Special drones collect environmental DNA from trees

Ecologists are increasingly using traces of genetic material left behind by living organisms in the environment, called environmental DNA (eDNA), to catalog and monitor biodiversity. Based on these DNA traces, researchers can determine which species are present in a given area.

Sampling from water or soil is easy, but other habitats—such as Forest canopy—very difficult for researchers to access. As a result, many species remain untracked in less-explored areas.

Researchers at ETH Zurich and the Swiss Federal Institute for Forest, Snow and Landscape Research (WSL) and the company SPYGEN have collaborated to develop a special drone that can automatically collect samples on tree branches.

How drones collect materials

The drone is equipped with adhesive strips. When the plane lands on a tree branch, material from the branch will stick to these bands. The researchers can then extract the DNA in the lab, analyze it, and assign it to the genetic combinations of different organisms using database comparisons.

But not all branches are the same: they differ in thickness and elasticity. Branches also bend and bounce back when drones land on them. Programming the plane so that it can still approach a branch automatically and remain stable on it long enough to sample is a major challenge for robot builders.

Stefano Mintchev, Professor of Environmental Robotics at ETH Zurich and WSL explains: “Landing on tree branches requires complex control. Initially, the drone didn’t know how flexible the branches were, so the researchers fitted it with a force-sensing cage. This allows the drone to measure this element in the field and incorporate it into its flight maneuver.

Prepare rainforest activities at Zoo Zurich

The researchers tested their new device on seven tree species. In the samples, they found the DNA of 21 different groups of organisms, or taxa, including birds, mammals and insects. “This is very encouraging, as it shows that the collection technique is effective,” said Mintchev, a co-author of the study, published in the journal Nature. robotics science.

The researchers now want to improve their drones further to be ready for a competition where the aim is to spot as many different species as possible across 100 hectares of rainforest in Singapore in 24 hours.

To test the drone’s effectiveness under conditions similar to those it will experience at the competition, Mintchev and his team are currently working in the Masoala Rainforest of the Zurich Zoo. “Here we have the advantage of knowing which species are present, which will help us better gauge how thorough we are in collecting all traces of eDNA using this technique,” ​​says Mintchev. Or whether we missed something.”

However, for this event, the collector must become more efficient and mobilize faster. In home tests in Switzerland, the drones collected material from seven trees over three days; in Singapore, it must be able to fly in and sample ten times as many trees in a single day.

However, collecting samples in natural rainforests presents researchers with even more challenging challenges. Rain regularly washes eDNA from the surface, while wind and clouds get in the way Unmanned aircraft work. “We were therefore curious to know if our sampling method would also be self-proving hard condition in the tropics,” Mintchev said.