JOHN DANKOSKY: OK, as much as we may be loath to admit it, everybody farts. You may be able to pass your flatulence off on the dog or the cat, because, well, they fart too. In fact, most organisms with a fiber-rich diet and the right kind of gut bacteria can develop gas in the digestive system, gas that could be expelled in a room, clearing off of people.

Well, not all farts are created equal. Some animals don’t have the affinity for flatus. Others use their stench strategically. My next guest discovered this when they set out to write the only book you’ll need on the subject. It’s called Does It Fart? The Definitive Field Guide to Animal Flatulence. They join me now to talk about it.

Dani Rabaiotti is a zoologist studying wild dogs at the Zoological Society of London. Dani, welcome to Science Friday. Thanks for joining us. And Nick Caruso is post-doctoral ecologist in the Department of Fish and Wildlife Conservation at Virginia Tech. Nick, welcome to Science Friday. Thanks for being here.

NICK CARUSO: Hi, John. Good to be here.

JOHN DANKOSKY: Of course, if you’ve got a pressing question about animal flatulence, don’t hold it in. Give us a call. Our number is 844-724-8255. That’s 844-SCI-TALK. Or you can tweet us @scifri. I guess, Dani, I’ll start with you. This book has a pretty interesting backstory. How did it come about?

DANI RABAIOTTI: Yeah, so it all started the January before last, when I was on holiday with my family. And my younger brother, who was 19 at the time, he turned to me and he was like, Dani, do snakes fart? And I’m a zoologist, so I’m kind of expected to know these sorts of things. But I’ve never really studied snakes, so I didn’t really know the answer.

But fortunately, I’m quite active on Twitter. And I knew just the person to ask, David Steen, who’s a snake expert on Twitter. So I tweeted him, David, do snakes fart? And he responded super enthusiastically with, sigh, yes! Turns out he gets this question quite a lot, so that kind of kicked things off. And then Nick appeared on the scene, and he was like, oh my goodness! We’re zoologists. We get asked this all the time. We should totally start a hashtag.

And that was how #doesitfart was born. And in the true nature of science, I then suggested we turn it into a spreadsheet, which we did. And then our publishers wrote to us and they were like, hey, guys, do you want to turn your spreadsheet into a book? And me and Nick were like, yeah, that would be amazing. So this is kind of how this came about.

JOHN DANKOSKY: So it’s a book, Nick, that’s born on Twitter. I suppose we just start, though, with a definition for flatulence. You came up with a strict definition for the book. Explain what exactly, in your mind, a fart is.

NICK CARUSO: Sure. So the medical definition of flatulence is gas produced during digestion that is then expelled out the anus. While we have animals that don’t necessarily have this organ, or some gas may not be produced during digestion– that could be air that’s swallowed– we decided to expand the definition a little bit.

And so the definition, the working definition we had for the book is any sort of gas that could be gas that’s swallowed or that’s produced during digestion that it’s expelled out the opposite end of the mouth. So it could be, for some animals, an anus or a cloaca, for example.

JOHN DANKOSKY: OK, so that’s a fairly strict definition on your part. I’m John Dankosky. This is Science Friday from PRI, Public Radio International, and we’re talking with the authors of a book called Does It Fart? The Definitive Field Guide to Animal Flatulence, because I assume earlier field guides were insufficient. Dani, in the studies that you read, how were scientists testing whether or not any of these animals farted?

DANI RABAIOTTI: Oh, there’s an amazing wealth of literature out there, and to people studying animal farts, particularly domestic animal fats and pets. Someone devised a backpack that you can put on a cow that collects the farts from the cow into a giant balloon. And then some people just came across them from working with those animals.

We had some great stories from primate researchers, for example, who said that if they can’t find their study species in the forest, particularly chimps, they can listen out for the sound of them farting and follow them along in the rain forest. So yeah, people have devised a lot of ways of testing whether animals fart, but I think, by far, the common method was just listening and looking out for it.

JOHN DANKOSKY: So, Nick, does a certain diet make an animal more or less likely to be a farter?

NICK CARUSO: Yeah, definitely. Just like humans, diets higher in fiber tend to produce more farts, more gas. You know, and it can vary as well, depending on the animal, what their specific diet is. If they eat an incorrect diet or possibly if they have some infections, that could also lead to a higher frequency of flatus.

JOHN DANKOSKY: Is there anything else, Dani, that distinguishes the farting animal from the non?

