The drag of water makes both speed and distance a challenge in the marathon of the ocean.
Marine creatures are attuned to the drag of water in ways that we simply can’t be. We’re land creatures, striding from place to place as though in a vacuum, taking little note of the feeble atmosphere swaddling us. Water presents a greater obstacle to movement. The density, the weight, and most importantly, the way water clutches strongly at everything moving in it makes it a permanent, physical impediment.
The drag of water pulls at everything that moves in the ocean. Drag, and the stamina to withstand it, are important in the fastest sprints when fish muscle their way up to 40 miles per hour. Or when squid pump seawater through their bodies to become natural jet engines that fly. But drag and stamina are also a cruel tax during the longest treks of any species on our planet, journeys of tens of thousands of miles. Whales swim with a plateau of efficiency that no human machine can match. Even the albatross, soaring the greatest weather systems on Earth, sips strength from the waves to power their epic migrations.
A competitive swimmer, leaping from the block, hits the water with a shock. His heart jumps. His skin crawls. He keeps his head down, tucked into the prow between his arms—if it’s raised even a little, the water will rip the goggles off his face. At the moment of impact, his hands rip a corridor through the pool. As he finally breaches the surface to breathe, his hands split and arms twist into a new configuration. The movements are lightning fast, as powerful as young muscles can make them, and expertly angled. He labors to deny any grasp to the reaching water. Every movement trains the fluid around him; his muscles flow in a partnership with water. The fastest swimming Olympian burns his body to move at 5 miles per hour—slightly faster than a herring.1
The comparison is not fair. The human athlete has spent a life tuning a terrestrial body to perform in an alien, liquid environment. The herring is at home in the sea, and its evolutionary legacy is a set of adaptations that help solve the enduring problems of moving through water.
A sleek fishing boat rolls over an ocean swell. Twenty-five feet long, snow-white fiberglass shining in the Caribbean Sun, it’s a craft for tourism and commerce. But it is also a technical marvel. Powerful engines, advanced reels, fishing lines crafted to high-tech perfection—modern technology has expanded the pursuit of the ocean’s fastest fish, matching muscles, power, and speed with materials, power, and speed.
A fishing guide scans the sea from behind black mirrored lenses. As the vessel crests yet another swell and the prow plummets, he lets out a whoop. He points a yellow-gloved finger to a ripple in the water, a hundred yards out. Straining their eyes, the passengers can make out only a churning strip of bubbles. And then the fish jumps—as if on cue, to aid novice eyes. Silver and black, with a spear-like bill and gleaming scales stretched across slabs of rippling muscle, a sailfish soars into the sunlight. For an instant it hangs in the air above a galaxy of silver droplets. With a white explosion, it’s gone below, streaking just beneath the surface, its portrait split into a hundred Cubist slivers.
Sailfish, of the genus Istiophorus, are arguably among the ocean’s greatest natural athletes. They combine a streamlined muscular body and a tapering long menacing beak. All the members of the family of billfish—counting sailfish, marlins, and swordfish in their number—bear a strong resemblance to one another. They lead similar lives: large, solitary predators who stalk the continental shelves of the world’s oceans for smaller fish. Billfish are very fast, but the sailfish has adapted speed beyond any of its cousins. They are said to streak at 80 miles per hour during jumps and to hunt their overwhelmed prey at a consistent 30 miles per hour.2 The combination of fins and muscle—geometry and physics—gifts them unparalleled efficiency.3
Hatching from eggs thrown into the open ocean, sailfish begin life with an astonishing growth spurt. In their first 6 months of life, they’ll grow from specks to more than 4 feet long.4 Even when young, sailfish stand out for their distinctive “sail”: an enormous, fan-like dorsal fin that raises and lowers like a fan. It’s collapsed as the fish screams through the blue, but can spring to attention instantly.5
Careful analysis suggests that, just as a human sprinter does not run everywhere at full speed, billfish save their speed for special circumstances.6 Even feeding can be more orderly than once thought. Gilbert Voss, a fish biologist in Miami, described a famous event in Florida in 1940, when sailfish were seen to feed for the first time. There were six to thirty sailfish in each group, circling small herring-like prey to force them into tightly packed schools, scaring them into compliance by raising and flashing their huge sails. Once the ball of fish was nicely formed, one after another, the sailfish would strafe through the schools, stunning fish with up-and-down and side-to-side swipes of their bills, and snapping up stunned prey.
