DNA floating in the air can be used to identify nearby animals

Scientists have been able to identify an animal's presence without even being in the same room as them, just by sampling the air.

Teams working in the UK and Denmark independently showed that the identity of zoo animals could be narrowed down to the species solely from fragments of the animal's DNA floating through the air, even if they were hundreds of metres away.

The findings of both studies, published in Current Biology, have the potential to transform the ways scientists look for wild animals, especially rare species whose conservation depends on finding individuals in the wild.

Dr Elizabeth Clare, lead author of one of the papers, says, '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.

'Air sampling could revolutionise terrestrial biomonitoring and provide new opportunities to track the composition of animal communities as well as detect the invasion of non-native species.'

Airborne ID

DNA is all around us. All forms of life shed it into their surroundings whether intentionally, such as in faeces, or unintentionally, such as dead skin. Any DNA of organisms which can be found outside their bodies is known as environmental DNA, or eDNA.

Dr Raju Misra, the head of the Museum's Molecular Biology Laboratories and who was not involved in the study, says, 'eDNA techniques look for genes that are commonly found within a genome in high numbers, such as ribosomal, mitochondrial or photosynthetic proteins. These can then be searched within reference databases to allow deeper sequencing.

'While the concept of eDNA has been around for quite a while, it was mainly focused on attempting to isolate and extract bacterial DNA from water, soils and ice cores in its early days. However, as technology such as next generation sequencing has become more accessible, work has moved onto larger organisms such as animals.'

The development of sequencing technology has allowed researchers to analyse all genetic material found in the environment, rather than specific sequences of interest. This has also allowed scientists to move from analysing soil and water to the air, as Dr Matt Clark, a Research Leader at the Museum, explains.

Matt, who was not involved with these studies, says, 'Water has previously been more commonly used as there is more biological material in water and because the samples within it must come from a nearby animal or from upstream.

'With air, there are much lower amounts of genetic material which makes it more challenging to sample, and the eDNA can come from anywhere. The study of airborne eDNA is still in its early stages.'

Research into airborne animal eDNA is comparatively limited when compared to research into microorganisms, plants and fungi. Earlier this year, Elizabeth published one of the first scientific studies demonstrating that animal DNA could be sampled from the air.

While obtaining eDNA from a room an animal was present in may not sound impressive, it laid the groundwork to demonstrate the technique in the field. Hamerton Zoo in Cambridgeshire was chosen as the basis of Elizabeth's research, providing non-native animals which would be more easily identifiable from the surrounding wildlife.

Unbeknownst to Elizabeth, a Danish team of scientists were also having similar thoughts about the next stage of eDNA testing, conducting a study at Copenhagen Zoo. After learning of each other's research, they decided to join forces and submit their work together. 

Zoo quest

Using a mixture of fans and pumps, the teams sampled the air from different locations in each zoo to analyse for eDNA. The samples were then identified to a species, or as close as possible.

Samples were first taken within sealed enclosures to prove the technique, but the researchers found that they could still detect airborne DNA even when the zoo habitats were open to the environment. Not only that, but they also detected eDNA from animal food as well as from non-zoo animals such as hedgehogs living nearby.

'When we analysed the collected samples, we were able to identify DNA from 25 different species of animals, such as tigers, lemurs and dingoes, of which 17 were known zoo species,' Elizabeth says.

'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.'

The researchers hope that their research will aid conservation by allowing non-invasive monitoring of animal populations in the wild, while empowering nations across the world to monitor their wildlife in their country.

Raju says, 'eDNA is touching everything we do, whether it's biodiversity conservation or monitoring disease. Increasingly, it can be used in the field, rather than requiring centralised labs.

'New technologies have opened up a lot of opportunities now so you can work with DNA in the country it was collected from, so there's much less of a data grab and the research is now more democratised than before.'

However, while these results are promising, there is still work to be done before the technique can be used regularly in the field. The dilution of eDNA in air means that samples may need to be pooled together in the future, while further research is needed into how air movement affects how genetic material moves.

The scientists behind the papers remain hopeful that interest in airborne eDNA will foster work to refine these issues, just as with aquatic eDNA before it.

Co-author Dr Kristine Bohmann says, 'We did not think that vacuuming animal DNA from air would work. This was high-risk, high-reward science with the potential to push the boundaries of vertebrate biomonitoring. Clearly, the sky is not the limit.'