Science vs Snakes

Roman Mars:
This is 99% Invisible. I’m Roman Mars.

Roman Mars:
Pete Bethune is a conservationist, and while that job title doesn’t sound exciting, he’s basically GI Joe — but for nature.

Wendy Zukerman:
He’s stopped whalers on the Pacific Ocean. He rescued a dolphin held captive in an Indonesian resort. Oh, yeah, and he’s been stabbed twice.

Roman Mars:
That’s the host of “Science Vs,” Wendy Zukerman… who I’m pretty sure has only been stabbed once.

Wendy Zukerman:
And recently, Pete’s work brought him to Costa Rica, and that’s where his luck almost ran out. This was just before Christmas. Pete was deep in the rainforest with his team and they were looking for evidence of illegal logging and hunting. Picture it. It’s a lush forest, thick canopy, very hilly.

Pete Bethune:
But it’s up and down, up and down, up and down. Really steep. It’s got the most ferocious ants on earth. It’s got poisonous spiders. They were all over the place, and a lot of the trees have very spiky trunks on them, so you need to be really careful walking.

Wendy Zukerman:
That’s Pete, and while he was walking very carefully through the rainforest, something got him.

Pete Bethune:
I just felt this bang in the back of my leg, and my first thought was someone had hit me. It felt like someone had a big stick or a piece of wood and then whacked the back of my calf, and then I looked down and in horror I see this snake recoiling away from me with its head and it was sticking about two feet off the ground. As soon as I saw it, I knew it was a fer-de-lance.

Roman Mars:
The fer-de-lance, or spearhead, is the most deadly snake in Central America.

Wendy Zukerman:
Right away, Pete’s colleague grabbed his cellphone – he had one bar of reception – and called up emergency services.

Pete Bethune:
They did make it clear — you need to get that guy to a hospital as quickly as possible or he is going to die.

Wendy Zukerman:
Pete had maybe six hours to get to a hospital, and to get there, he had to dodge all the spikes and spiders and other snakes in the rainforest. Pete had two options. He could go up on the ridge of the mountain which would use up his six hours, or he could go down through muddy creeks. That would be harder but also faster, and he might get to the hospital in time.

Pete Bethune:
I remember looking at my map on my phone and thinking, the only option here is we need to go down one of these creek beds. So I’m crawling on my ass, crawling down these little waterfalls, escarpments, banks, but as we’re going down, I’m getting weaker and weaker, and this throbbing now has moved all the way up to my groin area and eventually gets to the stage where I just want to sleep, but I did think, “I’m not going to make this.” My number was up.

Wendy Zukerman:
After trudging his way through waterfalls and mud, Pete arrived at the edge of the rainforest and onto a beach where he saw the Coast Guard.

Pete Bethune:
They lay me down on the ground and I remember just closing my eyes, and, you know… just hang on a little bit more, hang on a little bit more.

Wendy Zukerman:
Pete arrived at the hospital around three and a half hours after he was bitten. His heart was racing and he passed out. When he came to, he started documenting everything that was going on.

Pete Bethune:
“Good morning, or good afternoon, depending on where you are in the world. Sort of give you guys an update on what’s happened over the last couple days.”

Wendy Zukerman:
By the time he got to the hospital, the snake venom has begun to destroy his muscles and blood vessels. Pete’s leg had ballooned to double its size, and uh… something else had happened. A warning — we’re about to talk about genitals.

Pete Bethune:
My (bleep) and (bleep) go all big and black. It is not an uncommon thing that happens with snakebite victims.

Wendy Zukerman:
That doesn’t mean it’s not quite a shock.

Pete Bethune:
I mean, look. I asked one of the nurses, “Is this normal?” She came over and she’s just, “Oh, yeah, kind of, maybe.”

Wendy Zukerman:
To turn things around, the doctors had injected Pete with snake antivenom. It raced through his body, fighting back against the toxins, and quickly, it was clear that it had worked.

Roman Mars:
Pete was going to be okay, and by day 11 he was up and about.

Pete Bethune:
“Feeling a lot better today. Um, so I’ve started walking around. For the first time, I’ve walked.”

Wendy Zukerman:
If you didn’t get antivenom, what would have happened?

Pete Bethune:
If I didn’t get antivenom, I would’ve died. No question. So yeah, I was pretty lucky, eh?

Roman Mars:
Well, that is a dramatic story, Wendy, but why are you telling us about it?

