IRA FLATOW: This is Science Friday. I’m Ira Flatow.

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You know, on our beat, we’re always looking for creative ways of talking about science. And Halloween presents us with a great opportunity– the spooky side of science. Imagine, if you will, running into a trifecta of Halloween monsters. You run into werewolves, vampires, and zombies. Well, how would you react?

After the initial terror of these unsightly specimens of matted fur, fangs, and flailing flesh, you might realize, hey, hey. These menacing monsters aren’t so different from us. They got to eat. They gotta find a way to survive. So like us, they must be teeming with microorganisms.

Yes. These beasts might have a microbiome– viruses, eukaryotes, bacteria. Each with their role to play in the composition of these creatures. In fact, thinking through the microbiomes of these Halloween monsters is a fun way to see what we understand, or still need to learn, about our own microbiome.

So joining us now to talk about the microbiomes of werewolves, vampires, and zombies, Rob Dunn. He’s author of The Wildlife of Our Bodies, and a professor of applied biology at North Carolina State University.

Amanda Hale. She’s a doctoral student of zoology at North Carolina State University.

They join us today from WUNC in Durham, North Carolina. We also have a beautiful info graphic on werewolf microbiomes– it’s gorgeous stuff– from Neil McCoy. And we have a blog post called Monster Microbiology 101, written by Rob Dunn. You can see it on our website at sciencefriday.com/werewolf.

Welcome to the program.

ROB DUNN: Oh, it’s our great pleasure to be here, Ira. Thanks for having us.

AMANDA HALE: Happy to be here.

IRA FLATOW: We’re happy to be here.

Rob, what would a werewolf smell like?

ROB DUNN: I think it would smell like wolf or dog with a hint of man. So a little bit arm-pitty, a little bit wet fur.

IRA FLATOW: Because there’s bacteria that’s living in the fur?

ROB DUNN: Yeah. I mean, every body of every animal is kind of like a template for the bacteria that live there. And so we know that our bodies, they feed specific things. And so in our armpits we have these glands that feed bacteria that produce our armpit odors.

But each mammal species has different glands and sort of a different template. And so if we imagine that magical transition from person to wolf, during that transition, these glands would be shifting around. And so you’d be going from something like that armpit smell to something like the special microbes that live in wet fur.

So the weird pseudomonas species. And so what’s amazing is that although the werewolf is a fictional creature, this trajectory is actually really pretty predictable, based on what we know.

IRA FLATOW: Really? Our number, 844-724-8255 if you’d like to participate. 844-724-8255. You can also tweet us @scifri.

Following this up a little bit, how similar are human and wolves microbiome to begin with?

ROB DUNN: Well, so we know the most about dogs. And dogs are different from wolves. But if we extrapolate, some features should be similar enough.

We have a measure of this if we look at houses. And so if we compare a bunch of houses in terms of which microbes live in them, we can actually tell if a dog has been in the house on the basis of the microbes that are there.

And that’s because the microbes of the dogs are really very different. They have specialized drool microbes that appear to help them in healing wounds. When they lick their wounds, they recover more quickly in part because of those microbes.

They have really enlarged anal glands and a bunch of microbes that live there. And so nobody talks about this with the sexy werewolves, but I think they would have great big anal glands too.

So those things are different. Their guts are also really different, too.

IRA FLATOW: Yeah? In what way?

ROB DUNN: Well, so the typical wolf diet has more meat and even some dead meat, some carrion, and so they have really acidic stomachs that serve as kind of a filter for what they eat. And it kills bacteria that might harm them.

But then they have shorter intestines. And they’re not quite as good at digesting say, a celery stick. And so if during the transition to being a wolf, if you’ve been eating some celery beforehand, and then you get to your wolf stage, the wolf couldn’t digest it. And so I think werewolves are very likely to be gassy, contingent on what they ate before.

IRA FLATOW: No wonder they want real red meat once they’re transitioned, right?

ROB DUNN: Yeah. It’s hard to look so strong and fierce on TV when you’re farting all the time.

IRA FLATOW: Can we quote you on that? And the Twitterdom will actually, I’m sure, do that.

