Episode 10: First ascent of a sky island

In the heart of a South American rainforest, a team of rock climbers and biologists are the first to climb Mount Weiassipu in search of new species of frogs—and adventure.

Mark Synnott hangs from the side of Weiassipu. Synnott was part of an expedition that trekked 60 miles through rugged jungle and scaled Weiassipu’s sheer cliff walls in order to search for new species of frog.
Photograph by RENAN OZTURK

In the most remote part of Guyana, unique plateaus called tepuis—also called “sky islands”—rise up from the jungle. At the top of these tepuis are unique ecosystems filled with plants and animals never before seen by human eyes. But getting there is no small feat. Unable to scale the sheer cliff face himself, 80-year-old biologist Bruce Means teamed up with professional climbers and indigenous people to trek through the jungle and get to the top of the tepui Weiassipu in search of frogs and adventure. 

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PETER GWIN (HOST): El Dorado, the legendary city covered in gold, doesn’t seem like a place that could really exist, but then neither do tepuis.

In the Guiana Highlands, a remote region of South American rainforest, flat mountains with vertical walls rise high above the forest canopy, poking into the clouds. These mountains are known as tepuis and are ringed by giant waterfalls which shoot out from their sides. In 1595, while on a quest to find El Dorado, 
English explorer Sir Walter Raleigh was probably the first European to see a tepui, off in the distance. He’d heard rumors that it was a “mountain of crystal.” But he had to turn back before reaching the mountain because the rainy season had started and his group was running low on supplies.

Even today, getting to the base of a tepui is an enormous undertaking.

BRUCE MEANS (HERPETOLOGIST): When you’re in a cloud forest, it’s often (whispers) completely quiet. Just no sound at all. So you look around, it’s misty. You don’t hear a thing. But it—a lot of people think that’s eerie.

GWIN: Bruce Means is a biologist who has been studying ecosystems like this for more than 35 years.

MEANS: It causes me to do what I’m doing—to shut up and just listen to the silence. And at night in a hammock, when it’s cloudy and there’s no moon and it’s completely dark, it’s pretty wonderful. Then it starts raining and the rain comes down, just like (growls) the rain in the tropics can come down—like somebody pouring a bucket on a tin roof. Just really, really come straight down. No wind, nothing, just roar. And then in a few minutes, (whispers) it’s quiet again. It’s quiet again.

GWIN: Sir Walter Raleigh never found a city of gold. But it’s easy to see why he thought something fantastical—maybe even impossible—was somewhere among these strange mountains.

MEANS: My word for tepuis is phantasmagorical. They are special, wonderful, remote, beautiful places on this planet that give me as much—what would you say?—euphoria as I have ever gotten from any place I’ve ever been, and I’ve been to a lot of them. (whispers) I wish I could go back. 

GWIN: I’m Peter Gwin, editor at large at National Geographic magazine, and you’re listening to Overheard, a show where we eavesdrop on the wild conversations we have here at Nat Geo and follow them to the edges of our big, weird, beautiful world.

This week, we follow scientist Bruce Means. He was traveling to the tepuis on a quest for his own kind of El Dorado: undiscovered species of frogs that would reveal a new chapter of life in the rainforest.

MEANS: If you really want to study some interesting evolutionary activity and some ancient stocks of organisms, go to tepuis.

GWIN: OK, let’s go to tepuis, right after the break.

GWIN: Bruce Means is the type of researcher who needs to be out in the wilderness to do his work. It’s what he calls alpha-level science: making discoveries of new species and their way of life. But in order to get to some of these unexplored parts of the world, he needs the help of people like Mark Synnott.

MARK SYNNOTT (WRITER): I am a climber, adventurer, sailor, writer, storyteller.

GWIN: Mark Synnott is an all-star in the mountaineering world. He’s been on climbing expeditions all over the planet from Pakistan to the Arctic Circle. But before any of that, in the late ’80s, he saw an article about tepuis in National Geographic.

SYNNOTT: And I read that article and I photocopied it. I paid a dollar per page to get color copies.

GWIN: The article had a lot to say about the history and biology of tepuis.

