[RADIOLAB INTRO]

RACHAEL CUSICK: If you've ever stepped foot on an American boardwalk, you've likely encountered a deep fried Oreo, a roller coaster you're surprised still functions, and maybe even a hermit crab.

LATIF NASSER: This is Radiolab. I'm Latif Nasser.

LULU MILLER: And I'm Lulu Miller.

LATIF: And today's episode is an ode to the not-so-cute-and-cuddly creatures. Get outta here, pandas! Don't even come near me, dolphins.

LULU: Puppies, we want nothing to do with you.

LATIF: Get outta here.

LULU: We're looking at two of the gnarly ones, the ones that literally poke and bite and—and eviscerate. [laughs]

LATIF: Right. And caw.

LULU: The first one comes to us from our producer Rachael Cusick. She originally told it live before an audience at Pop-Up Magazine.

LATIF: Lulu and I were both in that audience in different cities. Picture her in a fantastic purple jumpsuit. And behind her is a huge animation of a Ferris wheel and an oceanside boardwalk.

RACHAEL: The first time I saw a hermit crab I was 11, spending the weekend with my grandpa in Atlantic City. The crab was a boardwalk souvenir, tucked inside a shell painted to look like Spongebob SquarePants. I didn't know then that that hermit crab wasn't born on a boardwalk or in a pet store or a lab, he was snatched from the wild, likely from Indonesia or Central America, and given a one-way-ticket to the armpit of New Jersey.

RACHAEL: Virtually every single hermit crab you've ever seen has been stolen from its home in this way, and that's because no one has figured out how to mass-breed hermit crabs in captivity, not even biologist Chris Tudge.

CHRIS TUDGE: I think I could probably honestly say I've done more work on the reproductive biology of hermit crabs than anybody else pretty much ever.

RACHAEL: Now hermit crabs are elusive creatures. They change color and even the shells they call home.

CHRIS TUDGE: They pass through multiple stages, and change their shape and their size. And the environmental conditions you need for them are really quite specific.

RACHAEL: I first read about all of this in a science article by Samantha Edmonds in The Outline. She says hermit crabs are hard to study, even harder to breed. A few people tried to reproduce them, but none could crack the code of breeding them in large numbers. Partially because we didn't care enough about them to learn. They're not tasty, they're not cute. No one saw enough value in them. But then Mary came along.

MARY AKERS: They say scaly is the new fluffy.

RACHAEL: Who says that?

MARY AKERS: [laughs] I don't know.

RACHAEL: Mary Akers is an artist who fell into hermit crabs a few years back when her last kid left for college.

MARY AKERS: When I became an empty nester, my three kids had graduated, I said, "Now I can do what I wanna do, right?" I was going through menopause. It was kinda like get rid of all that estrogen. I'm 12 again!

RACHAEL: Mary needed hobbies. She started doing pottery again, and one day a woman in her group said she was looking to offload a hermit crab after her kid lost interest.

MARY AKERS: And I was immediately like, "Oh, could I? Do I? Will I?" I hesitated more because of my husband. Like, and I didn't confess to him right away that I said yes. I said, "We're gonna crab-sit while they go on vacation."

RACHAEL: Eventually she came clean to her husband. Said she wanted the crab to stay for good. But she quickly realized she didn't know much about how to care for her new pet.

MARY AKERS: And I Googled and I was like, "Oh my gosh, they need friends. They need more room. They need sand. They need real food."

RACHAEL: She learned they can live for decades if cared for properly. And when she realized her own hermit crab was stolen from its home, she felt a profound sense of injustice.

MARY AKERS: Any other creature that lives 50 years, we think of elephants, we think of whales, we think of even the great tortoises, right?  We revere. But we don't do that with hermit crabs. They are literally throw-away pets.

RACHAEL: These cracks in our world that most of us skip over or never see at all, they suck Mary in. Mary is the child of an alcoholic father, the sister of someone with mental illness, and a nurturing mother of three. She's spent her entire life caring for others, hoping she could protect them if she just loved them hard enough. Now in these hermit crabs, Mary found a new space for her love to fill.

RACHAEL: So Mary went out and bought more hermit crabs. Put 'em in a tank the size of a grand piano, and declared them the new tenants of her daughter's old bedroom.

RACHAEL: What is that called?

MARY AKERS: Oh, the—the crabs are in their crabitat.

RACHAEL: Things escalated. Mary watched them run on a hamster wheel for hours. She'd share her leftovers with them, and then give them popcorn as a midnight snack. She even named each crab—Artemis, Garbo, Lola—then started learning what made them tick.

MARY AKERS: I've noticed that some of them have personalities where they like either the blingy-er shells, and I have one that likes a green shell pretty much all the time. Sometimes I know, like, "He's gonna love that shell!"

RACHAEL: Then one day Mary saw one of her crabs walking funny.

MARY AKERS: And I got my little flashlight and I shone it in there and I'm like, "What is that in your sh—what? Do you have a growth? Do you have a tumor? Like, what is that?" Well, it was eggs in her shell. And I was like, "Oh yeah, baby!"

RACHAEL: That summer, Mary's Crabitat morphed into a laboratory, one dedicated to delivering these eggs into crabhood, and one that was a daily construction of love. She built a series of pools so the pregnant crab could pick which water she liked best to release her eggs into. Once the eggs hatched, Mary used a turkey baster to swap out the dirty water the crabs swam around in, changing the metaphorical diaper of thousands of baby crabs.

RACHAEL: All along the way, Mary lingered above her crabitat, cooing to babies.

MARY AKERS: And these little guys, I think about it sometimes, have been seeing my big moon face, you know, hovering over them, staring at them. What do they think? Like, am I the landscape of their life?

RACHAEL: Mary would have a few good days, but then the number of babies would plummet. The crabs' struggles, their needs, they consumed Mary.

MARY AKERS: What am I not giving them, right? That's the recurring refrain in my head. What do they need? What am I not giving them?

RACHAEL: She wanted to smooth out every speedbump life put in their way. Still the number of babies continued to drop until there were none left.

MARY AKERS: I got to the final stage. That's the closest they get to being a land hermit crab before they're a land hermit crab.

RACHAEL: She felt gutted, but not wholly defeated. Because the next summer, when one of her crabs waddled with eggs yet again, she got back to work.

