While Grant and Osborn incited alarm about the disorder caused by human migrants crossing geographical and biological borders, scientists in Britain pondered the challenges faced by growing populations constrained within those borders. In their vision of nature’s order, migrants played a macabre role. The most fitting end of migrant journeys, leading scientists said, was death.
The theory of migrant death began in the Arctic, where scientists first encountered local stories about furry Arctic-dwelling rodents called lemmings. In 1924 Charles Sutherland Elton was a twenty-four-year-old undergraduate in zoology at Oxford. Hired as an assistant on a series of expeditions to Spitsbergen, a then-uninhabited Arctic island halfway between Norway and the North Pole, he had helped conduct an ecological survey of the polar bears, walruses, reindeer, lemmings, and other Arctic creatures that roamed the snowy vistas.
The expedition provided a valuable opportunity1 for the ambitious young scientist. For weeks, Elton shared adventures and intimate living spaces with some of Oxford’s most accomplished scientists: Aldous Huxley’s brother, the geneticist Julian Huxley; the sociologist Alexander Carr-Saunders, who’d later become director of the London School of Economics; the Rhodes scholar Howard Florey. But while Spitsbergen provided the backdrop for Carr-Saunders’s writing of his magnum opus—Elton found it “full of exciting ideas of a general nature”—and Florey would go on to develop penicillin, opportunities for Elton to use the survey in Spitsbergen to catapult his own career appeared slim. Elton spied no unusual animals nor any never-before-seen behaviors that might help him make his mark in natural history. At one low point, he fell through the ice into a lake, whose waters submerged his body up to his neck.
Elton did not happen upon his chance2 until after he’d left the island. While sailing back to Oxford, he and the others stopped briefly in the northern Norwegian city of Tromsø. Elton ventured into the town, past its centuries-old wooden houses nightly illuminated by the Northern Lights, eventually finding himself in a small bookstore. Browsing, he encountered a book called Norway’s Mammals by the Norwegian zoologist Robert Collett, published in 1895. He pulled it off the shelf and paged through it. It was the only book in the store on natural history, his subject of interest, but it was written entirely in Norwegian. He couldn’t read a word. He’d likely have pushed the book back onto the shelf had it not fallen open to reveal a few pages that included something Elton could read: several charts listing columns of numbers.
Elton had no idea what the numbers meant, so he brought the book over to the shopkeeper to ask. “Peak lemming years,” he said.
Elton, though an accomplished student of zoology, had little interest in traditional natural history. To him, natural history consisted of idiosyncratic portraits of individual creatures, penned by eccentric animal-loving observers. It had little relevance to the urgent questions of the day, which revolved around issues like famine, war, and epidemics of pests and pathogens. He wanted to revolutionize natural history into something more like what early twentieth-century physics and chemistry had become: muscular, hard-hitting, and capable of rendering practical, economy-changing insights.
Instead of looking at the behaviors of individual animals, Elton thought, zoologists should study the “sociology and economics of animals,” that is, how whole populations behaved, in relation to one another and to the environment. And so while the descriptions of Norway’s mammals in Collett’s book held little appeal for him, the numbers in Collett’s charts did. He could see that the “peak lemming years” occurred intermittently, which meant that the numbers of lemmings rose and fell cyclically over time.
These changes in population size mystified zoologists at the time. Their confusion stemmed from their understanding that nature was divided into biologically discrete habitats. Naturalists described the places that wild species lived in as “niches,” from the Middle French word nicher, “to nest.” The word had originally referred to the recess in a wall carved out to nestle a statue. Zoologists imagined each wild species’ niche to be similarly specific and unique, carved out to fit the one species that occupied it. Each species lived in its own piece of nature with biological borders drawn around it.
