Study highlights elusive Cameroonian gorillas, and the threats encircling them

Study highlights elusive Cameroonian gorillas, and the threats encircling them

  • Ebo Forest in southwestern Cameroon hosts a rare and enigmatic population of western gorillas.
  • A new study analyzes how gorillas use the forest, finding they primarily inhabit just 2,200 hectares (5,400 acres) within the 200,000-hectare (490,00 acre) forested area, and seem to spend much of their time in small patches of grassland rather than forest.
  • Experts say they hope the findings will help guide conservation efforts for the critically endangered species.
  • While not directly targeted for hunting, the gorillas face a multitude of threats, including gathering of forest products, a road construction project, and the secondary effects of other species in their habitat being hunted for bushmeat.

Gunshots, grassland and a tiny population of critically endangered gorillas coexisting with nearby human populations in southwestern Cameroon: a new study analyzes a complex set of factors to help understand how to continue conserving the gorillas of Ebo Forest for future generations.

The last time the Ebo gorillas were counted in 2010, there were estimated to be just 25 of them. Some researchers think they could even represent a third subspecies of western gorilla, of which two others — the western lowland gorilla (Gorilla gorilla gorilla) and the Cross River gorilla (Gorilla gorilla diehli) — are found elsewhere in Cameroon.

The Ebo gorilla’s forest home is under threat from hunting, the bushmeat trade, and habitat loss.

A key finding of this study is that these gorillas stick to a relatively small 2,200-hectare (5,400-acre) area within the 200,000-hectare (490,000-acre) Ebo Forest.

The study also found that within that 2,200-hectare patch, which contains a rich diversity of mature and secondary forest and swamp, the gorillas mostly use small grassland areas. That was initially surprising to lead researcher Daniel Mfossa.

Daniel Mfossa, lead researcher of the study, in the field arranging plant samples for identification. Image © EFRP/SDZWA.

“I would have thought mature forest that has high coverage with fruit trees and other plants the gorillas feed on would be used proportionately more,” he told Mongabay.

But the preference makes sense, he added. Grassland patches, sometimes caused by falling trees or branches, are rich in plants from the arrowroot (Marantaceae) and ginger (Zingiberaceae) families. The gorillas eat these and use them for nesting materials.

The study, funded by San Diego Zoo Wildlife Alliance, was published in the African Journal of Ecology.

There are some similarities between the foraging behavior of Ebo’s gorillas and ones found near Odzala-Kokoua National Park in the Republic of Congo, said Robin Morrison, a postdoctoral researcher with the Dian Fossey Gorilla Fund, who was not part of the Ebo Forest study.

“Gorillas rely on a range of different habitat types for different activities,” she said. “This means that areas with a mosaic of different habitat types, like in the area studied [in Ebo Forest], seem to be particularly important for gorillas.”

She described the study as valuable.

The research team and other staff planning a survey.
The research team and other staff planning a survey. Image © EFRP/SDZWA.

“Being able to say, ‘Here is a charismatic and critically endangered species using this forest in exactly these places,’ makes it that much harder to justify things like logging in the area,” Morrison said.

Logging isn’t actually happening at the moment in the gorilla study site. But there are other threats, including the gathering of bark from essock trees (Garcinia lucida) for medicine and a major road construction project that has the support of some villages.

Though gorillas are not directly targeted, hunting of other species for bushmeat also has negative impacts. Gunshots heard by the gorillas as hunters target other animals can be a source of stress, the researchers say. That stress can affect the gorillas’ ability to breed. There’s also the risk that the gorillas or their babies get caught in traps meant for other animals.

Community-based Gorilla Guardian Clubs are working with villagers and traditional chiefs to limit human access and activities within the gorillas’ tiny enclave, with some success already. A recent resolution, taken jointly by three nearby villages, was “to declare the gorilla area a no-go zone for humans,” said Mfossa, who coordinates the clubs for the Ebo Forest Research Project (EFRP).

Daniel Mfossa in the field setting a camera trap.
Daniel Mfossa in the field setting a camera trap. Image © EFRP/SDZWA.
Camera trap image of an adult male and a baby gorilla in Ebo Forest. Image © EFRP/SDZWA.

Conservationist Vianny Rodel Nguimdo, a colleague of Mfossa’s at the EFRP, though not a co-author of the study, said it was critical to include local communities to find solutions for the conservation of endangered species and biodiversity like the Ebo gorillas.

“They have a good mastery of forests and other wild places, as well as the animals and trees found there,” he told Mongabay. “They also have sustainable solutions to overexploitation of resources through their traditional laws.”

Camera traps set up in the forest have since 2015 captured images of both baby gorillas and pregnant females, suggesting the Ebo gorilla population is expanding.

To gather their data on the distribution of the isolated Ebo population, Mfossa and colleagues conducted “recce surveys” over five years — random walks in search of gorilla signs, such as feces or nests or footprints — as opposed to more systematic line transects. The latter would have necessitated cutting paths through the forest that could also be used by hunters.

The team gathered most of their evidence indirectly, to avoid habituating the gorillas to humans while hunters are still active in the area.

A plant and mushrooms growing on gorilla feces.
A plant and mushrooms growing on gorilla feces. Image © EFRP/SDZWA.

Martha Robbins, a primatologist at the Max Planck Institute for Evolutionary Anthropology in Germany, who was not involved in this study, said while both the recce surveys and the lack of direct observation of the gorillas may have affected the quality of the study’s data, the results were still exciting to see.

“This study is another example of how gorillas are able to exist in an area with high levels of human disturbance,” she said.

“The Ebo population is unique because of its location, so it is wonderful to see how ecological research can contribute to their conservation and management strategies in a human landscape.”

Banner image: Camera trap image of an adult male and a baby gorilla in Ebo Forest. Image © EFRP/SDZWA.


Mfossa, D. M., Abwe, E. E., Whytock, R. C., Morgan, B. J., Huynen, M. C., Beudels‐Jamar, R. C., … Tchouamo, R. I. (2022). Distribution, habitat use and human disturbance of gorillas (Gorilla gorilla) in the Ebo forest, Littoral Region, Cameroon. African Journal of Ecology. doi:10.1111/aje.13052


This story first appeared on Mongabay

South Africa Today – Environment

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