Monitoring fish speed is notoriously difficult. Ocean life writer Richard Ellis relates that the oft-cited quotation for sailfish speed (68 miles per hour) comes from the Long Key Fishing Club in Florida, where fishermen conducted experiments with hooked sailfish and a stopwatch.7 Precise measurements of fast fish have been made a few times and have clocked some sprinters at the high speeds we would expect. Wahoo, a torpedo-shaped relative of the tunas and billfish, has a top speed of 48 miles per hour, similar to that of a yellowfin tuna (47 miles per hour).8 Some fish are said to go faster, and probably can. But moving that fast requires more than just muscle.
All that velocity also demands a body able to eat at high speed. Hunting at billfish speed is tricky, like driving at 40 miles an hour on a busy street while trying to snatch a coffee mug off the asphalt. Roaring through the open water, billfish plow through schools of prey with quick twisting movements, flashes of the eyes, and calculated swipes from sail and bill. Chewing is a waste of time; swordfish suck down their dazed prey with gulps like fingersnaps and don’t even have teeth as adults.9
All billfish and their cousins the tuna are cold-blooded animals, and they live in cool ocean waters that teem with food. But they nevertheless keep their muscles warm through strong exertion. Tunas even have a heat trap in their blood stream that limits how much warmth they lose through their gills.10 To generate heat besides that provided by muscles, these fish have evolved specialized tissues that function as heating units. They’re muscles with no ability to contract: dark brown flesh that converts calories directly into heat rather than motion. You may see them in a tuna as the dark brown flesh on either side of the spinal cord. But even if the core of the fish’s body is warm, other parts, especially close to the water, like the muscles of the eyes and the reflex nerves, stay cold and function slowly. In billfish, where eye and nerve reflexes are critical, the brown muscle heaters are also found where they’re most needed: right next to the eyes and braincase.11
Maintained at warmer temperatures, often more than 7° F (4° C) warmer than the surrounding water, the eyes in particular can operate at race-car speed and precision—the kind of suspended “bullet time” typically available only to Hollywood action stars. The retina of a swordfish can process information fast enough to detect the quick flash of prey fish during a high-speed pass. But if you cool down the retina enough to match the temperature of the ocean, its scanning speed drops to the point where a fast flash of prey is invisible.12 Warm retinas also see better at low light levels, meaning that eye heaters give swordfish an advantage 1,000 feet deep, where they often forage. So these predators enjoy razor-sharp vision and lightning-quick reflexes as they drive through schools of darting fish in a cold sea.
Skipping across the sea behind a Fijian barrier reef in a high-powered skiff, you unknowingly run down a school of 10-inch-long fish. Instead of scattering, they rocket ahead, erupting from the water in a torrent of turquoise. Fins held akimbo like wings, their tails thrash in furious sine waves—propelling the small creatures just as fast as your boat. With an air of bored disdain, they bank hard left in stunt-pilot unison and head for the horizon.
Powered flight evolved three separate times on planet Earth: in birds, insects, and mammals. In each case, evolution devised a different method for translating muscle movement into aerodynamic lift: wings with feathers, wings of exoskeleton, and wings of skin. While birds, insects, and mammals evolved flight in their own ways, a fourth model labored hidden under the waves. It was a one-off, an aerial exotic, an evolutionary miracle that has been given the ocean’s most appropriate name: flying fish.
More than fifty species populate the tropics.13 Their torpedo-shaped bodies are well muscled all along the fuselage. Their strength provides speed, but the density of water makes high speed an extravagantly expensive metabolic proposition. The power needed to move through water or air increases as the square of the velocity.14 But air is much less dense than water, and the drag air creates against fast travel is far, far less. So, fast travel is expensive in water, but cheaper in air. In response to this simple physical fact, the flying fish, family Exocoetidae, evolved their fins into technological marvels of flight.
Those fish seen from your skiff took flight for a reason. Imagine them just a few moments before, cruising in a loose echelon just below the water’s surface—gorgeous animals proudly marked with blues and purples and yellows. Their pectoral (shoulder) fins are the most eye-catching feature. Elongated into wings, stretching to either side, their delicate spines and translucent planes resemble insect wings: butterflies birthed in the sea. The school swims in formation, feeding on plankton and tiny fish.15 Suddenly a mahi mahi appears from the dark Tartarus below, 20 pounds of needle teeth and muscled fury on an intercept path. The formation’s left outrider—a little cerulean female—is the closest to danger and the first to turn. Her companions follow, veteran wingmen instantly sensing the shift.
