Guns, germs, and trees determine density and distribution of gorillas and chimpanzees in Western Equatorial Africa

Citation

Strindberg S, Maisels F, Williamson EA, Blake S, Stokes EJ, Aba'a R, Abitsi G, Agbor A, Ambahe RD, Bakabana PC, Bechem M, Berlemont A, de Semboli B, Boundja PR & Jeffery KJ (2018) Guns, germs, and trees determine density and distribution of gorillas and chimpanzees in Western Equatorial Africa. Science Advances, 4 (4), Art. No.: eaar2964. https://doi.org/10.1126/sciadv.aar2964

Abstract
We present a range-wide assessment of sympatric western lowland gorillas Gorilla gorilla gorilla and central chimpanzees Pan troglodytes troglodytes using the largest survey data set ever assembled for these taxa: 59 sites in five countries surveyed between 2003 and 2013, totaling 61,000 person-days of fieldwork. We used spatial modeling to investigate major drivers of great ape distribution and population trends. We predicted density across each taxon’s geographic range, allowing us to estimate overall abundance: 361,900 gorillas and 128,700 chimpanzees in Western Equatorial Africa—substantially higher than previous estimates. These two subspecies represent close to 99% of all gorillas and one-third of all chimpanzees. Annual population decline of gorillas was estimated at 2.7%, maintaining them as Critically Endangered on the International Union for Conservation of Nature and Natural Resources (IUCN) Red List. We quantified the threats to each taxon, of which the three greatest were poaching, disease, and habitat degradation. Gorillas and chimpanzees are found at higher densities where forest is intact, wildlife laws are enforced, human influence is low, and disease impacts have been low. Strategic use of the results of these analyses could conserve the majority of gorillas and chimpanzees. With around 80% of both subspecies occurring outside protected areas, their conservation requires reinforcement of anti-poaching efforts both inside and outside protected areas (particularly where habitat quality is high and human impact is low), diligent disease control measures (including training, advocacy, and research into Ebola virus disease), and the preservation of high-quality habitat through integrated land-use planning and implementation of best practices by the extractive and agricultural industries.

Notes
Additional co-authors: Nicolas Bout, Thomas Breuer, Genevieve Campbell, Pauwel De Wachter, Marc Ella Akou, Fidel Esono Mba, Anna T. C. Feistner, Bernard Fosso, Roger Fotso, David Greer, Clement Inkamba-Nkulu, Calixte F. Iyenguet, Max Kokangoye, Hjalmar S. Kühl, Stephanie Latour, Bola Madzoke, Calixte Makoumbou, Guy-Aimé F. Malanda, Richard Malonga, Victor Mbolo, David B. Morgan, Prosper Motsaba, Gabin Moukala, Brice S. Mowawa, Mizuki Murai, Christian Ndzai, Tomoaki Nishihara, Zacharie Nzooh, Lilian Pintea, Amy Pokempner, Hugo J. Rainey, Tim Rayden, Heidi Ruffler, Crickette M. Sanz, Angelique Todd, Hilde Vanleeuwe, Ashley Vosper, Ymke Warren, and David S. Wilkie

Journal
Science Advances: Volume 4, Issue 4