The Devil Fish | Giant Manta Ray – Wings, Intelligence & the Cyclone of the Deep

They were once called Devil Fish — massive, dark shadows that sailors believed could drag ships to the bottom of the sea. The truth is far stranger, and far more beautiful.

In this episode, we follow the Giant Oceanic Manta Ray into the open blue to uncover what may be the ocean's most elegant design. With a wingspan wider than a small aircraft and a skeleton made entirely of cartilage, the Manta doesn't swim — it flies. We break down the hydrofoil physics that allow a 5,000-pound animal to glide for miles on almost no energy, and the retractable cephalic fins that transform it from a streamlined traveler into a living vacuum in seconds.

But the Manta's body is only half the story. We examine the remarkable brain — the largest relative to body size of any fish on Earth, physically heated to run faster than the cold water around it — and what happened when two Mantas were placed in front of a mirror. We explore the Cleaning Stations, where apex predators queue patiently to receive a service they seem to understand and value. And we witness the Cyclone: a formation of up to 150 Mantas rotating in an anticlockwise vortex, using the physics of fluid dynamics to concentrate prey that no individual animal could catch alone.

This is a creature that cooperates, plays, and may recognize itself. And it is endangered.

Secrets of Earth is a nature documentary podcast for all ages, exploring the why and how behind the planet's most extraordinary life.

