (2): 61–72. doi:10.1080/09669589509510711. ISSN 0966-9582.
  15. Kalema-Zikusoka, Gladys; Rubanga, Stephen; Mutahunga, Birungi; Sadler, Ryan (2018). "Prevention of Cryptosporidium and GIARDIA at the Human/Gorilla/Livestock Interface". Frontiers in Public Health. 6: 364. doi:10.3389/fpubh.2018.00364. ISSN 2296-2565. PMC 6302101. PMID 30619805.
  16. Fossey, Dian (2000). Gorillas in the Mist. Houghton Mifflin Books. ISBN 0-618-08360-X.
  17. The Dian Fossey Gorilla Fund: The GRACE Center for Rescued Gorillas. Archived 2013-07-19 at the Wayback Machine Retrieved 16 August 2013
  18. Senkwekwe Orphan Mountain Gorilla Center. Archived 2017-12-01 at the Wayback Machine Retrieved 16 August 2013
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