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A key part of protecting endangered species is figuring out where they’re living. Using environmental DNA, or eDNA, to track species isn’t new. For a few years now, researchers have been using DNA in water.

Two teams of scientists — one in Denmark led by Dr Kristine Bohmann and one in the UK led by Dr Elizabeth Clare — came up with the same question at about the same time: Could they identify the animals in an area from DNA that was simply floating in the air? DNA in the air is usually so small that it would take a microscope to see it. “I thought the chances of collecting animal DNA from air would be slim though much time had been spent on it, but we moved on,” said Bohmann who was trying to think of a crazy research idea for a Danish foundation that funds far-out science.

One team collected samples from different locations at Denmark’s Copenhagen Zoo, and the other at Hamerton Zoo Park in the UK. Clearly, they both chose the zoos. “We realized we have the Copenhagen Zoo,” Bohmann recalls. In fact, both the zoos in the UK and Denmark were almost like the zoos that were custom-built for the experiments: The animals in the zoos were non-native, so they really stuck out in DNA analyses. “If we detect a flamingo (火烈鸟), we’re sure it’s not coming from anywhere else but the zoo,” Bohmann says.

In the laboratory, by comparing their samples with examples of DNA from different animals, the scientists succeeded in identifying many different animals at the zoos.

Neither team knew that the other team was working on a similar experiment. The two were nearing submission to a scientific journal when they discovered about the other experiment. Rather than compete to rush out a publication first, they got in touch and decided to publish their findings as a pair. “We both thought the papers are stronger together,” says Clare.

“The next step is to figure out how to take this method into nature to track animals that are hard to spot, including endangered animals,” says Bohmann.