It is literally in the air. It is carried around by all life on Earth. Scientists have now discovered a way for scientists to detect invisible traces of genetic material and identify the animals that released it.
Independently, British and Danish research teams discovered rare wildlife in deserts, forests and other hostile environments earlier this year.
Professor Elizabeth Clare from York University said that this could revolutionize the way we study biodiversity. All other methods for tracking animals, such as camera traps or acoustic monitoring, depend on animals being present physically.
It is easier and more flexible to capture their DNA from the air than capturing it. For example, you could detect the presence and movement of creatures in caves by not disturbing them.
Clare, then at Queen Mary University of London, and her collaborators used sensitive filters to place vacuum pumps at 20 locations in Hamerton Zoo Park in Cambridgeshire last Christmas. Clare said that a zoo is a great place to test such a technique because the animals are non-native and kept in enclosed spaces. This meant that, if we could detect DNA in the air and were successful, we would know exactly from where it came from and how far it had traveled.
Hamerton Zoo Park was dominated by DNA from black and white ruffedlemurs. Photograph: Arto Hakola/Alamy
The team collected 72 samples of air and used polymerase chain reactions (PCR) to amplify the DNA fragments found in the filters. The team sequenced the genetic material, compared it with animal sequences and identified 17 species from the invisible DNA released into the atmosphere.
Clare said that we found DNA from tigers, dingos and most importantly, DNA from black-and-white ruffed lemurs. Their DNA was the most widespread. Although we don't know why, lemurs seem to be more active than other animals. They were jumping around in their cages and taking an interest in people passing by. However, many other animals were still lying low in winter.
It is interesting to note that similar discoveries were made by Kristine Bohmann and Christina Lynggaard, both of Copenhagen University. They collected air from various Copenhagen Zoo sites and identified 49 species using the DNA they found in their filters.
Bohmann said that we were stunned. We were astonished to discover that DNA was found in mammals, birds, reptiles, and fish. It also came from large and small animals. Even guppy fish were identified by their DNA.
Both teams were able to identify local wildlife, pets from the neighborhood, and animals used as food for the zoo.
Copenhagen Zoo found the DNA of 49 species. Photograph: Mads Claus Rasmussen/EPA
Bohmann said that we discovered DNA was being detected from animals that were being given to zoo animals. We also picked up DNA from local wild animals and cats. It was amazing what we were capable of detecting.
The British and Danish projects were both funded under high-risk, high reward strategies that support speculative research projects.
While there are many things to be aware of when it comes to tracking airborne DNA, the practical benefits are quite exciting, Bohmann said.
Airborne DNA detectors may be used to track insect pests and locate animals in burrows. Both scientists recognize that there are still many hurdles to overcome before this technology can be used as a standard method of studying biodiversity.
It is possible to detect some tiger DNA, but we don't know when. Clare said that it could have happened minutes, hours or even days ago. We don't know how long DNA can survive in the air. This is just one aspect of the technique we need to understand.
We have a head start. We would need to wait for other teams to duplicate our efforts if we were the only one to create this technology. We know this technology works because our colleagues in Denmark have done it independently, so we can both confirm that it is possible.