Monitoring and categorising eDNA, or environmental DNA, left behind by animals and insects is a difficult undertaking. Typically, insect DNA is detected using traps that kill the insect. Furthermore, while collecting samples from water or soil is simple, getting them from the forest canopy and other undiscovered locations is difficult.
According to a press release, researchers at ETH Zurich, the Swiss Federal Institute for Forest, Snow, and Landscape Research WSL, and the company SPYGEN have collaborated to develop a unique drone that can autonomously gather samples on tree branches.
DNA collection by landing on tree branches
The mechanism appears to be simple, yet it is far from reality. The drone is outfitted with adhesive strips; when it lands on a branch, tree material adheres to these strips. The eDNA can subsequently be extracted in a lab and catalogued using database comparisons.
According to Stefano Mintchev, professor of environmental robotics at ETH Zurich and WSL, “landing on branches requires complex control.” Branches can bend and rebound when a drone lands on them due to their thickness & elasticity.
As a result, the aircraft is programmed to approach a branch on its own and remain stable on it while collecting samples. The scientists faced a huge task. Furthermore, because a drone cannot fathom the flexibility of a branch, the researchers fitted it with a force-sensing cage that allows the aircraft to measure this factor on the spot.
The aircraft has been tested on seven different tree species. The DNA samples revealed DNA from 21 separate categories of species, or taxa, including birds, mammals, and insects. “This is positive since it shows that the collection technique works,” Mintchev added.
Preparing for a flight in a rainforest
Mintchev and his crew are currently preparing the drone for a competition in Singapore, where the aircraft must detect as many different species as possible in 24 hours across 100 hectares of jungle.
As a first step, the team is working at the Masoala Rainforest at Zoo Zurich. “We have the advantage here of knowing which species are there, which will help us better judge how comprehensive we are in capturing all eDNA traces with this technique or if we’re missing something,” Mintchev explained.
Collecting samples in a natural rainforest presents a number of challenges. Rain washes eDNA off surfaces, while wind and clouds might be a hindrance in drone operation. “We are therefore quite interested to see if our sample procedure will also hold up under harsh conditions in the tropics,” Mintchev added.
The study is published in the journal Science Robotics.