Gorilla gorilla ssp. gorilla
|Scientific Name:||Gorilla gorilla ssp. gorilla|
|Species Authority:||(Savage, 1847)|
See Gorilla gorilla
|Taxonomic Source(s):||Mittermeier, R.A., Rylands, A.B. and Wilson D.E. 2013. Handbook of the Mammals of the World: Volume 3 Primates. Lynx Edicions, Barcelona.|
The Western Lowland Gorilla (Gorilla gorilla gorilla) is one of two recognised subspecies of Western Gorilla (Gorilla gorilla) (Groves 2001). Genetic data suggest that Cross River Gorillas (Gorilla gorilla diehli) diverged from Western Gorillas approximately 18,000 years ago (Thalmann et al. 2011). Western Lowland Gorillas are genetically separated into subpopulations by major rivers (Anthony et al. 2007, Fünfstück et al. 2014).
|Red List Category & Criteria:||Critically Endangered A4bcde ver 3.1|
|Assessor(s):||Maisels, F., Strindberg, S., Breuer, T., Greer, D., Jeffery, K. & Stokes, E.|
|Reviewer(s):||Williamson, E.A. & Mittermeier, R.A.|
|Contributor(s):||Baillie, J., Butynski, T.M., Gatti, S., Tutin, C. & Walsh, P.D.|
Western Lowland Gorillas have a large geographic range, covering almost 700,000 km². Between 1983 and 2000, the country of Gabon lost half its Gorilla population (Walsh et al. 2003). A recent evaluation estimated population declines using a predictive model that incorporated survey data collected across the range of the taxon between 2003 and 2013. The results show an 18.75% decline between 2005 and 2013, corresponding to an annual loss of ~2.56% (Strindberg et al. in prep). These population decreases were driven by a combination of poaching and disease. The current size of the population is being evaluated, but thought to be in the order of a few hundred thousand.
Despite their abundance and wide geographic range, in 2008 Western Lowland Gorillas were listed as Critically Endangered under criterion A: a population reduction of more than 80% over three generations (one generation is ~22 years). This listing was based on population losses due to poaching, disease and habitat loss. Illegal hunting has not ceased despite intense anti-poaching efforts and the threat of Ebolavirus has not been removed: poaching is intensifying with the expansion of access routes into forests and Zaire Ebola virus is still present in the forests of the region. In addition, habitat loss due to industrial agriculture is increasing, and the effects of climate change will become more evident. At a conservative rate of reduction (2.56% per year rather than 4%, calculated from Walsh et al. 2003), the reduction in the Western Lowland Gorilla population is predicted to exceed 80% over three generations (i.e., 66 years, 2005–2071). Gorilla gorilla gorilla thus qualifies as Critically Endangered.
|Previously published Red List assessments:|
The total range of Gorilla gorilla gorilla covers close to 700,000 km². The northwestern limit of their distribution is the Sanaga River in Cameroon; the northern limit is the forest-savannah boundary to a maximum of roughly 5°N; the eastern limit is the Ubangi River; and the Congo River south of its confluence with the Ubangi forms the southeastern and southern limits. Most Western Lowland Gorillas are found below 500 m asl, but some reach elevations of 600–800 m asl in the mountains of Gabon.
Native:Angola (Angola, Cabinda); Cameroon; Central African Republic; Congo; Equatorial Guinea (Equatorial Guinea (mainland)); Gabon
|Range Map:||Click here to open the map viewer and explore range.|
Western Lowland Gorillas are found in almost all of the protected areas in their geographic range and many of the logging concessions; the majority (78%) live outside the protected area network (Strindberg et al. in prep). They can reach high densities (3–5 individuals/km²) over large areas of both swamp and terra firma forests (Blake et al. 1995, Rainey et al. 2010) and can persist at high densities in well-managed logging concessions (Morgan et al. 2013). Gorilla population estimates are made using a standard index of abundance: night nest abundance and distribution, sometimes combined with predictive modelling. Extensive surveys carried out since the mid-2000s have suggested that 150,000–250,000 Gorillas occur in the areas surveyed (Williamson et al. 2013, Sop et al. 2015), but the total population size is currently being re-evaluated. Based on surveys carried out between 2003 and 2013, most Western Lowland Gorillas are now known to reside in the Republic of Congo (60%), followed by Gabon (around 27%) and southwestern Cameroon (10%) (Strindberg et al. in prep).