That conception led to a paradox, though. Scientists understood niches by studying experimental versions in their labs. Since a niche was an enclosed space equipped with the necessities of life for its species, it could be easily replicated in a laboratory, for example by establishing a colony of yeast cells in a test-tube filled with sugar water. But real-world niches didn’t behave the way experimental niches suggested they should. In lab experiments, the size of a yeast colony in its test-tube niche would rise and fall in direct relation to the volume of sugar in the tube. If scientists kept adding sugar, the yeast would keep growing. If they stopped, the yeast would stop.
If wild species lived in closed-border niches, as scientists thought they did, then the size of their populations should similarly expand and contract in direct relation to the availability of food and water. But that’s not what zoologists saw in the wild. Animal populations did not grow until their food supply collapsed and they starved to death. Their numbers rose to a certain point, and then as if reaching some invisible ceiling, they started to decline again, in an endless series of cyclical spikes and falls. The availability of food and shelter made no difference. It was as mysterious as if yeast cells in a fully fueled test tube grew for a few days, then declined for a few days, then grew again.
Linnaeus had known about the conundrum of this so-called population cycle. He figured it had something to do with God. By Elton’s time, zoologists had ruled out divine intervention. But if God couldn’t explain it, neither could any of the other external factors zoologists looked at: food supplies, environmental disruption, predators, disease. It seemed as if some invisible factor X must secretly regulate population growth, like a finger pressing on a scale. But what was it?
The mysterious cycling of populations3 was no charming eccentricity of animal behavior. It was a phenomenon with great economic import. During low points in the population cycles of fur-bearing animals such as foxes, for example, hunters went hungry and the price of fur spiked; during the high points in population cycles of voles and locusts, the abundant creatures destroyed lucrative logging areas and agricultural fields. But with little scientific understanding of the factors that shaped population cycles, they could be neither predicted nor controlled.
Elton was young and ambitious. Hadn’t Einstein been just twenty-six when he revolutionized physics during his annus mirabilis in 1905? If Collett’s book allowed Elton to pinpoint how and why lemming populations rose and fell, he could pinpoint factor X and unlock an enduring mystery, too. Perhaps he could even distill the phenomenon of population cycles into a mathematical formula. He’d turn musty old natural history into a sturdy, quantitative science. He might even be able to predict and control the rise and fall of animal populations. Powerful companies such as the Hudson’s Bay Company and British Petroleum, among others, would surely be interested in funding such inquiries.
He bought the book. When he got back to Oxford, he acquired a Norwegian-English dictionary and eked out a crude, word-for-word translation.
From its pages, Elton learned of the strange and mysterious behavior of the lemmings.
The book described reports of lemmings gathering together4 in great masses and marching toward the Arctic cliffs, where they flung themselves into the sea. One observer named Duppa Crotch who spent his summers in Norway had observed the phenomenon more than once. His report appeared in an 1891 issue of Nature. When he saw the lemmings in the water, he rowed his boat toward them to block their way. They swam by him determinedly, he reported, making a beeline to their watery graves. “I know nothing more striking in natural history,” he wrote.
In 1888 a mass of lemmings formed5 “until the whole land was black with them,” then started “moving seaward on a 10 mile front” that took four days to pass by. “They kept on over the sea ice, finally leaping into the water and swimming ashore until drowned,” another observer wrote. Nineteenth-century sailors claimed to have seen millions of lemmings flailing in Norway’s deep, narrow fjords. “So many swam out into the inner parts of Trondheim Fjord,” one sailor recounted, “that a steamer took a quarter of an hour to pass through them.” The mass migration ended badly for them. Scores of lemming carcasses had been encountered, flung across the surface of iced-over lakes, frozen to death.
What did it all mean? According to ancient Laplander legend, lemmings originated in the heavenly mountains and appeared suddenly when they rained down from the sky. Then they gathered in flocks searching for a way to return. Some said they were poisonous to the touch. For Crotch, the lemmings’ migration into the sea suggested an ancient Atlantis. Crotch guessed that “blind and sometimes even prejudicial inheritance of previously acquired experience” caused lemmings to migrate into the sea. Perhaps, he speculated, their destination had once been dry land: an Atlantis hidden somewhere in northern Norway.