MARY AKERS: I had a plan. I had a lot more things I wanted to try.

RACHAEL: She built a new kind of tank, grew a different seaweed, bought better foods. She even built a ramp inside one of her tanks to simulate a hermit crab's journey from the ocean onto dry land. But far more radically, Mary did something she really, really does not like to do.

MARY AKERS: I had to figure out how to not care so much. I can't be God. I can't be God. I don't wanna be God, right? But I can be the ocean. I can be the ocean.

RACHAEL: That phrase—be the ocean—it became Mary's companion through all this.

MARY AKERS: A little mantra which sometimes I recite. "Be the ocean."

RACHAEL: Every time she found herself wanting to rescue the hermit crabs from some amorphous potential harm...

MARY AKERS: "Be the ocean."

RACHAEL: ...Mary would imagine the vast waters that raise hermit crabs. How these microscopic specks managed to float around in the maelstrom, and make it out the other side.

MARY AKERS: So I would actually agitate them more and move it around and give them, like, a low tide and a high tide. Today I'm the ocean, and today the ocean is dirty and mean!

RACHAEL: Eventually, the babies grew. They survived major milestones, they formed limbs, and then flew through the water like Superman. And then one day, Mary watched a single hermit crab pull its body up onto the staircase, and break through the border between water and land.

MARY AKERS: I cried. I wept. I wanted a soundtrack playing.

RACHAEL: Meanwhile, more crabs kept coming. Mary took out a piece of paper and began making a tally mark for each crab that made it to land.

MARY AKERS: And then by, like, day five, it's the march of the penguins, right? I'm like, "Oh God. Okay, there's another one. There's another one."

RACHAEL: By the end of the summer, Mary had added 204 new hermit crabs to the world. With a turkey baster and tender loving care, Mary accomplished the impossible. It's been five years since that first hermit crab climbed out of the water in Mary's crabitat. Each year she breeds a new batch. Some years she reaches up to 700 crabs. She's bred so many hermit crabs that now she adopts them out, making sure they go to responsible homes.

RACHAEL: Learning about all of this, I wondered why it was Mary who could figure out this thing and scientists couldn't. It was the question Chris Tudge asked himself too. Remember Chris? He was the guy who should have figured out what Mary did but couldn't. Late one night, he found himself reading Mary's blog, where she'd been documenting her entire breeding process.

CHRIS TUDGE: And by the end of it, my first impression was, "Oh my God, she actually did it!"

RACHAEL: The thing Chris found most impressive was Mary's ability to be the ocean.

CHRIS TUDGE: It's just stunning. You know, you have to keep the waste levels down, you have to keep the oxygen up. The light levels have to be right. The ocean's a constantly changing entity, and here she was reproducing the ocean in little tiny bowls.

RACHAEL: Why is it so hard to recreate? Like, what about it is hard to copy?

CHRIS TUDGE: The chaos. In the same piece of ocean, there's millions of other species who are trying to do the same thing that need slightly different conditions, so the chaos is benefitting everybody a little bit.

RACHAEL: That turbulence Mary originally resisted, it's the very thing Chris said the crabs needed to survive. I like to think these hermit crabs gave Mary the chaos she needed to survive too.

MARY AKERS: I could literally all day every day do nothing but try to get it perfect. But that's not best for the crabs, that's definitely not best for me. So it's a balance of how much do I allow myself to feel responsible.

RACHAEL: If you share your life with another creature—a hermit crab, a human—I think this is the maddening fact we're faced with every day: that our love can only do so much.

MARY AKERS: You're not responsible for everyone. You're not responsible for saving everyone. Well, I wanted to save my dad. I can't save my dad, I was a kid, you know? My kids, letting go—like, life for me, my lesson has always been just let go, Mary. Let them be crabs.

RACHAEL: Thank you.

LATIF: Producer Rachael Cusick. We should add real quick: Mary and Chris actually struck up a friendship after Rachael interviewed them for this story. Mary sends Chris photos of her crabs under the microscope. Chris regularly presents at Mary's annual hermit crab conference—CrabCon. He even started up a few projects in his lab inspired by Mary's online hermit crab society. It's beautiful.

LULU: Now when we come back, we are going to go even deeper into that strange relationship between crabs and chaos, and ask if it's not just that crabs that need chaos to be born—like, that was the secret ingredient the hermit crabs needed—but does chaos need a crab? Or, like, want a crab? Sort of. You'll see. The scientists are gonna straighten it out. Stick with us.

LATIF: Don't scuttle away.

LULU: Radiolab.

LATIF: Latif.

LULU: Lulu.

LATIF: Crabs.

JO WOLFE: Hi!

LULU: Hello!

LULU: So on to our next layer of the crab cake, our next crab story. We are here with this Harvard crab scientist, Dr. Jo Wolfe.

JO WOLFE: Am I allowed to say any, like, swear words?

LULU: Oh!

JO WOLFE: I should not do that, right?

LULU: You can!

LULU: And she probably should because she recently uncovered something f-ing bonkers about crabs that I have been dying to talk about on the radio.

LULU: So excited about this, Jo!

JO WOLFE: Yeah, awesome.

LULU: So the whole thing really starts with this kind of dry scientific crafting project.

LATIF: Okay.

LULU: Jo, along with her colleagues Heather Bracken-Grissom and...

JAVIER LUQUE: Hello, hello!

LULU: ...Javier Luque, wanted to take all crabs in the world and just make a massive crab family tree.

JAVIER LUQUE: The crab tree of life.

LULU: So to actually build this crab family tree, they're not taking photos and scrapbooking, they're taking DNA. They sequenced the DNA from hundreds of different crabs.

JAVIER LUQUE: Dungeness crabs.

LULU: Snow crabs.

JO WOLFE: The coconut crab.

LATIF: Huh!

LULU: They've got...

JAVIER LUQUE: Chesapeake Bay blue crabs.

LULU: Porcelain crabs.

JO WOLFE: They look more like a lobster...

LULU: Aren't lobsters crabs?

JO WOLFE: No, lobsters are not crabs.

LULU: Okay.

JO WOLFE: Lobsters are lobsters.

LULU: [laughs] Okay, sorry.

LULU: There are hairy crabs, mud crabs, tree crabs.

LATIF: Trees? There are tree crabs?

