A drone partially wrapped in sticky tape can gather DNA from the branches of tall trees and reveal which animals live in that habitat.
Collecting environmental DNA (eDNA) – which comes from the shed cells, waste and blood of organisms – has revolutionised wildlife surveys. Rather than needing to physically see and capture animals to take samples, we can simply analyse the DNA they leave in their surroundings.
People have often harvested such DNA from water and air and catalogued the animals living there, but tree canopies are harder to reach. Now, Stefano Mintchev at the Swiss Federal Institute of Technology in Zurich and his colleagues have developed a quadcopter drone that can gather samples from branches tens of metres above the ground.
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In experiments in Switzerland, the drone collected 14 samples from seven different tree species and identified eDNA from 21 animal species, including insects, mammals and birds.
The bottom of the 1.2-kilogram craft is equipped with a force sensor that can detect pressure from several directions and an attached fibreglass cage that is covered in either sticky tape or gauze soaked in a sugar-water solution that collects loose particles, including those left by animals.
The drone is guided by remote control towards a branch and when it is within a short distance, an automatic control system takes over. It uses data from the force sensor to steer into the branch hard enough to collect samples.
After a short time, the drone pulls away from the branch and returns to the ground, where people can remove the samples for analysis.
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Mintchev says less is known about the communities living in trees than those in water systems and soil.
“They’re a hotspot for biodiversity and they’re not well understood because there’s this problem of accessibility: how to get there in order to get the samples,” he says. “Of course, you can send a climber there. But you don’t necessarily always want to do that.”
The drone can visit several outer branches on a single tree, but Mintchev wants to develop a device that can push its way deeper into the canopy to collect samples there too.
Science Robotics DOI: 10.1126/scirobotics.add5762