Now what kinds of microbes would a vampire need to digest a vampire? All that blood it’s taking in.

ROB DUNN: Yeah. So the blood is actually really interesting. So blood is very nutritious. It has a lot in it.

But it also poses problems for gut microbes. And one is that a lot of the immune activity that’s in the blood– so in your blood right now, if somebody were to bite you and suck your blood, they would get some of the immune activity from your blood, which would kill a lot of microbes.

And then the other thing is your blood has lots of iron, which can be really toxic. And so almost all the blood-feeding organisms that have ever been studied have both a way of dealing with that extra iron, and specialized microbes that can deal with those immune cells.

And so there’s one group of microbes that’s found in mosquitoes, leeches, ticks, vampire bats, and lampreys, even though they’re super different lineages of animals, they all depend on this same group of aeromonas bacteria. And so almost certainly a vampire would have those bacteria.

IRA FLATOW: Amanda, where do a lot of the microbes in our bodies come from? Do we just pick them up as we go along?

AMANDA HALE: I don’t know that we pick them up as we go along. I mean, a lot of it’s influenced by our diet, the things that we intake, where we are geographically has a lot to do with the microbe composition in our guts.

ROB DUNN: And we get some during birth. We get a big messy dose from our parents. That would be true of werewolves too.

IRA FLATOW: That’s true. We’re born with them. Rob, where do these blood-breaking down microbes come from for the vampires?

ROB DUNN: We actually have no idea. So we know that all these different blood-feeding things have them. And so one possibility is that they’re getting them from their parents. But how did the lamprey and the vampire bat come to share a common bacteria?

We don’t know. And so if vampires existed, I think that would be a hot research topic to study is how they get these.

IRA FLATOW: We have a couple of comments coming through. For example, someone wanted– let me see if I can get to that tweet that came in about what would swamp gas smell like? Would we know that, because there’s always swamp gas in these things. Is there a microbiome in there, also?

AMANDA HALE: In swamp gas, I would imagine it probably smells a lot like rotting eggs and sulfur. Where you have a– I’m thinking about swamps. And you’ve got certain types of bacteria that could put off almost a sulfur smell at times. That’s what I would imagine swamp gas would look like. I don’t know. Rob?

ROB DUNN: Yeah. So you’ve got some methane. I mean, I guess it depends on is it the Scooby Doo style floating swamp gas? In which case, maybe a hint of Scooby snack.

AMANDA HALE: Yeah.

IRA FLATOW: We have a phone call. Let’s go right to the phones. So, let’s go, California. San Jose. Hi, David. Welcome to Science Friday.

DAVID: Hi. Thanks for taking my call. I was just wondering. If we had a really productive werewolf out and about roaming the night, wouldn’t you say that like, there would be a blood smell to its fur, as well as a wet dog smell? Kind of like tasting a penny or like a sodium, salty smell to it?

IRA FLATOW: Mm.

ROB DUNN: Yeah. That’s a good question. So you would probably have the smell produced by some of these bacteria that are good at breaking down blood. And so some of the things that you would find at a crime scene you would smell on the fur. You would get that wet dog plus hint of–

AMANDA HALE: Copper.

ROB DUNN: Yeah. Hint of copper. I mean, you would smell a lot more wet dog than you would hint of blood. And probably you would know they were there because well, people have phones enough, you get a nice photo of a werewolf. And so you wouldn’t have to worry about detecting them based on blood smell.

IRA FLATOW: Amanda, how do our microbiomes change when we die? What goes on inside our body?

AMANDA HALE: Well, most of the microbes are concentrated in our gut, of course. Then also you have a lot of gas being produced from the fermentation processes going on inside the gut. And most of the bacterial activity that occurs in early decomposition when we die is actually from those microbes that are found in our gut. That’s the most common bacterial diversity.

And so they’re actually starting to invade tissues and break them down and use the proteins and the lipids and carbohydrates that are available to them as a resource. And they’re really responsible for producing that decomposition fluid that’s really common, and just the coloring and the smell and that fresh bloody, putrescing odor that’s really common in early decomposition.

IRA FLATOW: Explain, we’ve all seen so many zombies on TV and movies, why do they look the way they do? The way we think that they should do?