|Current Population Trend:||Decreasing|
|Habitat and Ecology:||Western Lowland Gorillas inhabit both swamp and terra firma lowland forests throughout Western Equatorial Africa, occupying a variety of forest types, including open- and closed-canopy moist mature, seasonally-inundated, and disturbed and secondary (regenerating) forest (Williamson and Butynski 2013). They occur at high density in vast swamps in northern Republic of the Congo. They eat fruit, seeds, leaves, stems, bark, shoots, roots, petioles, bracts, vine tendrils, invertebrates and earth (ibid.) Staple and fallback foods are pith and shoots of the families Marantaceae and Zingiberaceae, whereas fruit consumption varies greatly between seasons according to availability (Rogers et al. 2004). Some populations feed on Gilbertiodendron dewevrei seeds during mast fruiting (Blake and Fay 1997). Gorilla g. gorilla is sympatric with Pan troglodytes troglodytes throughout its range, and the two species show a high degree of dietary overlap. Annual home range may be as large as 25 km², but is more usually 10–15 km² and the ranges of neighbouring groups’ overlap extensively (Cipolletta 2004). Western Lowland Gorillas live in relatively stable groups composed of 10 individuals, on average, with one “silverback” adult male, several adult females and their offspring (Parnell et al. 2002).|
Western Gorilla reproductive rates are lower than those of Eastern Gorillas due to a later age of parturition and longer interbirth intervals between surviving offspring (Breuer et al. 2009). Life history data are available from a few habituated Western Lowland Gorilla groups and 20 years of observations in the Republic of Congo, and demonstrate a slower life history than Mountain Gorillas (Breuer et al. 2009). Males reach full maturity at 18 years and age at first reproduction of females is around 11 years (ibid.). Inter-birth interval averages 5.2 years for surviving births with offspring being weaned at four years of age (Stoinski et al. 2013). Generation time is estimated to be 22 years (see Appendix I).
|Continuing decline in area, extent and/or quality of habitat:||Yes|
|Generation Length (years):||22|
|Movement patterns:||Not a Migrant|
|Use and Trade:||
Gorillas are completely protected by national and international laws in all countries of their range, and it is, therefore, illegal to kill, capture or trade in live Gorillas or their body parts.
The major threats to Western Lowland Gorillas are:
Gorilla gorilla is listed under Class A in the African Convention on the Conservation of Nature and Natural Resources and is on CITES Appendix I. All Gorillas are protected by national and international laws throughout their geographic range, but law enforcement is generally weak. Only 22% of Western Lowland Gorillas live in the protected areas that cover 14% of their geographic range, with a further 21% of of the population in FSC-certified logging concessions, which add up to 8% of their range (Strindberg et al. in prep). Although forest guards work in most protected areas and in the well-managed logging concessions, 58% of Western Lowland Gorillas and 78% of their range are unprotected and highly vulnerable to poachers.
Two targeted conservation action plans for the great apes of Western Equatorial Africa have been produced (Tutin et al. 2005, IUCN 2014). The areas where most of the world's Western Lowland Gorillas occur in geographically distinct blocks have been identified, and a series of actions outlined for each, which can be broadly encapsulated as:
Anthony, N.M., Johnson-Bawe, M., Jeffery, K., Clifford, S.L., Abernethy, K.A., Tutin, C.E., Lahm, S.A., White, L.J.T., Utley, J.F., Wickings, E.J. and Bruford, M.W. 2007. The role of Pleistocene refugia and rivers in shaping gorilla genetic diversity in central Africa. Proceedings of the National Academy of Sciences of the United States of America 104: 20432–20436.
Bennett, E.L. 2014. Legal ivory trade in a corrupt world and its impact on African elephant populations. Conservation Biology 29: 54–60.
Bermejo, M., Rodríguez-Teijeiro, J.D., Illera, G., Barroso, A., Vilà, C. and Walsh, P.D. 2006. Ebola outbreak kills 5000 gorillas. Science 314: 1564.
Blake, S. and Fay, J.M. 1997. Seed production by Gilbertiodendron dewevrei in the Nouabale-Ndoki National Park. Journal of Tropical Ecology 13: 885–891.
Blake, S., Rogers, E., Fay, J. M., Ngangoue, M. and Ebeke, G. 1995. Swamp gorillas in northern Congo. African Journal of Ecology 33: 285–290.
Blake, S., Strindberg, S. and Princée, F. 2012. Evaluation of the CARPO/GHOA Biological Monitoring Programme. Reporting on Consultancy Contract No. WWF CARPO/AFGAP/FY12/CC/030 and Project Activity No. 9F0865.01. World Wide Fund for Nature, Morges, Switzerland.