DANI RABAIOTTI: I think, well, the main criteria for some of these animals is, does it really have much of a digestive system? Some of the animals covered in the book, they don’t really have much of a digestive system. So, for example, we did the Portuguese man-of-war. It’s lots of little single-cell organisms, and some of them are specially adapted to basically dissolve food. But they don’t really eat the food, so obviously they couldn’t really fart, because they don’t have a butt really.

So that was one of the main things. There was also a few surprising things. If food passes more quickly through the animals, they’re less likely to fart. And also, the amount of gas produced in digestion relies heavily on what microorganisms in the animal’s digestive system. So certain microorganisms produce more gas than others, so some animals were lacking in those really.

JOHN DANKOSKY: And, Nick, what kind of gases are we talking about? You mentioned cows earlier. I mean, we know cows produce methane. But are there other gases involved here?

NICK CARUSO: Yeah, so there’s obviously, if it’s swallowed air, you have the composition of air. You could have carbon dioxide, oxygen, nitrogen as well as if you have a protein-rich diet, you might have some farts that are heavy in sulfur compounds, which I think most people are aware of that particular smell.

JOHN DANKOSKY: And, Nick, were you surprised at the amount of real science involved in flatology?

NICK CARUSO: Definitely surprised. You know, I think, going into it, when we first were starting our research on this book, thinking, OK, we’re going to get the most of our information first from people who have maybe heard or smelled a particular animal’s farts. But diving into the literature, we discovered there’s some scientific papers that include it, and so there’s quite a wealth of information.

JOHN DANKOSKY: We just have a few seconds before the break. Same with you, Dani? You were surprised at this?

DANI RABAIOTTI: Oh, yeah. There is so many scientific papers out there talking about the amount of gas that comes out of various animals. It’s actually really interesting to read. I learned an awful lot, just from the scientific literature, and then obviously from beyond as well.

JOHN DANKOSKY: OK, so we’re going to learn a lot more. We’re going to come back, and we’re going to do a “does it fart” quiz. I hope I pass. That’s coming up on Science Friday, with the authors of Does It Fart? The Definitive Field Guide to Animal Flatulence. We’re talking with Nick Caruso and Dani Rabaiotti. And this is Science Friday. This is Science Friday. I’m John Dankosky.

We’re talking with zoologist Dani Rabaiotti and ecologist Nick Caruso. They’re now experts in flatology, with their new book, Does It Fart? The Definitive Field Guide to Animal Flatulence. You’ve done all this work identifying animals that fart, so it’s only fair that you get to test us with this knowledge. So you’re going to be helping us with a little quiz here. If you’d like to play along on our quiz at home, you can check it out on our website, sciencefriday.com/farts.

Now, we played this game yesterday with our Twitter audience, and I’ll let you know how they voted during the game. OK, Dani, why don’t you kick things off with our first question? Go ahead.

DANI RABAIOTTI: All right. So, John, we’ll start off slow for the first one. The first question is, do sloths fart? Yes or no.

JOHN DANKOSKY: Sloths? You’re talking about sloths, correct?

DANI RABAIOTTI: Sloths.

JOHN DANKOSKY: OK, sloths.

DANI RABAIOTTI: Ah, my British accent.

JOHN DANKOSKY: Ah, yeah. OK, so sloths or “slow-ths.” They hang out all day, they eat leaves, they’re mammals. I don’t know, the evidence I think points to yes. I’ll say yes, sloths fart.

[BUZZER]

Ah! So I thought most mammals fart. What’s going on with the sloth?

DANI RABAIOTTI: So actually, the sloth was the only mammal that we found that did not fart. We had quite a– well, I had quite a fun and lengthy time finding this out. So my first stop was I delved into the scientific literature, and I found this paper. And it said, oh, sloths produce a whole lot of methane, but it didn’t say where the methane came from. So I was like, are they burping it? Are they farting it? I don’t know what end it’s coming from.

So I put the question out to the internet, and someone got in touch with me. And they said, oh, I work at Glasgow University, and they’ve just invented this camera that can pick up methane on camera. And I work at a zoo, so I was like, well, maybe we could put a sloth in front of it, and we could find out what end the methane is coming from.

And unfortunately, before this plan actually took effect and I got to do an in-real-life experiment, the person who wrote the paper wrote back to me and he said, oh, it’s not farted out. They reabsorb the gas into their gut, and they breathe it out. And this was seconded by a sloth sanctuary, who said, if sloths get gas in their digestive system, they’re really sick. They’re probably going to die, so sloths definitely don’t fart. But they do have farty breaths, though. That was a term for the books.