SYNNOTT: But what I saw, at least initially, was the pictures of these incredible quartzite cliffs. My mission in life at that point was to try to find and climb and pioneer first ascents in all the biggest, best cliffs in the world. And so I put tepuis on the list.

GWIN: Tepuis are tabletop mesas that over millions of years eroded out of an ancient plateau of rock, where today, the borders of Venezuela, Guyana, and Brazil meet.

SYNNOTT: And they are sticking up out of the jungle like islands poking out of a foggy ocean.

GWIN: Tepuis are sometimes called “sky islands” because of their strange appearance. But they are also like islands in another important way: Their sheer rock walls isolate the environment on the top from the jungle hundreds, sometimes thousands, of feet down below.

Like the Galápagos Islands, this isolation over millions of years of evolution has made the tops of tepuis a wonderland for biologists. Some frog species only live on the top of a single tepui.

Discovering those species is part of the work Bruce Means has devoted his life to. But Bruce is a biologist, not a mountain climber. So he and Mark were a perfect match.

GWIN: Do you remember your first impressions of Bruce Means?

SYNNOTT: So he’s an 80-year-old dude now. When I first met him, he was 60. But the guy is a stud.

GWIN: Bruce’s specialty is herpetology, so reptiles and amphibians. In his long career he’s sprinted after venomous snakes in the Australian outback and has had life-threatening bites from diamondbacks in the U.S., not once but twice.

Since they first met, Mark has gone with Bruce on several trips to the tepuis,

helping him get to the hard-to-reach places in this crazy landscape where new species might be discovered.

Here’s a quick story about Bruce that I think will give you a sense of the kind of biologist he is. It has to do with a South American pit viper called the fer-de-lance.

SYNNOTT: I believe the fer-de-lance is one of the most deadly snakes in the world.

GWIN: As dangerous as the fer-de-lance is, finding one is fairly rare. On Bruce’s first three trips to the tepuis—a total of 26 days—he didn’t see a single snake of any kind.

So on one trip with Mark, when local guides spotted a fer-de-lance, nothing was going to stop Bruce from studying it.

SYNNOTT: Well, on that trip, the Akawaio started yelling that they had found the snake. And at that moment Bruce was down at the river washing up, and he came running up to see what was going on, wearing only a pair of Tevas and his glasses. And he’s like, “Where’s the snake? I’m going to catch the snake.” And the man is naked. And then he did—and he found a fork stick, and he pinned the snake’s head down, and he picked it up. And he caught the fer-de-lance. And I have this picture of him holding the snake with the two fangs out, and you can see the venom shooting out of the fangs.

GWIN: So for a biologist like that, tepuis are the perfect place to go. But it’s about more than adventure. Bruce says tepuis are one of the few places in the world a biologist can go, see an animal, and instantly know that it’s new to science.

The frogs around the tepuis have some truly strange and interesting biology. Each one has an adaptation like its own weird superpower. There’s the glass frog with transparent skin—you can see its heart beating—the pebble toad which curls into a ball and rolls downhill to avoid predators, and a whole genus of frogs called Stefania which skip the tadpole stage by gluing eggs onto the mother’s back.

MEANS: And for a while, when they first hatch from their eggs, you can see maybe a dozen little froglets riding around on mamas’ backs.

GWIN: These adaptations are nature’s way of solving difficult problems.

Bruce thinks Stefania skips the tadpole stage because at some point in their history they had to adapt to a drought. And humans can learn a lot from these adaptations.

MEANS: Frogs, especially, are noted for having noxious skin secretions. They’re very complicated organic molecules.

GWIN: In a way, rainforests are like gigantic pharmaceutical laboratories. Over all those millions of years of evolution, nature’s been perfecting chemicals in living things—think poisons and perfumes. And all of these are designed to impact other forms of life.

MEANS: Some of them are blood thinners. Some of them are clotting characteristics. They all have potentially high value to man.

GWIN: There’s a long list of medications that got their start as natural defenses. For example, quinine, the first effective treatment for malaria, comes from the bark of an Amazonian tree. Frog secretions are used in many folk remedies, but their medicinal potential is still largely unexplored.

So finding new frog species is the first step in taking advantage of natural selection’s research and development.