Bour, P., Drori, O., Elkan, P., Feistner, A., Froment, J.M. et al. 2013. La crise du trafic d’ivoire et la gestion de la faune en Afrique Centrale. Contribution aux réflexions initiales menées pour le développement des Plans de Lutte Anti-braconnage proposées par la CEEAC. Available at: http://cms-family-ors.unep-wcmc.org/answers/1959658/documents/383.
Breuer, T., Hockemba, M.B.N., Olejniczak, C., Parnell, R.J. and Stokes, E.J. 2009. Physical maturation, life-history classes and age estimates of free-ranging western gorillas–insights from Mbeli Bai, Republic of Congo. American Journal of Primatology 71: 106–119.
Breuer, T., Robbins, A.M., Olejniczak, C., Parnell, R.J., Stokes, E.J. and Robbins, M.M. 2010. Variance in the male reproductive success of western gorillas: Acquiring females is just the beginning. Behavioral Ecology and Sociobiology 64: 1–14.
Caillaud, D., Levréro, F., Cristescu, R., Gatti, S., Dewas, M., Douadi, M., Gautier-Hion, A., Raymond, M. and Ménard, N. 2006. Gorilla susceptibility to Ebola virus: the cost of sociality. Current Biology 16: R489–R491.
Cipolletta, C. 2004. Effects of group dynamics and diet on the ranging patterns of a western gorilla group (Gorilla gorilla gorilla) at Bai Hokou, Central African Republic. American Journal of Primatology 64: 193–205.
Edwards, D.P., Sloan, S., Weng, L., Dirks, P., Sayer, J. and Laurance, W.F. 2014. Mining and the African environment. Conservation Letters 7(3): 302-311.
Fünfstück, T., Arandjelovic, M., Morgan, D.B., Sanz, C., Breuer, T. et al. 2014. The genetic population structure of wild western lowland gorillas (Gorilla gorilla gorilla) living in continuous rain forest. American Journal of Primatology 76: 868–878.
Genton, C., Cristescu, R., Gatti, S., Levrero, F., Bigot, E., Caillaud, D., Pierre, J.S. and Menard, N. 2012. Recovery potential of a western lowland gorilla population following a major Ebola outbreak: results from a ten year study. PLoS One 7: e37106.
Gilardi, K.V., Gillespie, T.R., Leendertz, F.H., Macfie, E.J., Travis, D.A., Whittier, C.A. and Williamson, E.A. 2015. Best Practice Guidelines for Health Monitoring and Disease Control in Great Ape Populations. IUCN SSC Primate Specialist Group, Gland, Switzerland.
Global Forest Watch. 2016. Available at: http://www.globalforestwatch.org/map/6/0.74/15.68/ALL/grayscale/none/581.
Groves C. 2001. Primate Taxonomy. Smithsonian Institution Press, Washington, DC, USA.
IUCN. 2014. Regional Action Plan for the Conservation of Western Lowland Gorillas and Central Chimpanzees 2015–2025. IUCN SSC Primate Specialist Group, Gland, Switzerland.
IUCN. 2016. The IUCN Red List of Threatened Species. Version 2016-2. Available at: www.iucnredlist.org. (Accessed: 04 September 2016).
James, R., Washington, R. and Rowell, D.P. 2013. Implications of global warming for the climate of African rainforests. Philosophical Transactions of the Royal Society B: Biological Sciences 368: 20120298.
Korstjens, A.H., Lehmann, J. and Dunbar, R.I.M. 2010. Resting time as an ecological constraint on primate biogeography. Animal Behaviour 79: 361–374.
Kühl, H., Maisels, F., Ancrenaz, M. and Williamson, E.A. 2008. Best Practice Guidelines for Surveys and Monitoring of Great Ape Populations. IUCN/SSC Primate Specialist Group, Gland, Switzerland.
Lanjouw, A. 2014. Mining/oil extraction and ape populations and habitats. In: Arcus Foundation (ed.), State of the Apes 2013: Extractive Industries and Ape Conservation, pp. 127–161. Cambridge University Press, Cambridge, UK.
Laporte, N.T., Stabach, J.A., Grosch, R., Lin, T.S. and Goetz, S.J. 2007. Expansion of industrial logging in Central Africa. Science 316: 1451.
Laurance, W.F., Clements, G.R., Sloan, S., O/'Connell, C.S., Mueller, N.D., Goosem, M., Venter, O., Edwards, D.P., Phalan, B., Balmford, A., Van Der Ree, R. and Arrea, I.B. 2014. A global strategy for road building. Nature 513: 229–232.
Laurance, W.F., Sloan, S., Weng, L. and Sayer, J.A. 2015. Estimating the environmental costs of Africa's massive development corridors. Current Biology 25: 3202–3208.