LULU: Yeah!

LATIF: What? In my head, crabs go with water. You're telling me crabs can live in trees.

LULU: Yeah!

LATIF: Amazing.

LULU: So they're putting all this data into some super powerful computer. And when they're done, they press a button and they're watching this computer build this tree. Branches and branches and crabs and crabs...

JAVIER LUQUE: It would have been great if it was like that, but no it was less—less dramatic. It was more like...

JO WOLFE: You put all your data in, you press a button, and you wait.

LULU: For a pretty long time.

JO WOLFE: For, like, months.

LATIF: Whoa!

LULU: The computer takes a while to do its thing.

JO WOLFE: And then you get the email, and it's like, "Your analysis is finished!" And...

LULU: And it is shortly after that that they realize crabs have evolved five separate times.

LATIF: What does that mean?

LULU: Like, on five completely different branches, from creatures that are not crabs, five different times the crab form has evolved. It's just like—it's like, bloop! Here's a crab over here! Bloop! Here it is over there. Bloop! Whoa! Way over there!

LATIF: And the thing that you're say—and it's the—it's the body shape is what we're talking about. So it's like, this body shape came up again and again and—and—hmm.

LULU: A pancake. A pancake with 10 legs, two of which—at least two of which have pincers. Yeah. Yeah. Exactly.

JO WOLFE: That these multiple different lineages that start from things that are kind of different turn out to look kind of the same. That's just weird, right?

LULU: This is why I called Jo. Because when she published that paper, the internet freaked out.

[ARCHIVE CLIP, TikTok: Creatures that are not related to crabs are eventually evolving into crab-like shapes.]

LULU: People were making TikToks.

[ARCHIVE CLIP, TikTok: So we're talking, like, shrimp and lobster and other crustaceans. All of them are evolving into similar forms.]

LULU: There were...

[ARCHIVE CLIP, TikTok: [singing] I could be hurtful, I could be purple, I could evolve into a crab.]

LULU: ...songs.

[ARCHIVE CLIP, TikTok: [singing] I could be crab, I could be crab, I could be crab.]

LULU: It seemed to open this speculative trap door.

[ARCHIVE CLIP, TikTok: My first thought is when are—when am I gonna be a crab, you know? When are wolves gonna be crabs, right?]

LULU: I mean literally, tens of thousands of likes and comments...

[ARCHIVE CLIP, TikTok: Everything is slowly turning into a crab.]

LULU: ...that were converging around a pretty similar interpretation—which was honestly, the one that I had—which was basically: does evolution want a crab?

LATIF: Hmm.

LULU: Is it just, like, right for life?

[ARCHIVE CLIP, TikTok: What this also means is that statistically speaking, there are space crabs out there somewhere in the universe.]

JO WOLFE: I think crabs might be Mother Nature's favorite shape. I mean, it's such a surprise to me that it became a meme.

LATIF: Okay. Okay, not to, like, denigrate the scientists who, like, put a lot of—I think it's super fascinating sort of the evolutionary tree that they're building. The crab appearing five times? Like, I don't know. I don't—I don't see it as, like, a profound thing. Five times out of how many times? Like, out of how many things that are being created? Like, is it—is it so crazy that, like, bats fly and birds fly and they figured out how to do that separately! Or, like—like, giraffes have long necks but also brachiosauruses had long necks. Or, like, worms are, like, long and stringy and snakes are long and stringy. Like, you're like, "Oh, okay. Like, yeah, that makes sense." Like, with the crabs, I don't know. It doesn't seem so much crazier than all the other stuff.

LULU: Okay but, like, you're talking about a neck or a wing, like, one body part, one nifty adaptation. With the crabs, it's like this whole complex situation. You've got multiple limbs, some of which have pincers, and a little pancake body and the googly eyes and you often walk sideways. It's like a very bizarre beast that keeps rising from the ocean again and again and again and again and again.

LATIF: Right.

LULU: And so inaccurate, wild speculations aside about what that means for all life, where all life is heading, a real scientific question remains, which is why does it keep reappearing? Like, what does the crabby shape actually help you with? What does it give you?

LATIF: Yeah, right. Right. So what is it good for?

LULU: So...

JAVIER LUQUE: [clears throat]

LULU: ...Javier Luque has thought a lot about this, and he said that scientists think a very important clue lies in this one moment about a hundred million years ago.

JAVIER LUQUE: It was a world that was warming up. It became really, really hot. The temperature of the globe rose several degrees. The poles melted, so it raised also the sea level several hundred meters. And those floodings also made very shallow seas that can get into the lands.

LULU: It was a moment that looked eerily like the one we're entering now. And like now, a bunch of species began dying off.

JAVIER LUQUE: So lobsters and shrimp dwindled.

LULU: Because they just couldn't survive all that change. But crabs...

JAVIER LUQUE: They radiated and bursted all over the world.

LULU: And scientists think that that goofy, leggy complex body shape is what allowed crabs to MacGyver their way into surviving.

JAVIER LUQUE: They can use their body as a Swiss army knife with a bunch of different tools.

LULU: So the legs, you know, they can scuttle on land of course, but they can also swim or fight or grab prey.

JAVIER LUQUE: Some of those legs grab a sea urchin, an anemone, and just use them as hats and camouflage themselves.

LULU: [laughs] Whoa!

LULU: And that sleek little pancake body? It helps them hide from predators way better than, say, lobsters with that big, honkin' tail to grab. And then there are all these subtler parts we don't really see, like these incredible gill-like things that allow them to breathe in both air and water, which lets them live, like, anywhere. They can live underwater, they live on beaches, they can live in marshes, they can live in rocky shores, they can live in trees. So that, like...

LATIF: How do they climb the tree? That's the thing I don't understand.

LULU: I don't—I mean, I don't know, dude. If you've got 10 legs, it makes it a little easier, right? And you weigh like a paper clip.

LATIF: But they're so little! Like, they can't hug the tree. Like, they don't—what kind of—how do you get purchase on there?

LULU: Yeah, but if they weigh nothing, you just like, then you just—like, how do beetles climb trees? Why does every bug climb a tree? Because it has a hundred legs and it weighs nothing. I don't know. [laughs] Sorry. I'm, like, angry at you. But I actually don't have—I'm like, "Duh!" But I don't know why.

