Big Data Reveal More Gorillas and Chimpanzees in W. Africa than Previously Assumed

Baby gorilla with mother / Photo by Getty Images


A decade-long study showed that there are over 360,000 western lowland gorillas and 130,000 central chimpanzees in Western Equatorial Africa, according to

The study also uncovered a 2.7-percent annual decline in gorilla population, which merits its continued status as Critically Endangered on the IUCN Red List of Threatened Species. On the other hand, chimpanzees are listed as Endangered.

Higher Estimates

Both estimates are bigger than previously thought, with the gorilla population a third higher and the chimpanzee population a tenth larger than what was formerly known. The larger estimates were the result of improvements in the survey methodology, new data from areas not earlier included in the range estimates, and prediction of numbers between survey sites.



The study was a joint effort between several organizations and government agencies including the Wildlife Conservation Society, the World Wide Fund for Nature, the Max Planck Institute for Evolutionary Anthropology, and the Jane Goodall Institute. Field data were collected during foot surveys during a 10-year period study of the two great apes species covering an area of 192,000 square kilometers, which is approximately the size of the state of Washington and included some of the most remote forests in Africa. Researchers spent 61,000 days and walked more than 8,700 kilometers, which is equal to the distance from New York to London, in collecting the data.

Threats to Primate Populations



Samantha Strindberg of WCS and lead author of the study said it was good news knowing that the forests of Western Equatorial Africa are still home to numerous gorillas and chimpanzees, but as much as 80 percent of these primates are not in protected areas, putting them at risk to poaching, loss of habitat, and diseases. These three are the biggest reasons for the diminishing primate population.

Most of the great apes were found living in Gabon and the Republic of Congo. Smaller ape populations were found in Equatorial Guinea, the Central African Republic, Cameroon, and Angola.  

Strindberg added that the study’s findings will help in formulating national and regional management strategies for protecting the primates’ remaining habitat, increase anti-poaching efforts and control the effects of economic development on great apes and other wildlife. Although the majority of the gorillas and chimpanzees were not found in forest sanctuaries, they were still living in forest areas close to existing national parks and reserves and away from human pursuits. This makes it important to protect large and pristine forest lands which are crucial to the preservation of these primate species.    

Of the 14 great ape species, gorillas and chimpanzees have the biggest populations, but their conservation is not yet assured because of the availability of suitable habitats clashes with the great demand for the natural resources found in these habitats.

The study also noted the importance of wildlife guards or forest rangers, whose presence in protected areas in intact forests guarantee the survival of the gorillas and chimpanzees. Apes could live safely, and in great numbers, at guarded sites, according to David Greer of the WWF. He added that all great apes are being hunted down by poachers, particularly for the bushmeat trade.

Other suggestions given by the study’s authors include land-use planning at the national level to keep economic activities, such as agriculture and road construction, far from intact forests and protect areas that serve as the habitat of gorillas and chimpanzees.

Another priority being pushed by the study’s authors is the enforcement of strict logging practices that comply with the Forest Stewardship Council Standards for reducing environmental impacts on wildlife and habitats. These policies will control access to forests, the decommissioning of old forest roads, and the implementation of forest patrol systems to prevent poaching.

Protecting primates will also require a major increase in political will. Monetary pledges from various governments, international agencies, and the private sector are critical for the conservation of primates and their habitats, according to Hjalmar Kuhl of the Max Planck Institute for Evolutionary Anthropology.

Similarly, Liz Williamson, IUCN Red List Authority Coordinator, said a combination of responsible industrial practices, conservation policies, and a network of nature parks and corridors are the key to preserving the great apes in Central Africa.

The Threat of Ebola Virus

The Ebola virus disease remains a serious threat to apes and humans and developing a vaccine and the means of delivering it remain top priorities in preventing the spread of the disease between humans and apes.  

Great apes are protected by national laws and international conventions, which make it illegal to kill, capture or trade in live individuals or their body parts. Despite this legal protection, the combination of poaching and the Ebola virus has proven to be disastrous to gorilla and chimpanzee populations. Female primates take 11 to 12 years to mature and give birth every four years only.


Illustration of Ebola virus / Photo by Getty Images