Lake Télé is striking on the map. It’s a near-perfect blue circle in a sea of green. Yet it is not this peculiar shape, nor the rich biodiversity of the surrounding forest [1], that it is known for. Instead, it has its very own mysterious monster, Mokele Mbembe. Not to discount the importance of legend in explaining the unknown and bringing communities together, I wasn’t in the forests around Lake Télé to see this dinosaur-like creature, or to directly see any animal for that matter. Instead, I was here to look for signs of a critically endangered great ape.
For my PhD research, I am studying how western lowland gorillas (Gorilla gorilla gorilla) move through the forests around Lake Télé in the Republic of Congo. Like much of the Congo Basin in central Africa, the study area comprises two main forest types – swamp and terra firma, or drier “firm ground.” In the rainy season, the swamp forest becomes flooded with meter-high water. In the “dry season,” it’s mainly thick mud interlaced with puddles and rivulets, leaving researchers to hop from root to root, or succumb to very moist socks. Where swamp and terra firma forests intermingle across the Congo Basin, the terra firma forests are the much more accessible habitat type – including to road-building, logging, and poaching[2]. For this reason, understanding the extent to which gorillas rely on the two different forest types and how they move between them seasonally is one example of how studying animal behavior can provide insights for conservation.
With this in mind, I’m interested in how gorilla density changes in the two different habitat types throughout the year depending on seasonal flooding. Does this population of gorillas migrate from the swamp to avoid flooding, as suggested [3]. Alternatively, do they switch from spending most of their time on the ground to a life in the trees, like other primates?
Another reason why the forests around Lake Télé are an intriguing place to conduct research combining animal behavior and conservation is because they constitute a community reserve. Community reserves are different from national parks and other types of more commonly-studied biological preserves in that the local community drives conservation decisions. The Lake Télé Community Reserve (LTCR) is co-managed by the Congolese government as well as Wildlife Conservation Society (WCS), without whose logistical support this project would not be possible.
In January of this year, my advisor and I set out to the LTCR to conduct a preliminary study. Our goal was to find out if it would be possible to study primates there, including the seasonal movement patterns of gorillas. What “possible” means is (a) whether we could get there and (b) if we could find evidence of a sufficient density of gorillas to study. Along the way, I would meet people who I could work with, learn to identify animal signs, and learn to camp and walk through the dense, tangley forest, while evading dangers (such as honeybees). Coming from sunny California, cluing in on animal signs in the dense, tropical forest would be a new experience for me.
The journey there
After a few flights and some COVID-test nose-jabbing, my PhD advisor and I arrived in Brazzaville, capital of Republic of Congo, where we were welcomed by WCS staff. The next day, we boarded a pickup truck for the three-day journey north. As we traversed the country on a newly-paved road, the bustling metropolis faded into roadside market stalls, scattered villages, and expanses of grassland that gave way to swaths of forest. On Day 3, the scenery really began to shift, as we hurtled along dirt roads flanked by ever-taller trees, red dust streaming into the cramped closed trunk of the pickup that my advisor, the village priest, and I shared. It was from this unrivaled vantage point that my fellow passengers decided to randomly quiz me: “What’s gorilla in Lingala?” I replied “Ebobo,” thankful to have remembered. Less than a minute later, a flash of silver and black dipped into the bushes just ahead of us. And that is how I glimpsed for the first time the elusive species I was to study.
We took to the water for the last part of the journey through the swamp forest in pirogues (hand-fashioned boats similar to a canoe, and the primary means of getting around in the region). Just as we reached the main river, the Likouala-Aux-Herbes, the sun dipped below the horizon. The dim fog of twilight and the low water level during this drier-than-usual dry season made the river hard to follow, but several hours later, five days after leaving California, I was in the village of Épena, one of 27 villages that comprise LTCR.
The study site
We had successfully made it to the reserve, yet we were still days away from gorilla habitat. From Épena, we stocked up on food, organized logistics, and eventually boated down the Likouala-Aux-Herbes River. Our destination was the small village of Impongui, situated on the transition zone between swamp forest and terra firma, an ideal base for someone interested in how gorillas navigate between these two habitats. Our camp would be a three-day walk inland. My advisor and I chose this site by combing through satellite images (essentially looking at Google Maps) in search of features that resembled particularly good gorilla habitat. In Impongui, we were incredibly warmly welcomed and fed, despite the fact that no one in this electricity-less village knew that we were coming. The chief of the village and three other guides provided essential field support, and led us to their traditional hunting trails, which wove through the swamp-terra firma transitional habitat, away from the river and the village into prime gorilla habitat.
Having successfully made it to the forest, the next goal was to see if we could find evidence of gorillas. Gorillas live in social groups and build nests that they sleep in every night. That means that when you’re trying to study gorillas “non-invasively,” or without contacting them and thus potentially disturbing them, you can look for specific signs. These signs include trampled vegetation, feeding remains like fruit rinds, group nesting sites, and – my personal favorite due to its DNA content and thus individual-identification potential – poop. On day 2 of our walk, we were trekking along in peaceful silence when I nearly stepped right into a fluorescent green mass. Gorilla poop!! This gave us the opportunity to track back and look for other gorilla signs to see where the individual and group came from, what, if any, plants they were feeding on in the area, and their travel path through the forest. We lost the trail pretty quickly this time, but it was a promising first of many gorilla signs we identified. Next time, when I return to collect much more data on gorilla movement behavior in different habitats through changing seasons, my team and I will continue to build our skills in tracking as well as other research methods.
In sum, I made it to LTCR (and back!). With the critical help of WCS, my research advisor, and knowledgeable local field assistants, we collected evidence of a sizable gorilla population that has not been formally studied for over 10 years [1] and warrants continued research. Despite the voice in my head prodding, “Am I cut out for this??” every so often, the preliminary study was a success. And I just might be looking forward to going back to find out how gorillas cope with the challenges of the swamp forest, even if it means again being thigh-deep in mud, drenched in sweat, a colony of ants crawling up my arm, excitedly spotting a fresh gorilla nest.
Alice Michel is a 2nd year student in the Animal Behavior Graduate Group at UC Davis in Dr. Damien Caillaud’s lab. Her research investigates how wild animals respond behaviorally to extreme habitat changes, specifically through changes in movement and social behavior in group-living species such as gorillas.
References
[1] Rainey, H. J., Iyenguet, F. C., Malanda, G. A. F., Madzoké, B., Santos, D. Dos, Stokes, E. J., … Strindberg, S. (2010). Survey of Raphia swamp forest, Republic of Congo, indicates high densities of Critically Endangered western lowland gorillas Gorilla gorilla gorilla. Oryx, 44(1), 124–132. doi: 10.1017/S003060530999010X
[2] Kleinschroth, F., Laporte, N., Laurance, W. F., Goetz, S. J., & Ghazoul, J. (2019). Road expansion and persistence in forests of the Congo Basin. Nature Sustainability, 2(7), 628–634. doi: 10.1038/s41893-019-0310-6
[3] Poulsen, J. R., & Clark, C. J. (2004). Densities, distributions, and seasonal movements of gorillas and chimpanzees in swamp forest in northern Congo. International Journal of Primatology, 25(2), 285–306. doi: 10.1023/B:IJOP.0000019153.50161.58
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