One of the most amazing things I have ever witnessed involved an otherwise unprepossessing house cat named Billy. This was some years ago, shortly after I had moved into a little rental house in the Hudson Valley. Billy, a big, bad-tempered old tomcat, belonged to the previous tenant, a guy by the name of Phil. Phil adored that cat, and the cat—improbably, given his otherwise unenthusiastic feelings about humanity—returned the favor.
On the day Phil vacated the house, he wrestled an irate Billy into a cat carrier, loaded him into a moving van, and headed toward his new apartment, in Brooklyn. Thirty minutes down I-84, in the middle of a drenching rainstorm, the cat somehow clawed his way out of the carrier. Phil pulled over to the shoulder but found that, from the driver’s seat, he could neither coax nor drag the cat back into captivity. Moving carefully, he got out of the van, walked around to the other side, and opened the door a gingerly two inches—whereupon Billy shot out, streaked unscathed across two lanes of seventy-mile-per-hour traffic, and disappeared into the wide, overgrown median. After nearly an hour in the pouring rain trying to make his own way to the other side, Phil gave up and, heartbroken, continued onward to his newly diminished home.
Some weeks later, at a little before seven in the morning, I woke up to a banging at my door. Braced for an emergency, I rushed downstairs. The house had double-glass doors flanked by picture windows, which together gave out onto almost the entire yard, but I could see no one. I was standing there, sleep-addled and confused, when up onto his hind legs and into my line of vision popped an extremely scrawny and filthy gray cat.
I gaped. Then I opened the door and asked the cat, idiotically, “Are you Billy?” He paced, distraught, and meowed at the door. I retreated inside and returned with a bowl each of food and water, but he ignored them and banged again at the door. Flummoxed, I took a picture and texted it to my landlord with much the same question I had asked the cat: “Is this Billy?”
Ninety minutes later, Phil showed up at my door. The cat, who had been pacing continuously, took one look and leaped into Phil’s arms—literally hurled himself the several feet necessary to be bundled into his erstwhile owner’s chest. Phil, a six-foot-tall bartender of the badass variety, promptly started to cry. After a few minutes of mutual adoration, the cat hopped down, purring, devoured the food I had put out two hours earlier, lay down in a sunny patch of grass by the door, and embarked on an elaborate bath.
How Billy accomplished his remarkable feat remains a mystery, not only to me but to everyone. In 2013, after an indoor cat named Holly went missing during a road trip with her owners to Daytona Beach and turned up back home two months later, in West Palm Beach, two hundred miles away, the collective ethological response to the question of how she did it was “Beats me.” And that bafflement is generalizable. Cats, bats, elephant seals, red-tailed hawks, wildebeests, gypsy moths, cuttlefish, slime mold, emperor penguins: to one degree or another, every animal on earth knows how to navigate—and, to one degree or another, scientists remain perplexed by how they do so.
What makes this striking is that we are living in a golden age of information about animal travels. Three hundred years ago, we knew so little about the subject that one English scholar suggested in all seriousness that storks spent their winters on the moon. Thirty years ago, a herd of African elephants, the largest land mammals on earth, could still stage an annual disappearing act, crossing beyond the borders of a national park each rainy season and vanishing into parts unknown. But in the last few decades animal tracking, like so much of life, has been revolutionized by technology, including satellites, camera traps, drones, and DNA sequencing. We now have geolocation devices light enough to be carried by monarch butterflies; we also have a system for tracking those devices installed on the International Space Station. Meanwhile, the study of animal travel has acquired tens of thousands of new contributors, in the form of amateurs who use cell phones and laptops to upload observational data points by the billions. And it has also acquired—perhaps unsurprisingly, given the enduring, “Incredible Journey”-esque appeal of the subject matter—a spate of new books about advances in animal navigation.
Two main lessons emerge from those books—one tantalizing, one tragic. The first is that, although we are developing a clearer picture of where animals go, we still have a lot to learn about how they find their way. The second is that the creatures with a credible claim to being the worst navigators on the planet have steadily reduced the odds of all the others getting where they need to go, by interfering with their trajectories, impairing their route-finding abilities, and despoiling their destinations. Those feckless creatures are us, of course. While other animals lend this field of study its fascination, we humans distinguish ourselves chiefly by adding existential undertones to the fundamental questions of navigation: How did we get here? And where, exactly, are we going?