Wendy Zukerman:
I really want to zoom into the part of the story where he gets that treatment, that stuff that saved his life.

Roman Mars:
That’s the antivenom, that neutralizes the toxins.

Wendy Zukerman:
Exactly, the antivenom. So Pete got it and he survived, but many people around the world, they aren’t so lucky. Some 100,000 people die every year from snake bites. 100,000! And you compare that to sharks, they kill, maybe, about six people globally every year. Part of the reason that people are dying from snake bites is because they’re not getting antivenom fast enough. This is for a bunch of reasons, but the one that I want to zoom in on is the way that we make antivenom because the system we have now is this complicated, time-consuming, inefficient process that in many ways hasn’t changed for more than 100 years.

Roman Mars:
Okay, so then, why is it so hard to make antivenom?

Wendy Zukerman:
It all boils down to the thing that we’re battling against. It’s the stuff that we’re trying to save ourselves from, the venom. It turns out that snake venom is truly nefarious, and I spoke to Christina Zdenek who studies snake venom at the University of Queensland in Australia about this. She kind of told me all the horrible ways that snake venom can kill you.

Dr. Christina Zdenek:
It’s like you’re almost getting digested alive.

Wendy Zukerman:
So there’s that.

Roman Mars:
That sounds bad enough, yeah.

Wendy Zukerman:
We’re just at the beginning. Snake venom can have up to 200 different toxins inside it, and each of those toxins have slightly different tasks. Some start attacking your muscles. Others attack your nerves, and sometimes two different toxins can work together to really mess us up.

Dr. Christina Zdenek:
You’ve got one toxin that’s pretty bad on its own, and another one that’s pretty bad on its own, but when you put them together and they, like, tag team against you.

Wendy Zukerman:
Whoa.

Dr. Christina Zdenek:
Yeah. It’s like, “Suck eggs!!”

Roman Mars:
Suck eggs, indeed.

Wendy Zukerman:
I mean, look, that’s from a scientist, so, who are we to say? This is what she’s talking about. This is how the snake venom is saying, “Suck eggs.” You could have one toxin that is going through your body and making it difficult for your blood to clot, and then at the same time, another toxin that is kind of making you bleed out, like, it’s punching holes in your blood vessels.

Dr. Christina Zdenek:
You’ve got a hole caused by the toxins that’s now open and you’re spewing out red blood cells and plasma and platelets, but all of a sudden, you can’t stop the bleeding in that area.

Wendy Zukerman:
Christina says that sometimes people can bleed from all over their body.

Dr. Christina Zdenek:
Yeah, yeah. So like your gums, from your eyes, sometimes your ears or your sphincter, your butt hole.

Wendy Zukerman:
Oh, Jesus.

Dr. Christina Zdenek:
Even if it’s really bad, there was a Taipan bite in Australia where a guy was, it seemed like he was sweating blood from his back. With your body’s inability to clot and prevent this internal bleeding, little bit by little bit, really becomes a serious problem pretty quick.

Wendy Zukerman:
So basically, what this means is to make an antidote against snake venom, we need to have something that can battle against that soup of toxins. The thing is, you actually need different antivenoms from different snakes. What saved Pete’s life with the fer-de-lance antivenom, that wouldn’t have worked if he’d gotten bit by, I don’t know, a black mamba snake.

Roman Mars:
If you aren’t Pete, who can recognize a fer-de-lance, you could be in real trouble, then.

Wendy Zukerman:
You actually could, and Pete took a photo of the snake. He knew it was a fer-de-lance cause he’s Pete and he’s GI Joe, but they took a photo and showed it to the doctors at the hospital.

Roman Mars:
What happens if you take the wrong antivenom?

Wendy Zukerman:
It probably wouldn’t work. Like, it wouldn’t do anything. Bottom line, if they didn’t have the fer-de-lance antivenom for Pete, then he probably would have died. Now to be clear, if you take the correct antivenom, it works and this can save lives.

Roman Mars:
So if you know the snake, and there’s an antivenom for it, great, but you mentioned that making this antivenom is a complicated, old process. What are you talking about there?

Wendy Zukerman:
Okay. Let me take you on a little journey of how we make antivenom today. It all starts with a kind of snake whisperer.

Greivin Corrales:
Hello, Wendy. So, my name is Greivin Corrales.

Wendy Zukerman:
Greivin’s worked with snakes for about a decade and he loves them, but these snakes don’t always love him. Several years ago a Sri Lankan green pit viper bit his pinky finger. When you look at your finger now, what does it look like?