Bruce had made 32 trips to tepuis, studying the life at their tops and down below in the jungle. But neither he nor any other biologist had studied what was living on the vast cliff faces—the sides of the tepuis.

MEANS: So then Mark and I said, Hey, Weiassipu! It’s never been climbed, we know pretty much a lot about, you know, the logistics. Why don’t we try Weiassipu again?

GWIN: Mark and Bruce had been to the Weiassipu tepui before. Back in 2012, they flew to the top by helicopter. Mark remembers that at the time it was literally uncharted territory.

SYNNOTT: I’ve told people that Weiassipu wasn’t on our map, and people haven’t believed that. And so I found the old map, and there you go: It wasn’t there. There’s like a blank spot.

GWIN: Trekking from the bottom of a river basin to the top of a tepui could help Bruce understand about how life changes with elevation. Bruce wanted to know: Are the tepuis truly isolated like islands, or are frogs, over time, able to move up and down them. So Mark and Bruce began putting together a plan to return to Weiassipu.

SYNNOTT: But instead of flying in in a helicopter, we would trek in from Guyana, and that’s 60 miles. And then we would climb the tepui, which nobody had ever done. We would do an elevational transect, where he would look for new species and all the different elevation zones up the mountain. And then we would try to find this missing link species of a frog called Stefania that Bruce had seen on the top of Weiassipu when we were there, but he hadn’t been able to collect it and get its DNA.

GWIN: The whole plan was ambitious, but there was one part that seemed completely insane. The final climb to the top of the tepui would be tough for Mark—a professional rock climber with years of experience. But Bruce had almost no climbing experience and would turn 80 years old during the trip. How do you get an 80-year-old biologist to the top of a tepui?

SYNNOTT: We eventually came up with this idea where we were going to put Bruce into a portaledge and we were going to haul the portaledge up.

GWIN: It’s almost like a window washer kind of setup, the way big buildings have their window washers kind of move up and down the face.

SYNNOTT: And that was the idea. And so I kind of had this picture where he’s like, you know, laying on his little platform and we’re hauling him up through the sky, and Bruce is reaching out and like, “Oh, look, a cool little frog in this crack” and “Oh, look at this little plant,” and that kind of stuff. Of course, this was kind of a fantasy.

GWIN: Yeah, there was no way Mark could do all this by himself.

SYNNOTT: And so I just said to myself, I’m going to recruit a couple of ringers and I’m just going to make it a done deal. So no matter what, we’re getting up the cliff. The first person I called was Alex Honnold.

GWIN: Alex Honnold is one of the most famous rock climbers on the planet. You might remember him as the star of Free Solo, a documentary about his ascent of Yosemite’s El Capitan, where he didn’t use ropes. Yeah, nuts. Anyway, Mark and Alex are old friends.

SYNNOTT: There is no one on Earth who is better at getting a rope to go up a cliff than Alex Honnold. The thing is that Alex had never climbed a tepui before. And so I also wanted to have a real tepui specialist. And it turns out there’s a Venezuelan guy named Federico Pisani, and his nickname is Fuco. And Fuco is the world’s most experienced tepui climber.

FEDERICO “FUCO” PISANI (CLIMBING EXPERT): I’ve been exploring the tepuis for many years—20-plus years—but this was crazy.

GWIN: The thing that made this climb so crazy, even for a seasoned veteran like Fuco was that just getting to the base of the mountain would take days of hacking through wilderness. And on top of all that they would also be filming a National Geographic documentary so they had to bring along an entire film crew. Helping them carry all their equipment and just survive was a group of guides from an Indigenous group called the Akawaio.

PISANI: We did a long day of traveling through the river with these curiaras, these boats made out of—how are they called? Dugout canoes, made out of one tree.

GWIN: After a day on the river, the expedition spent 10 days traveling on foot.

At first they followed established hunting trails and then veered off, hacking through pristine jungle.

PISANI: We were opening trail in very thick jungle. The Akawaios were the masters of the jungle. They were using all their skills to open the trail in a really short time.

GWIN: Even with the help of the Akawaio, the trek was incredibly difficult. There was no escape from the relentless weather conditions.

