Gorillas, Chimpanzees and Forest Elephants Thrive in the Rio Campo Nature Reserve

Categories: Journal no. 67, Censuses, Other countries, Other protected areas, Western Lowland Gorilla

Gorillas detected by camera traps in Rio Campo Nature Reserve, Equatorial Guinea, during a camera trap survey of mammals conducted in 2017 and 2019 (© Tiff L. DeGroot)

Protected areas aim to conserve wildlife - particularly large, charismatic species like gorillas - while benefiting local communities. But in tropical forests, wildlife within protected areas is often threatened by habitat degradation and hunting, despite laws protecting them. Species particularly at risk in these areas are typically those that are large bodied and slow to reproduce, like the western lowland gorilla (Gorilla gorilla gorilla). Large mammals like gorillas face compounding threats such as human population growth, ever increasing access to remote forests, and an influx of cheaper hunting technology, such as shotguns.

At the same time, central African protected areas face funding challenges that lead to inadequate protection - both for threatened and more common species. This is the case in Equatorial Guinea (EG) in west central Africa, where despite hunting laws existing on paper, there is essentially no on-the-ground enforcement. There is a glimmer of hope, however: the simple presence of law enforcement or survey crews can positively affect wildlife through "passive" protection.

Challenges faced by Equatorial Guinea's protected areas

The government agency responsible for protected areas management in EG, INDEFOR-AP, is underfunded, but during wildlife surveys they have been able to shut down multiple poaching and illegal logging operations. Despite a lack of capacity for surveys and law enforcement, INDEFOR-AP is committed to protecting natural resources. They have previously designated roughly 20 % of the country's upland habitat as protected areas. INDEFOR-AP has also implemented legislation such as bans on hunting in protected areas and a total ban on primate hunting.

The agency is also undertaking wildlife surveys to determine new areas to prioritize for protection. Researchers play a positive role as well, by providing more in-depth survey reports to INDEFOR-AP, who then inform on-the-ground management. For example, research conducted using camera trap surveys of mammals across EG has led to the designation of a new national park, which will connect two previously isolated protected areas.

Rio Campo: A vital, but threatened, connection between Equatorial Guinea and Cameroon

Rio Campo Nature Reserve is a protected area that lies along continental EG's northern coast. It is sliced in half by a road leading from EG's largest city, Bata (also home to EG's largest wild meat market). It is a short 50 km trip by car from Bata to Rio Campo's boundary, on a nicely paved highway. This, and the multiple towns and villages within Rio Campo, make it an area particularly vulnerable to human impacts.

Rio Campo has previously been identified as an important area for endangered species such as African elephants (Loxodonta cylotis), western lowland gorillas, and common chimpanzees (Pan troglodytes), in part due to its connectivity with the neighbouring Campo Ma'an National Park in Cameroon (Murai et al. 2013). To assess the diversity and distribution of mammals in Rio Campo, we collected camera trap data at 66 sites across the majority of the reserve (except for the northernmost portion), in 2017 (n = 26) and 2019 (n = 40). We created a species inventory and determined patterns of distribution for six taxonomic groups of interest, including great apes (gorillas and chimpanzees). With this assessment, we built upon previous mammal survey work by Murai et al. 2013 and Larison et al. 1999 by providing an updated and more comprehensive snapshot of diversity and distribution of both endangered species and common, yet extensively hunted species in Rio Campo. Species distributions were reported to INDEFOR-AP to assist in their management of Rio Campo’s mammals.

Great ape distributions in Rio Campo

Our study resulted in nearly 3,000 days of survey effort (number of nights cameras were active). We recovered images from 55 camera traps with an average of 48 days of effort per camera. Throughout the duration of the study, we detected at least 32 mammal species in Rio Campo including threatened species such as African forest elephants, white-bellied and giant pangolins, mandrill (Mandrillus sphinx), chimpanzees, and gorillas - as well as common species such as duikers, brush-tailed porcupines (Atherurus africanus), and Emin's pouched rat (Cricetomys emini).

In addition to generating a mammal species list and distribution maps for groups of interest, we used two-step or 'hurdle' models to assess 1) presence of taxonomic groups and 2) relative abundance of each group. We included several explanatory variables representing human impact (e.g. distance to road) and habitat (e.g. distance to river) factors. Additionally, we calculated detection rates for each species, calculated by dividing the number of independent detections of a species by the number of nights the camera traps were operational.