LATIF: Okay, keep going. Keep going.

LULU: But let me just land the grand point here. The scientists think that what the crab body plan actually gets you, the reason it keeps evolving again and again is that its niche, the thing it is particularly good at is change.

LATIF: Hmm!

LULU: Upheaval. Chaos. Which Javier thinks will give crabs an edge in whatever world we humans are making for all of us.

JAVIER LUQUE: If we keep the world we're going, we are gonna be gone from here in the not-so-distant future, but crabs might start becoming more creative and using things and playing with sticks. Who knows, given enough time they might become the next us.

LULU: Given enough time, we probably won't become crabs, we'll more likely become obsolete and the crabs will keep surviving.

JAVIER LUQUE: [laughs] Exactly. Exactly. [laughs]

LATIF: This episode was reported by Rachael Cusick and Lulu Miller, and produced by Becca Bressler with help from Ekedi Fausther-Keeys.

LULU: With mixing help from Arianne Wack. It was edited by Pat Walters, who would love us all to take a brief hiatus on pitching crab stories.

LATIF: Yeah.

LULU: No promises, Walters. No promises.

LATIF: Rachael's Pop-Up Magazine piece had live music by Minna Choi and the Magic Magic Orchestra with sound design by Jeremy Bloom.

LULU: Special thanks to Heather Bracken-Grissom and her crab lab at Florida International University, Franz Anthony and the entire team at Pop-Up Magazine, Randi Rotjan, Jan Pechenik, Renae Brodie, Samatha Edmonds, whose story from The Outline introduced us to Mary.

LATIF: Stay tuned, because coming up next we're ditching the claws and we're gonna take flight.

LULU: Stay crabby. [laughs]

[LISTENER: Hi, this is Svend calling from Storrs, Connecticut. Leadership support for Radiolab's science programming is provided by the Gordon and Betty Moore Foundation, Science Sandbox, a Simons Foundation initiative, and the John Templeton Foundation. Foundational support for Radiolab was provided by the Alfred P. Sloan Foundation.]

LATIF: All right. We're gonna begin today's episode at a golf course/wedding venue, sort of.

AVIR MITRA: Okay.

LATIF: With our contributing editor and resident ER doctor Avir Mitra.

AVIR: Parsi time.

LATIF: Now one thing you need to know at the jump of this story is that Avir was raised in part in this religion that is mostly practiced in South Asia called Zoroastrianism. In particular, Indian Zoroastrians are called Parsis. It's not a big religion—less than 200,000 followers. But a fair number of them happen to be here in South Jersey.

[ARCHIVE CLIP, woman: Hi, how are you?]

[ARCHIVE CLIP, Avir: I'm good, how are you?]

[ARCHIVE CLIP, woman: You're Avir, right?]

LATIF: They rent out this space once a month to socialize, read scripture, eat tons of homemade Indian food. But this time, Avir, we did not send him there for any of that.

[ARCHIVE CLIP, Avir: I think I'll go grab some snacks.]

LATIF: Although it sounds like he did do some of that.

LULU MILLER: [laughs]

AVIR: Okay, so I'll have to be sticking this in your face. I hope you don't mind.

LATIF: This time, he was there to talk with his priest...

CAWAS DESAI: My name is Cawas Desai.

LATIF: ...about the mystery of what happens after you die. But not at all in the way that you think.

LULU: I'm Lulu.

LATIF: And I'm Latif. This is Radiolab.

LULU: And we should mention that this episode does deal with death, and there are a few brief graphic descriptions as well as a couple of swear words. Please listen with care. All right, here's Avir.

AVIR: Every time I tell people about how we—I guess our burial—well, it's not even—I don't know what the word is, not burial.

CAWAS DESAI: It's disposing of the dead.

AVIR: Yeah. I get a lot of weird looks.

CAWAS DESAI: Why? I mean...

AVIR: Well, maybe you could tell me what—what is our method of disposal of bodies?

CAWAS DESAI: The method of disposal is exposure.

LULU: Exposure?

AVIR: Mm-hmm.

LULU: What does that mean?

AVIR: We take our dead to this place called the tower of silence.

LATIF: The tower of silence.

AVIR: I've been to one in Mumbai. It's this hill in the middle of this big bustling city, but when you get there it's like just this super forested quiet area. It almost feels like a jungle, it's so dense. And at the top of it there's a flat, like, cement slab in a circle that's open to the sky.

LATIF: Okay.

AVIR: And there's walls around it but there's no roof on it. And there's different layers to it. The adult men go on the outer edge of this cement slab, women will go in the middle, and children, if they die, will go near the center.

LULU: Hmm.

AVIR: And there's thousands of vultures surrounding this place, just waiting.

LULU: Wow!

CAWAS DESAI: The vultures would ring the whole walls all the way—all the way around, hundreds of them. And then after the body was left, the vultures would descend in there.

AVIR: And yeah, the vultures just devour the body, and within a few hours all that's left is just a few bones.

LATIF: Whoa!

AVIR: Yeah. We call it a sky burial. And I don't know, I just think it's incredible. Like, in the religion the idea is that the second someone dies there's a corpse demon called Nasu. And they believe that that demon is what starts to cause the decay of the body. And so, you know, when the vultures eat the body, they're essentially protecting us from this demon.

LULU: Oh!

LATIF: Hmm.

AVIR: So that's one thing. There's also a more practical reason: if you were to bury the body, that's sort of polluting the earth which they don't wanna do. If they burn the body, that's polluting the sky. And they felt that if the vultures eat the body it recycles it back into nature.

AVIR: So these people were like environmentalists.

CAWAS DESAI: Yes, they were the original environmentalists.

AVIR: That's amazing.

LATIF: It's pretty metal.

LULU: It's beautiful.

AVIR: I—I agree. And that—that's the way it is, that's the way it's been for thousands and thousands of years up until 2006. This one Parsi woman named Dhun Baria, her mom died, and she had this suspicion. "Is my mom in the clear? Has her body been consumed? So she sneaks up into the tower, climbs up to the top, and what she saw there was completely horrendous. She felt like she had to tell the world.

[NEWS CLIP: This is CNN, IBN.]

[NEWS CLIP: Photographs from inside the towers of silence, where the Parsi community in Mumbai disposes of its dead. These forbidden photographs are creating big ripples in the small community.]