She pushes hard, but the mahi mahi is utterly committed. It’s bigger, stronger, and—over a 100-yard sprint—faster than our heroine. She’s got nowhere to go but up—and accelerates to 20 miles per hour,16 angling up toward the surface. Death churns inches behind. Reaching her world’s silver ceiling, she leaps and ignites a hidden engine—a tail with an elongated lower fork. The lower lobe churns water at 50–70 beats a second. The ultimate effect is that of a rocket.
Our heroine spreads wide her pectoral wings. A second set of smaller fins near her tail splay out too, making her like a biplane. As pectoral fins provide lift, the tail delivers power. With one final push from the long lower lobe of her tail, the only part of her still in the water, the sea abruptly falls away. The air cushions her now, hot and suffocating but simultaneously life-saving. Her wingmates form in on either side. The squadron hums low across the surface at double their waterborne speed, turning abruptly, to leave the predator behind.
But the mahi mahi isn’t ready to quit. It is capable of bursts of 40 miles per hour, following along below the surface.17 And although it seems as if the flying fish has escaped entirely, there remains an enduring problem. The problem is that flying fish do not fly—they glide. Their fins are not beating wings that provide powered flight; they are only gliders that merely prolong flight. And once out of the water, the flying fish—and the mahi mahi—are faced with the inevitable fact that the gliding flying fish will come back down.
Flying fish pursued by a dolphin fish. Published in 1889 in Popular Science Monthly, volume 35. Author unknown.
Each flight is only seconds long. Cruel gravity pulls her toward the water–– and beneath is the rainbow form of the mahi mahi matching speeds. When she starts to lose altitude, she dips her tail and tags the sea for another burst of power. Up to a dozen times she might graze the surface and glide again.18 The death race flashes across the sea, covering the 50-meter length of an Olympic-sized pool in seconds. The mahi mahi tracks the flyer, keeping up with the slow curves of its evasive maneuvers. It’s eaten many flying fish, and every new dip of our heroine’s tail offers a fresh attack window.19 But a missed strike will let the flyer escape, and so the predator holds fast. Both fish are at their physical peaks racing toward the horizon.
Only an abrupt splash in the distance tells you that one or the other has won.
Nothing in the ocean has quite the exuberance of a pod of dolphins on the move. Powering just under the surface, they slip through the water with barely a ripple, then leap into the air in a graceful arc, almost as if to give us poor landlubbers a good look at their beauty. But is it just impetuous joy that drive the leaps of a running dolphin? It turns out that it may be good common sense.
Rapid swimming is expensive, increasing in cost as the square of the swimming speed. By swimming and leaping, perhaps a dolphin is taking advantage of the lower drag in air compared to water—maybe the occasional leap reduces drag to save calories. But leaping involves a lot of energy too, so for leaping to be worthwhile, the cost of the leap must be lower than the energy saved by arcing through the air. A careful analysis confirms this, showing that leaping is only worth the cost above a critical speed threshold, the “crossover” speed. Dolphins swim smoothly just below the surface, up to about 10 miles per hour. Above this speed, leaping becomes more efficient than swimming, so dolphins jump.20 It’s more than fun, it’s simple economics. Size matters in this equation: the bigger you are, the more costly is a big jump— and the higher the cross-over speed should be.
The “great” whales are too big to travel this way. It costs a great deal to throw 30 tons of whale out of the water, and cross-over speeds would be in the range of 30 miles per hour. They rarely reach this speed while migrating. But some whales leap anyway. The question is, why?
Humpbacks (Megaptera novaeangliae) are medium-sized whales, up to about 60 feet long. They’re common and populous, have rebounded substantially from whaling, and are beloved by tourists for their legendary breaching behavior.21 With mighty strokes of their flukes, the giants hurl their upper bodies out of the water. Backs arched, they smash down in an explosion of glittering white spray. Fin whales, significantly larger, have been known to perform the same herculean leaps,22 but most of the biggest whales do not. What the humpback really boasts over its cousins is agility. Breaching requires contortion to a degree that freight-train blue whales never attempt. And a humpback’s pectoral fins are the key to its sinuous movements.
