26.04.2018 | Sustainability and Complexity in Ape Habitat, TOP NEWS, Media Release

Gorillas and chimpanzees: more than expected, but in danger

A western lowland gorilla in the rainforests of the Republic of Congo. A decade-long study on Western Equatorial Africa’s western lowland gorillas (Gorilla gorilla gorilla) and central chimpanzees (Pan troglodytes troglodytes) has revealed there are more of these animals in the wild than previously thought. (Picture: Forrest Hogg/WCS)

The study produced a total population estimate for the central chimpanzee (pictured here) of nearly 130,000 individuals, approximately one tenth more chimpanzees than previously believed (Picture: Emma Strokes/WCS)

Buka, a silverback gorilla in Republic of Congo’s Nouabale-Ndoki National Park. Researchers now estimate that there are more than 360,000 western lowland gorillas in the wild, approximately one third higher than earlier figures. However, those same populations are declining by 2.7 percent annually. (Picture: Zanne Labuschagne/WCS)

Massive study finds more gorillas and chimpanzees than previously thought, but 80% are outside the safe havens of protected areas

Based on a media release by the Wildlife Conservation Society (WCS):


New York/Leipzig. A study estimates that more than 360,000 gorillas and nearly 130,000 chimpanzees still inhabit the forests of Africa approximately – one third and one tenth more than previously thought. However, approximately 80 percent of these great apes live outside protected areas, and gorillas are declining at an annual rate of 2.7 percent. Efforts to stop poaching, illegal logging, and habitat degradation and destruction are key to saving great apes. Conservationists from several organizations and government agencies gathered and analysed data on western lowland gorilla and central chimpanzee populations in the largest ever survey of these great apes that live exclusively in Western equatorial Africa. The field work for the study collectively took 167 person-years, with the researchers walking a distance longer than the north-south axis of Africa. The study that has been published in the journal Science Advances was led by the Wildlife Conservation Society (WCS). Among the authors is Hjalmar Kühl from the iDiv research centre and the Max Planck Institute for Evolutionary Anthropology.

The massive, decade-long study has uncovered both good news and bad about our nearest relatives. The good news: there are one third more western lowland gorillas and one tenth more central chimpanzees than previously thought. The bad news: the vast majority of these great apes (80 percent) exist outside of protected areas, and gorilla populations are declining by 2.7 percent annually.

Researchers collected field data during foot surveys carried out over a 10-year period across the range of both western lowland gorillas (Gorilla gorilla gorilla) and central chimpanzees (Pan troglodytes troglodytes). They surveyed an area of 192,000 square kilometres (72,000 square miles – equivalent to the size of the state of Washington) and included some of the most remote forests on the African continent. The authors of the study report an estimated abundance of over 360,000 gorillas and nearly 130,000 chimpanzees across their combined ranges. Both numbers are higher than previously believed. The gorilla estimate is approximately one-third higher and the chimpanzee estimate is about one-tenth higher. These revised numbers come largely from refinements to the survey methodology, new data from areas not included in previous estimates, as well as predictions of numbers in the areas between survey sites. “It’s great news that the forests of Western Equatorial Africa still contain hundreds of thousands of gorillas and chimpanzees”, says lead author Samantha Strindberg of WCS, “but we’re also concerned that so many of these primates are outside of protected areas and vulnerable to poachers, disease, and habitat degradation and loss”.

Although the majority of great apes were found outside of protected areas, they were still in large forested landscapes close to or bordering existing national parks and reserves and away from centres of human activity. This suggests that protecting large and intact forested areas is critical to conserving gorillas and chimpanzees in this region. The data analysis also revealed a 2.7 percent annual decline in gorilla numbers, a finding that supports the continued status of the species as “Critically Endangered” on the IUCN Red List of Threatened Species. Chimpanzees are listed as “Endangered.”

Of all the 14 living great ape taxa, western lowland gorillas and central chimpanzees have the largest remaining populations. This is certainly good news. However, their future preservation cannot be taken for granted, given the fact that their dependence on suitable habitat collides with local to global demand for natural resources from their habitat. Hjalmar Kühl of the iDiv research centre and the Max Planck Institute for Evolutionary Anthropology says: “Protecting our gorillas and chimpanzees will therefore require a major increase in political will at all levels—national, regional, and global. Financial commitments from governments, international agencies for endangered species conservation and the private sector, are also critical for conserving our closest relatives and their habitats.”

The main factors responsible for the decline of gorillas and chimpanzees are illegal hunting, habitat degradation, and disease. At the same time, it was clear that where wildlife guards were present, above all in protected areas with intact forests, both gorillas and chimpanzees can thrive. David Greer of the World Wide Fund for Nature explains: “All great apes, whether in Africa or Asia, are threatened by poaching, especially for the bushmeat trade. Our study found that apes could live in safety, and thus in higher numbers, at guarded sites than if there was no protection.”