AVIR: There's just bodies, bloated, rotting bodies, disfigured bodies.

LULU: Oh, that’s horrifying.

AVIR: Just kind of plopped around that area.

LATIF: Ugh.

AVIR: And where you'd normally just see hundreds of vultures at the tower of silence, you don't see a single one.

CAWAS DESAI: The bodies were left to decompose at the tower of silence because there were not enough vultures to—to clean the body and pick the body clean.

AVIR: The vultures are just gone.

LATIF: At the tower?

AVIR: Like, everywhere. Millions of vultures. all over town, all over the state, all over India. Almost overnight they're all gone.

LULU: Wow, okay, so the question is where the heck did they all go?

AVIR: Yeah, that's the mystery. Which brings us...

MUNIR VIRANI: When species are in dire straits...

AVIR: ...to this guy.

MUNIR VIRANI: ...we wear our cape, we swing through the jungles and the forests and we—we save the day, right?

AVIR: A man by the name of Munir Virani.

MUNIR VIRANI: Here we go.

AVIR: He's a Kenyan biologist who studies birds. And back in the late-'90s he worked for the Peregrine Fund, which is this organization that basically saves birds of prey. And he had just gotten married, so he's at his new home in Nairobi just a couple weeks into his marriage.

MUNIR VIRANI: The telephone rang, it was Rick.

AVIR: ...his boss at the Peregrine Fund.

MUNIR VIRANI: And he said, "Well, I'm calling you because I wanted to find out, how do you feel about going to India?"

AVIR: So he tells his wife, "This whole marriage thing's been great. I'm really excited about all this stuff. I gotta go."

MUNIR VIRANI: So off I went.

AVIR: He flies from Kenya to India. Gets off the plane in Mumbai. And one of the first things he does he starts walking around this park. It's like a tiger reserve.

MUNIR VIRANI: And I remember distinctly this big banyan tree, which is a ficus tree, it's a tree of religious significance in the—in Hindu culture.

AVIR: It's like a tree of life type thing. And what he sees are, like...

MUNIR VIRANI: At least 17 vultures that were lying, sort of, you know, stomach down, wings spread out.

AVIR: You mean they were dead?

MUNIR VIRANI: They were all dead. They were dead.

AVIR: 17 dead vultures underneath him.

LULU: Oh, what a stark, like, image. What a metaphor, just the tree of life and then all this death.

MUNIR VIRANI: Yeah.

AVIR: And this makes no sense to Munir, because vultures are supposed to be super tough animals.

LULU: Hmm. Tough like how?

AVIR: I mean, they literally eat dead things, you know? The great thing about living things is they're pretty healthy, you know? They're healthy enough to be alive.

LULU: Yeah.

AVIR: And so I wanna get some of that, you know? Whatever you got going on I wanna put in my belly. But if you died, something went wrong with you, and now I'm just gonna make you part of me essentially by eating you, that's a bold move. But secondly, the second you die, you know, all these bacteria, viruses and fungi that you've been keeping at bay by being alive and having an immune system, you know, now all of a sudden they start taking over. So the way the vultures survive this is they have a super acidic stomach. It's up to a hundred times more acidic than our stomachs.

LATIF: It's like battery acid stomach.

AVIR: Yeah, exactly. Like, they can eat anything and it just melts away.

LULU: Wow!

LATIF: Wow!

AVIR: Some species also piss and shit acid, okay, onto themselves.

LULU: [laughs] Poop boots.

AVIR: [laughs] Poop boots. Because that keeps the bugs away.

LULU: It’s a little chemical defense?

AVIR: Exactly.

LULU: Wow.

AVIR: And if someone tries to eat the vulture, some species have evolved this response to just vomit acid on the predator.

LULU: Wow, that is gnarly!

AVIR: Yeah. And it turns out that all of this is so important because if you think about it, they're basically gobbling up all the diseases and bacteria, rabies, anthrax, all these things. And it stops with them. Like, they're the end of the line. They're like nature's immune system.

LULU: Rad!

LATIF: Yeah, that's a superpower.

AVIR: And they play such an important role that a bird just keeps evolving to become a vulture.

LULU: Whoa!

AVIR: This happened four times independently on Earth that we know of. Like, just across the world. Like, you know what I mean? It's almost like if I came out with, like, Dark Side of the Moon by Pink Floyd or some—like, I wrote that album and then someone else also wrote that album and, like, four people across the country just wrote that same album.

LULU: Why is that your metaphor? I love that.

LATIF: That's a really weird metaphor.

AVIR: And so going back to Munir looking at this banyan tree, it's super weird that there's all these dead vultures underneath it. And it gets even more puzzling because these vultures are not like old, decrepit, you know, vultures. And it doesn't look like someone shot them, you know, they didn't, like, get electrocuted in a power line or something. Like...

MUNIR VIRANI: The birds were in great body condition, they had a lot of body fat.

AVIR: There's just no reason for these birds to be dead.

LULU: Huh.

MUNIR VIRANI: This was like solving a detec—you know, like a murder mystery.

AVIR: So Munir's on the case, and what he needs is to get some dead vultures over to a lab in the US.

LULU: Okay.

AVIR: So he goes to India, and he's a young whippersnapper, and he's like...

MUNIR VIRANI: This is what we need to do. We need to get permits to send tissue samples so that people around the world can look at them.

AVIR: India's like, "No, you can't take these tissue samples."

LATIF: Why are they worried about that?

LULU: Yeah.

AVIR: You know, it just kind of got tied up in red tape because, you know, India doesn't want people taking their natural products and animals and seeds and wildlife and, you know, making money off of it.

LATIF: Okay.

AVIR: And by the time he's trying to negotiate with the Indian government, the vultures have already started dying off at an incredibly rapid rate. Like, in India, 95 percent of vultures are already dead.

LATIF: Oof!

LULU: Oh my God! That is—I mean, that is like a—just that's insane.

AVIR: It is. And so he's like, "Shit, like, what do I do now?" So he goes to Nepal, tries again. Same thing. They say no. And so he decides he's gonna go to Pakistan, a neighboring country, and see if he can get some dead vultures there. But...

MUNIR VIRANI: I look in the skies and there are thousands of vultures. And I mean thousands.

AVIR: Wow.