Proportionally, they’re the longest of any cetacean—18-foot fins aren’t uncommon on animals 65 feet long.23 Delicate like angel wings, streaked with white, are studded along their leading edges with knobbly protuberances often mistaken for barnacles. These are actually hair follicles, modified and swollen to rubbery fist-sized bumps called tubercles. The larger a fin is, the more water runs along its leading edge and the more drag it incurs. Tubercles, unique to humpback whales, break up the current to force water across the fin instead. The end result is a vastly improved hydrodynamic profile and increased underwater lift.24
Human engineers eventually took notice, admiring whale fins and learning the lessons they taught. A Canadian engineering firm recently designed wind turbines modeled after whale fins, with metal ridges cut like tubercles into the leading edges of the blade.25 They move air with absurd efficiency for such a slightly improved design: 32% less drag and 8% increased lift compared to a smooth model.26 A whale-fin cooling fan spinning at 16 feet per second moves as much air as a typical fan working 25% harder, a thrilling improvement for engineers used to small marginal gains.
(Left) View of humpback whale (Megaptera novaeangliae) pectoral flipper showing leading edge tubercles. Left image courtesy of W. W. Rossiter. (Right) Three-dimensional reconstruction of flip-per tip from CT scans. Both images from Fish, F. E., L. E. Howle, and M. M. Murray. 2008. “Hydrodynamic flow control in marine mammals.” Integrative and Comparative Biology 48(6):788–800, figure 5. Used by permission of Oxford University Press.
The speedsters we have described so far all have bones. They carry their bodies’ skeletal structure inside, like fish and marine mammals. Other fast actors we’ll get to next rely on armored exoskeletons. But in both cases, muscles are anchored to hard components. Those hard components transmit power to bones or shells, which move water and generate thrust.
But some of the most numerous mobile creatures get by without skeletons. Squid are the finest example: without a single bone in their bodies, they slash through the seas powered by nature’s own jet engine.27
Squid are cephalopods, “head-foots,” members of a large class including cuttlefish and octopuses. Large, prominent eyes take in the world with a cold alien intelligence. Eight arms and two longer appendages (properly called tentacles to differentiate them from arms) dangle below the eyes. They typically surround a cephalopod beak. The end result is a giant eye-defined “head” married to a confused, tentacled “foot.” Behind this head-foot, a squid’s mantle is a long muscular tube containing most of the organs, tapering into a fleshy conical tip. The animals have no teeth or bones, except for some cuttlefish that have the remnants of a coiled shell buried within them as a ‘cuttlebone’.
Squid move by pumping water in and out of their bodies. Propulsion comes from using the water itself, sucked into the mantle and squeezed out through a smaller tube called a siphon in a series of strong pulses. By finely manipulating their siphons, squid maintain precise control the water stream: volume, intensity, and direction.28 All cephalopods carry siphons, even the lumbering octopus, but squid get the most mileage from them.
Water is heavy, so you’d expect slow acceleration from a squid. Not so: powerful rings of muscle surround the mantle, squeezing a huge amount of water through the siphon and creating large accelerations. They’ve also got a secret weapon for emergencies: a lightning-fast escape mechanism. It’s similar to a lobster’s caridoid reflex: a highly specialized nerve structure called a giant axon,29 a single supersized nerve fiber thicker than a human hair running down the mantle. Its unusual size facilitates the extremely rapid transit of nerve signals to all the muscles of the mantle, so that the maximum amount of water will shoot from the mantle and jet the squid away. The giant axon is a way to translate a simple imperative (“Run!”) into a complex escape response.
The waterborne jet propulsion of squid has been well known for centuries. Since the 1800s, observers have described squid gliding above the water. It was a marine legend, but a recent survey recorded a group of squid off the coast of Brazil doing more than gliding. A fan of 6-inch silver missiles burst from the water and accelerated away, trailing streams of high-pressure water.30 A second report concerning Japanese squid shows the same capability in ocean-going animals best known as a fishery.31 The aerodynamic details are not yet completely understood, but jet propulsion allows a flying squid to do something flying fish cannot: accelerate in the air. The Brazilian species Sthenoteuthis pteropus accelerates at more than two g’s. However, fuel runs out quickly—limited by how much the mantle can store—and such brief acceleration can’t get the animals past about 8 miles per hour while airborne. It’s a rare testament to the power and grace of these animals—a phenomenon few people have ever witnessed.