Greivin Corrales:
So I actually lose a little part of my finger. It’s like one centimeter or less than it used to be.

Wendy Zukerman:
Oh, wow.

Greivin Corrales:
I like it. It’s really nice for scratching.

Wendy Zukerman:
You kind of got to have this attitude if you do what Greivin does. He works at a lab in Costa Rica called the Clodomiro Picado Institute, and they make the antivenom that saved Pete’s life. Inside Greivin’s workplace, there are rows of boxes filled with snakes.

Greivin Corrales:
We have about 500 snakes.

Wendy Zukerman:
What?

Greivin Corrales:
Yeah.

Wendy Zukerman:
Okay, to cook up antivenom, first up, we need venom from a snake. To make that stuff for Pete, Greivin had to go to a box with a fer-de-lance in it.

Greivin Corrales:
We know before we open the box, it’s going to fight, because they are very explosive. They strike many times.

Wendy Zukerman:
Greivin and his colleagues carefully take this writhing, angry snake out of the box using wooden poles, then they sedate the snake by popping it in a basket with carbon dioxide gas.

Wendy Zukerman:
“When it goes under, when it’s sedated, how long do you have before it wakes up, generally?”

Greivin Corrales:
“Around five minutes.”

Wendy Zukerman:
“Five minutes. So what’s going through your mind as you’re doing this?”

Greivin Corrales:
“I know it sounds kind of crazy, but nothing. In this moment I have to be very focused. You’re holding not just the snake, but your partner’s life. In that moment, you cannot feel no fear. You have to be fearless.”

Wendy Zukerman:
And then, Greivin picks up the snake’s head while his colleague holds the snake’s body, and then Greivin milks the snake.

Roman Mars:
What does milking the snake entail?

Wendy Zukerman:
I’m so glad you asked. Let me get this photo for you.

Roman Mars:
Okay. Oh, my goodness. Okay, they’re holding the snake, and there’s a metal object prying the mouth open, and the fangs are popped out and they’re bringing the snake’s head to a jar to collect the venom.

Wendy Zukerman:
Yes. So this is Greivin in the picture and you can see that his index finger is kind of over the top of the snake’s head. What he’s going to be squishing down on is the venom gland of the snake, which is like this pouch, basically, that’s filled with venom.

Greivin Corrales:
“So we have to do a little massage …”

Wendy Zukerman:
“Massage?”

Greivin Corrales:
“A massage, yeah.”

Wendy Zukerman:
I asked Greivin to try and tell me what this feels like, as someone who’s never milked a snake, and he was, like … He just couldn’t tell me. He was like, it’s like nothing you’ve ever felt before. The closest thing he got was, he was like, it’s a bit like if you imagine a slice of an orange under snakeskin and you’re kind of squishing the orange and then the juice comes out of the snake fangs.

Roman Mars:
I see, I see. So it’s a little tough. It’s not, like, squishy. It had some resistance, but you’re pushing on the back of the head and it pushes out a little bit of venom.

Wendy Zukerman:
Yes.

Roman Mars:
Wow.

Wendy Zukerman:
Yeah, and Greivin says that he can get around a teaspoon of venom from one fer-de-lance snake.

Roman Mars:
Okay, so, now, he’s massaged the venom out of the snake into a jar. What happens to the venom then?

Wendy Zukerman:
Okay. Here’s where it gets kind of ridiculous, because now …

Roman Mars:
Oh, here’s where?! Ok. I was waiting for it to get ridiculous.

Wendy Zukerman:
Well, because, here’s where we need a second group of animals.

Roman Mars:
Oh, goodness, okay.

Wendy Zukerman:
We’re going to call in the cavalry because we literally need a farm of horses.

Roman Mars:
Whoa! Okay, this is a turn.

Wendy Zukerman:
Some labs do use sheep but, basically, we need a large animal for reasons that will become clear later, but at the center where Pete’s antivenom was made, there’s about 120 horses, and there’s also this guy, José María Gutiérrez.

Dr. José María Gutiérrez:
“They’re really fantastic animals.”

Wendy Zukerman:
“Do they have names?”

Dr. José María Gutiérrez:
“Yes. They have names. In fact, there was one horse one time with my name, so I was very proud of that.”

