Bonus Episode: The Surprising Superpowers of Sharks

Over the course of 400 million years, sharks have adapted to every part of the ocean world, thanks to a suite of senses—including the abilities to detect electromagnetic fields and sense heartbeats.

A bonnethead shark—the species Lauren Simonitis studies to learn more about sharks' extra senses—swims over coral-like structures in a tank at the New England Aquarium.
Photograph by Brian Skerry

Sharks have never been able to outswim their reputation as mindless killers, which is so entrenched that the U.S. Navy once even tried to weaponize them. But are sharks really just “remorseless eating machines” on the hunt for blood? Hop in the water with marine scientists for a look at sharks’ extraordinary senses and unique adaptability.

TRANSCRIPT

PETER GWIN (HOST): Our shark story starts in the late 1950s. Elvis Presley has just released “Jailhouse Rock.” Jane Goodall is taking her very first trip to Kenya. Physicists will invent the laser soon, although they don’t quite know what to use it for.

And the space race is in full force. The Soviet Union has successfully launched the satellite Sputnik 1. And the U.S. has rushed to get their first satellite into orbit. But they’re not just looking at the sky. In August 1958 a Navy submarine makes the first undersea journey to the geographic North Pole.

The Cold War’s scramble has the U.S. looking for every available advantage. The military is pouring funding into science like never before. They’re even looking at the animal world, which brings us to the sharks. The Navy is making a big effort to understand more about these animals. And some researchers are pursuing projects that, shall we say, are a bit more fringe.

That’s where you see a project that hinges on sharks being the brutish, simple-minded killers people thought they were. The Navy wants to see if it can take down an enemy ship—using a shark.

MARY ROACH (AUTHOR): Basically torpedo the ship without a torpedo, just using a shark.

GWIN: Sharkpedo.

ROACH: That was the hope.

GWIN: That’s author Mary Roach. For decades, these sharkpedo project records were classified. But Mary managed to get the records as part of a story for Undark magazine.

Even though this project sounds like a wacky historical footnote, the researchers had quite a plan.

ROACH: Strap explosives onto the shark.

GWIN: The idea was to have a shark wear a kind of headset and carry a bomb. 

ROACH: And then come up with a way to guide them remotely to the ship that you want to sink.

GWIN: The shark would have electrodes on the left and the right. Electrical signals would steer the shark.

ROACH: Let them go, let them swim over there, explode, take down the ship.

GWIN: The official name of this directive? Project Headgear.

I’m Peter Gwin, and this is Overheard at National Geographic, 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.

SharkFest is back this summer on National Geographic, and in this special bonus episode, we’ll take a new look at these magnificent but misunderstood creatures.

We’ll meet a pioneering scientist who spent her career riding on their backs and diving among their shivers—that’s what you call a group of sharks. Who knew? We’ll explore their ancient past and their strange superpowers, and we’ll also debunk the myth of them being mindless killers. It turns out, you might have a little more in common with a shark than you’d think.

More after the break.

GWIN: Project Headgear almost sounds like something a James Bond villain would dream up. Problem at sea? Send out the sharkpedo.

But in the 1960s, it’s scientists, not movie villains, who are working on this thing. For years, they research options. They build prototypes. They run tests. They are committed to this project.

A man named Perry Gilbert is one of the leaders, and, remember, the sharks are supposed to move according to an electrode steering system. Author Mary Roach again.

ROACH: So at one point they had Perry Gilbert in the water with electrodes on either side in the swimming pool, and they’re trying to steer Perry Gilbert around the pool. They're like, I think this works?

GWIN: Oh, great. Yeah, our stand-in for the shark.

Tests with actual sharks don’t go quite as well as Perry Gilbert’s trial run.

ROACH: No shark ever stayed on course the entire time. They would go for a little while and then they would just have none of it.

GWIN: That might sound obvious now. So how does something like Project Headgear even happen? For the U.S. military, sharks really become a consideration around the time of World War II. The 1940s bring way more sailors and fliers to Pacific waters.

ROACH: So if the boat goes down, if they're sunk, that's potentially shark-infested water.

GWIN: That’s new compared to the European theaters of World War I. And service personnel are worried. Training programs start to include shark-specific reassurances.

Military training video clip: Yes, there are sharks in the South Seas, but some of us have been close enough to touch 'em and didn't lose anything more than about ten years' pleasant dreams. 