Collett’s stories struck Elton differently.6 Perhaps, he speculated, the lemmings headed out to sea not because they were trying to get somewhere, but for the opposite reason: because they knew it would get them nowhere. It was a behavior similar to one that Elton’s mentor Alexander Carr-Saunders had described in his best-selling book, which Elton had “devoured.” On the Pacific island of Funafuti, Carr-Saunders had written, people ritually murdered every other baby born until each woman had four living children, after which every baby they bore also would be ritually murdered. This cultural practice, Carr-Saunders wrote, formed a crude but effective form of population regulation. (Sentimental outsiders would ruin it if they interfered, he warned, setting off a population explosion.)
By migrating to their certain deaths, the lemmings achieved the same result as the Funafuti. They culled the population, protecting it from the calamity of straining the limits of their food supply. Perhaps, Elton speculated, the suicidal lemming migration was no error or artifact but had emerged and continued to persist for that precise reason. Lemming populations expanded to a certain point, after which they committed mass suicide by migration, causing a consequent decline. That would explain why their mysterious population fluctuations did not coincide with famines or disasters.
Elton wrote up his novel spin on Collett’s findings7 into a scientific paper, which appeared in the British Journal of Experimental Biology in 1924. The paper started out with a fairly neutral description of the phenomenon. “For many years,” Elton explained, “the lemmings have periodically forced themselves upon public attention in southern Norway by migrating down in swarms into the lowland in autumn, and in many cases marching with great speed and determination into the sea, in attempting to swim across which they perish,” he explained. As the son of a literary scholar and a children’s book author—and the future husband of a poet—Elton could not resist the temptation to wax lyrical, even though he’d never seen a lemming, let alone a lemming migration. He wrote of lemmings “ecstatically throwing themselves over the ends of railway bridges,” making a “bee-line across crowded traffic oblivious to danger,” and the sea “strewn with dead lemmings like leaves on the ground after a storm.”
Such colorful descriptions sparked the attention of his fellow zoologists. Even better, Elton had a tidy explanation for why the lemmings did it, one that shed light on the broader and economically urgent question of the origins of population fluctuations. “The phenomenon,” he explained,8 “is analogous to infanticide among human beings … the immediate cause of the migration is overpopulation.”
Elton had discovered the mysterious factor X9 that explained why animal populations rose and fell in cycles: it was a secret drive to regulate the size of one’s population. Elton’s paper, hailed as “visionary” and “seminal,” renewed zoologists’ interest in the issue of population fluctuations. It became “one of the cornerstones of contemporary ecology,” as a 2001 paper in Biological Reviews put it. Oxford established a new research institute, the Bureau of Animal Population, installing Elton as its director. Scientists organized conferences focused entirely on population cycles, and across Europe and the United States they conducted lab experiments, performed field research, and searched for mathematical formulas to describe and explain animals’ drive to regulate their own numbers.
Biologists discovered manifestations of this secret drive10 for suicidal migration in other species besides lemmings. The University of Michigan zoologist Marston Bates, for example, wrote of “mass suicide” committed by South American butterflies. “The pressure of built-up numbers seems to result in an explosive migration into new areas, where the migrating individuals die,” he explained. “It is a sort of mass suicide.” He had watched millions of South American butterflies fly out to sea “to certain death,” a result of the “balance of nature.” Scientists speculated about shoals of fish purposely dashing themselves to death on the hulls of boats, and suicidal whales beaching themselves on shore. Perhaps their self-destructive impulses, too, were compelled by their awareness of the size of their own populations, and a concomitant drive to sacrifice themselves for the good of their brethren.
The fact that established and highly trained scientists readily accepted the supposition that people purposefully murdered their children and that wild animals purposefully killed themselves is striking. They had faith in their conception of a nonmigratory, closed-border world. In fact, species were not confined to niches with impassable borders around them, like yeast trapped in a glass-walled test tube. Individuals moved into and out of populations. And the environments within habitats were dynamic, too, which individuals responded to in idiosyncratic ways. Some did well at some times; others less so at other times. The size of a population rose and fell because both the composition of the population and the environments it lived under continually changed.