AMANDA HALE: Well, a lot of that is actually dependent on their microbial activity. So in our typical zombies, they have that green coloring to them because of the compounds that are being produced by the micro breakdown of our bodies. They tend to have skin slippage, because as they digest the proteins and all in our epidermal layers, we start losing the adhesion that allows our skin to hold together.

So that’s why a lot of times you see sort of their face almost dripping. And also they sort of had that bloated appearance because of the gases that are being produced in their bodies. So all of that’s really common to a rotting corpse. So the appearance of zombies, to me, it’s just very similar to what I’ve seen in terms of early decomposition in any kind of carrion.

IRA FLATOW: Why would they be oozing their guts out like we say the zombies do in The Walking Dead?

AMANDA HALE: Oh, absolutely. And it would depend on what kind of climate. Yeah I’d be more scared to find a zombie in the Arctic than I would in the tropics, simply because that process is much slower for the ones in the Arctic. And so they probably hold together a lot better and have a better chance of infecting me and spreading whatever their mechanism is to create zombies.

Whereas ones in the tropics, you’re going to see that oozing happen a whole lot faster. And they’re going to lose that putrescing odor and transfer into that musky, funky smell that is common in later decomposition than in early decomposition.

IRA FLATOW: Our number 844-724-8255, if you’d like to talk about zombies, werewolves, anything that we’re talking about having to do with Halloween and all kinds of stuff. And if you could also Tweet us @scifri, if you’d rather do it that way. Lots of tweets coming in.

[INAUDIBLE] wants to know, do you think vampires would love fruit, going off the thought that they share DNA with fruit bats?

ROB DUNN: So what we know about vampire bats is that vampire bats tend not– which are related to a lineage that includes a fruit feeding bat– they’re not very partial to fruit. They spend most of their time focused on blood. And they’ve actually lost sweet taste receptors.

And so even if you gave them fruit, they wouldn’t find much joy in it. Their joy is in running up on something, biting down, and enjoying that blood.

They’re interesting critters. The vampire bats then go back and they’ll share blood even, a relatively altruistically with others that might not have been able to feed. And so that’s another interesting– maybe they’re sharing some microbiome when they’re doing that too. Do vampires go back and share a little blood? And when they do that, do they share some good microbes?

IRA FLATOW: Mm. That’s a good question.

ROB DUNN: I don’t know.

IRA FLATOW: That’s a good question. Have to answer that someday. We’re talking about vampires, anything ghoulish this hour, especially about the microbiomes of vampires, werewolves, bats, you talk about it. With Amanda Hale and Rob Dunn on Science Friday from PRI, Public Radio International.

What happens if they– you know– so a zombie. Let’s stick with the zombies. What would happen to a zombie’s microbiome after a couple of days versus a couple of weeks? Would they have to switch back the microbiome around? Or could they keep from days to weeks? Amanda.

AMANDA HALE: Well, I mean, it depends on how fast their microbes are breaking down. Sort of their internal environment.

I mean, we know once you die, your microbial diversity changes a lot as you progress through that process. And so I would imagine with zombies, they’re going to pick up a lot of external bacteria as time goes on. So I’d imagine their diversity would increase the longer a zombie exists than when they initially were reanimated or possessed– however you view your zombies– that you would have a lot more species existing simply because it’s a bigger haven for food resources. And its own sort of ecosystem as a rotting corpse.

And also because of the smell that they give off. I watch a lot of shows with zombies, and I always wondered why you didn’t see a horde of zombies coming, and then vultures following them, and then maybe a pack of canines that are coming behind, because that smell, you know, it brings– and not only that. You’ve got these big fly masses that are sort of coming towards the horde.

All of that’s triggered by the odors that are given off by the microbial breakdown. And so you know, vultures are drawn to that smell. Canines and other scavenging animals are drawn to smell. But also flies and beetles and all sorts of insects feed off of that ecosystem. And that’s all driven mostly by odor succession.

