Gathering genetic material from treetops in tropical rainforests would be a near-impossible task to perform safely by hand. That's why scientists have developed a system that allows a drone to do the job, without even touching the trees itself.
If you want to know which animals are present in an area, a relatively new way of finding out involves gathering and analyzing what is known as environmental DNA – or eDNA, for short.
eDNA is found in the biological substances such as feces and sloughed skin that animals regularly cast off into their environment. This means that if you analyze a water, soil or even air sample gathered from that environment, you can tell which animals are present in the area simply by seeing which species' eDNA shows up in the sample.
Over the past several years, eDNA analysis has been used for everything from assessing insect biodiversity to searching for the Loch Ness monster. Last year, scientists from Switzerland's ETH Zurich research institute utilized the technique to see which species make their home high up in the forest canopy.
In order to do so, the team built a quadcopter drone with adhesive strips on its underside. When the aircraft gently landed on branches, genetic material which was present on those branches got transferred onto the adhesive for subsequent analysis.
While this was a considerably faster, safer and easier alternative to sending biologists up into the treetops, there was still a risk of damaging the drone and/or the tree in the event of an unintentional hard collision. Additionally, samples could only be gathered from branches on which the aircraft could land.
That's where the new system comes in.
Developed by a team led by ETH Zurich robotics PhD student Steffen Kirchgeorg, it utilizes a flat, disc-shaped fabric probe that is lowered on a tether from a winch mounted on the underside of a quadcopter.
As that drone hovers in place safely above the treetops, the probe makes its way down through the foliage, brushing against plenty of leaves and branches as it does so. Once the probe has had a chance to gather some good eDNA, it's winched back up to the drone. The copter then returns to its base, so the probe can be removed and its contents analyzed.
In proof-of-concept demonstrations performed in a rainforest in Southeast Asia, Kirchgeorg and colleagues remotely controlled the drone via a live feed from its onboard camera, flying it beyond their line of sight to gather 10 samples from the forest canopy. The samples were found to contain the eDNA of 152 different species. Most of these were spiders and insects such as ants and termites, although the eDNA of the long-tailed macaque monkey was also present.
"If we want people to protect nature, we need to tell them what we are actually protecting – with our solution, we hope to better understand the life in the canopy," says Kirchgeorg.
A paper on the study was recently published in the journal Environmental Science & Technology. The system can be seen in eDNA-gathering action, in the silent video below.
Source: American Chemical Society
