First Ascent of a Sky Island | Podcast | Overheard at National Geographic

El Dorado, the legendary city covered in gold, doesn't seem like a place that could really exist. But then, neither did tapuis in the Guyana 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 tapuis, and they're ringed by giant waterfalls that 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 tapui 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 tapui is an enormous undertaking. When you're in a cloud forest, it's often completely quiet—just no sound at all. You look around; it's misty, you don't hear a thing. A lot of people think that's eerie. Bruce Means is a biologist who's been studying ecosystems like this for more than 35 years. "It causes me to do what I'm doing, to shut up and just listen to the silence," he says.

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 all the rain in the tropics can come down—like somebody pouring a bucket on a tin roof. It just really comes straight down, no wind, nothing. And then, in a few minutes, it's quiet again. 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.

"My word for tapuis is phantasmagorical," Bruce adds. "They are special, wonderful, remote, beautiful places on this planet that give me as much—I'm just saying euphoria—as I have ever gotten from any place I've ever been, and I've been to a lot of them. I wish I could go back."

I'm Peter Guinn, 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 tapuis on a quest for his own kind of Eldorado: undiscovered species of frogs that would reveal a new chapter of life in the rainforest.

"If you really want to study some interesting evolutionary activity and some ancient stocks of organisms, go to the tapuis." Mark Sennett shares his perspective: "I am a climber, adventurer, sailor, writer, storyteller." Mark's 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 tapuis in National Geographic.

"I read that article and I photocopied it. I paid a dollar per page to get color copies. The article had a lot to say about the history and biology of tapuis, 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, climb, and pioneer first descents on all the biggest, best cliffs in the world. So, I put tapuis on the list."

Tapuis 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. They stick up out of the jungle like islands poking out of a foggy ocean. Tapuis 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 Galapagos Islands, this isolation over millions of years of evolution has made the tops of tapuis a wonderland for biologists. Some frog species only live on the top of a single tapui. 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.

"Do you remember your first impressions of Bruce Means?" Mark recalled. "So, uh, he's an 80-year-old dude now. When I first met him, he was 60, but the guy's a stud." Bruce's specialty is herpetology—reptiles and amphibians. In his long career, he 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 tapuis, 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. "I believe the fer-de-lance is one of the most deadly snakes in the world. As dangerous as the fer-de-lance is, finding one is fairly rare. On Bruce's first three trips to the tapuis, 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. "Well, on that trip, the Yakawayo started yelling that they had found the snake, and at that moment, Bruce was down at the river washing up. He came running up to see what was going on, wearing only a pair of Teva sandals and his glasses. He's like, 'Where's the snake? I'm gonna catch the snake!' The man is nearly naked!"

And then he did. He found a forked stick, pinned the snake's head down, picked it up, and caught the fer-de-lance. Mark adds, "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." So, for a biologist like that, tapuis are the perfect place to go.

But it's about more than adventure. Bruce says tapuis are one of the few places in the world where a biologist can go see an animal and instantly know that it's new to science. The frogs around the tapuis 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 skipped the tadpole stage by gluing eggs onto the mother's back for a while. When they first hatch from their eggs, you can see maybe a dozen little froglets riding around on Mama's back.

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. Humans can learn a lot from these adaptations. Frogs, especially, are noted for having noxious skin secretions. They're very complicated organic molecules. In a way, rainforests are like giant pharmaceutical laboratories. Over all those millions of years of evolution, nature's been perfecting chemicals and living things—think poisons and perfumes; all these are designed to impact other forms of life.

Some of them are blood thinners; some have clotting characteristics. They all have potentially high value to man. 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 tapuis, 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 tapuis.

"So then, Mark and I said, 'Hey, why is a tapui that's never been climbed? We know pretty much a lot about, you know, the logistics. Why don't we try?'" Mark and Bruce had been to the Wyiosupu tapui before. Back in 2012, they flew to the top by helicopter. Mark remembers that, at the time, it was literally uncharted territory. "I've told people that Wyiosupu wasn't on our maps, and people haven't believed that."