IRA FLATOW: Would

IRA FLATOW: Would all these animals becomes zombies themselves? If they–

AMANDA HALE: Well, that’s an interesting question, Ira. It depends on your mechanism for infection. I would say depending on the evolution of the viral species or the bacterial species that are involved in the infection, almost yeah. If they can jump species, then biting these zombies, if they’re able to infect with saliva and blood, then yeah, you could expect them to also turn into zombie animals and see zombie vultures.

IRA FLATOW: Yeah. Well, I’m sure there’s a great discussion forming up now in the Twitterdom to talk about this, because they always talk about what might happen.

Well, we’re going to take a short break, come back more with Rob Dunn, Amanda Hale. Also going to talk about putrid smells that Amanda was talking about, how that sort of is formed. So stay with us.

Our number, 844-724-8255. Love to take your questions. Lots of tweets coming in. You can tweet us @scifri– S-C-I-F-R-I. Stay with us. We’ll be right back.

This is Science Friday. I’m Ira Flatow. In case you’re just joining us, we’re talking this hour about the microbiomes of Halloween monsters. Hey, where else would you hear anybody talk about that, right?

My guests are Rob Dunn. He’s author of The Wildlife of our Bodies, and a professor of applied biology at North Carolina State University.

Amanda Hale is a doctoral student of zoology at North Carolina State University. Our number 844-724-8255. You can also tweet us @scifri.

Representative of Greer Martin wants to know who is gassier? Werewolves or zombies? Hm.

You opened that door, Rob, with the farting question.

AMANDA HALE: I mean, internally, zombies.

ROB DUNN: Yeah. I would say that the gas of the werewolf is more focused. And so if you could stay toward the head, you’d be OK. Whereas the zombie gas is sort of just coming out from everywhere.

AMANDA HALE: Everywhere.

ROB DUNN: Yeah.

IRA FLATOW: Huh. If you’re a zombie forever, do you keep making that gas all the time?

AMANDA HALE: I guess if you’re a zombie forever, you’re sort of stuck in this decomposition stasis almost. So I would imagine so since most zombies seem to be putrefying instead of decaying. Then yeah, they’d continue to have this internal gassy environment.

ROB DUNN: One of the neat things we know about decomposition is it’s a kind of war between different organisms. And so it would depend on who’s winning. And one of the reasons they’re producing some of these smells is to compete with the things that also might eat the body.

And so if the bacteria are winning, it will smell like this putrescing and other smells. But if the flies get there, the flies actually produce a lot of things that kill bacteria. And so you might get very different smells from the parts of the body where maggots have taken over.

IRA FLATOW: Wow. Yeah, and I know that maggots attack corpses all the time. But that’s an interesting take on that.

AMANDA HALE: Yeah. Maggots are drawn to corpses. It’s also a temperature thing. And I would say the biggest competitors for bacteria and decomposition are maggots.

IRA FLATOW: Let’s see if I’ve got a quick phone call. Ed is in Chicago. Hi, Ed. Welcome to Science Friday.

ED: Oh, thank you. I’m loving the show. This is great.

My question is, there seems to be, listening to your panel guests here, a high correlation between zombies and werewolves as represented in fiction and TV and so on, and the science that your guests are backing us into.

So the question has to do with the zombie writers. Are they doing research? Or did they just get lucky by saying, let’s have their skin fall off. Let’s give them green skin, and let’s make them smell.

IRA FLATOW: Great question. Rob? Or Amanda, do they consult with folks like you?

AMANDA HALE: I don’t know if they consult so much. But I feel like the zombie myth itself kind of comes from our fear of the dead as a way to deal with where we dispose of corpses, how we view them, and the process they’re undergoing. So I do think there is a strong correlation between how writers have created zombies and the actual process rotting corpses are undergoing. But Rob may be able to speak a little more to that.

ROB DUNN: I mean, I think in general there’s an interesting tension between our fears and science and what we fear at different times and the kinds of monsters we create. And so if you think about Frankenstein, there’s another case example monster. Mary Shelley is inspired by Erasmus Darwin and experiments that he’s doing to shock frogs and maybe bring them back to life.

And so I think there’s this back and forth between the magic of monsters and science. And Frankenstein’s interesting, because what I always wondered is does Frankenstein need a fecal transplant to keep going?

