The Democratic Republic of Congo's (DRC) tropical forests stretch across an extraordinary landscape of rivers, wetlands, savannas and towering trees. But in a forest this vast, biodiversity doesn't exist on a single plane. It climbs into the canopy. It moves between branches and vines, disappears into the understory and travels across the forest floor.
Now, Florida Atlantic University researchers and collaborators have found a non-invasive way to see more of this hidden world.
Using infrared cameras from the forest floor to the canopy, researchers created a 3D view of biodiversity in the DRC's Lomami National Park – revealing which mammals share the forest, how they use that 3D space, and which environmental factors shape the community.
Published in the Journal of Mammalogy , the first study developed the method to examine species richness, community composition and vertical habitat use across three survey areas in Lomami National Park and its buffer zone.
Researchers identified 47 mammal taxa representing primates, carnivores, rodents, artiodactyls (even-toed hoofed mammals like red river hogs), and pangolins, which are among the world's most heavily trafficked mammals. Eight species were detected outside their currently documented geographic ranges, providing records that could help inform future range assessments. The study generated thousands of videos that researchers and trained volunteers reviewed for species identification and behavior.
The cameras revealed a remarkably layered community, with 32 taxa detected on the ground, 23 in the understory and 22 in the canopy. While ground cameras captured most mammal diversity, they missed many arboreal species – underscoring the importance of the higher layers of the forest. Surprisingly, 25% of arboreal mammals preferred the understory, highlighting the value of surveying the lower-mid forest strata in complex forests tangled with vines.
For Daniel Alempijevic, Ph.D., lead author of the Journal of Mammalogy study and FAU alumnus, getting the cameras into those locations was quite the undertaking. Alempijevic's mentor and senior author, Kate Detwiler, Ph.D., an associate professor of biological sciences in FAU's Charles E. Schmidt College of Science , sent him to Panama to learn climbing techniques, skills that became essential for conducting canopy research in the Congo Basin.
"The cameras essentially gave us a way to turn a single point in the forest into a vertical column of observation" said Alempijevic. "We could put one camera facing the ground, one just a few meters higher in a tangle of vines, and a third 20 to 30 meters up in a tree crown, and then watch what was happening across those layers simultaneously. It was particularly fascinating to see how related species shared the same space. At the Bartho survey site, we found at least 10 species of primates; and probably the first camera trap recording ever captured of the enigmatic black-bellied pangolin back in 2016. This is the first study to get three species of pangolins within a single survey, which is really amazing."
High-quality video also captured behaviors rarely documented in the field, from bats investigating fruit in the canopy to small insect-eating bats repeatedly approaching other mammals, possibly feeding on insects attracted to their hosts.
And the cameras captured far more than mammals. Researchers recorded more than 1,500 bird events across the three forest levels, including interactions between birds and mammals, such as raptors preying on mammals and Eastern Long-tailed Hornbills following groups of monkeys.
The findings also show how understanding where species live within the forest can inform conservation. For example, white-bellied pangolins used the canopy more often in mature forests but were detected closer to the ground in areas cleared for agriculture, potentially increasing their vulnerability to poaching by bringing them into more frequent contact with people.
In the study published in ECOLOGY , Daniel Gorczynski, Ph.D., lead author and a post-doctoral researcher in FAU's Department of Biological Sciences, used the data from 25 mammal species that were detected most often to develop a multispecies, multi-scale occupancy model. The animals included bonobos, red-tailed monkeys, African palm civets, red river hogs, long-nosed mongooses, rope squirrels, among others.
Combining observations from the ground, understory and canopy revealed patterns that would have been missed at any single level. Most notably, mammal occupancy increased with elevation – a surprising result considering how little elevation gain there is within the swampy central Congo Basin. Even across such subtle topographic variation (43 meters), the full camera-column approach revealed an important relationship that would have been missed from the forest floor alone.
"Most biodiversity surveys essentially flatten the forest into a two-dimensional world," said Gorczynski. "What's unique is that we were able to look at the same forest from the ground all the way into the canopy and then ask how that additional dimension changes what we think we know about an entire mammal community. We found that it can fundamentally change the ecological story."
The Congo Basin is one of the world's most intact rainforests, with 60% of its forest in the DRC. Insecurity and limited infrastructure have left major gaps in biodiversity data, with basic ecological information still lacking for many species.
"Growing up in this region, I've always understood that the forest is more than a landscape – it is home to an extraordinary diversity of life that we are still only beginning to understand," said Junior Amboko, co-author of both studies, a Ph.D. student in FAU's Department of Biological Sciences and a National Geographic Explorer. "Being able to document that hidden biodiversity is deeply meaningful to me, especially because what we learn today can help ensure these forests and the species that depend on them are here for generations to come."
For Detwiler, the approach offers an important new tool for studying and protecting one of the world's most biologically important – and least studied – forest regions.
"The Congo Basin is simply too complex to monitor effectively from the ground alone," said Detwiler. "Camera columns give us a scalable way to see the forest as the animals experience it, from the leaf litter to the canopy. That can change how we identify important habitat, detect rare or threatened species, understand how animals respond to disturbance and ultimately make better conservation decisions across the Congo Basin."
Study co-authors of the two papers are Charlene Fournier, Ph.D., a recent Ph.D. graduate in FAU's Department of Biological Sciences; Martin Balimu, Department of Fauna and Flora, Kindu University, DRC; and David Essian, Ph.D., a recent FAU Ph.D. graduate, now with Harte Research Institute, Texas A&M University, Corpus Christi.
The research was supported by the Margot Marsh Biodiversity Foundation, Mohammed Bin Zayed Species Conservation Fund, Primate Conservation, Inc., Re: wild, International Primatological Society, Lukuru Foundation, Dynamic Youth Community, crowd funding, FAU Primatology Lab and FAU Foundation, Inc.
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