So, I found the old map, and there you go; it wasn't there—there was like a blank spot. Trekking from the bottom of a river basin to the top of a tapui could help Bruce understand how life changes with elevation. Bruce wanted to know: Are the tapuis 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 Wyiosupu, but instead of flying in by helicopter, they would trek in from Guyana. That's 60 miles! Then, they would climb the tapui, which nobody had ever done. They would do an elevational transect where he would look for new species in all the different elevational zones up the mountain. And then they would try to find this missing link species of a frog called Stefania that Bruce had seen on the top of Wyiosupu when they were there, but he hadn't been able to get its DNA.

The whole plan was ambitious, but there was this one part that seemed completely insane—the final climb to the top of the tapui 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 tapui?" Mark wondered. "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. It almost sounds like a window washer kind of thing, like the way big buildings have their window washers move up and down the face—that was the idea. 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 like, 'Oh, look! A cool little frog in this crack, and look at this little plant!' And of course, that was kind of a, yeah, there was no way Mark could do all this by himself."

Mark decided to "recruit a couple of ringers and make it a done deal, so no matter what, we're getting up the cliff." The first person he called was Alex Honnold. "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. 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 tapui before, and so I also wanted to have a real tapui specialist. But it turns out there's a Venezuelan guy named Federico Passani, and his nickname is Fuco. Fuco is the world's most experienced tapui climber."

"I've been exploring this with the tapuis for many years, 20-plus years," Fuco says. "But this was crazy. 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.

A group of guys from an indigenous group called the Akawa did a long day of traveling through the river with these curiara—boats made out of a single tree—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.

"We were opening a trail in very thick jungle," Mark recalls. "The Akawaya were the masters of the jungle, and they were using all their skills to open the trail. Even with the help of the Akawaya, the trek was incredibly difficult. There was no escape from the relentless weather conditions. We were supposed to be there during the dry season, but 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 covered in vegetation. The earth is super rich. Guess what you get? Mud! So, we called it 'Mud World.'"

At the end of the day, your legs are covered in mud—if you're lucky, just up to the knee—completely and utterly covered in mud. And then, after an exhausting day of slogging through Mud World, just getting into his hammock was a challenge.

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

The jungle seeped and crawled into every part of their clothing and gear. The further they got into the wilderness, the more wild it became. "Imagine what the world was like before there were human beings," Mark reflects. The final valley leading up to Wyiosupu, according to the Akawaya, was a place where no one had ever been—ever. No person, no human being—only animals.

Mark and the team finally reached the tapui right after the break. Along the trail, the group stopped frequently to collect specimens, especially frogs. Fuco, an amateur biologist, learned some of the basics of frog-catching from Bruce.

"You know, South America is famous for its poisonous frogs. Were you at all concerned about picking up the wrong kind of frog or a frog that might somehow have venom that would be dangerous to you?" Mark asked.

"Oh, well, I thought it was dangerous to me until I saw Bruce licking the frogs to test if they were poisonous or not." Mark adds, "Wait a minute! He's licking the frogs?"

"So, every frog I capture, I smell it and I lick it," Bruce explains. "What do those toxins do for the frog? They cause aversive, repulsive reactions to the mammals and birds and other organisms that eat them. I'm a mammal, so I'm going to respond exactly like their predators would respond if I taste their skin secretions."

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.

"I didn’t realize how challenging the trek was going to be for Bruce," Mark says. "He didn't train, and his plan was that he was going to toughen up along the way—which, 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're whooped."

About a week into the trip, Mark and the climbing team left Bruce at a camp to scout the path ahead to Wyiosupu. As they got closer to the tapui’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.

"It 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." 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 on top of Wyiosupu, 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're able to move up and down tapuis."

Fuco radioed down to Bruce and promised to try to find the frog. "Okay, Bruce, I'm gonna do my best to try to find the lucky Stefania."

"Fantastic! I know if anybody can do it, it will be you!" Finally, after 10 days, the climbing team made it to the base of Wyiosupu and began their ascent.

"You know, the thing about the tapuis is it's not entry-level climbing. The walls are crazy! The walls of Wyiosupu were more than vertical; they actually angled backward. If you put your back to the wall and tilted your head back, the view would be similar to if you were standing at the base of a battleship at the bow."