Lehmann, J., Korstjens, A.H. and Dunbar, R.I.M. 2010. Apes in a changing world – the effects of global warming on the behaviour and distribution of African apes. Journal of Biogeography 37: 2217–2231.
Lewis, S.L., Sonke, B., Sunderland, T., Begne, S.K., Lopez-Gonzalez, G. et al. 2013. Above-ground biomass and structure of 260 African tropical forests. Philosophical Transactions of the Royal Society B-Biological Sciences 368: 20120295.
Lovett, J.C. 2015. Modelling the effects of climate change in Africa. African Journal of Ecology 53: 1–2.
Magliocca, F., Querouil, S. and Gautier-Hion, A. 1999. Population structure and group composition of western lowland gorillas in north-western Republic of Congo. American Journal of Primatology 48: 1-14.
Maisels, F., Ella Akou, M., Douckaga, M. and Moundounga, A. 2004. Mwagne National Park, Gabon: large mammals and human impact. WCS/WWF Gabon.
Maisels, F., Nishihara, T., Strindberg , S., Boudjan, P., Breuer, T. et al. 2012. Great Ape and Human Impact Monitoring Training, Surveys, and Protection in the Ndoki-Likouala Landscape, Republic of Congo. Final Report. Wildlife Conservation Society, Brazzaville, Congo.
Maisels, F., Strindberg, S., Kiminou, F., Ndzai, C., Ngounga, R. et al. 2013. Wildlife and Human Impact Survey 2012, and monitoring 2005–2008–2012. Odzala-Kokoua National Park, Republic of Congo. Fondation Odzala-Kokoua and Wildlife Conservation Society, Brazzaville, Congo.
Maisels, F., Strindberg, S., Rayden, T., Kiminou, F., Madzoke, B., Mangonga, P. and Ndzai, C. 2015. Wildlife and Human Impact Survey of the Ngombé Ntoukou-Pikounda Forest Landscape, Republic of Congo. Feb–Oct 2014. Wildlife Conservation Society, Brazzaville, Congo.
Morgan, D. and Sanz, C. 2007. Best Practice Guidelines for Reducing the Impact of Commercial Logging on Great Apes in Western Equatorial Africa. IUCN/SSC Primate Specialist Group, Gland, Switzerland.
Morgan, D., Sanz, C., Greer, D., Rayden, T., Maisels, F. and Williamson, E.A. 2013. Great Apes and FSC: Implementing ‘Ape Friendly’ Practices in Central Africa’s Logging Concessions. IUCN/SSC Primate Specialist Group, Gland, Switzerland.
Poulsen, J.R., Clark, C.J., Mavah, G. and Elkan, P.W. 2009. Bushmeat supply and consumption in a tropical logging concession in northern Congo. Conservation Biology 23: 1597–1608.
Rainey, H.J., Iyenguet, F.C., Malanda, G.-A.F., Madzoké, B., Santos, D.D., Stokes, E.J., Maisels, F. and Strindberg, S. 2010. Survey of Raphia swamp forest, Republic of Congo, indicates high densities of critically endangered western lowland gorillas Gorilla gorilla gorilla. Oryx 44: 124–132.
Reed, P.E., Cameron, K.N., Ondzie, A.U., Joly, D., Karesh, W.B. et al. 2014. A new approach for monitoring Ebolavirus in wild great apes. PLoS Neglected Tropical Diseases 8: e3143.
Rival, A. and Levang, P. 2014. Palms of Controversies: Oil Palm and Development Challenges. CIFOR, Bogor, Indonesia.
Robbins, M.M., Bermejo, M., Cipolletta, C., Magliocca, F., Parnell, R.J. and Stokes, E.J. 2004. Social structure and life-history patterns in western gorillas (Gorilla gorilla gorilla). American Journal of Primatology 64: 145–159.
Rogers, M.E., Abernethy, K., Bermejo, M., Cipolletta, C., Doran, D., McFarland, K., Nishihara, T., Remis, M. and Tutin, C.E.G. 2004. Western gorilla diet: a synthesis from six sites. American Journal of Primatology 64: 173–192.
Ryan, S.J. and Walsh, P.D. 2011. Consequences of non-intervention for infectious disease in African great apes. PLoS One 6: e29030.
Sop, T., Cheyne, S.M., Maisels, F.G., Wich, S.A. and Williamson, E.A. 2015. Abundance annex: ape population abundance estimates. In: Arcus Foundation (ed.), State of the Apes 2015: Industrial Agriculture and Ape Conservation, pp. 1–41. Cambridge University Press, Cambridge, UK.