SYNNOTT: We were supposed to be there during the dry season, and it rained pretty much all day, every day. So I would hate to see what the rainy season is like. You’re just soaked. When it rains all the time and you have a ground that’s covered in vegetation and the Earth is super rich, guess what you get? Mud. And so we called it mud world. So at the end of the day, your legs are covered in mud. If you’re lucky, just up to the knee, like completely and utterly covered in mud.

GWIN: And then after an exhausting day of slogging through mud world, just getting into his hammock was a challenge.

SYNNOTT: I and I looked over and there was this Akawaio guy next to me in his hammock, and he took these two wooden stakes and he drove them into the ground right next to his hammock. And then he took his boots and he put them upside down on top of the sticks. So I was like, “That’s it. That’s brilliant. That’s what I want to do.” So I put two sticks in. I didn’t realize that I shoved one of the sticks into a termite nest, and so, I mean, we’re talking thousands of termites went into my boot that night. And they liked it. And they stayed in my boot. And so the next morning, I pulled the boot off the stick and I’m just thinking, Oh, my boots on a stick, like I’m all set. And so I just shoved my foot in. I didn’t check it, and I just shoved my foot into thousands of termites.

GWIN: Rain, mud, termites. The jungle seeped and crawled into every part of their clothing and gear. And the further they got into the wilderness, the more wild it became.

SYNNOTT: Imagine what the world was like before there were human beings. So the final valley leading up to Weiassipu according to the Akawaio was a place where no one had ever been—ever. No person, no human being, only animals.

GWIN: Mark and the team finally reach the tepui, right after the break.

GWIN: Along the trail the group stopped to collect specimens. Especially frogs. Fuco—an amateur biologist—learned some of the basics of frog catching from Bruce.

GWIN: You know, South America is famous for its poisonous frogs. And you guys were out there looking for frogs. Were you concerned at all about picking up the wrong kind of frog or a frog that might somehow have venom that would be dangerous to you?

PISANI: Oh, well, I thought it was dangerous to me until I saw Bruce licking the frogs to test if they were poisonous or not.

GWIN: Wait a minute. He’s licking the frogs?

MEANS: So every frog I capture, I smell it and I lick it. What do those toxins do for the frog? They cause aversive-repulsive sort of reactions to the mammals and birds and other animals that try to eat them. I’m a mammal! So I’m going to respond exactly the same way a predator would respond if I taste their skin secretions.

GWIN: Bruce was definitely in his element. But his 80-year-old body was having a hard time keeping up with the trailblazing. Canoeing for miles, hiking up and down the jungle, slogging through mud, and trying to keep his footing was exhausting.

SYNNOTT: I didn’t realize how challenging the trek was going to be for Bruce. He didn’t train, and his plan was that he was going to toughen up along the way. Which, you know, hypothetically could work. But not if you’re 79. If you’re 79 and you go out and you just beat the crap out of yourself, you’re not stronger the next day, you know, you’re whupped.

GWIN: About a week into the trip, Mark and the climbing team left Bruce at a camp to scout the path ahead to Weiassipu. As they got closer to the tepui’s base, the ground became a minefield of loose boulders and dead, rotting trees. Everybody started to wonder if it was a good idea to stick to the plan to take Bruce to the top.

MEANS: I was going to put everybody else at risk. And it didn’t take much to convince me that, yes, for the good of the expedition and the ultimate results I was looking for, there was no problem for me to agree not to continue beyond where I stopped.

GWIN: From then on, it was up to the small team of climbers to complete the expedition and search for the frogs that would help complete Bruce’s research. The last time Bruce was at the top of Weiassipu, a decade earlier, he caught a glimpse of what he thought was a new species of Stefania, the frog that raises its babies on its back. Catching a specimen of that frog would give Bruce valuable genetic information that could help reveal whether frogs are truly isolated or if they are able to move up and down tepuis.

Fuco radioed down to Bruce and promised to try to find the frog.

FUCO: OK, Bruce, I’m going to do my best to try to find the lucky Stefania.

MEANS: Fantastic, Fuco. I know if anybody can do it, it’ll be you.

GWIN: Finally after 10 days, the climbing team made it to the base of Weiassipu and began their ascent.

SYNNOTT: The thing about the tepui is it’s not entry-level climbing. The walls are crazy.