Wendy Zukerman:
José María is a professor at the Clodomiro Picado Institute. All right, so, they’re using all these horses because the antivenom is actually going to be created inside the horse’s body. And here’s how. José María’s team will take that venom that Greivin coaxed out of the snake, and then …

Dr. José María Gutiérrez:
You inject little amounts of venom into horses.

Wendy Zukerman:
“When a horse is first injected with, say, a tiny amount of venom, how do they react? Are they, like …neigh! Do you think it would be, like, a mosquito bite?”

Dr. José María Gutiérrez:
“I think it would be a little more than that because we are injecting a toxic substance.”

Roman Mars:
So does this hurt the horse?

Wendy Zukerman:
Well, we don’t know for sure, because the horse doesn’t talk human speak, but from what we can tell, there’s a little bit of swelling around where they do the injection. Nothing too serious, though, and they’re just injecting tiny, tiny amounts. What’s going to happen next is that the horse is going to be injected with venom every two weeks or so. What they’re doing is actually waiting for the horse’s immune system to start building up antibodies against the venom. That’s what we’re here to harness. That is actually the antivenom. Another way to think about it is that you’re kind of vaccinating the horses against the venom.

Dr. José María Gutiérrez:
Then, after several of these injections, usually a couple of months, for instance, at that point the horses are bled.

Wendy Zukerman:
They take around six liters of blood, which sounds like a lot, but José María says it’s kind of the horse equivalent of donating a bag of blood at a blood bank.

Roman Mars:
Okay, that’s not so bad. You get a cookie, you get some orange juice, you’re all right. You go about your day.

Wendy Zukerman:
Yeah, that’s right. This is actually why we need horses because they’re these big animals that can donate a lot of blood.

Roman Mars:
Right.

Wendy Zukerman:
After all this, we get the very thing that we’ve been waiting for, this miraculous drug that fends off that super complicated cocktail of venom — the horse antibodies. They’re purified, then freeze-dried and put into a vial, and that is the stuff that gets injected into people like Pete.

Dr. José María Gutiérrez:
“These horse antibodies would get into the bloodstream, they find the toxins and then they block the action of the toxins.”

Wendy Zukerman:
“And so even though we say antibodies as if it’s like one thing, within that vial of antivenom, there could be 50 different antibodies that go after 50 different toxins in the blood.”

Dr. José María Gutiérrez:
“Exactly. Actually, it’s a mixture of antibodies, and there are antibodies against each of the toxins.”

Wendy Zukerman:
And we need horses for this because they’re these big animals and they can donate a lot of blood. Horses actually have a similar enough immune system, so their antibodies work for humans. José María reckons that each bag of horse blood gets you enough antivenom to treat around 15 people.

Roman Mars:
It’s a super cool process and fascinating but it also seems just way too complicated.

Wendy Zukerman:
Yeah, and then, just to add a tiny bit more complexity here is that to make antivenom for all the venomous snakes in the world, you actually need to inject horses with this specific venom from all those snakes in the world. This all means we’ve got labs in Indonesia, in India, in South Africa, in Australia, that are just piled high with horses all getting injected with venom. And the thing is, we’ve basically made antivenom the same way since the late 1800s.

Roman Mars:
Wow, really nothing has changed in that time period, just the personnel and the horses, but it’s the same process.

Wendy Zukerman:
Yeah. I mean, there have been some improvements, like, in some cases, for example, the horses will go through this whole process and instead of just being injected with one kind of venom, they’ll be injected with three different kinds of venom, so that means they’ll make all these antibodies for, then, three different kinds of venom.

Roman Mars:
I see, so, it’s a little bit more efficient but the process is still basically the same.

Wendy Zukerman:
Yes, I think that’s fair, yes.

Roman Mars:
I guess, the obvious question is, we’ve been doing this for 100 plus years, why are we still doing it this way? Why haven’t we come up with a better way to do this?

Wendy Zukerman:
Yeah, it’s a great question, and I think the dream for a lot of the people who work on this problem, is to create a universal antivenom. So, something that you could make in a lab and that could be used for heaps of different kinds of snakes, for black mambas, for fer-de-lances, for rattlesnakes, and you wouldn’t need to go through this whole process so many times in so many different countries.

Roman Mars:
It sounds super easy. Why don’t we just do that?

Wendy Zukerman:
It’s not easy, and it takes a lot of time and innovative thinking, and the big thing is, money.

Roman Mars:
Oh, I see.

