Looking up at the treetops won’t help you spot the minuscule creatures inhabiting them. Yet, these tiny beings leave behind traces of DNA on leaves and branches. Researchers have now announced a breakthrough in collecting this genetic information: a drone equipped with a unique fabric probe. This team piloted their drone over the rainforest and, utilizing the DNA gathered by the probe, was able to identify various invertebrates residing in the upper canopy.
“To encourage people to protect nature, we must illustrate exactly what we are safeguarding — with our method, we aim to gain a deeper understanding of the canopy’s inhabitants,” explains Steffen Kirchgeorg, the lead author of the study.
Drones can access areas that are difficult or unsafe for humans, such as remote or protected environments. As a result, researchers are increasingly employing these aerial devices to capture images, set up sensors, and gather samples from the forest canopy. To identify the species that live in trees, they collect genetic material left on foliage and branches. This environmental DNA (eDNA) can originate from mucus, feces, and shed skin cells. However, if a drone fitted with swabs to carefully collect eDNA collides with a tree, it could result in damage to both the drone and the plant. Therefore, Kirchgeorg, along with Stefano Mintchev and their team, sought to create a sampling mechanism that would prevent the drone from crashing into vegetation.
They engineered a drone sampling system that employs a specialized fabric probe designed to brush against leaves and branches to gather eDNA. When the remote pilot activates a pulley system below the drone, it can lower and raise the probe through the tree canopy. The setup utilizes a circular piece of fleece, akin to a coffee filter, with fiberglass strips attached for structural support. Furthermore, a sensor is in place to prevent the probe’s tether from tangling in branches. If an impact is detected, the system is programmed to automatically adjust its position before finishing the drop or retrieval of the probe.
In initial testing, the researchers deployed their drone in a Southeast Asian rainforest, sending it beyond their visual range to collect genetic samples from trees on ten different occasions. Upon its return from each flight, the team would detach the fabric and extract eDNA from the probes, then transport the samples to a laboratory for analysis and species identification. Across the ten samples collected, the majority of the identified organisms were arachnids and insects. Notable species included the long-tailed macaque (a type of monkey), several species of ants and termites, and a species of fly called the gall midge. This research introduces a new method for investigating biodiversity in hard-to-reach ecosystems, which the scientists argue is crucial for conservation and restoration efforts.
The authors express gratitude for the support received from the Swiss National Science Foundation via an Eccellenza Grant and a Bridge Discovery Grant, the European Research Council as part of the European Union’s Horizon 2020 research and innovation program, as well as funding from Rütli-Stiftung, the ETH Foundation, XPRIZE Foundation, and the Alana Foundation.
