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Population analysis suggests Grauer's gorilla is Critically Endangered

The great apes live only in the Democratic Republic of Congo, experienced 77 percent population decline in a single generation



IMAGE: This is a photo of the powerful Silverback Cimanuka of Kahuzi-Biega National Park, Democratic Republic of Congo. Shortly after this, Cimanuka led his group deeper into the swamp where it... view more

Credit: Jose McKenna, Flickr

Grauer's gorilla, which is confined to the eastern Democratic Republic of Congo, is now Critically Endangered, according to a study published October 19, 2016 in the open-access journal PLOS ONE by Andrew Plumptre from Wildlife Conservation Society, USA, and colleagues.

This is the first analysis of the Grauer's gorilla population since civil war broke out in the region in 1996. Since the war, armed miners have hunted bushmeat including gorillas, but the presence of militia has complicated assessments of the gorilla population. Plumptre and colleagues assessed local community and ranger-collected data that included encounter rates at gorilla nests at 10 sites as well as spatial occupancy across the species' range.

Before the war, the population was estimated at 16,900 individuals. The researchers now estimate that there are only 3,800 Grauer's gorillas left in the wild, a 77% decline in a single generation. While this species was previously classified as Endangered, the gorillas are now listed as Critically Endangered on the IUCN Red List of Threatened Species based on this new population estimate. The new analysis also suggests that the gorilla's range is about 19,700 km2, and identified three key areas that are the most critical for the remaining population of this great ape.

The researchers believe that Grauer's gorilla could be lost from many parts of its range within five years, and call for greater conservation efforts. Approaches include halting mining in protected areas as well as motivating the military to protect wildlife in this biodiversity rich region.

"While we knew that Grauer's gorilla was in trouble nobody had realised how much they had declined", stated Andrew Plumptre of the Wildlife Conservation Society who led the study. "The results in this paper provide the evidence to list this ape, which is the world's largest primate, as Critically endangered on the IUCN Red List of threatened species".


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Citation: Plumptre AJ, Nixon S, Kujirakwinja DK, Vieilledent G, Critchlow R, Williamson EA, et al. (2016) Catastrophic Decline of World's Largest Primate: 80% Loss of Grauer's Gorilla (Gorilla beringei graueri) Population Justifies Critically Endangered Status. PLoS ONE 11(10): e0162697. doi:10.1371/journal.pone.0162697

Funding: Support for this analysis was primarily provided by the generous support of the Arcus Foundation through the Jane Goodall Institute (Arcus 1202-03). The surveys referred to in the report were funded by other donors, notably Critical Ecosystem Partnership Fund, Frankfurt Zoological Society, KfW, Rainforest Trust, UNESCO, USAID/CARPE, US Fish and Wildlife Service and World Bank. We are also grateful to Wildlife Conservation Society for supporting Andrew Plumptre and Deo Kujirakwinja to compile and analyse the data; CIRAD, who supported Ghislain Vieilledent to help with the R-analyses, Chester Zoo, who supported Stuart Nixon's time during the writing of this report, and the University of York, who supported Rob Critchlow.

Competing Interests: The analysis presented in this paper was funded by the ARCUS Foundation using data collected by Wildlife Conservation Society (WCS), Fauna and Flora International and Institut Congolais pour la Conservation de la Nature and funded by a variety of donors listed in the financial disclosure section. Two of these funders, KfW and World Bank are a commercial source of funds but this does not alter our adherence to PLOS ONE policies on sharing data and materials." (as detailed online in our guide for authors as the IP and data sharing rights are owned by WCS.

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