Crustaceans are among the ocean’s most common and successful creatures, but they’re still so awkward. Consider, as David Foster Wallace once did, the lobster. Cursed with legs in a world of fins, he scuttles across the bottom while fish cruise above. Weighed down by interlocking plates of armor, he turns like an old station wagon. If bowled over by a passing wave, he thrashes around on his back, waiting for the next wave to save him.
That heavy carapace has advantages: large adult lobsters have few natural predators. But as juveniles, they’re devoured by a host of threats from octopuses to their own grown relatives.32 Smaller crustaceans like shrimp face predation all their lives. In response, many crustaceans evolved a stunning adaptation: an escape reflex so powerful that it single-handedly catapults these scuttling tanks into the realm of elite speedsters.
Our chitinous subject is under attack, or thinks he is—a diver approaches, holding out her camera for a great shot. At this provocation, he suddenly contracts, pulling his tail down and around to his underside in a series of rapid-fire spasms. Extending back, curling down from the thorax, a crustacean’s abdomen is built of heavy muscles.33 The escape motion is like your outstretched hand, palm up, contracting into a tight grip. It launches the animal backward in an eyeblink: a medium-sized lobster can accelerate at 330 feet per second squared,34 ten times the acceleration due to gravity, seeming to teleport the animal 5 feet back in an eyeblink. A Bugatti Veyron Super Sport, among the world’s fastest production cars, manages an acceleration of only about 40 feet per second squared.35 Like the Looney Tunes roadrunner taking off, our lobster is gone—leaving nothing behind but a swirling cloud of sediment. Six days out of the week, his tail is a slab of deadweight best served with Hollandaise sauce. On the seventh day, it saves his life.
The motion is called the caridoid escape reaction, or more simply, lobstering (though it has been most studied in the crayfish).36 It’s supported by delicate infrastructure throughout the nervous system, neurons and nerves that propel the animal’s whole body into fast action. Crustaceans carry their tails perpetually cocked for lobstering at a moment’s notice. When threatened, they can trigger the caridoid reflex in as little as one hundredth of a second.37 But can their brains really operate that fast? Lobstering, it turns out, is not a choice in the typical sense. Instead it’s the product of a command neuron—a system integrating thousands of nerve processes into a single hair trigger.38
In the lab, one electrical stimulation of the giant neuron, or just a poke at the animal’s abdomen, triggers a joint muscle response of artificial panic.39 Once started, it just happens, like the effortless and unwavering precision of a Ray Allen jump shot. The giant nerve fibers provide a very fast response— but it is limited in versatility. Through countless repetitions and eons, a simple desperate tail-flip movement evolved into a permanent panic circuit in crustaceans’ wiring. Their brains surrender to a hard-wired routine baked deep in their bodies, sacrificing control for raw speed. Among all the world’s animals, no escape reflex is faster.40
You’re on vacation in the Caribbean, taking a snorkel cruise over a local reef. Bobbing on the stepladder, rubber fins on corrugated steel, you bite down on your snorkel and take the plunge.
It’s warm as bathwater. Purples and pinks and blues checker the bottom, crisscrossed with the heavy fish traffic of a healthy reef. You can’t hear much through the gurgle of water in your ears, but it’s impossible not to notice a persistent clicking sound. It’s more than a few clicks; they’re beyond counting, like a thousand pebbles thrown into a tumbler. Your first thought: currents churning stones on the bottom. But in fact, this is a biological sound—that of a tiny and fascinating crustacean, the snapping shrimp in the family Alpheidae.
But snapping shrimp do not make a sound the way you might think. They do not bang two parts of the claw together to make their signature snaps. Instead, they manipulate the basic physics of water, and hugely amplify the sounds of their rapid-fire claws.41 They take advantage of cavitation, the tendency of water at ultra-low pressure to vaporize into small bubbles. When the pressure falls, the bubbles form, and when it rises again, the bubbles suddenly collapse to release a great deal of energy in a small space and brief time. Cavitation is a major engineering problem in boat propellers—they spin so fast that they create millions of tiny bubbles that collapse with a small bang. That bang eats into the metal of even the hardest propeller blade, limiting its operational life. Snapping shrimp have invented a biological way to create these cavitation bangs, shaping their shockwaves into weapons fired like an old flintlock pistol.