Wendy Zukerman:
For a long time, no one was really putting a lot of money into this space, and that’s for all kinds of complicated reasons, but if we had to boil it down to a word, I would say that word was capitalism. As we talked about, snake bites kill around 100,000 people ever year. This is a serious problem, but most of those deaths are happening in rural areas in Africa and Asia for people who can’t afford a lot of money for medication, and drug companies haven’t put a lot of funding into this to try and make things better, basically.

Roman Mars:
Yeah.

Wendy Zukerman:
But since 2017, things have started to change.

Roman Mars:
What happened in 2017?

Wendy Zukerman:
The World Health Organization gave snake bites this special designation. They listed them as the most important kind of neglected tropical disease. This sounds terribly nerdy and in the weeds, but basically, what it means for a disease is that its kind of like winning an Oscar. You get extra attention, you get extra money. That is basically what’s happened. We’ve seen this real change in what’s going on. You see more research in this space, and after more than 100 years of making antivenom with the horses and the snakes, now there’s all these new ideas on the horizon. José María says that this has all been huge.

Dr. José María Gutiérrez:
Things have really changed. The world in general is paying much more attention to this disease, and it’s really exciting.

Roman Mars:
So now that snake bites have gotten the amount of attention they deserve, where are we with the universal antivenom?

Wendy Zukerman:
We’re starting to see some really exciting things in the science. One of them is that, at the same time as snake bites have gotten all this extra attention, scientists also developed these better tools to be able to look inside venom and analyze those toxins, and what we’re realizing is that even though there are thousands of toxins doing slightly different things, you can actually group them together into families of toxins, and then try and tackle those families, and it’s a much easier target.

Wendy Zukerman:
You can think about it like this. Are you a basketball fan?

Roman Mars:
Not especially, but… continue on.

Wendy Zukerman:
Excellent. Huge basketball fan in the corner, here. All right, so, this is kind of how I’ve been thinking about the way that they’re tackling this universal antivenom problem. Say, you’re in the NBA, and you’ve got to play against hundreds of players in the league.

Roman Mars:
Okay.

Wendy Zukerman:
One way to do that would be to try and figure out the defense of all the individual players, you know, Curry and LeBron, and even all the middle-level players and all the ones on the bench, like even Boban, you’ve got to work out what’s going on with him.

Roman Mars:
Of course. I think about Boban all the time, but, I guess, contextually, I am to assume that Boban is not exactly a LeBron or a Curry.

Wendy Zukerman:
No, but he’s doing his best.

Roman Mars:
Okay, great.

Wendy Zukerman:
Exactly, so you’ve got to work out each player’s individual tricks. Instead, what we’re doing now is we’re just looking at what the big, dangerous players are doing, and grouping them together, and then working out a defense against them, so just focusing on Steph Curry and all the Curry copycats out there.

Roman Mars:
Okay, that makes sense, so, if you know that the toxin, you know, hits a lot of three-pointers, you’re basically making a medicine to deal with that particular attack. It’s the anti-three pointer medicine.

Wendy Zukerman:
Exactly, exactly.

Roman Mars:
Okay, and so has this approach been working so far?

Wendy Zukerman:
It’s been going well. For example, there’s this big family of enzymes that are swimming inside venom, and what they do is damage blood vessels, and they’re called metalloproteinases. They’re found in vipers all around the world, and so, scientists have now been searching for a way to basically stop metalloproteinases from working. This is one of those scientists. Go on, introduce yourself.

Dr. Laura Albulescu:
Yeah, so, I’m Laura Albulescu. I work at the Liverpool School of Tropical Medicine.

Wendy Zukerman:
Scientists like Laura are trying to figure out how to protect us against that big family of nasty enzymes. To do that, she’s been thinking, “What do the enzymes need to survive?” They’ve discovered that one of the things these enzymes need is zinc. Laura says there’s actually already a drug on the market that messes with zinc. Laura and her team took this drug and then combined it with another drug, and then they enlisted some heroic little white mice and injected them with some snake venom from some of the most dangerous snakes in the world.

Dr. Laura Albulescu:
We are looking at vipers from Africa, from India, from Central America..

Wendy Zukerman:
They waited a bit to let the venom set in, then gave them the concoction, the two drugs. If this didn’t work, most likely …

Dr. Laura Albulescu:
These mice would all die within a four-hour window.

Wendy Zukerman:
Instead, the team saw something different. The mice started moving around, sniffing. They seemed to be recovering.

Dr. Laura Albulescu:
These animals are still alive and look healthy.

Wendy Zukerman:
“And how were you feeling?!”