JOHN DANKOSKY: I guess that kind of counts. Our Twitter audience, by the way, was stumped by that one, too. Only 7% guessed correctly. All right, Nick has the next question. Go ahead, Nick.

NICK CARUSO: OK, John. Which of these water animals is a known farter? The goldfish, the herring, or the sea cucumber?

JOHN DANKOSKY: Hm. OK, so two of them seem pretty similar, the goldfish and the herring. The sea cucumber’s an entirely different animal. I’m going to guess sea cucumber.

[BUZZER]

Ugh. OK, so, Nick, what was the right answer?

NICK CARUSO: Herring is the correct answer.

JOHN DANKOSKY: OK, herring. Hm. How do herrings fart?

NICK CARUSO: Well, not only do they fart, but they use their farts for communication. It’s pretty fascinating. Both Atlantic and Pacific species can gulp air from the surface and then store that air within their swim bladders. They later expel that air through their anal ducts, which then produces a high-pitched raspberry sound that is very wonderfully named the fast repetitive tic, or FRT.

JOHN DANKOSKY: Ah. Very, very nice. So maybe we’ve answered one of Parker’s questions. Parker is calling from Modesto, California. Do you have more questions about fish, Parker?

PARKER: Yes. How do you see when they fart? Because when I’m in the tub and I fart, you see bubbles.

JOHN DANKOSKY: So I think that probably happens to all of us, Parker. So is that how you can tell? Or I assume that you have to, Nick, find out in different ways with different fish.

NICK CARUSO: Yeah, that’s actually a pretty common way that we found out for various animals if they farted, was you’d see the air bubbles coming from their end opposite of their mouth. And so that was a good way for some of the aquatic organisms, to figure it out.

JOHN DANKOSKY: It turns out only about 20% of you, by the way, who played on Twitter, guessed the herring was the correct answer there. The most popular answer was the sea cucumber. Are you sure, Nick, that sea cucumbers don’t fart?

NICK CARUSO: Yes. Yeah, they’re one of those animals that has a primitive digestive system. So while they don’t fart, they do have some really interesting things going on in their back end. So there’s some species of pearl fish that will actually live inside their cloaca. And not only do they live within the sea cucumber, but the sea cucumber provides it a food source. The pearl fish will slowly consume the sea cucumber’s gonads as a food source.

JOHN DANKOSKY: That sounds horrible!

DANI RABAIOTTI: The great thing about sea cucumbers is that they regenerate, though, so it’s a never-ending supply of food. I’m almost tempted to move in myself, to be honest.

[LAUGHTER]

JOHN DANKOSKY: OK, Dani, you’ve got the next question. We should probably move on.

DANI RABAIOTTI: So next up, I have a question about an animal that I think a lot of people probably won’t know about. It’s the larvae of the beaded lacewing, which is a small, brown flying insects. And it uses its farts for something really useful. Do you reckon it is to, A, propel itself across a leaf, B, kill its prey, or C, emit a distress signal when under attack?

JOHN DANKOSKY: Oh, wow. OK, so– well, propulsion seems to make sense, and we’ve heard about animals that use farts to communicate. But I have to say, Dani, I really want the answer to be B. I want the answer to be, kill its prey.

[DING]

Hey! I got one right!

DANI RABAIOTTI: Hurray!

JOHN DANKOSKY: So what makes the farts so lethal?

DANI RABAIOTTI: So the beaded lacewing, it lays its eggs near a termite nest, and the larvae hatch out, and they crawl in. And what they do is they feed on termites. So while they’re in the termite nest, they fart out what’s called an allomone, and it’s a special chemical that only affects termites. And what it does is it stuns the termites and then slowly kills them so that they can eat them.

But the really cool thing about this chemical is it doesn’t affect other insects. So in the scientific paper on this, they put different kinds of insects in there. They weren’t affected. It only kills termites, so don’t worry, guys. You’ve got nothing to worry about from the beaded lacewing larvae farts.

JOHN DANKOSKY: On Twitter, 19% of our audience guessed that time correctly. OK, Nick has the next question. Go ahead, Nick.

NICK CARUSO: OK, John. So which of these animals can do both fart and breathe, breathe oxygen, using the same organ? Is it, A, the painted turtle, B, the llama, or C, the humpback whale?

JOHN DANKOSKY: The painted turtle, the llama, or the humpback whale. That doesn’t seem like something that the llama would have. But to me, I guess it makes sense that it would be a sea mammal, so I’m going to say, humpback whale.

[BUZZER]

Ah! I got that one wrong, too. So it must be the painted turtle.

NICK CARUSO: Yes.

