So Long, Congo’s King Kong? Dramatic Population Decline of World’s Largest Gorilla

So Long, Congo’s King Kong? Dramatic Population Decline of World’s Largest Gorilla

The largest living primate, Grauer’s gorilla, lives only in the eastern Democratic Republic of Congo. Before civil war broke out in the region in 1996, the population was estimated at 16,900 individuals, but it has since been difficult to conduct population assessments.

Andrew PlumptreAndrew Plumptre, senior conservation scientist for the Wildlife Conservation Society’s Africa Program, and colleagues assessed local community and ranger-collected data and found a dramatic 77% decline to an estimated 3,800 wild Grauer’s gorillas. To learn more about the study and the significance of its results, I interviewed Dr. Plumptre via email.


What drew you to conservation science and to gorillas?

AP: I have always wanted to work with wildlife: even as a young kid I wanted to be a zookeeper! I was born in Uganda, but when I was six, Idi Amin took over as president and my family left for the UK. Even at this early age, the amazing national parks made an impression on me, and after school I took a year out to travel in Rwanda, Burundi and the Democratic Republic of Congo, visiting Grauer’s gorilla and the mountain gorilla. That visit got me hooked and I decided to work on the conservation of mountain gorillas for my Ph.D.

Tell us about Grauer’s gorilla. How does it differ from other gorillas and great apes?

AP: Grauer’s gorilla is a subspecies of the eastern gorilla, which includes the mountain gorilla. At up to 300 kilograms, it is the largest ape on the planet and has longer limbs and longer hair than the western gorilla of the Democratic Republic of Congo, Gabon, Cameroon and Nigeria. It is the most poorly understood of the four gorilla subspecies with few studies of its biology and distribution, though it is known to exist only in the east of the Democratic Republic of Congo. Since there are very few Grauer’s gorillas in zoos, conservation relies totally on protecting the gorillas in the wild.

How has the Democratic Republic of Congo civil war affected conservation work in this country?

AP: The civil war in the Democratic Republic of Congo has led to the wide availability of arms and created a plethora of militia groups who control different territories in the east of the country.

This has been terrible for conservation of its wildlife: populations of most large mammals have been decimated across the country, particularly those of elephants and apes. I co-authored a PLOS ONE paper in 2013 that documented the terrible decline in forest elephant numbers; this paper does likewise for Grauer’s gorilla and chimpanzees.

You found a 77% population decline over a single generation to an estimated 3,800 wild gorillas, making Grauer’s gorilla critically endangered. Did this decline surprise you, and why do you believe it may have occurred?

AP: A decline had been suspected for some time, and ‘back of the envelope’ calculations had predicted a 30-50% decrease. However, we received a major shock upon pulling together all the regional survey data: none of us were prepared for such a large decrease. The main reason seems to be a great increase in artisanal mining sites controlled by armed militias deep in the forest. In such remote places, miners rely on bush meat for food. Sadly, gorillas are easy to find and kill, and provide a lot of meat for one bullet.

What impact do you hope your study might have, and what are the next steps for your research?

AP: In the paper, we recommend better protection of gorillas in Punia Gorilla Reserve and Itombwe Massif. We have been involved in extensive surveys and consultations with the Democratic Republic of Congo government and the local people, resulting in the establishment of the Itombwe Natural Reserve in June this year. We are currently starting the same process in the Punia Gorilla Reserve. Our paper also highlights the importance of managing artisanal mining sites in the country to enable people to benefit from mineral riches without hunting large mammals, and we will pilot an approach which uses local chiefs and their communities in and around the Punia Gorilla Reserve.

Is there any hope for these gorillas?

AP: The only site we surveyed where gorilla numbers have actually increased was a highland region of Kahuzi-Biega National Park which has a tourism program and focused protection efforts. So there is hope that with sufficient targeted resources, Grauer’s gorillas can be protected successfully.

In the light of the recent escape of a gorilla from its enclosure at London Zoo, what are your thoughts about keeping gorillas in captivity?

AP: I personally think that, in the right settings, zoos can play a useful role in conservation. For example, the gorilla exhibit at the Bronx Zoo, which charges an entry fee to go towards field projects, has raised several million dollars for conservation. They also have a classroom overlooking the gorilla exhibit which educates hundreds of children each year about the rarity of gorillas in the wild and the need to do something to conserve them.


Research Article: 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

Images Credits: Joe McKenna, Flickr; Andrew Plumptre


Beth works at PLOS as Journal Media Manager. She read Natural Sciences, specializing in Pathology, at the University of Cambridge before joining PLOS in 2013. She feels fortunate to be able to read and write about the exciting new research published by PLOS.


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