GWIN: The walls of Weiassipu were more than vertical, they actually angled backwards.

SYNNOTT: If you put your back to the wall and you tilted your head back and looked up, the view would be similar to if you were standing at the base of a battleship at the bow.

(Climbing noises)

SYNNOTT (IN FILM): The roof is really not looking good. It’s kind of extreme.

GWIN: At the end of their first day of climbing, they hit a major challenge—150 feet above South American jungle, the wall became a “roof.”

SYNNOTT: So a roof, you know, in climbing terminology, it’s a spot where the cliff just goes horizontal. So it’s like looking up at the ceiling, you know, and you’re in your living room and then climbing out across that.

GWIN: This mountain had never been climbed before. So no one knew exactly which handholds were trustworthy.

SYNNOTT: And then there was this diving board of rocks sticking out. It was obvious that you could go out it if you felt like it would stay stuck to the mountain. But if it didn’t, it would be an absolute, unmitigated disaster. If it comes in contact with your rope, it could cut it. And so it can’t—that cannot happen. 

GWIN: To make matters worse, the sun was starting to set and the climbers hadn’t brought headlamps to help them find their way back to their shelter for the night.

SYNNOTT: Any normal person wouldn’t launch out this thing, you know, pitch-black without a headlamp. But they’re not Alex Honnold. And so he just reached out on this diving board thing and went out hand over hand on it.

HONNOLD: All right, Mark, here we go. This is the crux.

SYNNOTT: OK, I gotcha.

(Climbing and grunting sounds)

GWIN: Mark watched as Alex worked his way along the edge, paused, and then calmly dangled by one hand over the void.

SYNNOTT: Nice, Alex.


SYNNOTT: And it was one of the most incredible bits of climbing that I’ve ever seen because he was just dangling out in space.

GWIN: On day two of the climb, Mark was leading when they came to the next dangerous spot.

SYNNOTT: The rock went from perfect, beautiful, super solid quartzite to something that I would describe as resembling a real-life game of Jenga.


SYNNOTT: So none of the rocks were attached to the mountain; they were just stacked up like bricks that didn’t have any mortar in between, and climbing up through that was one of the scariest things that I’ve ever done.

GWIN: Seven hundred feet up on the side of the tepui, they remained shrouded in the ever present fog. But the third morning, heavy rains cleared away the clouds. And now they could see the green canopy of the jungle stretching out far below and across the valley, Weiassipu’s neighboring tepui, Mount Roraima, 
with its gushing waterfalls.

SYNNOTT: It had rained so much that all the waterfalls were just pumping off the cliff and out from inside of the cliffs. And it was rainbow, rainbow, rainbow, rainbow, rainbow, every single one. I mean, a dozen waterfalls the size of the Empire State Building crashing into these incredible plunge pools at the base of the cliff and the spray is this halo of rainbow. I think that was the most spectacular thing that I have ever seen in my entire life.

GWIN: They finally made it to the top of Weiassipu and found themselves in the midst of the alien world of the top of the tepui.

SYNNOTT: A lot of the horizontal surfaces are covered with bogs. When you stand on the land and you and you bounce up and down a bit, and the whole land all around you, it’s like jiggling. So the whole thing is like this weird jelly surface on the top of the rock with bizarre plants. There was sort of a little bit of forest with these bizarre, little stunted Dr. Seussian trees.

GWIN: The clouds and rain returned, and soon they were shivering. Mark says they were borderline hypothermic, but they kept pushing through the heavy vegetation, searching for the Stefania frog in the rain. Since most frogs are nocturnal, night was the best time to search. Mark and Fuco could hear frogs all around them. But stumbling around at the top of a cliff in the dark is awfully dangerous.

SYNNOTT: I could hear the chirp of this frog, which, I don’t know, may have been the Stefania. And it was on this tree and it was sticking out over the cliff. And it was right there. It was like 10 feet away and there was no way to get to it.

GWIN: After a full day and night of searching on top of the tepui, they only collected a centipede and a cricket before they ran out of supplies. And then it was time to head back down to meet Bruce and the rest of the team.

GWIN: How did Bruce react when you guys got back and told him you couldn’t find the Stefania?