For this reason, snapping shrimp are often called pistol shrimp. One of their two claws is a delicate prong, but other has swollen to enormous size— as though Bruce Banner’s fist decided on its own to enter Hulk mode. This claw carries a modified pincer: one side a notched blocky mass and the other a hinged finger-like protrusion. Think of that “finger” as a hammer, and its blocky counterpoint as an anvil. The former fits into the latter’s notch as though they were shop-machined.42 The hinge joint has powerful musculature, and the shrimp carries the whole assembly cocked open like a revolver, complete with locking catch. When the shrimp triggers the joint, the hammer slams into the anvil socket.
Snapping claw of the snapping shrimp Alpheus californiensis. (Top) the snapping hammer is held open by a catch mechanism. The moveable hammer, the plunger, and the socket are shown. (Bottom) The snapping mechanism is closed, with the moveable hammer and the plunger fitting precisely into the anvil socket. From Johnson, M. W., F. A. Everest, and R. W. Young. 1947. “The role of snapping shrimp (Crangon and Synalpheus) in the production of underwater noise in the sea.” Biological Bulletin 93:122–138.
The descending hammer displaces all the water from the notch reservoir. An intense jet of water shoots forward directed by the notch’s lip, moving so fast that cavitation produces an air bubble in its wake.43 The bubble rockets away, but slows rapidly under the drag of water and grows unstable as the pressure rises. It dies with a pop just an instant after birth, collapsing explosively to release heat and light. Temperatures inside the bubble spike to 8,500° F (4,700° C): more than enough to melt tungsten.44
The “pistol” casts a powerful shockwave forward into the water, giving the shrimp a hunting tool. A snapping shrimp lies in its burrow like an under-sea highwayman, weapon ready to ambush small prey. Its shot erupts from the tiny aperture faster than any possible reaction and hits the prey with the force of a hammer blow. The flash and moving water are too quick for the human eye, so the target appears stricken backward by an invisible force—as though smote by some vengeful reef god. Having stunned the victim or killed it outright with a single attack, the shrimp scoots out from its burrow and hauls the meal back.45
As you might imagine, this unique tool is good for more than violence. The family Alpheidae comprises hundreds of shrimp species, many given to claw wrestling or chesty displays of noise. A rare few have formed hive societies, similar in some ways to social insects like bees and ants. In hives, comrades signal greetings and call out threats with pistol shots, holding their weapons overhead for safety. For such able fighters, the hive-living species tend to avoid conflict. Disputes are resolved with posturing and warning shots, but competitors rarely injure each other.46
Moving fast in water burns your energy budget at ruinous rates, but another challenge presented by the wide ocean is the possibility of long-distance migrations. From some spots of Antarctica, a gaze due north runs across open ocean all the way to the Arctic Circle. Such broad swaths of habitat are opportunities for very long distance travel—and some ocean species use them. Powering those migrations demands different solutions than the solutions for speed.
Thirty feet deep in the open ocean, the blue ranges in every direction from transparent to a dusky dark that seems to swallow light. Waves march above in a long repeating line, striving for the nearest shore, thousands of miles away. A silence lies throughout the sea like unbroken fog.
Unexpectedly, a shape slips past, giant and dark, with a powerful flat tail and two wide fins splayed out to either side. A second, smaller shape ghosts behind. They rise to the surface synchronously, blow several fishy-smelling notes in quick succession, and sink back to their placid hike. When they are gone, the ocean returns to empty waiting.
Some of the longest migrations on our planet are by swimmers. Blue whales slip from the Southern Ocean near Antarctica to subequatorial seas. Humpbacks announce their annual return to Hawaii, after a long swim from Alaska, with shows of exuberance above the water and majestic operas beneath.47 Gray whales leave their foraging grounds in the Bering Sea and meander down the coast of California to breeding lagoons in Baja Mexico.48
For humans, swimming is wonderful exercise, because water is heavy. Moderate-speed swimming burns as many calories as fast running, rowing, or cycling. As any parent of a competitive swimmer can attest, it takes tremendous food energy to swim. Olympic swimmers may consume upward of 10,000 calories per day.49 Given these huge costs, how and why do whales manage such long migrations?
Whales tank up before a long swim. Often their feeding areas are in far polar seas, and they spend their summers feasting on the bonanza of food that a short, intense polar summer can produce. But as winter approaches, the water gets colder, and the plankton fade into a fallow offseason. So the feeding grounds are abandoned, and migratory whales turn for the tropics at summer’s close.