Nature, in her infinite creativity, has devised many ways for animals to get from A to B. Birds fly, fish swim, gibbons swing from tree branches (the technical term is “brachiate”), basilisk lizards walk on water, and web-toed salamanders curl up in a ball and roll downhill. Certain spiders drift about on homespun balloons, certain cephalopods use jet propulsion, and certain crustaceans hitch rides on other species. But, however they get around, all animals move for the same reasons: to eat, mate, and escape from predators. That’s the evolutionary function of mobility. The evolutionary problem it presents is that anything capable of moving must also be capable of navigating—of finding that meal, that mate, and that hiding place, not to mention the way back home.
Some impressive examples of this ability are widely known. Salmon that leave their natal stream just months after hatching can return after years in the ocean, sometimes traversing nine hundred miles and gaining seven thousand feet in elevation to do so. Homing pigeons can return to their lofts from more than a thousand miles away, a navigational prowess that has been admired for ages; five millennia ago, the Egyptians used them, like owls at Hogwarts, as a kind of early airmail. Many other exceptional navigators, however, are humble and unsung, and learning about them is one of the pleasures of “Supernavigators: Exploring the Wonders of How Animals Find Their Way,” by David Barrie, and “Nature’s Compass: The Mystery of Animal Navigation,” by the science writer Carol Grant Gould and her husband, the evolutionary biologist James L. Gould. Each winter, a member of the crow family, the Clark’s nutcracker, recovers the food it has previously cached over a hundred square miles in up to six thousand separate locations. When spiders of the Salticidae family are confined to a maze and shown a prey animal, they will reach it even when doing so initially requires moving in the opposite direction. Rock lobsters migrate en masse from colder waters to warmer ones, travelling, as the Goulds write, “in tandem conga lines, antennae to tail” and maintaining a perfectly straight course, despite powerful currents and the uneven ocean floor.
All this is to say nothing of the greatest navigational feats in the animal kingdom: the long-distance migrations undertaken by many bird species. If, like me, you live in North America and don’t know much about ornithology, you probably associate those migrations with a jagged V of Canada geese overhead, their half-rowdy, half-plaintive calls signalling the arrival of fall and spring. As migrants go, though, those geese are not particularly representative; they travel by day, in intergenerational flocks, with the youngest birds learning the route from their elders. By contrast, most migratory birds travel at night, on their own, in accordance with a private itinerary. At the peak of migration season, more than a million of them might pass overhead every hour after dark, yet they are no more a part of a flock than you are when driving alone in your S.U.V. on I-95 during Thanksgiving weekend.
The stories of these avian travellers are told in abundance in Scott Weidensaul’s “A World on the Wing: The Global Odyssey of Migratory Birds.” An ardent ornithologist, Weidensaul sometimes shares a few too many details about a few too many species, but one sympathizes: virtually every bird in the book does book-worthy things. Consider the bar-headed goose, which migrates every year from central Asia to lowland India, at elevations that rival those of commercial airplanes; in 1953, when Tenzing Norgay and Edmund Hillary made the first ascent of Mt. Everest, a member of their team looked up from the slopes and watched bar-headed geese fly over the summit. Or consider the Arctic tern, which has a taste for the poles that would put even Shackleton to shame; it lays its eggs in the Far North but winters on the Antarctic coast, yielding annual travels that can exceed fifty thousand miles. That makes the four-thousand-mile migration of the rufous hummingbird seem unimpressive by comparison, until you realize that this particular commuter weighs only around a tenth of an ounce. The astonishment isn’t just that a bird that size can complete such a voyage, trade winds and thunderstorms be damned; it’s that so minuscule a physiology can contain a sufficiently powerful G.P.S. to keep it on course.
More generally, the astonishment is that any physiology can contain a navigational system capable of such journeys. A bird that migrates over long distances must maintain its trajectory by day and by night, in every kind of weather, often with no landmarks in sight. If its travels take more than a few days, it must compensate for the fact that virtually everything it could use to stay oriented will change, from the elevation of the sun to the length of the day and the constellations overhead at night. Most bewildering of all, it must know where it is going—even the first time, when it has never been there before—and it must know where that destination lies compared with its current position. Other species making other journeys face additional difficulties: how to navigate entirely underground, or how to navigate beneath the waters of a vast and seemingly undifferentiated ocean.
