DNA is like a fingerprint. Each species’ DNA signature is distinctive. And it can be found on the scene long after the individual has gone.

For some time, scientists have gathered the DNA that organisms leave behind—in saliva, urine, feces, fur, and flakes of dry skin—to detect their presence and study them.

They’ve found this so-called environmental DNA, or eDNA, in water, soil, even snow.

But scientists wondered if they could gather it more easily and broadly by capturing it out of thin air.

To test this, they set up vacuum devices at zoos and sucked in the air, trapping all particles within it on very fine filters.

They then used a polymerase chain reaction—the same PCR methodology that’s become well known in Covid tests—to amplify DNA signatures of the particles.

Surprisingly, from DNA in the air alone, they could catalog the animals in the zoo, from huge giraffes to tiny guppies in ponds.

They also found eDNA of native animals, like squirrels and deer. Domesticated pets like cats and dogs. And of course, human visitors.

The technique was not perfect however, missing the presence of some of the biggest creatures.

But as it matures, gathering eDNA from the air has powerful potential to measure populations, track elusive animals, detect pathogens, even solve crimes.