The population cycles that scientists pondered appeared paradoxical only because they didn’t know that the borders around habitats were permeable and allowed migration to flourish. And they accepted the idea of suicidal migrations because Darwin’s theory of natural selection was not widely accepted at the time. It allowed for no mechanism by which suicidal migrations could evolve. The traits of individuals who successfully reared more young than others dominated populations, not the traits of those who purposely destroyed themselves. If suicidal lemmings did emerge, they’d kill themselves and be replaced by lemmings who didn’t recklessly leap from cliffs. Repeated acts of mass suicide, in other words, could not exist in nature.
But for zoologists at the time, the idea that uniform populations enclosed within niches migrated as a form of population control made sense. Twentieth-century zoologists imagined migration, in reality a vector of life-giving biological and cultural diversity that ecosystems and societies depended on, as a vector of death.
For Elton, as for Linnaeus, the conviction11 that drove his antimigrant ideas concerned the past. For him, nature had always existed in stasis. Geography was immortal. The “principal masses of land and water,” he wrote, “have existed mainly in their present shapes throughout all ages.” Over time the unchanging landscape had been populated by wild creatures, each species establishing itself in its own niche. “Nearly all animals,” Elton explained in one of his books, had become “more or less specialised for life in a narrow range of environmental conditions” through eons of habitation in their unique niches.
This conception of the past conformed12 to popular customs that elevated the native over the newcomer. The idea that plants and animals already resident in a place enjoy a special and privileged relationship to their habitats found expression across society. In museums, curators explained the specimens in their collections with little information other than their country of origin, as if that detail alone explained everything viewers might want to know. In English common law, people who lived in the countries of their birth enjoyed special rights of automatic citizenship, a provision known as jus soli, Latin for “right of the soil.” The underlying idea about history necessarily turned migrants, whether they introduced defective germplasm or not, into ecological troublemakers.
In Elton’s vision of nature, there was no excess capacity for newcomers, no “extra” niches. The most famous experiments proving the point had been conducted in the early 1930s. In 1932 the Russian biologist Georgii Frantsevich Gause introduced into a test tube filled with sugary liquid two different species of yeast: one called Saccharomyces cerevisiae, and the other, Schizosaccharomyces kefir. Every so often he shook the little tubes to ensure their contents remained fully mixed. He added nutrients for them to feed on. He refreshed them with water. He nourished the test tube with plenty of food to sustain both yeast species—but trapped inside the same tube, the two would have to share.
At first, populations of both species of yeast, fattened on the continuously replenished nutrients available to them, grew. But then, despite the abundance of available food and water, one yeast type started to suffer. Its numbers fell. Soon, as the population of its rival yeast type strengthened, the population of the declining yeast crashed, poisoned by all the ethyl alcohol in the waste of its tubemate. The phenomenon became known as “competitive exclusion” or, more simply, Gause’s Law.
According to Gause’s Law,13 there is no such thing as what we might colloquially call “sharing.” Regardless of the abundance of resources, it is biologically impossible for two species to share the same niche. Either the newcomer or the native will be destroyed, poisoned into extinction like an alcohol-sensitive yeast in a glass test tube.
Years of experimentation and mathematical modeling14 confirmed Gause’s findings. In part, that was due to the ease with which negative results could be dismissed. Biologists would dump two species with similar characteristics into the same location. Sometimes one would flourish while the other suffered, in which case they’d conclude that Gause’s Law had been proved. Other times both would flourish, but instead of concluding that two similar species could in fact share the same niche, they’d instead claim that the two species must have been dissimilar, with some as-yet-undiscovered ecological difference between them. That is, they survived together because they didn’t, in fact, share the same ecological niche.
