Every other Friday on Morning Edition, Outside/In host Sam Evans-Brown tackles a question from a listener.
Sarah from South Carolina Asks: “My husband and I were discussing the very interesting topic of dog toots. So we were curious as to whether or not all animals can pass gas?”
This is how it ends. We all start out doing important journalism — holding the powerful to account — but you keep at it long enough and it all devolves into flatulence.
Fortunately for our listener, one such individual who wondered the exact same thing set out to find an answer. Dani Rabaiotti is a zoologist in London who studies wild African dogs and after being asked by a family member if snakes fart (big reveal: they do) started a google spreadsheet.
She and her collaborator Nick Caruso tried to convince fellow zoologists to contribute and say whether or not the species they studied could fart. Eventually, they turned those entries into a book, which (perhaps predictably) landed on the New York Times bestseller list.
What is a Fart? What is an Animal?
For starters, Dani and her coauthor had to define terms, because while there is a scientific definition for flatulence — gas generated during digestion — that doesn’t fully encompass our understanding of farts, which include any gas that might have been swallowed.
But more to the point, what is an animal? If we take that to include all of the species included within the Kingdom Animalia, then the answer to this question is rather different.
“Actually probably the number of species that don’t fart outweigh the number of species that do,” says Dani, “but a lot of the ones that don’t fart, they’re very simple organisms. So there’s not that much to write about them other than 'this animal doesn’t really have a digestive system!'”
This just points us back to a long-standing bias that humans have, which is we fixate on the cute, the fuzzy, and the feathered, versus say, the invertebrates that constitute 95 percent of the species on the planet.
[Steps off soapbox]
The Greatest Flatulence Hits
The one large branch of living things that doesn’t seem to fart are birds. They don’t have the right kind of gut bacteria, and their intestines are super short, and are frequently evacuated. (As anyone who has ever parked under the wrong tree has discovered.) That’s not to say they can’t fart, but rather that generally as a rule they don’t. Bird biologists say that seeing gas in a bird’s gut would be a sign of illness.
Herring — the little fish that form very large schools — famously communicate with their flatulence, producing something called Fast Repetitive Ticking sounds, which for 20 years the Swedish military repeatedly mistook for Russian submarines, until a biologist figured it out in 1996.
Dani’s favorite are sea cucumbers — one of the few species included in her book that don’t fart, despite having a digestive system. However, fascinatingly, they have a little fish that lives in their butt and eats them from the inside.
My favorite from the book: sloths. Dani explains that it was a whole saga to track down the answer. Sloth researchers (strangely!) weren’t responding to her emails asking if their study subjects farted, despite having published papers showing they produce large amounts of methane.
She was considering actually taking a sloth from the zoo that she works at and placing it into a special chamber equipped with precision infrared cameras to see where the methane was coming from, when finally one of the researchers responded to her strange query. “Actually what happens is they reabsorb the gas into their gut, and then they breath it out. So they’ve got like fart breath, but no farting,” she says.
So: while there are some edge cases, a general rule is that if it digests its food through an intestine, it probably farts, unless it has feathers.
Sam Evans-Brown, is host of NHPR’s Outside/In which you can subscribe to where-ever you get your podcasts. If you’d like to submit a question you can record it as a voice memo on your smartphone and send it to firstname.lastname@example.org, OR call the hotline, 1-844-GO-OTTER, OR submit it here.