GWIN: While that narrator is waiting for his pleasant, shark-free dreams to return, the military is looking into shark repellents, which means they’ve got to test repellents on sharks.

ROACH: The Navy got to be pretty good at dealing with captive sharks. They knew where to get them. They knew how to take care of them, how to feed them, keep them in captivity.

GWIN: If you want to study sharks around the time of Project Headgear, you could head to Scripps Institute in San Diego or Mote Marine Lab in Florida, formerly known as the Cape Haze Marine Lab.

So when scientists get assigned to the sharkpedo job, Project Headgear, they have a bit of a head start. The sharks are already around and they seem like a logical choice for a bomb-delivery system. They’re stealthy. They’re used to swimming long distances. And unlike other fish, sharks don’t have an air-filled swim bladder that a sonar system would pick up.

ROACH: The other thing, though, I think they felt—they kind of bought into that “the shark is the mindless killer.”

GWIN: To the researchers, a shark seems like a simpler animal, more likely to take orders.

ROACH: We can dominate this creature in a way we cannot do with, say, porpoises or some animal that's more known for its intelligence.

GWIN: And the military actually had some experience trying to use animals as bombers. During World War II, they had looked at sending bombs along with flying animals, like bats or pigeons.

With time, these animal-training efforts became more dangerous. Later on, in the Cold War, the Soviet Union tried to train dolphins to attack and bomb enemy ships. Even in the last decade, in the Middle East, insurgents have sent bombs along via donkey.

But in the 1960s, sharkpedos never pan out. Sharks weren’t as malleable as the Project Headgear scientists had hoped. They’re capable of much more than that mindless killer image gives them credit for. Another scientist working with sharks made that clear. Rather than trying to dominate sharks, she wanted to understand them.

That scientist was Eugenie Clark. She was one of the first biologists to dive with the sharks she studied.

NEWS REPORTER (from clip): Could you estimate how many hours, days, or weeks that you have been diving the sharks?

EUGENIE CLARK: No. I guess I ought to try to write that down sometime. It's been thousands of times. My first shark was back in the early 1940s.

That’s Eugenie in 1981. She was in Washington, D.C., answering questions at a press conference for her most recent article for National Geographic magazine. It was titled, “Sharks: Magnificent but Misunderstood.”

At that point, Eugenie had been diving with sharks for nearly 40 years, all over the world. And she’s got plenty of cool stories to show for it. 

CLARK: I'd like to start by telling you about the most thrilling shark encounter I've ever had with the largest shark in the world and one of the most harmless.

GWIN: That’s the whale shark. Whale sharks are often 20 to 30 feet long. That’s roughly the length of a school bus. They’re gray and spotted, with a huge, vacuum cleaner-like mouth. But despite the animal’s size, Eugenie was comfortable sharing the water.

CLARK: And I had a chance to crawl up on the back and ride on the back of the whale shark, first just hanging like a streamer from its first dorsal fin.

GWIN: So while the rest of the country is in shark panic after seeing the movie Jaws, Eugenie is riding the world’s biggest shark. She dove all over the world, conducting groundbreaking research. For example, her team was the first to discover that whale sharks give birth to live young, rather than laying eggs. Along the way, she collected all kinds of wild stories.

CLARK: And we dropped directly into a school of hammerhead sharks in the middle of the Straits of Tiran. I couldn't believe it.

GWIN: Naturally, people called her the Shark Lady. Eugenie passed away in 2015, but she made some giant contributions to shark science. She founded the lab that would become Mote Marine Lab, in Florida, and for a while, she worked with lemon sharks there. These sharks are about 10 feet long, and their yellow-brown skin helps them stay hidden in sandy waters. Eugenie did a lot of experiments with them in an oceanside pen.

CLARK: And that's when I realized that they weren't dumb creatures.

GWIN: Eugenie realized that every time she came onto the dock with the food bucket, the sharks went straight to their feeding platform. In other words, the sharks were able to learn her cue, and respond to it—the same way your dog bolts for his bowl as soon as you reach for his food.

CLARK: And then gradually we did experiments like putting a target underwater, training them to push the target and ring a bell in order to get their food.

GWIN: The lemon sharks she worked with could handle more than a simple target, it turned out.

CLARK: It can tell a square from a square turned 45 degrees to a diamond shape. It could always pick out the correct one.