I think in retrospect, almost certainly. And so the other fun thing about these monsters is as we learn new things– because Mary Shelley didn’t have the advantage of knowing about fecal transplants– as we learn new things we can update how we think about these monsters. I think there’s a lot of fun there.

IRA FLATOW: It’s interesting you brought that up, because we had a few people tweeting in asking about that, about mummy poop and stuff. We also had an audience monster pick. And we asked our audience to choose between mummies and the headless horseman.

And after more than 700 votes, mummies won. So what would a mummy’s microbiome look like? You’re right. It doesn’t have its own– there’s no guts inside a mummy. Or is there? Does it have a microbiome?

AMANDA HALE: Well, that depends on what kind of mummy you’re talking about. Egyptian mummies are a little scarier, because they’re going to last a lot longer. They were properly prepared, eviscerated, so to speak. And so you don’t have that microbiome really present to contribute to their breakdown.

And they were treated with a salt mixture that prevents a lot of bacterial activity. Whereas some Chilean mummies and other parts of the world, where mostly it’s an environmental driven mummification. You didn’t have preparation. So their microbiomes do still exist.

ROB DUNN: Yeah. So I mean, I think that if you’re being chased by an Egyptian mummy, it’s bad news, because they’re kind of like beef jerky. They’re salted and they’re ready to deal with new conditions.

Whereas if you have a Chilean mummy– I mean, we know from what’s happening to Chilean mummies right now, they’re starting to get wet with dew because of changes in climate, and they’re turning to black ooze.

And so if you’re getting chased by a Chilean mummy, just run for water, and you’re all clear. But an Egyptian mummy’s after you, I mean, you’re really in trouble.

And maybe they do smell like beef jerky. That’s probably no. I don’t know.

AMANDA HALE: I don’t know what Egyptian mummies smell like. That is a good question.

ROB DUNN: Somebody knows that. We just don’t happen to know that.

IRA FLATOW: I’m sure we’ll get the answers. Further speculation. Time for one last call from Charlotte, North Carolina. Tony. Hi. Welcome.

TONY: Thank you for taking my call.

IRA FLATOW: Yeah. Go ahead.

TONY: I was curious with the werewolf transformation, going back and forth between wolves and completely human, how long would the microbiome from a wolf survive in a completely human host?

IRA FLATOW: Hm. Yeah.

ROB DUNN: So the best cognate for that would probably be thinking about something like when you do a treatment on people’s stomachs, on human stomachs, and change the acidity. And so when you change the acidity of a human stomach, you can change the microbiome really quickly, because you let lots of new things in, and the old things don’t do as well, because the stomach is kind of this filter.

And so if we imagine all these sorts of physiological changes happening to the system of the werewolf as it makes this change, we can see a bunch of shifts, especially in the abundance of what’s already there. Now it may be the case if the werewolf needs special microbes to deal with his diet, then it might take awhile to get those. And so maybe it has to share those with other werewolves, or maybe it comes from the food.

And so you have this mix of things that are already there becoming more abundant or less abundant, and then the need for the new things. One of the interesting places we kind of see this is in children who were raised with dogs. I mean I don’t mean the dogs were their parents. But they’re in the same house.

We actually see the kids picking up fecal microbes from the dogs that become part of their gut microbiome. And so that’s kind of the closest we get to this transition, which maybe is less glamorous than was originally imagined in the mythology, and nonetheless exists.

IRA FLATOW: It just shows you how much fun you can have with this and still learn something. And still learn something about the microbiome. And it’s been a lot of fun.

I want to thank Amanda Hale, doctoral student in zoology at North Carolina State University. Rob Dunn, author of The Wildlife of our Bodies. Great book. And professor of applied biology at North Carolina State University. Thank you both for taking time.

ROB DUNN: Oh, thank you so much.

AMANDA HALE: Thank you for having us.

IRA FLATOW: You’re welcome. And just to remind you, you can check out an info graphic on werewolf microbiomes from Neil McCoy, and a blog post– Monster Microbiology 101, written by Rob Dunn. It’s all on our website at sciencefriday.com/werewolf.

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