How might an animal accomplish such things? The Goulds, in “Nature’s Compass,” outline several common strategies for staying on course. These include taxis (instinctively moving directly toward or directly away from a given cue, such as light, in the case of phototaxis, or sound, in the case of phonotaxis); piloting (heading toward landmarks); compass orientation (maintaining a constant bearing in one direction); vector navigation (stringing together a sequence of compass orientations—say, heading south and then south-southwest and then due west, each for a specified distance); and dead reckoning (calculating a location based on bearing, speed, and how much time has elapsed since leaving a prior location). Each of these strategies requires one or more biological mechanisms, which is where the science of animal navigation gets interesting—because, to have a sense of direction, a given species might also need to have, among other faculties, something like a compass, something like a map, a decent memory, the ability to keep track of time, and an information-rich awareness of its environment.
The easiest of these mechanisms to understand are those that most closely resemble our own. Most humans, for instance, routinely navigate based on a combination of vision and memory, and we are not alone. One scientist, puzzled to find that his well-trained rats no longer knew their way around a maze after he moved it across his lab, eventually determined that they had been navigating via landmarks on the ceiling. (That was a blow to the notion, much beloved by behaviorists, that such rats were just learning motor sequences: ten steps forward, turn right, three steps forward, there’s the food.) Other animals use senses that we possess but aren’t very adept at deploying. Some rely on smell; those migrating salmon can detect a single drop of water from their natal stream in two hundred and fifty gallons of seawater. Others use sound—not in the simple, toward-or-away mode of phonotaxis but as something like an auditory landmark, useful for maintaining any bearing. Thus, a bird in flight might focus on a chorus of frogs in a pond far below in order to orient itself and correct for drift.
Many animals, however, navigate using senses alien to us. Pigeons, whales, and giraffes, among others, can detect infrasound—low-frequency sound waves that travel hundreds of miles in air and even farther in water. Eels and sharks can sense electric fields and find their way around underwater via electric signatures. And many animals, from mayflies and mantis shrimp to lizards and bats, can perceive the polarization of light, a helpful navigation cue that, among other things, can be used to determine the position of the sun on overcast days.
Other navigational tools are simultaneously more prosaic and more astounding. If you trap Cataglyphis ants at a food source, build little stilts for some of them, give others partial amputations, and set them all loose again, they will each head back to their nest—but the longer-legged ones will overshoot it, while the stubby-legged ones will fall short. That’s because they navigate by counting their steps, as if their pin-size brains contained a tiny Fitbit. (On the next journey, they’ll all get it right, because they recalibrate each time.) Similarly, honeybees adjust their airspeed in response to headwinds and tailwinds in order to maintain a constant ground speed of fifteen miles per hour—which means, the Goulds suggest, that by tracking their wing beats the bees can determine how far they have travelled.
I have presented these navigation mechanisms serially, but most creatures possess more than one of them, because different conditions call for different tools. What works at noon might not work at night, what works close to home might not work far away, and what works on a sunny day might not work in a storm. Yet even all these tools in combination cannot account for the last of the way-finding strategies described by the Goulds, which is by far the most arresting and confounding: true navigation.
True navigation is the ability to reach a distant destination without the aid of landmarks. If you were kidnapped, taken in pitch darkness thousands of miles away, and abandoned somewhere uninhabited, true navigation would be your only option for finding your way home.
To do so, you would need a compass, along with the know-how to use it—for instance, an awareness that magnetic north and geographic north are not identical. Failing that, you would need to be able to orient based on the movement of the sun—a tricky business, especially if your kidnappers weren’t kind enough to inform you of your latitude. If you plan to travel after dark, you’d better hope that you aren’t in the Southern Hemisphere, which has no equivalent of the North Star, or you’d better be able to rival Galileo with your knowledge of the nightly and seasonal course of the constellations. But, even if all this applied, you would still be in trouble if you did not also have a map. Being able to maintain a given bearing with perfect precision isn’t much help if you have no idea where you are vis-à-vis your destination.
Some animals plainly do have such a map, or, as scientists call it, a “map sense”—an awareness, mysterious in origin, of where they are compared with where they’re going. For some of those animals, certain geographic coördinates are simply part of their evolutionary inheritance. Sand hoppers, those tiny, excitable crustaceans that leap out of the way when you stroll along a beach, are born knowing how to find the ocean. When threatened, those from the Atlantic coast of Spain flee west, while those from its Mediterranean coast flee south—even if their mothers were previously translocated and they hatched somewhere else entirely. Likewise, all those birds that embark on their first migrations alone must somehow know instinctively where they are going.
