DNA is in the air – literally. It is wafted around by all the Earth’s creatures, and now scientists have found a way to detect these invisible traces of genetic material so they can identify the animals that released them.
The discovery – made independently by British and Danish research groups earlier this year – opens up a powerful way to pinpoint the presence of rare wildlife in deserts, rainforests and other hostile environments.
“This could transform the way we study biodiversity,” said Professor Elizabeth Clare of York University. “Every other technique we have for tracing animals – camera traps, say, or acoustic monitoring – relies on the animals being physically present near or in front of you.
“Trapping their DNA from the air is much less invasive, and much more flexible. You could detect the presence of creatures in caves without disturbing them, for example.”
In their experiments, Clare – then at Queen Mary University of London – and her colleagues used sensitive filters fitted to vacuum pumps placed at 20 locations across Hamerton Zoo Park in Cambridgeshire last December. “We realised a zoo would be an excellent place to test a technique like this because animals there are non-native and are spatially confined in enclosures,” said Clare. “It meant that if we were successful and could detect DNA in the air, we would know exactly where it was coming from and how far it had travelled.”
A total of 72 air samples were collected by the team, who used polymerase chain reaction (PCR) to amplify the tiny fragments of DNA isolated in their filters. They sequenced this genetic material and compared the results with known sequences of animals – and identified 17 species of zoo animal from invisible traces of their DNA released into the air.
“We found tiger DNA, dingo DNA and, most of all, DNA from black and white ruffed lemurs,” said Clare. “Their DNA was the most widely distributed. We are not sure why but lemurs are certainly very active compared with other animals. They were bouncing around their cages, taking great interest in the people wandering past them. By contrast, a lot of other animals were lying low as it was winter.”
Intriguingly, similar discoveries were made at the same time by researchers led by Christina Lynggaard and Kristine Bohmann of Copenhagen University. In their research, they sucked up air from several sites in Copenhagen Zoo and detected a total of 49 species from the DNA found in their filters.
“We were astonished,” said Bohmann. “We got DNA from mammals, fish, birds and reptiles, from big animals and small animals, from creatures with feathers and others with scales. We even detected the DNA of guppy fish that swim in a pond in the zoo’s tropical house.”
For good measure, both teams found they could also pinpoint the presence of local wildlife, neighbourhood pets and the animals that were there as feed for the zoo animals.
“We realised we were detecting DNA from animals that were being fed to zoo animals, for instance fish,” said Bohmann. “We were also picking up the DNA of local cats and dogs and local wild animals. It was astonishing what we were able to detect.”
Both the Danish and British projects were funded as part of high-risk, high-reward strategies set up to back speculative research projects considered to be worth financing for their widespread potential benefits.
“There are all sorts of things we have to clear up now about tracking airborne DNA but the practical benefits are very exciting,” added Bohmann.
Future uses of airborne DNA detectors could include tracing insect pests from air samples and pinpointing animals living in burrows without disturbing them. However, both sets of scientists acknowledge there are hurdles to be overcome before the technology becomes a standard method for studying biodiversity.
“You might detect a piece of tiger DNA but at present we are not sure when it might have been released by the animal. It could be minutes or hours or days ago,” said Clare. “At present, we have no way of working out how long DNA survives in the air. That is one of the many aspects of this technique that we have to work out.
“However, we have already got a head start. If we were the only team to come up with this, we would have to wait for others to replicate our work. Our colleagues in Denmark have already done that independently so we both know that this technology works, and it should have a really exciting future.”