MUNIR VIRANI: You come across a dead buffalo or a cow, and there may be 200 vultures that are trying to get into it.

AVIR: But is—but isn't it bad because the vultures don't seem to be dying over there so you may miss the problem?

MUNIR VIRANI: Oh, there's a twist: we're still finding a few dead vultures, and they're showing the exact clinical signs they. Should not be dead. Right?

AVIR: He's there right before it happens. It's almost like he gets to rewind time just a little bit.

LULU: Wild!

LATIF: Hmm.

AVIR: So he's like, oh, this is perfect.

MUNIR VIRANI: Like, okay, this is where we should work, right? But of course, the question lies: are we gonna get tissue samples out of that country?

AVIR: He goes to the main guy in Pakistan, the bureaucrat who's gonna give him permission, and he's like, "All right, I gotta change my approach. So how am I gonna do this?"

MUNIR VIRANI: First of all, the India-Pakistan cricket series was going on, right? And as people know, there's a big rivalry between India and Pakistan. He looks at me and he says, "Munir, you want me to give you a permit to export tissue samples? Give me one reason why I should give you that." And I said, "Doctor Khalid, if you don't give us this permit then the Indians will beat you to it."

LULU: He bluffs?

AVIR: He bluffs.

MUNIR VIRANI: Boom, I just knew I had him!

LULU: Oh!

MUNIR VIRANI: So they gave us permits to export tissue samples.

LULU: Wow, go Munir!

AVIR: Yeah.

MUNIR VIRANI: So off we started.

AVIR: They get together a group of young research assistants, and basically had them pick up these dead vultures and cut them open. And what they see is striking.

MUNIR VIRANI: The inner organs were covered with a white, chalky paste.

AVIR: Does that look like toothpaste? Like, what does it look like?

MUNIR VIRANI: There's like powder, white powder all over the liver, the heart, the lungs, everywhere.

LULU: Can you wipe it off? Like, it's literally a substance?

AVIR: Yeah, yeah. Exactly.

LATIF: Weird.

LULU: Weird!

AVIR: So he goes to his senior colleague, this guy Lindsay Oaks.

LATIF: Mm-hmm.

AVIR: Oaks takes one look and he's like, "Oh, I know what that is. It's kidney failure."

LULU: Huh, what?

AVIR: It turns out that if you shut down a vulture's kidneys all this stuff backs up, turns into a paste, and gets deposited in all the organs.

LULU: What stuff?

AVIR: What that stuff is is uric acid.

LULU: Oh, birdshit!

AVIR: Which is bird pee, birdshit. It's the stuff that's making their pee and poop so acidic. They can't pee it out, and so now it's just—it's just depositing in their joints, in their organs, and you die.

LULU: Wow!

AVIR: So now they know, like, what's killing the vultures is kidney failure, but no one knows what's causing the kidney failure. As this story is progressing, the situation is escalating, and people are starting to get spooked.

LATIF: So it is happening in Pakistan, too?

AVIR: Yes, it's happening really quick. Like, when he first got there, there were 3,000 nesting vultures. And the next year it was half that. And the year after that it was half that again. And four years in they're down to just 400 nesting vultures.

MUNIR VIRANI: Yeah.

AVIR: Just like that. So the leading theory at this time...

LULU: Yeah?

AVIR: ...is that this is a virus.

LULU: Oh!

AVIR: Right? Because look, it started in Southeast Asia, so they're thinking okay, maybe going east to west this virus is spreading, Southeast Asia, Nepal, India.

MUNIR VIRANI: And if this virus moves further west into Pakistan, Afghanistan, into the Middle East and comes into Africa where vultures play such an important role, the consequences would be completely dire.

AVIR: Remember, these vultures are like nature's immune system.

MUNIR VIRANI: They perform probably the most important role than any other animal or groups of animals combined.

AVIR: Like, if we don't have them digesting all this bacteria, diseases and viruses, who knows what's gonna happen to the entire world?

MUNIR VIRANI: So we're really fighting against time.

AVIR: And, you know, just to step back, we know they're dying of kidney failure. Now what's causing the kidney failure? In theory, it could be any number of things. It could be a virus, it could be bacteria, fungi, it could be environmental changes, it could be toxins. And so people are testing for this and that, and they're just not finding anything.

LULU: Hmm.

AVIR: And then in 2001, Munir and his colleague Lindsay Oaks...

MUNIR VIRANI: We were in a meeting in Spain.

AVIR: ...they're at some sort of bird conference.

LATIF: Vulture Con.

AVIR: Vulture Con, exactly. They're in their head-to-toe vulture costumes.

LATIF: Yep. I could picture it. I could picture it.

AVIR: And, you know, this is not a great year for Vulture Con. Everyone's covered in talcum powder.

AVIR: And I remember Lindsay and I sitting in the square in Seville, sipping espressos.

AVIR: So Lindsay's like, let's just start from scratch here.

MUNIR VIRANI: You know, just get a piece of paper.

AVIR: They pull out, like, a napkin and just start writing on the napkin.

MUNIR VIRANI: We were like kids putting down these flow diagrams, right?

AVIR: "Okay, what do we know? Kidney failure. What can cause kidney failure?" Toxins. Nothing. Viruses. Nothing. And then, Munir says, Lindsay asks this question...

MUNIR VIRANI: He said, "Okay."

AVIR: ...that kind of cracks the whole thing open.

MUNIR VIRANI: "What's going into the vultures?" I was like, "Well, food."

AVIR: Generally cattle, right? Livestock. And so Lindsay's like, "We've been focusing so much on what goes into the vultures..."

LULU: Hmm.

MUNIR VIRANI: Have we seen what's going into the livestock?

LATIF: Huh.

AVIR: So they take a new approach. They go back to Pakistan, and they start going around to different villages, and just knocking on people’s doors being like, "Hi, I have a bunch of questions for you about your cattle," you know?

LATIF: Mm-hmm.

AVIR: And as they're processing the surveys they're noticing, like, oh, this phrase keeps popping up over and over again.

MUNIR VIRANI: It just stood out.

AVIR: We give them...

MUNIR VIRANI: Diclofenac.

LULU: Diclofenac.

LATIF: Huh.

