Two groups of researchers working independently, one based in Denmark and the other in the UK and Canada, tested whether airborne DNA could be used to detect different animal species by collecting samples at Copenhagen Zoo in Denmark and Hamerton Zoo Park in the UK.
All living organisms, including humans, leach genetic material
known as eDNA into the environment when they excrete waste, bleed, and shed skin or fur. In recent years, conservation scientists have sequenced waterborne eDNA to track certain species, such as the UK's great crested newt population
, in aquatic environments.
However, monitoring airborne eDNA was more of a challenge because it's more diluted in air than it is in water.
Their work was published in two proof-of-concept studies in the journal Current Biology on Thursday.
The team working at the Hamerton Zoo Park was able to identify DNA from 25 different species of animals, including tigers, lemurs and dingoes, said UK study
lead author Elizabeth Clare, an assistant professor at York University in Canada and a former senior lecturer at Queen Mary University of London, where she undertook the work.
"We were even able to collect eDNA from animals that were hundreds of metres away from where we were testing without a significant drop in the concentration, and even from outside sealed buildings. The animals were inside, but their DNA was escaping," Clare said in a news release.
The Copenhagen team was able to detect 49 vertebrate species, including 30 mammals.
"We were astonished when we saw the results," said Kristine Bohmann, an associate professor from the Globe Institute at the University of Copenhagen and the lead author of the Danish study
, in the statement.
"In just 40 samples, we detected 49 species spanning mammal, bird, amphibian, reptile and fish," Bohmann said. "In the Rainforest House (at the Copenhagen Zoo) we even detected the guppies in the pond, the two-toed sloth and the boa. When sampling air in just one outdoor site, we detected many of the animals with access to an outdoor enclosure in that part of the zoo, for example kea, ostrich and rhino."
The Copenhagen team used a fan to draw in air from the zoo and its surroundings, which may contain genetic material from breath, saliva or fur -- or anything small enough to become airborne and float in the air.
The air was then filtered, and DNA was extracted and copied before being sequenced. Once processed, the DNA sequences were compared to a reference database to identify the animal species.
Both teams also detected the presence of animals not living at the zoos. They identified animals living in the surrounding areas, including the Eurasian hedgehog -- endangered in the UK -- which was detected from outside of Hamerton Zoo, while the water vole and red squirrel were detected around the Copenhagen Zoo.
While the researchers said the density of animals in the zoo's enclosures may have artificially increased the likelihood of detection, they believe the technique could shape the way scientists map species, potentially removing the need for camera traps, in-person monitoring and intensive field work.
"The non-invasive nature of this approach makes it particularly valuable for observing vulnerable or endangered species as well as those in hard-to-reach environments, such as caves and burrows. They do not have to be visible for us to know they are in the area if we can pick up traces of their DNA, literally out of thin air," Clare said in the statement.
"Air sampling could revolutionise terrestrial biomonitoring and provide new opportunities to track the composition of animal communities as well as detect invasion of non-native species."
Techniques involving eDNA from other environments already have made a significant impact across scientific research. Archaeologists are using eDNA found in cave dirt to understand ancient human populations
, while eDNA from cores of Arctic earth has revealed where mammoths and other Ice Age animals used to roam.
Similar techniques also are used to sample eDNA in sewage to detect and track Covid-19 in human populations.