SYNNOTT: Well, we were really apprehensive about, you know, telling Bruce that we had come up empty-handed. But I just noticed right off the bat that he didn’t really seem that upset.

GWIN: While the climbers had been up on the tepui, Bruce wasn’t just sitting around down in the jungle. He’d set up a field station and worked with the Akawaio to collect any living creatures they could find. He led Mark and Fuco over to a little table where there was a brown, rubbery frog in a metal tray.

SYNNOTT: He held it up for us to look at. And I realized immediately that it looked exactly like this picture that he had drawn of the frog that he wanted us to find on Weiassipu. And this huge grin broke out on his face and he was like, Yeah, it’s a new species of Stefania.

GWIN: It wasn’t the Stefania they were looking for, but this frog’s DNA will bring biologists one step closer to completing the puzzle of their evolutionary history.

And it’s not just Stefania. So far Bruce thinks they’ve identified at least two other new species of frog, plus a lizard and a snake.

Today most tepuis remain wild and pristine, but they might not stay that way for long. It’s not exactly El Dorado, but it turns out the area actually is rich in gold and diamonds. And mining operations have started eating away at this wilderness.

Bruce hopes that by showing how much biological treasure is in the tepuis—much of it still unknown—he and others can convince people to find ways to protect this area.

In the meantime, Bruce is already thinking about when and how he might be able to go back.

SYNNOTT: We kind of billed this as Bruce’s swan song. But just so everybody knows, he doesn’t like that. He’s already telling me, just so you know, this doesn’t really have to be the last one. Each trip is his swan song. I mean, now he’s 80, so, I mean, maybe it really is. But just so you know, like, he’s not done.

(Forest sounds)

GWIN: Just watching Bruce walk through the jungle you can see why he would want to go back. You begin to see the rainforest through his eyes.

MEANS: Unfortunately, this is probably my last trip involving, you know, jungle hiking …

(Means’s voice fades under narration)

GWIN: Every soaring branch and rotting log is a microcosmos of biology that you could study for a lifetime. He looks like a librarian in a room full of books 
that he might not have time to read.

MEANS: This is as pristine as it gets. Only our feet have been here that I’m aware of. It’s wild and remote and beautiful as can be. I just want to be quiet and love it. Let it sink in. (in a hushed tone) I’ll be leaving the planet … sometime. And I’ll miss it.

GWIN: Hey, if you like what you hear and want to support more explorers 
like Bruce Means and Mark Synnott to tell stories like this, please rate and review us in your podcast app and consider a National Geographic subscription. 
That’s the best way to support Overheard. Go to natgeo.com/explore to subscribe.

And to learn more about the expedition to the top of Weiassipu, 
take a look at Mark Synnott’s feature story in the April issue of National Geographic magazine. We’ve included a link to the story in our show notes.

And to see these stunning sky islands for yourself, check out the National Geographic special, Explorer: The Last Tepui. It’s streaming on Earth Day, April 22, exclusively on Disney+.

All this and more can be found in our show notes, they’re right there in your podcast app.


This week’s Overheard episode is produced by Brian Gutierrez.

Our producers are Khari Douglas, Ilana Strauss, and Marcy Thompson.

Our senior producer is Jacob Pinter, who also edited this episode.

Our senior editor is Eli Chen.

Our manager of audio is Carla Wills.

Our executive producer of audio is Davar Ardalan.

Our fact-checkers are Robin Palmer and Julie Beer.

Our photo editor is Julie Hau.

Ted Woods sound-designed this episode. Hansdale Hsu composed our theme music.

This podcast is a production of National Geographic Partners.

The National Geographic Society, committed to illuminating and protecting the wonder of our world, funds the work of National Geographic Explorers Bruce Means and Mark Synnott.

Whitney Johnson is the director of visuals and immersive experiences.

David Brindley is National Geographic’s interim editor in chief.

And I’m your host, Peter Gwin. Thanks for listening, and see y’all next time.


Want more?

To learn more about the expedition to the top of Weiassipu, take a look at Mark Synnott’s feature story in the upcoming April issue of National Geographic magazine.

And to see these stunning sky islands for yourself, check out the National Geographic special Explorer: The Last Tepui, streaming on Earth Day, April 22, exclusively on Disney+.