With full bellies, they still face 5,000 miles of cold water between their food supplies and winter havens. They aren’t explosive athletes; if a dolphin is a supercharged cherry red motorcycle, these migratory titans are freight trains rumbling from coast to coast. Like those trains, they take a while to get up to speed. Acceleration isn’t nearly as valuable as efficiency, so the giants propel themselves with powerful deliberate strokes. A blue whale routinely cruises at about 1–4 miles per hour, wasting not a scrap of strength or movement.50 Once a great whale reaches cruising speed, it doesn’t take much energy to maintain that speed.51
Their size draws the most attention, but migratory whales are marvels of engineering. A blue whale (Balaenoptera musculus) is the greatest example, stretching 200 tons of mass out to a surprisingly slender 100-foot length. The tail fluke delivers thrust at 90% efficiency—far higher than the best commercial ship propellers, which churn and grasp desperately for thrust that the whale fluke seems to calmly command.52 Backing up these traits is a steely endurance, pushing the traveler across entire oceans in just weeks, without feeding.53
They arrive on wintering grounds, rest, nurse their young, and sing the melancholy songs that attract mates (whales are big into Morrissey). They choose warmer water, gamboling across the reefs of Tonga, frolicking in Baja’s lagoons. Shivering less than they did in the cold polar seas, the energy saved by summering in warm water can recoup migration’s costs. New calves likely benefit most from the heat; being small, they lose more heat per unit body mass than their parents do. They also avoid their fiercest predator: Orcas hunt in colder waters and feed on helpless yearling whales when they can. Warm winter waters are a haven against some of these dangers.
The end of winter is a hungry time for a migrating whale—especially a mother who has nursed her young calf, drawing on the food reserves she laid down the summer before. Yet the reverse migration lies ahead for these animals, thousands more miles, this time on an empty stomach. Food at the end of this journey looms as a critical need for even the biggest animals on Earth, and they arrive ravenous in their polar summer seas.
Lately, that food has been harder to find for some whales. In 1999, a large fraction of gray whales (Eschrichtius robustus) were observed to be thin, even emaciated. The death rate of calves on migration was huge, and hundreds died. The reason has been traced to the northerly retreat of their food supply: instead of a wide field of tasty crustaceans that gray whales normally find in the Bering Strait, the whales found nothing. Their food supply had responded to warming waters and had retreated to the north. Grays weren’t helpless— they followed the trail and found meals at last, at the cost of hundreds more miles and countless calories.54 Some whales probably didn’t find enough food fast enough, and their calves died. Others plowed north into the Chukchi and Beaufort Seas, victims of a warming ocean, looking for food.55
Gray whales are regularly seen much farther to the north than they used to be. But one animal stunned the whale-watching world in 2010 by turning up off the coast of Israel in the Mediterranean Sea.56 No gray whale had ever been seen in the Mediterranean, and the species was hunted out of the Atlantic around the year 1700. For 300 years, this species has been restricted to the Pacific. This one whale may have slipped through the Bering Strait and across the Canadian Arctic ice fields, swimming thousands of extra miles, pushing the normal migration distance far, far longer. Once the wanderer emerged in the North Atlantic with a full belly, it simply followed instinct: head south for the winter and eventually turn east into a nice warm lagoon. This lagoon happened to be the Mediterranean, not a breeding site in Baja.
However it managed the journey, this whale disappeared and has not been seen in either ocean since.
Mile for mile, only one animal on the planet can match the great cetaceans. It’s a seabird, skimming inches above the water’s surface with the vast white wings and inner peace of a seraph: the albatross. Long celebrated by poets as a symbol of natural beauty and by sailors as an augur of death, the bird’s image resonates through maritime history. Though hatched on land and bound by memory to strands of beach, albatross are really creatures of the sea. They spend most of their lives in flight, feeding from the water as they cover endless open miles. Living in solitude except for brief stretches during the breeding season, albatross drift across the sea in lazy gyres the size of continents.
Flying in air doesn’t have the same energy demands as swimming—the drag of air is far, far less than that of water. But the sheer length of migrations for some seabirds qualifies them as extreme by any metric. The wandering albatross, Diomedea exulans, is the largest seabird in existence and boasts the longest wingspan of any living bird—outstripping even the California condor. Those wings, luminous white streaked with sooty black feathers, stretch up to 6 feet each from the slim white body—12 feet in total wingspan. Yet these sleek birds weigh less than 30 pounds; a long hooked beak and dark eye highlights complete their striking appearance.