Other conservation recommendations made by the authors include land-use planning at national scales to keep ecologically harmful activities, such as agriculture and new road construction, away from intact forests and the protected areas that serve as important gorilla and chimpanzee refuges. Another priority is the implementation of careful logging practices in existing logging concessions that follow Forest Stewardship Council (FSC) Standards for reducing impacts on wildlife and habitats. These standards require that access to forests is controlled, old logging roads are effectively decommissioned and effective patrol systems are put in place to prevent illegal hunting. An additional threat to great apes – as well as human health – is the Ebola virus disease. Continued research into developing a vaccine is a priority, as are educational efforts on how to avoid spreading the disease and transmission between humans and great apes.

The combined field time spent by researchers collecting data for the study totalled approximately 61,000 days (or 167 person-years) of time. Researchers walked more than 8,700 kilometres – a distance longer than the north-south axis of the African continent, or from New York to London. They collected data on great ape nests that was used to generate population estimates and trends. “The ‘boots-on-the-ground’ research teams and partnerships are crucial to the success of these programs and the conservation of gorillas and chimpanzees”, says co-author Dave Morgan of the Lincoln Park Zoo and Goualougo Triangle Ape Project.

The study titled “Guns, germs and trees determine density and distribution of gorillas and chimpanzees in Western Equatorial Africa” appeared in the latest edition of the journal Science Advances. The paper was written by 54 co-authors from several organizations and government agencies, including WCS (Wildlife Conservation Society), World Wide Fund for Nature, Max Planck Institute for Evolutionary Anthropology / iDiv research centre, Jane Goodall Institute, Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) – Monitoring the Illegal Killing of Elephants (MIKE), Lincoln Park Zoo, and the Universities of Stirling and Washington, and involved the protected area authorities of five countries.


Similar media release of iDiv and MPI-EVA

Dramatic decline of Bornean orangutans, 06.02.2018:

Original media release by the Wildlife Conservation Society (WCS)

Massive Study Across Western Equatorial Africa Finds More Gorillas and Chimpanzees Than Expected, but 80% Are Outside the Safe Havens of Protected Areas, 25.04.2018:


Original publication

S. Strindberg; F. Maisels; E.A. Williamson; S. Blake; E.J. Stokes; R. Aba’a; G. Abitsi; A, Agbor; R.D. Ambahe; P.C. Bakabana; M. Bechem; A. Berlemont; B. Bokoto de Semboli; P.R. Boundja; N. Bout; T. Breuer; G. Campbell; P. De Wachter; M. Ella Akou; F. Esono Mba; A.T.C. Feistner; B. Fosso; R. Fotso; D. Greer; C. Inkamba-Nkulu; C.F. Iyenguet; K.J. Jeffery; M. Kokangoye; H.S. Kühl; S. Latour; B. Madzoke; C. Makoumbou; G.A.F. Malanda; R. Malonga; V. Mbolo; D.B. Morgan; P. Motsaba; G. Moukala; B.S. Mowawa; M. Murai; C. Ndzai; T. Nishihara; Z. Nzooh; L. Pintea; A. Pokempner; H.J. Rainey; T. Rayden; H. Ruffler; C.M. Sanz; A. Todd; H. Vanleeuwe; A. Vosper; Y. Warren; and D.S. Wilkie (2018): Guns, germs, and trees determine density and distribution of gorillas and chimpanzees in Western Equatorial Africa. Science Advances, 25 Apr 2018, Vol. 4, no. 4, DOI: 10.1126/sciadv.aar296.



This research was supported by the Agence Française de Développement; Arcus Foundation; Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) - Monitoring of the Illegal Killing of Elephants (MIKE); Columbus Zoo and Aquarium; Conservation International and the Margot Marsh Biodiversity Foundation; the European Union's Ecosystèmes Forestiers d’Afrique Centrale; the European Union's Espèces Phares; Fondation Odzala-Kokoua; Foundation for Environment and Development in Cameroon; Global Environment Facility; Liz Claiborne and Art Ortenberg Foundation; Max Planck Institute for Evolutionary Anthropology; Spain-United Nations Environment Programme Lifeweb; The Aspinall Foundation; Total (Gabon); United Nations Educational, Scientific and Cultural Organisation's Central Africa World Heritage Forest Initiative; United States Agency for International Development’s Central Africa Regional Program for the Environment (CARPE); U.S. Fish and Wildlife Service (USFWS) Great Ape Conservation Fund, USFWS African Elephant Conservation Fund; Wildlife Conservation Society; the World Bank Group; and the World Wide Fund for Nature Germany, Netherlands, and USA.



Dr Hjalmar Kühl
Head of the Research Group
'Sustainability and Complexity in Ape Habitat'
German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig
Max Planck Institute for Evolutionary Anthropology (MPI-EVA)
Phone: +49 341 3550236
Email: kuehl@eva.mpg.de
Web: www.idiv.de/en/groups_and_people/employees/details/eshow/kuehl_hjalmar.html


Dr Tabea Turrini
Media and Communications
German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig
Phone: +49 341 9733106
Email: tabea.turrini@idiv.de
Web: www.idiv.de/en/groups_and_people/employees/details/eshow/turrini_tabea.html


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