JOHN DANKOSKY: Ah, so what’s so special about the painted turtle?

NICK CARUSO: So they’re able to draw in water through their cloaca, and they use specialized sacs called bursae to absorb oxygen, which allows them to stay under water for longer periods of time, which is, as you can imagine, pretty useful during their winter hibernation, when they’re burrowed in the mud.

JOHN DANKOSKY: Wow, interesting. So the audience did better than I did on that one. 48% of people who played our quiz guessed the painted turtle. OK, Dani, we’ve got one last question here. Let’s give it a try.

DANI RABAIOTTI: All right then. This one is relevant to my research. Researchers once thought this animal’s flatulence could have helped solve climate change. Is it, A, dinosaurs, B, kangaroos, or C, humans?

JOHN DANKOSKY: So listening to the way that that’s worded, it could have helped to solve climate change, I’m going to say that that’s a clue here. And I’m going to say dinosaurs.

[BUZZER]

Ugh! All right, so dinosaurs, kangaroos. Was it the kangaroo then? It probably wasn’t humans.

DANI RABAIOTTI: Yeah, it is indeed the kangaroo. So researchers used to think that kangaroos didn’t actually produce much methane when they farted, especially when compared to cows. So cows produce an awful lot of methane, although actually most of it is burped out, not farted out. And this is a really big contribution to climate change, because we farm so many cows for food.

So they thought that maybe if they took the microorganisms out of the kangaroo’s gut, and they put it into the cow, that they might be able to make cows produce less methane. However, sadly, more recent research found that actually kangaroos do fart quite a lot, and quite a lot of gas is coming out, maybe equivalent to a horse, if a horse was the same size as a kangaroo. So sadly, that area of research ended there. Kangaroos farted too much to save us from climate change.

JOHN DANKOSKY: And our audience guessed that one pretty well. 51% of you guessed the kangaroo. You guys are pretty smart. I mean, one of the questions in there came up from one of our callers we weren’t able to get to, but how about dinosaurs? I mean, do we assume, Dani, that dinosaurs farted, or no?

DANI RABAIOTTI: Well, we know that they don’t fart anymore. But yeah, so we assume–

JOHN DANKOSKY: Fair enough.

DANI RABAIOTTI: –that the larger herbivorous dinosaurs probably did fart. We know that they would have produced a lot of gas, just from the structure of their digestive system, although it’s really hard to tell what was in their gut, because obviously, we only know from fossils. However, we know that birds don’t fart, so maybe the birds, the dinosaurs that birds evolved from– although birds are dinosaurs themselves– but the ancestors of birds, they probably didn’t fart. We don’t really know where farting died out in that lineage.

JOHN DANKOSKY: Hm. I want to give out our phone number again, because people have questions about this, believe it or not. 844-724-8255 or 844-SCI-TALK. We just were talking about birds and dinosaurs, Nick. So most birds don’t fart. Why not? What is it about birds?

NICK CARUSO: Well, there’s a couple things that go against them for farting. One, since they fly, they don’t want to keep a lot of food in their digestive system for very long, because it is heavy. So food passes relatively quickly through the bird’s digestive tract. And two, they don’t quite seem to have the same gas-producing microbes to produce the necessary gases for a fart.

JOHN DANKOSKY: And another one that we’re not sure of, another flying animal, what about bats? What do we know about bats and farting?

NICK CARUSO: It’s pretty similar. They have a pretty quick digestive system, so there may not be enough time for gas to build up and then fart out. However, if they do fart, it’s likely not audible. So it’s a little harder to find out, so I think that is definitely an area that we need more research.

JOHN DANKOSKY: We’re talking with Nick Caruso and Dani Rabaiotti, and they’re the authors of a new book called Does It Fart? It’s the definitive field guide to animal flatulence. It’s a book that was born on Twitter, and a lot of people want to join our conversation as well, and we’ll get to some questions in a minute. This is Science Friday from PRI, Public Radio International.

Let’s go to a caller here. Esther is calling from Tallahassee, Florida. Hi there, Esther.

ESTHER: Hi, how are you?

JOHN DANKOSKY: I’m doing well. What’s on your mind?

ESTHER: So I recently became pregnant, and I am flatulating a lot more than usual. So I’m curious to know if that happens with animal, too, primarily cows, because I know they have four different stomachs.

JOHN DANKOSKY: Yeah, that’s right. Four stomachs. They’re eating grass all day. Thanks for the question, Esther. What do you know about, I don’t know, Dani, pregnant animals? Do they fart more than the non-pregnant animals?

