It’s in the air

Zoo animals

What if it were possible to sample the air to identify all of the animals that are in the surrounding area, even the ones we can’t see?

A recently published study demonstrated that this is possible. Two groups of scientists, working independently, recently developed a process to capture airborne animal DNA and analyze it. Using filters set up near zoos, they identified the DNA that was captured on the filter as the air wafted through it. They could ‘see’, using airborne DNA, the zoo animals as well as some passers-by (like a random hedgehog).

As reported by Wired:

The results of these two zoo-based experiments were published last week in the journal Current Biology. The first paper is from Bohmann’s team at the University of Copenhagen; the second report is from a group at Queen Mary University in London and York University in Toronto.

The Danish researchers set up three air filters for 30 hours at a time and were able to identify 49 vertebrates, including 30 mammals, 13 birds, four fish, one amphibian, and one reptile. They found DNA from captive zoo animals like the okapi and an armadillo, a guppy living in a pond in the rainforest house, and even pests like the brown rat and house mouse. Tiny bits of DNA from fish used to feed other animals in the zoo were also lofted skyward and detected by the filter.

….

The UK group identified 25 animal species, including 17 captive animals, such as gibbons, dingoes, meerkats, sloths, and donkeys. They also found random visitors, like squirrels and a hedgehog that was likely prowling around the park looking for food. The team detected movement of the zoo animals through space, not just their presence in one part of their enclosures. Clare expects that air sampling will soon be used in the field—which would be a huge deal for biologists trying to figure out where endangered animals live, breed, or migrate and to protect those areas from human development.

Eric Niler, “Scientists Capture Airborne Animal DNA for the First Time”, Wired.com

What the scientists did with the DNA strands on their filters is familiar to all of us living in a COVID world: polymerase chain reaction or PCR. This method rapidly copies each original DNA strand many times over. To detect viruses, the genetic labels identifying an organism are marked with fluorescent dye. Technicians use these visual markers to identify the DNA source in real time.

These studies demonstrate how we humans, with our strong preference for sight over smell, can identify organisms we can’t visually spot around us.

Grassy foreground with trees in back, and fox running through the trees
Fox sighting in Tower Grove Park

The picture above was taken across a wide field from the park walking path. My husband Dave was walking with our dog Ellie, who stopped in her tracks to point her nose across the field towards the Botanical Gardens. Fortunately, Dave’s vision is much better than Ellie’s so he was able to see what Ellie was smelling. She was smelling an intruder. The fox was about 400 feet away, but with good eyesight and the camera zoom, Dave was able to capture it. (If you’re having trouble seeing the fox, look on the left just in front of the line of trees.)

Dogs are able to do exactly what the scientists’ DNA capture filters, PCR process and DNA marking methods can do. Even better, using smell is much quicker than the multiple processes to identify by sight. Dogs can also differentiate each of the different organisms in the surrounding area, and can identify outliers. What they lack is a shared language with us. Scent training is a means of creating a shared communication (by behavior) so that the dog can tell the human that it’s smelling the target scent.

If we had the olfactory sense of a dog, we too could stand outside a zoo and identify every animal within it. Since we don’t, I applaud the recent work by these like-minded scientists to help us use our first sense to identify what our third sense can’t.

2 thoughts on “It’s in the air

  1. Wow. Great post. I read a Margaret Renkle NYT piece today that reminded me that in the snow, we humans can see the traces of animals who have been through that space before us, but our dogs, especially, can ‘see’ those traces with their noses all of the time.

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