But instinct alone does not explain what such birds can do. In 2006, scientists in Washington State trapped a group of white-crowned sparrows that had begun their annual migration from Canada to Mexico and transported them in a windowless compartment to New Jersey—the avian equivalent of the kidnapping thought experiment. Upon release, the juvenile birds—those making their first trip—headed south along the same bearing that they had been using back in Washington. But the adult birds flew west-southwest, correcting for a displacement that nothing in their evolutionary history could have anticipated. That finding is consistent with many others showing that birds become better navigators during their first long flight, in many cases learning entirely new and more efficient strategies. Subsequent experiments found that mature birds can be taken at least six thousand miles from their normal trajectory and still accurately reorient to their destination.
How do they do it? At present, the most compelling theory is that they make use of the earth’s magnetic field. We know about this ability because it is easy to interfere with it: if you release homing pigeons on top of an iron mine, they will be terribly disoriented until they fly clear of it. When scientists went looking for an explanation for this and similar findings, they found small deposits of magnetite, the most magnetic of earth’s naturally occurring minerals, in the beaks of many birds, as well as in dolphins, turtles, bacteria, and other creatures. This was a thrilling discovery, quickly popularized as the notion that some animals have built-in compass needles.
As with many thrilling and popular scientific ideas, however, this one started to look a little strange on closer inquiry. For one thing, it turned out that birds with magnetite in their beaks weren’t navigating based on north-south alignment, as we humans do when using a compass. Instead, they were relying on the inclination of the earth’s magnetic field—the changing angle at which it intersects the planet’s surface as you move from the poles to the equator. But inclination provides no clues about polarity; if you could sense it, you would know where you were relative to the nearest pole, but you wouldn’t know which pole was nearest. Whatever the magnetite in birds is doing, then, it does not seem to function like the needle in a compass. Even more curiously, experiments showed that birds with magnetite grew temporarily disoriented when exposed to red light, even though light has no known effect on the workings of magnets.
One possible explanation for this strange phenomenon lies in a protein called cryptochrome, which is found in the retina of certain animals. Some scientists theorize that, when a molecule of cryptochrome is struck by a photon of light (as from the sun or stars), an electron within it is jolted out of position, generating what is known as a radical pair: two parts of the same molecule, one containing the electron that moved and the other containing an electron left unpaired by the shift. The subsequent spin state of those two electrons depends on the orientation of the molecule relative to the earth’s magnetic field. For the animal, the theory goes, a series of such reactions somehow translates into a constant awareness of how that field is shifting around it.
If you did not quite grasp all that, take heart: even researchers who study the relationship between cryptochrome and navigation do not yet know exactly how it works—and some of their colleagues question whether it works at all. We do know, though, that the earth’s magnetic field is almost certainly crucial to the navigational aptitude of countless species—so crucial that evolution may well have produced many different mechanisms for sensing the field’s polarity, intensity, and inclination. Taken together, those mechanisms would constitute the beginnings of a solution to the problem of true navigation. And it would be an elegant one, capable of explaining the phenomenon across a range of creatures and conditions, because the magnetic field is omnipresent on this planet. Given some means of detecting it, you could rely on it by day and by night, in clear weather and in foul, in the air and over land and underground and underwater.
That kind of sweeping explanation would be convenient, because true navigation, which was once thought to require the kind of advanced reasoning and sophisticated toolmaking exclusive to humans, seems increasingly likely to be a widely shared capacity. Countless bird species can do it, as can salmon. Those conga-line rock lobsters are so good at it that they appear to be impossible to disorient, which we know because scientists have gone to outlandish lengths to try to do so. As Barrie describes in “Supernavigators,” you can cover a rock lobster’s eyes, put it in an opaque container filled with seawater from its native environment, line the container with magnets suspended from strings so they swing in all directions, put the container in a truck, drive the truck in circles on the way to a boat, steer the boat in circles on the way to a distant location, drop the lobster back in the water, and—voilà—it will strike off confidently in the direction of home.
Needless to say, you and I cannot do this. If you blindfold human subjects, take them on a disorienting bus ride, let them off in a field, remove the blindfolds, and ask them to head back toward where they started, they will promptly wander off in all directions. If you forgo the bus and the blindfolds, ask them to walk across a field toward a target, and then conceal the target after they start moving, they will stray off course in approximately eight seconds.