AVIR: Yeah. This drug diclofenac. It's actually a painkiller. It's in this class of drugs called NSAIDs, Nonsteroidal Anti-Inflammatory Drugs. That includes, you know, drugs like Advil, Motrin, Aleve, ibuprofen.

LULU: Hmm.

AVIR: And these farmers were giving diclofenac to cattle, because cattle, just like people, you know, get old, get aches and pains.

LATIF: Mm-hmm.

AVIR: They wake up one morning and their knees hurt.

MUNIR VIRANI: If your cow had a limp and was unable to carry the produce to market, you just pumped it with diclofenac. You just did.

AVIR: And even after the cow gets, like, too old to pull your cart or whatever, the farmers a lot of times, at least the Hindu ones, would still give them diclofenac because they're seen as sacred animals. Half of me is Zoroastrian, the other half of me is Hindu. So Hindus, you know, they don't eat cows. I mean, I do eat beef, but don't tell my grandma, or whatever. I'll never forget, I was like in eighth grade, and I was like telling my grandma who doesn't speak much English and I don't speak much Bengali, and she's like, "We don't eat cow." And I was like, "Yeah I do, because I love burgers, and that's made of cow." And she's like, "No, no, it's not. You don't eat cow." So then I called my dad into the room. I was like, "Dad, aren't burgers made out of cows?" And he just straight up was like, "No," and just walked out of the room. And I was, like, confused for, like, five years after that as a child.

LULU: [laughs]

AVIR: So anyway, Munir and the team realize that farmers are giving their cattle this drug, this painkiller diclofenac. So they take some organs, send them to the US, and test for levels of the drug. And sure enough, all the vultures that were covered in that chalky white paste...

MUNIR VIRANI: Came back positive.

LULU: Huh.

LATIF: Huh.

MUNIR VIRANI: And so suddenly a pattern was evolving.

LATIF: But that's still not a—I feel like we've gotten—you've connected the dots but it's the dot that needs to be connected. It's now in the vulture, but it—we don't know for sure it's causing the sickness.

AVIR: I love that you said that, Latif, because we see diclofenac in the vultures that are dead, but is that the reason that they're dead?

MUNIR VIRANI: And so now we have to show that experimentally.

AVIR: So this is where things have to get really dark.

LATIF: Oh, this story has been just a funfetti cake until now.

LULU: [laughs]

AVIR: Yeah. So I told you, you know, vultures dying left and right. Munir and his team studying these vultures, they see all these poor baby vultures...

MUNIR VIRANI: These were birds that fell off the nests after their parents died.

LATIF: Mm-hmm.

AVIR: And so they have been over time sort of sheltering some of these baby vultures and raising them.

LULU: And giving them what to feed? Like little dead rats?

AVIR: Yeah, little dead rats. All the little, you know, whatever. Like, bougie vulture food.

LULU: Okay.

AVIR: These vultures are doing great. And they realize the only way that they can really...

LULU: Don't tell me.

AVIR: Yeah.

LULU: Keep telling me. Say it.

LATIF: I—I don't know where you're going. Where are you going?

AVIR: Okay. The only way they can really prove for sure if diclofenac kills vultures is to poison their babies.

LATIF: Oh, okay.

AVIR: They swapped out their perfect Whole Foods meals with some buffalo that had been given diclofenac. And they died. And on top of that, they realized all the vultures died in India first because the drug was approved there, like, four years before it was approved in Pakistan.

LULU: Whoa!

LATIF: Oh!

LULU: So it wasn't an ecological spread, it was a market spread that they were seeing, like, wash across the continent.

LATIF: Whoa!

LULU: That's wild.

AVIR: Yeah.

MUNIR VIRANI: It was amazing. It just—it felt like a huge burden had been lifted off my back.

AVIR: And so in May, 2003, Munir and his team go back to Vulture Con. And Lindsay Oaks gets up on stage and announces it.

MUNIR VIRANI: With his very soft voice and he just talks about the meticulous way...

AVIR: Here's what we studied, here's what we found, here's what we did to our pet vultures, here's what happened.

MUNIR VIRANI: And then there was pin-drop silence. And then there was this applause that just went on and didn't stop and people stood up.

AVIR: They all realized, like, this is it.

LULU: Wait, I guess I'm just wondering, was there any parallel? Were US vultures dying off?

AVIR: Yeah, I think the difference is, like, we don't care as much about cows in the US.

LULU: Oh, so they're not living—we're eating the meat, so the vultures aren't getting it.

AVIR: Right, we just eat them when they're, like, young and healthy before they have any problems.

LULU: It's so weird that this is about, like, caring for the cow. It makes you want to, like, make the cow not be in pain which then surprisingly apparently kills all the vultures.

AVIR: Yeah, it's weird. And, you know, as a doctor I can kind of relate to that. I prescribe these NSAID drugs like ibuprofen, Motrin, Aleve, Advil. You know, I prescribe these all the time. And believe it or not, one of the most common causes of kidney injury in humans is also NSAIDS.

LATIF: Really?

AVIR: Yeah. Which is funny, right? Because, like, we were looking at these vultures saying, like, "Oh, that's so bizarre that this diclofenac is messing up their kidneys." Meanwhile, in a different parallel universe of medicine, because we're not talking to—I don't talk to vulture biologists, they don't talk to me, right? We’re figuring the same thing out in humans.

LATIF: Wow.

LULU: Wow. Wait, so when did humans become—when did we become aware of this?

LATIF: This sounds really bad.

LULU: Yeah, it does.

AVIR: There were case studies coming out all along the way, but the landmark study was in the year 1999.

LATIF: Okay.

LULU: Okay.

AVIR: So interesting, right? Because the vulture thing is happening at the same time.

LULU: Yeah. Yeah.

AVIR: And we've also learned that they can cause intestinal bleeding, strokes, heart attacks. All these problems trickle down from the use of NSAIDS.

LATIF: Whoa! Why?

AVIR: Yeah, basically, you know, NSAIDS are inhibiting this molecule that cause pain. And so you take them and you don't feel pain, which is great. But it turns out that these same molecules do a lot of really important stuff in the body, and so when you inhibit them, you know, you cause all these other problems that no one anticipated when we made these drugs.

LATIF: I—okay, I have a million questions but I'm gonna just cut to the chase. Like, we take these drugs all the time. All of us. Like, should we stop taking these drugs?