Transcript

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Welcome to Secrets of Earth. I'm Patrick Fiersbah, your guide into the world's most remote corners. Today, we ascend, not descend, into the most graceful dimension of the ocean. In the history of human imagination, we have always looked to the birds to understand flight. We studied the hawk, the albatross, the effortless arc of a soaring eagle to learn how to lift ourselves off the ground. But if you want to truly understand the physics of a body in motion, the poetry of a form designed to move through a medium rather than fight it, you shouldn't look at the sky. You should look down into the open blue of the tropical ocean. Gliding beneath you is a creature that defies the common definition of a fish. It doesn't dart, it soars. It doesn't wiggle and pump, it banks, adjusting its trim with the smallest flexion of a wingtip, reading the invisible architecture of a current the way a bird reads a thermal. With a wingspan reaching nearly 29 feet, wider than many small aircraft, the giant oceanic manta ray is the closest thing our planet has to a living stealth bomber. But, while its silhouette commands your attention, a vast, dark, angular shadow materializing from the blue, the manta is one of the gentlest and most curious creatures in the sea. For centuries, sailors who hauled them aboard called them devil fish, frightened by their scale and by the strange horn-like structures flanking their heads. In some accounts, they were said to grab anchor chains and drag ships off course. The truth, as we now know, is almost the opposite. A creature of extraordinary calm, of surprising intelligence, and of a beauty that belongs fully to the open ocean. Today, we are not just exploring a species. We are analyzing the physics of underwater flight, the architecture of a mind that shouldn't exist in a fish, and the deep cooperative intelligence of a creature that has been soaring through these waters for tens of millions of years. To understand the manta ray, you have to start with the material it is built from. Like their cousins, the sharks, manta rays have no bones. Their entire skeleton is made out of cartilage, the same flexible material that gives shapes to your ears and nose. This makes them lighter per unit of size than any bony fish, and it gives their wings a suppleness that solid bone could never achieve. A living flexibility that allows the pectoral fins to flex, twist, and generate lift across their full span in a single fluid motion. And consider the shape of those wings. They are not flat paddles beating water. They are hydrofoils, airfoils, really, refined by evolution over millions of years into the same fundamental geometry that aeronautical engineers arrived at independently when designing aircraft. If you were to take a cross section through a thickness of a manta's wing, you would see a form thick and rounded at the leading edge, tapering to a fine trailing edge, a shape that as it moves through the water, generates a pressure differential between the upper and lower surfaces. It produces lift. It is the same physics that gets a 747 off the ground, applied to a creature that never evolved to fly at all. This means the manta doesn't have to fight to remain buoyant. While other fish must constantly pump their fins to maintain position or rely on a gas-filled swim bladder for neutral buoyancy, the manta can lock its wings at a slight angle, catch the great oceanic currents, the underwater winds that move billions of tons of seawater across ocean basins, and glide. Miles of open water for the cost of almost nothing. And then there are the structures the sailors found so alarming. The two projections flanking the head, which are called cephalic fins. These are, in fact, forward extensions of the pectoral fins, the same hydrofoil wings folded forward, positioned on either side of the enormous rectangular forward-facing mouth. They are a masterpiece of dual-purpose engineering. When the manta is traveling, covering the vast ocean distances between feeding grounds and cleaning stations, it rolls these fins into tight spirals, tucking them against the head like a sailor furling a sail. The silhouette becomes pointed and streamlined, the drag profile shrinks, and the manta slips through the water as efficiently as possible. But when it reaches a dense patch of zooplankton, the transformation is immediate. The cephalic fins unfurl, two great scoops opening like hands, and they begin to funnel thousands of gallons of plankton-rich water directly into the waiting mouth. One moment a streamlined traveler, the next, a living vacuum, harvesting the microscopic life of the ocean at industrial scale. Inside that cavernous mouth, the water passes over comb-like gill raker plates, complex interlocking structures made of cartilage that act as filters, trapping the tiny zooplankton as the water streams through the gills. The food is concentrated, channeled, swallowed. At peak feeding, a single manta can process hundreds of tons of seawater in a day, extracting from it the tiny crustaceans, fish eggs, and copepods that fuel this immense body. This design, the hydrofoil wing, the retractable funnels, the gillraker filter, is not the product of recent evolution. The manta lineage has been present in the fossil record for roughly 20 million years. A form so aerodynamically and hydrodynamically complete that evolution has seen little reason to substantially revise it. We tend to fall into the trap of thinking that intelligence is a trait reserved for mammals. We look at fish as cold, instinct-driven machines governed only by the imperatives of eating and avoiding being eaten. But the manta ray is a radical challenge to that assumption and to the very definition of where intelligence lives. Inside the skull of a giant manta is something that shouldn't be there by most assumptions about fish biology. The largest brain relative to body size of any fish species on earth. Not just large in absolute terms, though that is true. A fist-sized organ in a creature that can weigh over 5,000 pounds, but large in proportion. The mantis encephalization quotient, the measure of brain size relative to body mass that scientists use as a rough proxy for cognitive capacity, is closer to some birds and primates than it is to most other fish. But the architecture of that brain matters as much as the size. The manta's brain is physically warmer than the surrounding tissue. Like the great white shark, the manta uses a system of blood vessels around its brain and eyes to retain metabolic heat, keeping its most computationally intensive organs running faster and more efficiently than the cold water around it would otherwise allow. The warmth is not accidental, it is a feature. It is why researchers believe the manta can do things that cold brains cannot. In 2016, marine biologist Celia Ari presented two captive giant manta rays with a mirror in their tank and documented what happened. What she observed was striking. Rather than attacking the reflection, treating it as a rival, the way most fish respond, the mantas exhibited a suite of unusual, repetitive behaviors that looked remarkably like what dolphins and great apes show when confronted with their own reflections. Contingency checking, rolling and unrolling their cephalic fins in front of the mirror at a rate ten times higher than usual, blowing bubbles, turning to expose different parts of their body to the glass. These are the signatures of an animal trying to understand what it is seeing, possibly recognizing that what it sees is itself. The results are contested. Mirror self-reflection is difficult to establish definitively in any non-primate animal, and