GWIN: That work showed that sharks were a lot more capable than people thought. They could see pretty well at close range and learn to pick shapes and targets for food too. But speaking of food, sharks’ eating habits are pretty much one of the things dragging their reputation into that “scary predator” zone. We asked a researcher who’s working with sharks today to clear that up for us.

GWIN: OK, we got to back up a second. You have a shark tank? You have your own shark tank?

LAUREN SIMONITIS (SHARK RESEARCHER): Yeah (laughs), well I work—

GWIN: I guess I shouldn’t be surprised, right?

Lauren Simonitis has a shark tank. Well, it really belongs to the aquarium at Moody Gardens. She gets to borrow it for her work studying sharks at Texas A&M at Galveston. We’ll talk more about her work in a moment, but first let’s get into the wild stuff sharks sometimes eat. Tiger sharks, especially, are known for eating items that are certainly not food, like license plates and tires. There have been records of sharks eating even wackier stuff: a fur coat, a chicken coop, and a full suit of armor. What gives?

SIMONITIS: So a big part of that is that all this stuff is human introduced.

GWIN: It’s not that humans are intentionally feeding sharks these things, at least as far as we know. But lots of our weird refuse does end up in the ocean. And sharks scope it out. For hundreds of millions of years, sharks have been fine to check out whatever they liked. Puffer fish? Sure. Lobsters? Any time. Stingrays? No problem. Big-bodied sharks need lots of calories to survive, and they’re curious about anything that could be a meal. 

SIMONITIS: The way that they investigate things is with their mouth because at their mouth, that's what's closest to their eyes. Their nose is right there. Their taste buds are right there.

GWIN: And sharks do have some exit routes if they take a bad bite. Some sharks can actually turn part of their stomach inside out, outside their body.

SIMONITIS: And you'll actually be able to see it like out of their mouths.

GWIN: This isn’t pretty for the shark. For a moment, their insides become… outsides.

SIMONITIS: And they kind of open their mouths and do this like head-shaking thing and that'll flush out that part of their stomach.

GWIN: Oh wow, huh.

Here’s something even more startling. A couple of years ago, divers off the coast of Florida noticed a lemon shark with an odd dark bump coming out of its stomach. Then a few weeks later, they noticed the same shark... with a larger dark object sticking out of its side. And months later, an even larger object sticking out.

SIMONITIS: It actually passed out this giant, curved metal rod.

GWIN: It took a while. For at least a year, the shark survived with more and more of the rod sticking out through its body wall.

SIMONITIS: And they have full, time-lapse photos of like every time they saw the shark with more and more of it out of its body wall, and then it was healed up.

GWIN: Oh my gosh.

SIMONITIS: Yeah. Sharks are—they're hardy. They're really surviving these giant things that should kill them. But they're like, Nah, I'm good. I'm going to stick around here a little bit longer. Just going to pass metal spike out of my stomach.

GWIN: That’s totally Avenger territory.

And we haven’t even gotten to sharks’ real super powers yet. Those would be their extra senses. Like us, sharks explore their world with smell, sound, taste, touch, and vision. But they’ve got some sensory surprises for us too.

So let’s get back to the shark tank where Lauren does her work. It’s light blue plastic, 12 feet across, almost like a jumbo hot tub. In the tank, she studies sharks’ senses. She works with bonnethead sharks, the smallest member of the hammerhead family. They’re slender and about a yard long.

SIMONITIS: And instead of a hammer, they have like a little shovel, or like a bonnet, which is where they get their name from.

GWIN: Lauren studies how these sharks respond to all kinds of smells. One of those odors is the smell of food. So she dunks something nice and pungent, like fish blood, into the tank. And if the sharks are hungry and interested, they come over.

SIMONITIS: And then they do these really tight circles.

GWIN: They circle around to figure out what they’re smelling. But they don’t instantly go into attack mode. Sometimes they don’t show much interest in the food smells at all.

SIMONITIS: They can choose whether or not they want to respond to a smell.

GWIN: So sharks aren’t necessarily taken over by a smell, partly because they don’t actually have the megapowered noses everyone expects them to have.

SIMONITIS: In reality, sharks smell at the same sensitivity as other fish.

GWIN: At most, dolphins and whales can barely smell, so sharks can out-smell undersea mammals. But they don’t beat out other underwater smellers.

SIMONITIS: They don’t have these super noses that we think about when we think about sharks.