The roof is really not looking good; it's kind of extreme! 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. "So a roof, you know, in climbing terminology, is a spot where the cliff just goes horizontal. It’s like looking up at the ceiling in your living room and trying to climb out across that."

This mountain had never been climbed before, so no one knew exactly which handholds were trustworthy. Then, there was this diving board of rock sticking out. It was obvious that you could go out on it if you felt like you 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 you can't— that cannot happen!" 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. Any normal person wouldn't launch out on this thing, you know, pitch black without a headlamp! But they're not Alex Honnold.

"So, he just reached out on this diving board thing and went out hand over hand on it."

"All right, Mark. Here we go; this is the crux!"

"Okay, I gotcha!" Mark watched as Alex worked his way along the edge, paused, and then calmly dangled with one hand over the void. "Nice, Alex!" It was one of the most incredible bits of climbing that I've ever seen because he was just dangling out in space.

Day two of the climb, Mark was leading when they came to the next dangerous spot. The rock went from perfect, beautiful, super solid quartzite to something that I would describe as resembling a real-life game of Jenga—rock. None of the rocks were attached to the mountain; they were just stacked up like bricks that didn't have any mortar in between. Climbing up through that was one of the scariest things that I've ever done.

700 feet up on the side of the tapui, 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. Across the valley was Wyiosupu's neighboring tapui, Mount Roraima, with its gushing waterfalls.

It had rained so much that all the waterfalls were just pumping off the cliff and from inside the cliffs. "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. The spray created this halo of rainbows. I think that was the most spectacular thing that I have ever seen in my entire life."

They finally made it to the top of Wyiosupu and found themselves in the midst of the alien world at the top of the tapui. A lot of the horizontal surfaces are covered with bogs. "When you stand on the land and bounce up and down, the whole land all around you is like jiggling. So the whole thing is like this weird jelly surface on the top of the rock—with bizarre plants."

There was a little bit of forest with these bizarre little stunted trees, like something from Dr. Seuss. And then the 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. "I could hear the chirp of this frog, which I don't know, may have been the Stefania, and it was on this tree sticking out over the cliff. It was right there; it was like 10 feet away, and there was no way to get to it."

After a full day and night of searching on top of the tapui, 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.

How did Bruce react when you guys got back and told him you couldn't find the Stefania? "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."

While the climbers had been on the tapui, Bruce wasn't just sitting around down in the jungle. He'd set up a field station and worked with the Akawaya 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.

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 he wanted us to find on Wyiosupu. A huge grin broke out on his face, and he was like, "Yeah, it's a new species of Stefania!"

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 tapuis 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 reflects. He hopes that by showing how much biological treasure is in the tapuis—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. "We kind of build this as Bruce's swan song, but just so everybody knows he doesn't like that, and he's already telling me, 'Just so you know, like, this doesn't really have to be the last one.' Each trip is his swan song. I mean, now he's 80, so maybe it really is. But just so you know—he's not done."

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." Unfortunately, this is probably my last trip involving, you know, jungle hiking. Every soaring branch and rotting log is a microcosm 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. "This is as pristine as it gets. Only our feet have been here, that I'm aware of. It's wild, remote, and beautiful—can as can be. I just want to be quiet and love it, let it sink in. I'll be living the planet."

Hey, if you like what you hear and you want to support more explorers like Bruce Means and Mark Sennett 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 Wyiosupu, check out Mark Sennett'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 Tapui." It's streaming on Earth Day, April 2nd, 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 Kyrie Douglas, Alana Strauss, and Marcy Thompson. Our senior producers include Jacob Pinter, who also edited this episode. Our senior editor is Eli Chen. Our manager of audio is Carlo Wills. Our executive producer of audio is Dvar Ardellon. Our fact checkers are Robin Palmer and Julie Beer. Our photo editor is Julie Howe. Ted Woods designed the sound for this episode. Hansdale Supe composed our theme music.

This podcast is a production of National Geographic Partners. The National Geographic Society is committed to illuminating and protecting the wonder of our world, and it funds the work of National Geographic explorers, Bruce Means and Mark Sennett. 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 Guinn. Thanks for listening, and see y'all next time!