Dr. Laura Albulescu:
“Yeah, I was feeling great. I didn’t expect it to work so well against venoms that are so different from each other.”

Wendy Zukerman:
“Yeah, to work for a fer-de-lance from Central America and then an Asian … you had saw-scaled viper.”

Dr. Laura Albulescu:
“Yeah.”

Wendy Zukerman:
“How big is that in the world of antivenom?”

Dr. Laura Albulescu:
“This is amazing. It’s really great. It’s really important.”

Wendy Zukerman:
There you have it. After 100 years of needing to inject horses with all these different kinds of venom, Laura’s drug has worked. We did it, Roman!

Roman Mars:
I have a feeling that we did not do it. That’s not how science works. One clinical test doesn’t do it.

Wendy Zukerman:
No… and actually, one of the mice did die 18 hours later, but, but, but, but, this tactic is actually showing so much promise that there’s already a clinical trial in humans underway that’s focusing on another drug that messes with zinc.

Roman Mars:
That’s great, and this is a completely different approach. Using drugs rather than using antibodies from another animal is completely novel.

Wendy Zukerman:
Exactly. It’s novel in the world of snake bites, but it’s what we do for basically every other disease out there. The antivenom that we have now, it does work when you can get it, so scientists are thinking that maybe in the short-ish term, we might have these new and exciting treatments that kind of work alongside the antivenom from the horses.

Roman Mars:
It’s funny, because we’ve spent a year with COVID-19, and we saw a series of vaccines go from design to trial to approval in under a year, and that’s not how science normally works, ever. Usually, it’s a process where you try things, lots of mice die, and after years of experiments, maybe we have a small breakthrough.

Wendy Zukerman:
Yeah. I think the COVID-19 story, it could tell us two things and time will tell. Perhaps this virus was actually surprisingly easy to make a vaccine for, and we were kind of lucky, and a nastier virus could have come around that we couldn’t have had a vaccine for, but maybe the other lesson here is that if scientists get bucket loads of money and basically you encourage nerds from all around the world to tackle a problem, that they could solve it very quickly.

Roman Mars:
Yeah, yeah. It’s like a Manhattan Project or sending a person to the moon. If you put enough money and will behind it you can make it happen.

Wendy Zukerman:
Exactly, exactly, and so maybe that will happen with snake antivenom too if enough scientists and there’s enough excitement around this area.

Roman Mars:
Okay. I have one more question before we go. What happened to Pete? He got bit by this snake, he nearly died. Is he still traipsing around as this conservationist GI Joe?

Wendy Zukerman:
Yes. There’s no change in Pete whatsoever. He is still in Costa Rica. He’s going to be patrolling the jungle soon, and he said his leg is doing all right. In the meantime, he actually still holds a little place in his heart for the snake that got him.

Pete Bethune:
I’m hoping that guy is still alive and up there.

Wendy Zukerman:
You don’t hold a grudge against the snakey?

Pete Bethune:
No, I don’t hold a grudge against the snake. He was just doing snake things.

Roman Mars:
Pete has a good attitude. Thank you, Wendy.

Wendy Zukerman:
Thanks, Roman.

Roman Mars:
More strange, fascinating, snake content with Wendy Zukerman, after this.

[BREAK]

Roman Mars:
So I’m back with Wendy Zukerman from the Science Vs. Wendy, let us talk more about snakes.

Wendy Zukerman:
Yes, please. So, as I’ve been researching this episode, I realized there were all these things about snakes that I had never thought about before. They’re quite beautiful, they have all these different colors on their scales. And I also realized how little science knows about some… what I would have thought were pretty basic snake things.

Roman Mars:
Like, for example?

Wendy Zukerman:
Like scientists still aren’t sure if snakes can hear.

Roman Mars:
Like, hear at all?

Wendy Zukerman:
Yeah.

Roman Mars:
Wow.

Wendy Zukerman:
Yeah, yeah. So, Dr. Christina Zdenek, who we heard from in the first half of the show, she’s like, “We know snakes can feel vibrations.” That’s what we’re taught. I actually don’t know if you’re taught this, but every Australian knows that if you see a snake, you got to stamp your feet to try and get them to feel. Okay, so we know snakes can feel vibrations, but we didn’t know whether they could hear sounds through the air.

Roman Mars:
Huh.

Wendy Zukerman:
And a big reason for that is that they don’t have external ears, which, ever since she told me that, I just can’t stop imagining a snake with external ears.