In the 1977 Disney film The Rescuers, the heroes (a pair of animated, anthropomorphized mice) hire an albatross to fly them from New York City to a Louisiana bayou. Their charter, a klutzy aeronaut named Orville, offers great comedic relief with hair-raising takeoffs and slapstick landings. It’s neither Orville’s fault nor Disney’s invention: albatross, collectively, have a rocky relationship with the ground. They don’t so much land as crash in slow motion, cutting speed until they can hit the ground without injuring themselves.57 A fierce headwind helps.58 Taking to the air is clumsy, too, but the bird has to work much harder. He can’t fly until he’s reached a decent speed, getting air moving over his huge wings. After some spastic stretching, he starts down the runway with a furious waddling gait and wings a-flap. Some tentative hops, testing the breeze, hoping he gets a well-timed gust. He finally catches some air and keeps it, angling up into the wind. If he avoids an early stall, he’s more than airborne: he’s home. You don’t need a degree in ornithology to appreciate an albatross in flight. Wings stretched and motionless, angled edges perfectly slicing the wind—more gliding than flying. The tranquility of an albatross cruising over a swell at twenty knots is the key to his beauty and his entire way of life.59
Flight is easy for birds, but flapping is exhausting. Every stroke of their wings takes energy, so each moment of powered flight needs fuel. Hummingbirds are the prime example of high-energy reliance: a single pause in ever-beating wings would drop them like stones to the ground. Albatross are the polar opposite, accruing 75,000 miles per year with a bare minimum of effort.60
Such long hauling wouldn’t be possible for a flapping albatross. She’d collapse from exhaustion or starve to death. So she puts those enormous wings to use as a static airfoil, like a hang glider, stretching them out to full extension once she’s in the air and keeping them fixed. Most birds’ wings would tire after a few minutes; the albatross can endure for days. Special tendons in her shoulders lock them in place, needing no energy whatsoever to hold her wings outstretched.61 Following large weather patterns over the oceans, the albatross rides for thousands of miles on a cushion of air. But for the slightest twitches of her tail and subtle turns of her abdomen, she is completely inert. Her heart rate during flight is no higher than at rest.62
How albatross soar. The wind and the waves are moving from upper right to lower left. A bit of an updraft acts on the upwind side of each wave, and the albatross can catch it and be lofted up to 15 meters. They turn to the right and glide down, moving upwind and then along the trough of the wave until they again bank into the updraft. Reprinted from Progress in Oceanography 88, P. L. Richardson, “How do albatrosses fly around the world without flapping their wings?” 46–58, © 2011, with permission from Elsevier.
Gliding, even at its most efficient, requires some kind of extra thrust. Albatross find it in the same winds that carried sailing ships between continents, using tactics identical to those of experienced glider pilots.63 If in need of a boost, the birds dip their wings and lose altitude while rapidly gaining speed. After dipping into the valley between two swells, they turn 90° and bank upward. They turn into the wind, rushing up the peak of the second wave, losing a bit of speed but rocketing up in the air to continue their lonely odysseys.64 Large, broad wavefronts in the open sea can serve as glider mass transit, with several albatross hugging the front of the swell. They’re surfing—not on the water, but on the thin current of air pushed ahead by the wave. By using these tricks in favorable spots, albatross are able to cover more than 500 miles each day.
When the wind dies, unlucky albatross must either burn energy flapping or sit in the drink until their fortunes to change. Physical oceanographer Phillip Richardson lays out the rules albatross must follow “No wind, no waves, no soaring.”65 Becalmings are common in the world’s warmest climates, and for that reason, albatross are seldom found in the deep tropics. They’re particularly fond of the planet’s southern reaches, underburdened with land mass and home to vast empty tracts of cold sea and variable winds. Wandering albatross live long lives—up to 70 years—and may forage over 9,000 miles during a single breeding season.66 They don’t match the awe-inspiring size of the great whales, but the sight of an albatross hanging suspended by the invisible threads of the wind should still take your breath away.
Sailors long believed the albatross, soaring forever and making its own way through the world, actually created the wind that propelled them all across the vasty deep. In Samuel Taylor Coleridge’s immortal poem, the eponymous Ancient Mariner disastrously kills one of the white birds—a beautiful thing with ghosts in its eyes and a cold wind at its back:67
And I had done a hellish thing,
And it would work ‘em woe:
For all averred, I had killed the bird
That made the breeze to blow.
Ah wretch! said they, the bird to slay,
That made the breeze to blow!