researchers continue to debate what the manta's behavior proves or doesn't prove about self-awareness. But the behaviors Ari documented have no clean alternative explanation. The mantas weren't reacting to a stranger, they were doing something else, something harder to name. They are social creatures that recognize individuals returning to the same cleaning station, associating with the same other rays over periods of years, building what look from the outside like sustained social relationships. They exhibit what can only be described as play behavior, leaping entirely clear of the water in massive crashing breaches, their 5,000-pound bodies clearing the surface and coming back down in explosions of white water that can be heard for miles. Why they breach, scientists are still working out. The most commonly proposed explanations include parasite removal, the impact of hitting the water's surface may dislodge skin parasites, and communication, the sound of a breach carrying across great distances to signal location to distant individuals. Some researchers suspect courtship, others simply the pleasure of motion. What is clear is that these animals do not spend all their time maximally efficient. They have room in their lives for behaviors that serve no obvious survival function. They have, in a word, curiosity. That is a rare thing in fish. It is a reminder that intelligence in its many forms is not the exclusive property of the warm-blooded. The manta's intelligence is perhaps most visible in the rituals surrounding the cleaning stations. The open ocean is not kind to large, slow-moving surfaces. Any creature that travels continuously through thousands of miles of sea accumulates passengers, parasites embedding in the skin, bacteria colonizing the gill folds, rumoras anchoring themselves to the wing surfaces and feeding opportunistically. A manta ray in full oceanic health has to manage this biological load constantly. The solution is a social contract that plays out daily at special coral outcrops and seamounts scattered across the tropical ocean. These are the cleaning stations, known locations often passed down within populations across generations, where cleaner fish wait for clients. When a manta approaches a cleaning station, it performs what researchers call a solicitation display. It slows, reducing its great wings to a near stall, hanging in the current with its mouth slightly open, its cephalic fins partially unfurled. The posture is unmistakable to the cleaner fish, rass, butterfly fish, angelfish, that have been waiting on the coral below. They respond immediately, swarming the manta in dozens, sometimes hundreds, systematically moving across its surface, into the gill slits, along the trailing edges of the wings, inside the mouth itself, picking parasites and dead tissue from surfaces that the manta cannot reach alone. Mantas will wait in line for this service, circling the station in what researchers call a manta train. Individual rays queuing patiently, sometimes for an hour, before their turn arrives. If a cleaner fish accidentally bites sensitive tissue, the manta shudders, a ripple moving through 5,000 pounds of cartilage and muscle. But it doesn't flee. It knows what it is there for. There is in this something that functions like delayed gratification, the ability to tolerate discomfort for a future benefit. That is not a simple cognitive operation. It is also a masterpiece of interspecies cooperation. The cleaner fish receive a steady supply of protein-rich parasites. The manta receives maintenance that keeps its skin hydrodynamically smooth, reducing drag, improving the efficiency of every mile it travels. Each party gets what they need. No coercion, no hierarchy, a mutual agreement renewed at specific locations every day of a manta's 45-year lifespan. But the most extraordinary feeding behavior the manta performs happens when the conditions are exactly right, when an unusual concentration of zooplankton is carried by tide or current into a bay or lagoon and becomes dense enough to make cooperative feeding worthwhile. When this happens, documented most famously at Hanuferu Bay in the Maldives and at a handful of other sites in Fiji and elsewhere, the mantas do something remarkable. Something that looks, to the first-time observer, like a choreographed performance, but is in fact one of the ocean's most efficient feeding machines. It begins with chain feeding. Individual mantas aligning behind each other, mouth to tail, gliding through a plankton cloud in a column, each one filtering the water that has been slightly concentrated by the body of the animal ahead of it. Then the lead animal curves. It arcs back toward the trailing end of the chain. The circle closes. More mantas join. The circle tightens. The column builds vertically through the water, animals stacking above one another until there are dozens, sometimes as many as 150 individual manta rays circling in a vortex that reaches 15 to 20 meters across and drops from the surface to the seafloor below. The formation always rotates counterclockwise when viewed from above, a consistency that suggests coordinated behavior rather than accident. The rotating mass of bodies creates a gentle current, a mini eddy that draws zooplankton inward toward the center, concentrating it further and feeding it into the open mouths of 150 circling mantas simultaneously. This is what researchers call the cyclone, a living vortex that produces a result no individual manta could achieve alone. The hydrodynamic concentration of prey that is otherwise too dilute to feed on efficiently. It is collective intelligence in action, a group of individually large-brained animals using coordinated movement to solve a fluid dynamics problem that would defeat any one of them. It is the physics of hunger solved by cooperation. To see a manta ray in the wild is to see a creature that has solved with extraordinary elegance most of the problems the ocean poses. They are patient, long-lived. Some individuals have been tracked for over forty-five years. They are intelligent and socially complex. They cooperate, they play. They may, in some sense, we do not yet fully understand, recognize themselves. And yet, they are endangered. Because they grow slowly and produce only one pop every two to three years, manta populations cannot quickly recover from losses. They are hunted in some parts of the world for their gillraker plates, which are sold in traditional medicine markets under claims that have no scientific basis. They are struck by vessel traffic that crosses their migratory routes. They become entangled in fishing gear never designed for something this large. When we lose a manta, we lose an animal that may have known that specific stretch of ocean for 40 years. We lose a node in a social network. We lose a mind that was doing something in front of that mirror that we do not yet know how to name. But there is reason to hope. International protections for manta rays have expanded significantly. The evidence that these animals are worth far more alive to research, to tourism, to the health of the ecosystems they move through is growing. And the more people that understand what a manta actually is, the harder it becomes to see them as anything but irreplaceable. We share this planet with millions of stories, most of them unfolding in the silence of the deep or the shadows of the canopy. Thank you for journeying with me into the world of the Mantor Ray. I'm Patrick Viersba. There are many secrets of Earth if you only know where to listen. I'll see you on the next horizon. Until then, follow our coordinates by subscribing to or following the show. It ensures you never miss a step into the unknown.