Arboreal camera traps add ‘tons of value’ to forest canopy research

Over the past few decades, scientists have used camera traps to detect rare and elusive animals, document species diversity, and record new interactions and behaviors. But most of these studies were conducted on the ground; what was going on higher up in the canopy remained a mystery.

Recent advances in camera technology, climbing techniques and safety equipment have brought the forest canopy more easily within researchers’ reach. By setting up cameras in trees, scientists are beginning to plug gaps in our understanding of arboreal, or tree-dwelling, species.

Now, a team of researchers have gathered together global knowledge on the burgeoning field of arboreal camera trapping. The study authors draw on the experiences of researchers working in 24 countries across six continents on 90 studies, ranging from monitoring the effects of forest restoration projects and assessing the success of natural and artificial canopy bridges, to species inventories in intact tropical forests and viewing nesting birds and pollinating mammals in isolated trees.

“The forest canopy is probably the area we know the least about,” Jennifer Moore, a postdoctoral researcher at the University of Florida and lead author of the study, told Mongabay. “[Arboreal animals] are a group of high conservation concern and cameras are a great way to study them.”

Their study, published July 30 in Methods in Ecology and Evolution, provides a foundation from which to develop a set of best-practice approaches for this new technique. Such standardized approaches will allow researchers to compare data across projects and locations, revealing important global biodiversity patterns in the canopy realm, and arm policymakers with knowledge to effect positive conservation outcomes.

Pollinators and seed dispersers

Arboreal animals play a vital role in forests around the world. In tropical rainforests, for instance, tiny, obscure rodents to large and familiar orangutans add to overall ecosystem resilience by pollinating plants and dispersing seeds, thereby helping ecosystems regenerate and recover after disturbances.

Scientists are now uncovering evidence that suggests tree-dwelling mammal diversity rivals that of ground-level forest communities, and may even be higher in some tropical forests.

But with their heavy reliance on trees, arboreal species are more vulnerable to forest loss and fragmentation. Many species spend their entire lives in the canopy and never venture down to the ground, even to cross seemingly narrow barriers like roads and pipelines. Such barriers between pockets of forest permanently sever access to suitable resources and potential mates.

Arboreal camera trapping is expanding our understanding of how these vulnerable species are affected by both human and natural disturbances. Part of that new knowledge includes studies of how mitigation measures, such as canopy bridges between forest fragments, can lessen these impacts.

“Cameras can really help demonstrate whether conservation solutions are actually working. One bridge design won’t work for every species, so cameras can help to facilitate the implementation of these techniques,” said Tremaine Gregory, a conservation biologist at the Smithsonian Conservation Biology Institute and co-author of the study.

And studies are leading to new discoveries. For example, while Gregory and her team were monitoring the branches of large trees that form a natural canopy bridge over pipeline clearings in Peru, they discovered a population of dwarf porcupines unknown in the region — their closest known range was 900 kilometers (560 miles) to the north. “Because no monitoring is ever done that high … it’s really impossible to know what’s going on up there. If an animal is only active at night and it’s 30 meters [100 feet] up in a tree, you’re never going to see them without a camera. You just can’t do it through regular observation,” Gregory said.

Challenges abound

There is always an element of trial and error to any arboreal camera-trapping project, according to Gregory. But she hopes that the new study, which pools information from across the globe, will inspire future researchers and boost the data yield from their surveys.

The first challenge is accessing the canopy. This must be done as safely and efficiently as possible, since teams need to visit operating cameras roughly once a month to conduct maintenance checks and to download data. Although modern cameras fitted with Wi-Fi allow researchers to do these processes from the ground, this is often ineffectual in dense forests.

Accordingly, arboreal camera teams often include qualified tree climbers. The new study emphasizes the need for safety and rescue protocols that support aerial access skills, since study sites are typically remote, so teams must be able to deal with immediate danger themselves.

Once up a tree, researchers have to decide where exactly to position the cameras, a process that is being continually refined through the development of custom-built camera mounts that allow tilting and panning to adjust the field of view.

“There are so many more aspects to take into account when you’re working in an arboreal setting … because you have that whole third dimension of space and height,” Moore said. “If you place [cameras] incorrectly, you just get hundreds of photographs of leaves swaying in front of the lens.”

It is a process of continual perseverance and problem-solving. Even the study subjects themselves can inadvertently thwart the process. “When we checked the cameras in Peru, we found many of them open and flooded with rainwater. Then I realized it was these same porcupines that were gnawing on the casing … and their little feet would pop the camera open.” Gregory now prevents this by putting locks on the cameras.

The authors included a set of “mini guides” in their study to help people design, plan and execute successful arboreal camera-trapping studies. They include a synthesis of past studies, different types of camera mounts, tree-climbing protocols and safety tips, methods to place cameras at height without climbing, and ways to protect cameras from overly curious wildlife.

Although the majority of arboreal camera-trap studies have focused on mammals, new camera systems equipped with close-focusing lenses, variable frame rate and time-lapse have led to breakthroughs with reptiles, amphibians, invertebrates and plants. “There are still so many avenues that need to be explored,” Moore said.

For Gregory, one of the joys of arboreal camera trapping is using the photographs and videos to convey the mysteries of life in the canopy to local communities.

“I think arboreal cameras have tons of value with regard to communications and getting people excited about the wildlife in their area,” Gregory said, adding that photographs of animals in the canopy tend to be more appealing, since they are often moving through the trees in family groups and displaying interesting behaviors. “It’s a great way to get people engaged.”

Banner image: Grey-cheeked mangabey (Lophocebus albigena) in Nyungwe National Park, Rwanda. Image courtesy of Wildlife Conservation Society-Rwanda Program

Citation:

Moore, J. F., Soanes, K., Balbuena, D., Beirne, C., Bowler, M., Carrasco-Rueda, F., … Gregory, T. (2021). The potential and practice of arboreal camera trapping. Methods in Ecology and Evolution. doi:10.1111/2041-210X.13666

Editor’s note: This story was supported by XPRIZE Rainforest as part of their five-year competition to enhance understanding of the rainforest ecosystem. In respect to Mongabay’s policy on editorial independence, XPRIZE Rainforest does not have any right to assign, review, or edit any content published with their support.

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