Roman Mars:
With ears.

Wendy Zukerman:
Right?

Roman Mars:
I mean, that is the only way we’d really know, is if they had big old ears…

Wendy Zukerman:
Right.

Roman Mars:
At the side of their heads.

Wendy Zukerman:
For a long time, some scientists were like, “Well, we just don’t think they can hear.” And then Christina heard this amazing story from one of her colleagues, Damian Candusso. I don’t want to tell you. I mean, in some ways, I can’t imagine a more stereotypical Australian story, so I am nervous to bring this to more Americans.

Roman Mars:
You’re in a safe space here.

Wendy Zukerman:
Thank you. Thank you. So this guy, he sometimes makes the sound effects for films, and he noticed that while he was working on what he called low-end frequencies, so think like bombs exploding and earthquakes, where you hear those tremors in a cinema.

Roman Mars:
Yeah.

Wendy Zukerman:
And so while he was creating those sounds, he would notice that brown snakes would start slithering next to his house from seemingly nowhere. He didn’t know why. It could have been a coincidence. It could have been that they were feeling vibrations, or maybe because they really could hear the sound waves through the air.

Roman Mars:
Hmm.

Wendy Zukerman:
And so he ends up telling this story to Christina, and Christina was like, “Yeah, there are a few studies suggesting maybe snakes can hear, still this huge debate.” And so just this year, they teamed up and decided to test it.

Dr. Christina Zdenek:
“We’ve got a soundproof room, and we’ve got 19 captive snakes.”

Wendy Zukerman:
What her team does is they take the snake out of its holding container, which is essentially like a rubbish bin with some holes in the lid.

Dr. Christina Zdenek:
“Grabbing a snake with a hook and then with his hand when it’s safe.”

Roman Mars:
Mm-hmm (affirmative).

Wendy Zukerman:
And then they put the snake into this soundproof room.

Dr. Christina Zdenek:
“We’ve got a half wall, which we’ve just secured the door for, for security.”

Wendy Zukerman:
Christina sent me a photo. It’s literally fancier than the Gimlet studios and definitely more secure. And then they give the snake some time to settle. So then they play some sounds through this very special setup they have that’s basically designed so that the sounds come through the air and they don’t make vibrations on the floor.

Roman Mars:
I see. Right.

Wendy Zukerman:
And then she’s basically recording the snake’s behavior.

Dr. Christina Zdenek:
“Just started the sound, and she dropped her lower jaw, which is quite interesting. A defensive pose. And now she’s flicking her tongue and slightly moving around, head raised off the ground, peering into the distance. Still flicking the tongue, not making any large movements.”

Roman Mars:
So what did they find? Do snakes actually hear the sound?

Wendy Zukerman:
Okay, she’s still analyzing the data, but here’s what she told me about it.

Dr. Christina Zdenek:
There’s some very interesting behaviors. I think it will be clear, at least with some of the individuals, that they’re absolutely going to be aware of the sound.

Wendy Zukerman:
What I think is pretty cool with what Christina is starting to see is that the behavior she’s seeing is really dependent on the individual snake. Right? And so here’s what she said about that.

Dr. Christina Zdenek:
How they respond, I think, it seems to be based on the individual personality or whether they’re a type of a timid snake or whether they’re more defensive and willing to give more defensive behaviors. And by that, in a snake, would be dropping their lower jaw to show their fangs or hissing.

Wendy Zukerman:
Had you thought about snakes as having personalities?

Dr. Christina Zdenek:
Yes. We see it all the time. So my husband and I, we have 24 snakes as pets, and so we see it on a very intimate level. One snake doesn’t like to be touched, another one could care less. One basically falls asleep in your hands. He’s like this old man. He’s literally 21 years old. He’s like 2.2-meter coastal taipan. They’re very predictable in their personalities.

Wendy Zukerman:
And so to take this back to the experiment, in the tape where we were hearing about the experiment, Christina’s describing the snake that’s hissing and getting all pissy at the sound.

Roman Mars:
Mm-hmm (affirmative).

Wendy Zukerman:
That’s a coastal taipan, but it’s not the sleepy guy that she’s talking about here. That sleepy guy was also in the experiment, and she said that he basically fell asleep when he heard the sounds. So there was a perfect example of how she’s seen these different reactions. By the way, just to get a sense of how big that sleepy snake is, she said 2.2 meters. It’s about the same height as Boban, the basketball player.