GWIN: What sharks do have is extra senses. They’re alert to more signals than we are. And they’re wearing some of their extra senses right on their faces. Take the bonnethead sharks Lauren studies. They’ve got that shovel-shaped head, and if you flip one of these sharks over, the underside of their face is covered in tiny squiggly lines and pores. All these markings are actually tiny sensors covered in a jellylike substance. They pick up weak electrical fields.

SIMONITIS: So this can be anything as small as whenever a heart beats. It sends off little electrical signals, it can sense that.

GWIN: Think about that. So at close range, sharks can track prey animals by their heartbeats. All sharks have these sensors. Those same squiggles and pores also come in handy for sensing currents in the ocean. When lots of water moves around, it makes a small electrical field. And sharks can sense it.

Scientists also think those pores help with another sense sharks have. This one sounds like something out of the X-Men: magnetoreception. Sharks can use Earth’s magnetic field to navigate.

SIMONITIS: They can basically sense the compass of the Earth.

GWIN: Wow. So they kinda have a built-in GPS, and they can sense this water movement beyond their location.

SIMONITIS: Yeah, they're being very greedy with all their senses. They're taking all of them.

GWIN: This is a bunch of information to take in, but sharks can manage.

SIMONITIS: They're able to integrate all of these sensory cues and use them together, perfectly in concert, to find what they're looking for.

GWIN: That’s all thanks to something we think very little about. Not shark’s teeth, or their noses, but their brains. And this brings us to Kara Yopak. She’s a marine biologist at the University of North Carolina Wilmington who looks at sharks through the window of their brains.

KARA YOPAK: If you're going to understand brain evolution, I think you kind of have to start looking for the weird and wonderful species.

GWIN: Like the Greenland shark, which lives deep under Arctic ice. Kara has a bit of a shark-brain bucket list, and Greenland sharks were on it for a long time.

YOPAK: And I remember watching years ago, an episode of Dirty Jobs, as you do.  

GWIN: In that particular episode, the dirty job was dissecting Greenland sharks for research off Baffin Island, in northern Canada. So the researchers were doing their full dissection.

YOPAK: And I was yelling at my TV, “Get the brain!”

GWIN: Unfortunately, the distance from Kara’s TV to the Arctic was just too far. They didn’t get the brain. But the researcher’s name was listed as part of the episode. So of course, Kara emailed him.

YOPAK: I was like, Hello, you don't know me, but I saw you on Dirty Jobs last night, and it ended up being this fantastic collaboration.

GWIN: A few years later, the researchers sent her a Greenland shark brain to take a look at. Including that one, she has studied about 180 shark species so far. When she tells anyone she works with shark brains, she always gets the same question: So, are sharks smart? That’s what I asked, but it’s not a question she likes. Intelligence is a finicky metric—it depends on your yardstick.

YOPAK: So if it's, Oh, you're smart if you can do calculus, then you might say, OK, sharks aren't doing so well.

GWIN: But you can also tip the scales in a shark’s favor pretty easily.

YOPAK: If we're going to measure it as well, has, you know, successfully persisted and invaded every aquatic niche in the ocean for over four hundred and fifty million years, then you might argue, actually, you know what, sharks are doing pretty well.

GWIN: Kara is looking for patterns in brain structure because a shark’s brain may be able to tell her something about how a shark behaves and uses its senses. Sharks with similar lifestyles tend to have similar brains, and she’s always looking for the next specimen.

YOPAK: I get weird stuff in the mail. I really do.

GWIN: Researchers all over the world know if they’ve got a shark brain, Kara Yopak is interested.

YOPAK: Probably one of the coolest, which happens to be—we're actually still working up the data now with colleagues—but I got a two-headed shark in the mail.

GWIN: It’s actually a shark embryo.

YOPAK: Yes, it probably wouldn't have survived, to be honest. But with my collaborators, of course, they said, This is weird. Mail it to Kara. She'll know what to do.

GWIN: And she does. With really rare specimens, like that two-headed shark, she can actually do an MRI scan to understand the shark’s brain structure without doing a full dissection.

There’s another cool benefit of scanning brains in an MRI machine. You can actually use that scan to 3D-print an exact replica of a brain. So as we chat on Zoom, Kara can take out actual models. The mako shark, which is my personal favorite, is about as long as a kayak, and can hit 45 miles per hour chasing prey underwater. And she shows me its brain first.

YOPAK: Think less shaped like a baseball and more shaped like a spark plug.

GWIN: Then she pulls out a great hammerhead’s brain.