AVIR: No. No, I don't want to scare you into thinking, like, these are evil drugs. They are great drugs, they work really great. But they're not candy. The way we think about it in the hospital as a sure—as a quick, like, thing is like, if you're over 65 and taking these drugs every single day for months on end, like, see a doctor. Let's figure something out for you.

LULU: Oh, interesting. Okay.

AVIR: If you're young, like, don't worry about this. If you're healthy, don't worry about this. And in general, don't freak out about this at all, but this is more of a macro scale, you know?

LULU: Hmm.

LATIF: Like, I just see there being a vulture-faced reaper who is like, "Oh, you're trying to avoid pain? Oh, you're trying to avoid death?" Like, it's—like—like, if you—if you budge it over here it's gonna budge right back over there, you know?

AVIR: Mm-hmm. That's how it feels to me. As, like, a doctor it's very frustrating because, you know, what am I supposed to do? And, you know, I'm—I'm gonna keep taking these meds, I'm gonna keep giving these meds. They work. They do—they—they do help people a lot. But yeah, like you said Latif, there's—there's a little cost there.

LATIF: Yeah.

LULU: Or, like, a big cost I guess if you're one of those unlucky people who gets sick and dies from the drug.

AVIR: Yeah.

LATIF: Or, I guess, if you're a vulture.

AVIR: Well, the vultures are doing okay, actually. Scientists found an alternative drug for the cows, and India, Pakistan and Nepal, they all got together and actually banned diclofenac for veterinary use.

LATIF: Wow.

LULU: Okay.

AVIR: And the populations of vultures stabilize.

LULU: Caw!

AVIR: So that's that story.

LATIF: Huh. Does that—what does that mean for the tower of silence? Is it back?

AVIR: No, not exactly. Because, you know, these vultures only have, like, one offspring per year.

LULU: Oof.

AVIR: So it's a slow process, you know?

LULU: Huh. So what are Zoroastrians doing in the meantime when they—when they lose somebody?

AVIR: So yeah, for Parsis, it's still rough. They started by trying to use chemicals that they would put on the bodies to help them decompose faster. Another thing they considered was putting a big sun glass. Like, basically think of, like, a magnifying glass where you, like—if you were a kid you'd, like, burn ants with a magnifying glass.

LULU: Yeah, this feels dangerous.

AVIR: So they were—they were thinking about that.

AVIR: We have to sit. Here, sit over here.

AVIR: Eventually I started wondering...

AVIR: Well, what about you? When you die, what do you want to do?

AVIR: ...what does my mom want?

JASMINE MITRA: Well, since there are no vultures anymore—which I actually think is a great idea, but since there aren't any vultures left, I would prefer to be cremated. Or the new green burial thing, you know, I wouldn't mind if a tree grew using my body.

AVIR: But when my mom said that, I kind of thought, like, wait a minute, like, no. Like, I thought the whole point was that the only way to get to heaven was to go through the tower of silence.

CAWAS DESAI: Oh, yeah. The orthodox believe that they won't go to heaven if their bodies are disposed of except in a tower of silence.

AVIR: But my priest says...

CAWAS DESAI: As far as I'm concerned they're—they're—they're daft, they're nuts.

AVIR: There's no vultures right now. So the tower of silence is off the table.

CAWAS DESAI: My father died in hospital in Boston, and we had his body cremated. He—he himself had said that, "Look, if I die, don't take—don't have my body shipped back to India. Have it cremated over here." You don't go to heaven or hell depending on how your body's disposed of. I mean, who cares? Once you—once you're dead, you're dead. I mean, really.

AVIR: You're sort of a rebellious priest.

CAWAS DESAI: I'm not a rebellious priest, I mean, I just think for myself.

AVIR: He says he's just being practical, which is what Parsis do.

CAWAS DESAI: It's what Parsis do, what they should do. [laughs]

AVIR: The whole reason our religion created the tower of silence in the first place is because it was practical, simple, elegant. And now it's not—until the vultures come back, anyway.

AVIR: Cool, thank you. I don't have anything else.

CAWAS DESAI: You're very welcome.

AVIR: I'm glad to have an uncle that knows everything about everything.

CAWAS DESAI: Stop calling me uncle, for crying out loud. Makes me feel old and decrepit.

AVIR: [laughs]

LULU: Contributing editor Avir Mitra. That's our show for this week. This episode was reported by Avir Mitra with help from Sindhu Gnanasambandan. It was produced by Sindhu Gnanasambandan with music and sound design by Jeremy Bloom, with mixing help by Arianne Wack. It was edited by a rebellious editor Pat Walters who has been known to think for himself, and to occasionally spit battery acid urine when—when attacked. Watch out for that one. Special thanks to Daniel Solomon, Heather Natola and the Raptor Trust in New Jersey, and Avir's uncle Hoshung Mola who told him about this story over Thanksgiving dinner. That's how the reporting gets done, over mashed potatoes and stuffing and not hamburgers because Avir doesn't eat hamburgers. I'm Lulu Miller.

LATIF: I'm Latif. Let us know if you want us to include vulture poop boots in our next round of merch.

LULU: [laughs]

LATIF: That's it. Thanks so much for listening.

LULU: Thanks, vultures. Caw! Caw! Bye bye!

[LISTENER: Radiolab was created by Jad Abumrad, and is edited by Soren Wheeler. Lulu Miller and Latif Nasser are our co-hosts. Dylan Keefe is our director of sound design. Our staff includes: Simon Adler, Jeremy Bloom, Becca Bressler, Rachael Cusick, Ekedi Fausther-Keeys, W. Harry Fortuna, David Gebel, Maria Paz Gutiérrez, Sindhu Gnanasambandan, Matt Kielty, Annie McEwen, Alex Neason, Sarah Qari, Anna Rascouët-Paz, Sarah Sandbach, Arianne Wack, Pat Walters and Molly Webster. With help from Andrew Viñales. Our fact-checkers are Diane Kelly, Emily Krieger and Natalie Middleton.]

[LISTENER: This is Joel Masbacher calling from New York City. Leadership support for Radiolab's science programming is provided by the Gordon and Betty Moore Foundation, Science Sandbox, a Simons Foundation initiative, and the John Templeton Foundation. Foundational support for Radiolab was provided by the Alfred P. Sloan Foundation.]

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