Roman Mars:
It all comes back to Boban. That’s fantastic.

Wendy Zukerman:
Right? Did you ever think of snakes as having personalities?

Roman Mars:
I mean, I had a snake, and I didn’t have a lot of exposure. That one seemed to have a personality. It was named Chewbacca. It was a corn snake. But I didn’t have a lot of other snakes to compare it to, so it had personality, but I didn’t realize how maybe different it was from other corn snakes. But Chewy was a great snake and would escape on occasion and then show up four days later right next to the cage.

Wendy Zukerman:
Oh wow.

Roman Mars:
Yeah.

Wendy Zukerman:
Like a cat. Cats do that.

Roman Mars:
Yeah. Exactly. Yeah. So it doesn’t surprise me that they have some personality. The fact that one would get really exorcized upon watching a Christopher Nolan movie and another one would be completely nonplussed by it is new to me, though. That’s fantastic.

Wendy Zukerman:
And new to science, I think.

Roman Mars:
I like it. Thank you.

Wendy Zukerman:
Thanks.

Roman Mars:
A version of this episode can be heard on the wonderful podcast Science Vs, a production of Gimlet, a Spotify company. I’m a huge Science Vs fan. I’ve been a fan since the very first episode that I heard when they were just a little Australian show, and now they’re this big global phenomenon. I am so excited we had this chance to work with them. Special thanks this week to Wendy Zukerman and the whole team at Science Vs, including Blythe Terrell, Rose Rimler, Meryl Horn, Nick DelRose, Michelle Dang, and Taylor White. Also a special thanks to Maxwell Simeon at Gimlet.

———

Roman Mars:
99% Invisible was produced this week by Chris Berube. Music by our director of sound, Sean Real. Sound mix by Bryson Barnes. Fact checking by Erica Akiko Howard. Our senior producer is Delaney Hall. Kurt Kohlstedt is the digital director. The rest of the team includes Emmett FitzGerald, Joe Rosenberg, Vivian Le, Christopher Johnson, Abby Madan, Katie Mingle, Sofia Klatzker, and me, Roman Mars.

We are a project of 91.7 KALW in San Francisco and produced on Radio Row. We’re just scattered across the continent right now, but we’ll always be centered in beautiful downtown Oakland, California. We’re a founding member of Radiotopia from PRX, a fiercely independent collective of the most innovative listener-supported, 100% artist-owned podcasts in the world. Find them all at radiotopia.fm.

You can tweet me @romanmars and the show @99piorg. We’re on Instagram and Reddit, too. And you can find our home on the internet at 99pi.org.

Credits

Production

Science Vs is host and executive producer Wendy Zukerman, producer Meryl Horn, producer Rose Rimler, associate producer Michelle Dang, associate producer Nick DelRose, and intern Taylor White. Editor Blythe Terrell. Fact checking by Erica Akiko Howard.

Science Vs spoke with Captain Pete Bethune; Dr. Christina Zdenek, a post-doc and lab manager of the Toxin Evolution Lab at The University of Queensland; Greivin Corrales Chaves of Universidad de Costa Rica’s Instituto Clodomiro Picado; Dr. José María Gutiérrez, is an emeritus professor at Instituto Clodomiro Picado; and Dr. Laura Albulescu is a post-doc at the Liverpool School of Tropical Medicine in the UK

Special thanks to Professor Abdul Razaq Habib, Dr. Gavin Smith, Professor Abina Crean, Professor Nick Casewell, Dr. Jessicah Kurere, and Dr. Tarek Mohamed.

This episode was edited for 99% Invisible by Chris Berube.

  1. Allen Karsina

    Very interesting episode! I did have one question about the experiment to see if snakes can hear. It seemed as if the researchers were adding sound and observing the snakes closely to see if their behavior changed. Have the researchers tried pairing the sounds with environmental events? Adding a sound right before food is delivered, for example, or right before doing something the snake does not like. Once the sound was paired with the same event for a time, then just the sound could be presented periodically. If the snakes respond to the sound the same way they do to the event it is paired with, that would be very strong evidence they can hear. If the researchers haven’t been doing this, perhaps it could be a follow up study, particularly if the results they get from the current study aren’t as clear as they would like.

  2. jenn

    American culture is talking about insides liquifying but needing a content warning for talking about someone’s c**k and b***s.

  3. Scott McRandle

    So…does that mean that the horse is immune to the snake bite of the snake which it’s making the anti-venom for?

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