GWIN (to Yopak): I mean, that looks almost like a big cotton candy ball, in a way.

YOPAK: And with cauliflower sort of sticking out of it?

GWIN: And then she produces a copy of her own brain.

YOPAK: Actually would fit in there.

GWIN: “In there” being her head.

YOPAK: So my favorite brain region—who else has a favorite brain region except me?— is the cerebellum, because sharks were the first to have it. And so it's going to be the bit right at the back of your brain.

GWIN: These three brains look pretty different. The mako shark brain fits in Kara’s hand, about the size and shape of a chicken tender. The great hammerhead model is a little too big to hold with one hand, closer to the size of a turkey breast. Her brain is, to stick with the poultry theme, about as big as a cornish game hen.

Looking at these three examples, it’s pretty hard to imagine that our brains and these shark brains would have anything in common.

YOPAK: But you can actually see a little shark brain within our brain. So just to orient you, that's the cerebellum there. That's our cerebellum.

GWIN: Oh wow, OK.

And then, when Kara lines up these brains at the cerebellum, including our brain, you can see what she means. All three brains are laid out in the same core structure. It’s known as the vertebrate brain blueprint. And sharks were the first to have it.

YOPAK: There's a developmental plan that originated at least as early as sharks for the brain. And then it's been carried through vertebrate evolution all the way to you and me.

GWIN: OK, so sharks—the animal people have long thought of as a mindless killing machine—actually set the stage for our brains to become what they are. In the end, maybe the reputation we’ve stuck on sharks says more about us than it says about them.

YOPAK: The perception of anything as a mindless killing machine, or it's usually that kind of fear, is driven by a lack of understanding. So it really emphasizes how little we know and how much further we still have to go.

GWIN: So when it comes to shark intelligence, we humans have been kind of stupid.

And there’s still a lot more to understand about these creatures: how sensitive their taste buds are, and how their magnetoreception really works. Hopefully, one day, we’ll get our brains around those things and more.

Still hungry for more cool facts about sharks? National Geographic’s SharkFest swims onto screens this July and August with six weeks of programming. Watch Shark Beach With Chris Hemsworth, the feature documentary Playing With Sharks, and other shark-infested programming all summer long on National Geographic and Disney+.

You can read our stories about how sharks can navigate via the Earth’s magnetic field and even band together to hunt. And be sure to check out our list of the most fascinating shark discoveries in the last decade. Also, Lauren Simonitis is a member of a cool group called Minorities in Shark Sciences, which promotes inclusivity and diversity in shark sciences. You can read about them at misselasmo.org.

And you can read more about shark repellent research in Mary Roach’s book Grunt: The Curious Science of Humans at War. And her latest book comes out September 14. It’s called FUZZ: When Nature Breaks the Law.

That’s all in the show notes, right there in your podcast app.

CREDITS

Overheard at National Geographic is produced by Menaka Wilhelm, Ilana Strauss, Brian Gutierrez, Laura Sim, and Jacob Pinter.

Our senior producer is Carla Wills.

Our senior editor is Eli Chen.

Our executive producer of audio is Davar Ardalan.

Our fact-checkers are Julie Beer and Robin Palmer.

Thanks to Karen Cerka for archival research and for providing the recording of the Shark Lady, Eugenie Clark, heard in this episode.

Our copy editor is Amy Kolczak.

This episode was sound-designed and engineered by Ted Woods.

Hansdale Hsu composed our theme music.

This podcast is a production of National Geographic Partners.

Whitney Johnson is the director of visuals and immersive experiences.

Susan Goldberg is National Geographic’s editorial director.

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

SHOW NOTES

Want more?

National Geographic’s SharkFest swims onto screens this July and August with six weeks of programming! Watch Shark Beach With Chris Hemsworth, the feature documentary Playing With Sharks, and other shark-infested programming all summer long on National Geographic and Disney+.

You can read our stories about how sharks can navigate via the Earth’s magnetic field and even band together to hunt. And be sure to check out our list of the most fascinating shark discoveries in the last decade

Also explore:

Lauren Simonitis is a member of a cool group called Minorities in Shark Science, which promotes inclusivity and diversity in shark science.

You can read more about shark repellent research in Mary Roach’s book Grunt, and her latest book comes out September 14. It’s called FUZZ: When Nature Breaks the Law.

If you like what you hear and want to support more content like this, please consider a National Geographic subscription. Go to natgeo.com/explore to subscribe today.