The problem isn’t that humans don’t have any innate way-finding tools. We, too, can steer by landmark, and we can locate the source of sounds or other environmental cues and make our way toward them. (With sounds, we do this much like frogs: by unconsciously assessing either the intensity differential or the time delay between a noise in our right ear and in our left one.) We also have a host of specialized neurons to help keep us oriented: head-direction cells, which fire when we face a certain way (relative to a given landscape, not to cardinal directions); place cells, which fire when we are in a familiar location; grid cells, which fire at regular intervals when we navigate through open areas, helping us update our own position; and boundary cells, which fire in response to an edge or obstacle in our field of vision.
All this is key to our day-to-day functioning, but none of it enables us to navigate even half as well as a newt. Still, we do sometimes perform extraordinary acts of way-finding; unlike rock lobsters, however, we have to learn how to do so. If you are the kind of person who never really grasped the parallax effect and doesn’t know your azimuth from your zenith, that process can be painful. But basic way-finding competence was once far more widespread in our species than it is today, simply because it was crucial to survival: you can neither hunt nor gather without straying from home.
Moreover, some individuals and cultures have long excelled at navigation. In “From Here to There: The Art and Science of Finding and Losing Our Way,” the British journalist Michael Bond rightly marvels at the navigational brilliance of the early Polynesians, who, about five thousand years ago, began paddling their canoes around a vast area of the Pacific Ocean now known as the Polynesian Triangle: ten million square miles of water, bounded by New Zealand, Hawaii, and Rapa Nui, with perhaps a thousand other islands scattered throughout. To steer from one of those islands to another, on routes as long as twenty-five hundred miles, those early navigators relied on “the patterns of waves, the direction of the wind, the shapes and colors of clouds, the pull of deep ocean currents, the behavior of birds, the smell of vegetation, and the movements of sun, moon, and stars.” The price of distraction or error was dire; in the vast open waters of the South Pacific, the odds of hitting an island by chance are close to zero. Understandably, then, those early Polynesians revered good navigators, and began training each new generation of them very young.
Give or take some centuries and miles, you can find similar feats in almost every culture. Many indigenous peoples of the Far North were wonderfully adept at navigating terrain that most of us would find all but featureless; the Inuit, for instance, made their way overland using extensive systems of landmarks and could navigate coastal waters in dense fog, by means of careful attention to wave patterns and the birdcalls of their home cove. In the equally unforgiving landscapes of the American Southwest and central Australia, native peoples navigated in part by cultivating an oral tradition full of toponyms, each one containing detailed geographic information. By the fourth century B.C., the Greeks had made their way to the Arctic Circle; by the second century A.D., the Romans had reached China; and by the ninth century Indonesians had landed in Madagascar. As time went on, we began supplementing observation and memory with more and more physical tools: the astrolabe, the sextant, the compass, the map, the nautical chart, the global-positioning system.
Perversely, it is partly because these tools got so much better that so many of us got worse at navigating without them. In the past twenty years alone, the ubiquity of G.P.S.-enabled maps has all but eradicated the need to orient on our own. But long before the advent of that technology other factors were already eroding our aptitude for way-finding. High on the list was urbanization: after some three hundred thousand years of living in close proximity to wilderness, we migrated, in vast numbers and for the most part in just a few centuries, into cities. Those can be navigationally demanding in their own way, but they are full of obvious landmarks, written signage, public-transportation systems, cab drivers, and throngs of locals more or less able to offer directions. Moreover, all those artificial aids have rendered unusable certain helpful natural features. Rivers that were once easy to follow have been routed underground; the movement of the sun over days and seasons is largely obscured by narrow streets and tall buildings; and ninety-nine per cent of Americans live someplace where light pollution has reduced, sometimes to just a handful, the number of visible stars in the night sky.
On top of these changes to our natural environment, and arguably more deleterious, are changes to our social norms. We know from countless studies that the more children explore the world the better their sense of direction. But, as Bond notes, how far they are allowed to roam on their own has declined drastically in just two or three generations. In England, in 1971, ninety-four per cent of elementary-age kids were permitted by their parents to travel alone somewhere other than to and from school. By 2010, that percentage had dropped to seven.
Those factors take a toll on our navigational abilities. Compared with neighborhood maps drawn by kids who regularly walk or bike, maps drawn by children who are driven everywhere are woefully impoverished, and the spatial memory of adults who rely heavily on G.P.S. declines more than that of those who do not. We do not know what other price we might pay for letting our navigational abilities atrophy; Bond goes too far beyond the current science when he ponders a relationship between diminished way-finding and Alzheimer’s. But we do know, from other areas of learning as well as from other species, that what we do or don’t internalize in our earliest years can be determinative. Perhaps there are Canada geese living year-round on a golf course or in a local park in your home town. If so, that’s because they or their ancestors, having somehow missed that first flight with the rest of the flock back when they were goslings, never learned how to range far away and still find their way home.