The general distribution patterns we observed suggest that threatened species such as gorillas, chimpanzees, giant pangolins, and elephants were mainly detected in the northeast of Rio Campo, while common species were more evenly distributed throughout the reserve. Our models suggest that great apes (gorillas and chimpanzees) were detected closer to the border between Rio Campo and Campo Ma'an in Cameroon, though the effect was marginal. We detected gorillas on five occasions throughout the study period, a rate of one detection per 600 days of survey effort. This rate was similar to that of chimpanzees in Rio Campo. Most gorilla detections consisted of groups, ranging from: 1) one adult, 2) two adults (one being a pregnant female), 3) a female and infant, 4) at least two adults (one being an adult silverback) and four juveniles, and 5) six adults and a juvenile. All but one of these groups were detected in the eastern arm of Rio Campo; the lattermost group was detected in the southeast portion of the reserve near River Mbia approximately 5 km from the main highway leading towards Bata.

We detected hunting activity at five stations during the study. All human detections were under 1 km from the nearest road, and two camera traps that were reportedly stolen were located within 5 km of the nearest populated place. The two missing camera traps were also within 2.5 km of one camera station that detected gorillas. INDEFOR-AP also shut down an illegal wild meat operation in the eastern portion of Rio Campo during the deployment of camera traps.

The threat of development: gorillas in Rio Campo and beyond

EG is unique in its relatively intact forests and the presence of populations of threatened mammals, including African forest elephant, western lowland gorilla, common chimpanzee, and three of the four African pangolin species, among many others. Rio Campo is close to EG's largest city, Bata, is intersected by a major road, and contains several populated areas within its boundaries. Thus, it represents an important region to assess the distributions of large-bodied mammals which are under increasing threats from human impact.

This study represents the most comprehensive camera trapping effort in Rio Campo to date. While we did not survey the northernmost tip of the reserve, we expect that wildlife is abundant due to the area's relative inaccessibility. This northern region is under a new threat, with the planned development of a bridge across the Ntem River. Our research suggests that sensitive species like gorillas tend to avoid developed areas, and so it is crucial that the remote parts of Rio Campo remain remote. We recommend additional camera trap surveys to assess diversity and distribution of mammals, and the possibility of great ape presence in this area.

Previous surveys detected gorillas in eastern Rio Campo (Murai et al. 2013). We also detected gorillas in this region, but note one group detected in southern Rio Campo, closer to the main road and potentially more at risk from human impacts. Additionally, our models indicate that the connectivity between Rio Campo and Campo Ma'an may be an important factor - not only for great apes, but other species as well. Concerningly, hunting activity was also detected in this same region of Rio Campo. Since camera traps were reportedly stolen, hunters may be aware of and avoid camera traps and hunting pressure is likely higher than represented by our study.

Development is an ongoing threat to mammals in EG, for example with the proposed Ntem River bridge - and further inland, the new capital city, Ciudad de la Paz (previously the village of Oyala), which has been built in a previously remote forest. The models developed in this study are a first step at assessing mammal distributions across mainland Equatorial Guinea and the factors affecting them. The aim of our work is to directly impact management of both threatened species like gorillas, and the common species that are so important to local livelihoods. We are beginning to see the fruits of this labour: work from this and other camera trapping efforts in continental EG have helped gather wildlife data to guide the creation of a new national park, which will connect two other protected areas, Altos de Nsork and Piedra Nzas, and be the second largest protected area in the country.

Tiff L. DeGroot, Luke L. Powell, Jared D. Wolfe and Kristin E. Brzeski

Larison, B. et al. (1999): Biotic Surveys of Bioko and Rio Muni, Equatorial Guinea. Central Africa Regional Program for the Environment (CARPE)
Murai, M. et al. (2013): Priority areas for large mammal conservation in Equatorial Guinea. PLoS ONE 8 (9), e75024

The above is a summary of:
DeGroot, T. L., Wolfe, J. D., Powell, L. L., Esono, F., Ebana, A., Barrientos, C., Torrent, L. & Brzeski, K. E. (2023): Human impacts on mammal communities in Rio Campo Nature Reserve, Equatorial Guinea. African Journal of Ecology 61, 262-276. doi.org/10.1111/aje.13108