DANI RABAIOTTI: It wasn’t something we came across in the research, but I know for a fact that pregnant animals tend to eat a lot more, because they’re supporting their offspring. So I can imagine that more food in means more gas out. So yeah, I would say it was a pretty safe bet, that pregnant animals probably do fart out at least a greater quantity of gas.

JOHN DANKOSKY: We’re getting a lot of questions from Twitter, Nick, about bugs, whether it’s spiders or insects. What do we know about that? That seems unlikely that insects, for some reason, would flatulate.

NICK CARUSO: Yeah, well, spiders is definitely a huge question mark. That’s something that we couldn’t say yes or no definitively in the book. But there are some insect farters out there. I think most people know these particular bugs as either pill bugs or roly-polies. In fact, they can emit ammonia gas out through their exoskeleton.

Now, it doesn’t just excrete out from the rear end. It can excrete out their whole exoskeleton. But it is a really long, drawn-out fart lasting up to about an hour or so. So there is some farting going on in the insect world.

JOHN DANKOSKY: Lasting up to an hour?

NICK CARUSO: Yes.

JOHN DANKOSKY: Oh my goodness! Well, we have to ask, because we don’t want to run out of time before we do this. And, Dani, we can’t not ask about the cephalopod. This is Science Friday’s favorite animal, so does it fart?

DANI RABAIOTTI: No, they do not fart. Their digestive systems don’t really have any way of producing gas or storing gas, so they do not fart. But they do kind of ink, but as it wasn’t a gas, we decided it’s not quite classified as a fart. But we were disappointed, too, but they are included in the book, because we love them so much, too.

JOHN DANKOSKY: You guys clearly had a lot of fun putting this together. Dani, what are some of your other favorites in here? Because each one of the animal has– or most of them are accompanied with some pretty hilarious drawings as well. I mean, what are some of your favorite little bits of research in here?

DANI RABAIOTTI: Oh, I think my favorite paper that I came across is for this species of fish. It’s called the Bolson pupfish, and it lives in these little tiny pools in Mexico. And in the summer, it gets really hot in these pools. And these fish feed on algae. They, as many fish do, take up the sediment off the bottom and eat the algae off it. Then in the summer, the algae produces a lot of gas, so the fish eat the algae. They get really bloated, they get really full of gas, and they become really buoyant.

And normally, they hide in the sand, but they pop back up to the surface. And they’re just really fat and really bloated, and they’re bobbing around. And they can get eaten by predators, and if they can’t fart in time, then there was even some recorded cases of them exploding.

JOHN DANKOSKY: Oh no! Oh dear! Nick, how about you? Did you have any favorites in all of this?

NICK CARUSO: I think that one may have been one of my favorite illustrations. I think the dinosaur one as well. And just to give a quick mention to the person who illustrated the book, Ethan Kocak did a fantastic job with it. I think just the types of illustrations he provided for the descriptions of the animals farting, it really makes it a complete book.

JOHN DANKOSKY: I have to ask you, Nick. This sort of research, such as it is, if it happens on Twitter, we’re able to crowdsource all these scientists and people. This really is a new way for scientists to talk about something in some ways funny and fun here, but also about really serious topics. I mean, this probably couldn’t have come together if it wasn’t for Twitter, right?

NICK CARUSO: No, and in fact, Dani and I have never actually met in person. So we’ve wrote this book primarily over email and doing Skype and Twitter and getting input from various scientists we know on Twitter. And we’ve known this ever since we started our science career, that science is collaborative. We’re not able to do this alone. And so even in something like figuring out which animals farts takes a lot of input.

JOHN DANKOSKY: It takes a lot of input from a lot of people. I really appreciate your input today. Nick Caruso, a post-doctoral ecologist in the Department of Fish and Wildlife Conservation at Virginia Tech, and Dani Rabaiotti, a zoologist studying wild dogs at the Zoological Society of London. Thank you both so much. This was great fun.

NICK CARUSO AND DANI RABAIOTTI: Thanks for having us.

JOHN DANKOSKY: One last thing before we go. Science Friday is hitting the road for Pennsylvania next month. Yeah, they’re going to my hometown, Pittsburgh, the Carnegie Library Music Hall, Saturday, May 19th. We’ll have roboticists and artificial intelligence designers, lots of smart people there. Musical robots, musical humans, too, Pittsburgh’s own townspeople. More information and tickets at sciencefriday.com/pittsburgh. That’s sciencefriday.com/pittsburgh. Ira’s back next week, in New York. I’m John Dankosky.