But it is not just our own navigational capacities that we humans are endangering. Everything that has caused those to deteriorate—our increasing urbanization, our overreliance on automobiles, our ever more distant relationship to the natural world—is also wreaking havoc on the ability of other animals to get where they are going.
That havoc now takes countless forms. Illegal logging is destroying the mountain ecosystems of western Mexico, where monarch butterflies overwinter. Glyphosate, one of the world’s most commonly used herbicides, is interfering with the navigational abilities of honeybees. Our cities stay lit all night, confusing and imperilling both those animals that are drawn to light and those that rely on stars to plot their course. And as we appropriate more and more land for those cities and for timber and agriculture, the portion available for other species grows correspondingly smaller. The Yellow Sea, for instance, was once lined with nearly three million acres of wetlands that served as a vital stopover for millions of migrating shorebirds. In the past fifty years, two-thirds of those wetlands have vanished, lost to reclamation—a word that suggests, Weidensaul writes, bitterly but accurately, “humanity taking back something that had been stolen, when in fact the opposite is true.” Species that rely on those wetlands are dwindling at rates of up to twenty-five per cent per year.
And then there is climate change, which poses by far the greatest threat to the customary movement of animals around the earth. No species is unaffected by it, but long-distance navigators are particularly at risk, partly because they are reliant on more than one ecosystem and partly because the cues they use to get ready for their journeys—typically, the ratio of daylight and darkness—are increasingly decoupled from the conditions at their destinations. That is bad for the migrant, which even under optimal circumstances arrives desperately depleted from its travels, and terrible for its offspring, which may be born too late to take advantage of peak food availability. In no small measure, this pattern is to blame for the plummeting numbers of countless bird species.
Problems like these aren’t caused by higher temperatures, per se. The Goulds point out that, throughout the two-hundred-million-year evolutionary history of birds and the six-hundred-million-year evolutionary history of vertebrates, “average global temperatures have ranged from below freezing to above one hundred degrees Fahrenheit.” During that time, the ocean has been both hundreds of feet higher and hundreds of feet lower than it is today. Not every species survived those fluctuations, but most animals can adapt to even drastic environmental change, if it happens gradually. Ornithologists suspect that those bar-headed geese fly over Mt. Everest because they have been doing so since before it existed. When it began rising up from the land, some sixty million years ago, they simply moved upward with it.
The first problem with our current climate crisis, then, is not its nature but its pace: in evolutionary terms, it is a Mt. Everest that has arisen overnight. In the next sixty years, the range of one songbird, the scarlet tanager, will likely move north almost a thousand miles, into central Canada. All on its own, the bird could make that adjustment fairly swiftly—but there is no such thing in nature as a species all on its own. The tanager thrives in mature hardwood forests, and those cannot simply pick up their roots and walk to cooler climates. Compounding this problem of pace is a problem of space. Over the past few centuries, we have confined wild animals to ever-smaller remnants of wilderness, surrounded by farmland or suburbs or cities. When those remnants cease to provide what the animals need, they will have nowhere left to go.
If there is a silver lining to any of this—and one must look hard to see it, as with the stars at night now—it is that the more we learn about how animals travel the more we can help them keep doing so. Knowing that salmon follow the scent of their natal stream, scientists added an odor to hatcheries and used it to lure the fish back to the Great Lakes, years after pollution levels there, now ameliorated, caused a local extinction. Knowing that peak songbird migration lasts no more than six or seven days in a given area, ornithologists have led successful efforts to dim lights during the relevant time frame. Knowing that a shorebird migrating twenty thousand miles a year uses less than a single square mile of land along the way has helped conservationists engage in smaller, more affordable, more effective preservation.
All these examples are arguments for continuing to refine our understanding of animal navigation. Some of what we stand to learn may prove existentially critical, not only for other species but for our own. In “Supernavigators,” which came out the year before the pandemic, Barrie presciently notes that we cannot control the spread of zoonotic diseases if we don’t understand the travel patterns of the animals that carry them. Other findings might simply satisfy some long-standing curiosity, like that piqued by Billy’s adventure; even today, Barrie writes, “the navigational skills of dogs and cats have received surprisingly little serious scientific attention.” But the chief insight to be gleaned from how other animals make their way around the world is not about their behavior but about our own: the way-finding we must learn to do now is not geographic but moral. ♦
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