Stoinski, T.S., Perdue, B., Breuer, T. and Hoff, M.P. 2013. Variability in the developmental life history of the genus Gorilla. American Journal of Physical Anthropology 152: 165–172.
Stokes, E.J., Strindberg, S., Bakabana, P.C., Elkan, P.W., Iyenguet, F.C. et al. 2010. Monitoring great ape and elephant abundance at large spatial scales: measuring effectiveness of a conservation landscape. PLoS One 5: e10294.
Strindberg, S., Maisels, F. et al. In prep. Guns, germs and trees: key factors influencing the status of gorillas and chimpanzees in Western Equatorial Africa.
Thalmann, O., Wegmann, D., Spitzner, M., Arandjelovic, M., Guschanski, K., Leuenberger, C., Bergl, R.A. and Vigilant, L. 2011. Historical sampling reveals dramatic demographic changes in western gorilla populations. BMC Evolutionary Biology 11: 85.
Transparency International. 2016. Corruption Perceptions Index 2015. Transparency International, Berlin.
Tutin, C.,Stokes, E., Boesch, C., Morgan, D., Sanz, C., Reed, T., Blom, A., Walsh, P., Blake, S. and Kormos, R. 2005. Regional Action Plan for the Conservation of Chimpanzees and Gorillas in Western Equatorial Africa. IUCN/SSC Primate Specialist Group and Conservation International, Washington DC.
Walsh, P.D., Abernethy, K.A., Bermejo, M., Beyersk, R., De Wachter, P., Akou, M.E., Huijbregts, B., Mambounga, D.I., Toham, A.K., Kilbournk, A.M., Lahmq, S.A., Latourk, S., Maiselsk, S.F., Mbinak, C., Mihindouk, Y., Obiang, S.N., Effa, E.N., Starkeyk, M. 2003. Catastrophic ape decline in western equatorial Africa. Nature 422: 611–614.
Walsh, P.D., Bermejo, M. and Rodriguez-Teijeiro, J.D. 2009. Disease avoidance and the evolution of primate social connectivity: Ebola, bats, gorillas, and chimpanzees. In: M.A. Huffman and C.A. Chapman (eds), Primate Parasite Ecology: The Dynamics and Study of Host–Parasite Relationships, pp. 183–198. Cambridge University Press, Cambridge, UK.
Walsh, P.D., Biek, R. and Real, L.A. 2005. Wave-like spread of Ebola Zaire. PLoS Biology 3: 1946–1953.
Walsh, P.D., Breuer, T., Sanz, C., Morgan, D. and Doran-Sheehy, D. 2007. Potential for Ebola transmission between gorilla and chimpanzee social groups. American Naturalist 169: 684–689.
Walsh, P.D., Tutin, C.E.G., Baillie, J.E.M., Maisels, F., Stokes, E.J. and Gatti, S. 2008. Gorilla gorilla ssp. Gorilla. The IUCN Red List of Threatened Species.
White, A. and Fa, J.E. 2014. The bigger picture: indirect impacts of extractive industries on apes and ape habitat. In: Arcus Foundation (ed.), State of the Apes 2013: Extractive Industries and Ape Conservation, pp. 197–225. Cambridge University Press, Cambridge, UK.
Wich, S.A., Garcia-Ulloa, J., Kühl, H.S., Humle, T., Lee, J.S. and Koh, L.P. 2014. Will oil palm's homecoming spell doom for Africa's great apes? Current Biology 24: 1659–1663.
Wilkie, D., Shaw, E., Rotberg, F., Morelli, G. and Auzel, P. 2000. Roads, development and conservation in the Congo basin. Conservation Biology 14: 1614–1622.
Williamson, E.A., Maisels, F.G., Groves, C.P., Fruth, B., Humle, T.H., Morton, F.B., Richardson, M.C., Russon, A. and Singleton, I. 2013. Hominidae. In: R.A. Mittermeier, A.B. Rylands and D.E. Wilson (eds), Handbook of the Mammals of the World, pp. 792–854. Lynx Edicions, Barcelona, Spain.
Williamson, E.A., Rawson, B.M., Cheyne, S.M., Meijaard, E. and Wich, S.A. 2014. Ecological impacts of extractive industries on ape populations. In: Arcus Foundation (ed.), State of the Apes 2013: Extractive Industries and Ape Conservation, pp. 65–99. Cambridge University Press, Cambridge, UK.
|Citation:||Maisels, F., Strindberg, S., Breuer, T., Greer, D., Jeffery, K. & Stokes, E. 2016. Gorilla gorilla ssp. gorilla. The IUCN Red List of Threatened Species 2016: e.T9406A17989591.Downloaded on 01 October 2016.|
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