In the belief that nature was in essence “filled up,”15 experts in the United States and Britain started to target wild migrants as dangerous intruders. The arrival of newcomers, for them, signaled the certain demise of natives, as Gause’s Law made clear. And according to Elton, migratory movements had no positive ecological function. Migrants embarked on their journeys in futile attempts to flee, not to arrive anywhere, Elton said. “Many animals migrate on a large scale,” he wrote, “in order to get away from a particular place rather than to go towards anywhere in particular.” If they did not “fit harmoniously,” these newcomers caused “disastrous results.” Zoologists in Europe complained about the arrival of American gray squirrels and other North American species (a “terrific invasion of aliens,” as one expert put it in an early 1930s BBC radio series); in the United States they complained about the intrusion of English sparrows and starlings. (A “European invasion of America is upon us,” one zoologist wrote in the New York Times. The starlings were “bad citizens,” and “undesirable aliens,” according to government officials.) The ecologist Aldo Leopold, a friend of Elton’s, railed against the “thoughtless importation of Mexican quail” and how they “diluted the hardy northern bobwhite blood in Massachusetts,” as a journal article entitled “Game System Deplored as a Melting Pot” reported.
In Germany, people purged plants deemed foreign16 from the landscape. Nazi leaders instructed locals to banish “foreign” plants from their gardens and to practice a new kind of landscape design in keeping with their superior race. (The traditional gardens many kept, the Nazi garden architect Willy Lange lamented, were characteristic of the inferior “south Alpine” race.) Heinrich Himmler, in addition to masterminding the genocide of millions, issued rules for landscape design forbidding the use of any plants deemed “nonnative.” The head of the Reich Central Office for “Vegetation Mapping” called the delicate flowering herb Impatiens parviflora a “Mongolian invader” and recommended its extermination. The Nazis zealously protected wild species considered “native.” Under their regime, killing an eagle was a crime punishable by death.
Elton did not explicitly extend the implications17 of his ideas about the dangers of wild migrants to human migrants. But he generally considered his findings about population movements and cycles to elucidate universal principles applicable beyond the specific wild species in which he’d discovered them. For Elton, the line separating nature and human society, as the historian Thomas Robertson put it, “was often a thin one.” He made that clear in the way he described animal behaviors in terms generally reserved for humans. At one point, for example, he referred to the lemming migration as a “rather tragic procession of refugees, with all the obsessed behavior of an unwanted stranger in a populous land.”
Elton’s ideas shed “considerable light18 on the way the human population should be regulated,” one well-heeled Elton fan sniffed. Principles such as Gause’s Law “ha[ve] applications in many academic fields of study,” added the University of California ecologist Garrett Hardin. Accepting its premises would bring about “a renaissance of understanding.”
By the 1930s, the popularity of eugenics19 had started to diminish in the United States, even as it gained momentum in Germany and elsewhere in Europe. Anxieties about newcomers subsided with the closing of the borders, and the Depression dulled enthusiasm for talk of superior races and their automatically superior lives.
But scientists did not abandon their suspicions20 about the abnormality of migration in the closed-border world that Linnaeus had described. The New York Zoological Society provided Elton with funding for his research at Oxford. Madison Grant had ascended to the presidency of the society in 1925.
Scientific portrayals of wild migrants as sacrificial zombies and malevolent intruders succeeded, in large part, because the true scale and extent of the journeys migrants undertook remained obscure.
Purposeful, dynamic movements swirled all around, both slow and steady and grand and dramatic. Tiny monarch butterflies weighing no more than half a gram fly three thousand kilometers between eastern North American and central Mexico, where they meet en masse on stands of fir trees. Bar-headed geese soar over the jagged peaks of the Himalayas, climbing from sea level to six thousand meters at a rate of over a kilometer an hour, in the thin, cold night air. Eels in the Sargasso Sea metamorphose into unrecognizable shapes and colors in preparation for grand journeys across the Atlantic.
But scientists can’t study migratory behavior in the lab. A rat’s ability to learn can be demonstrated by trapping it in a box in which it has to pull a lever to get a morsel of food. A monkey’s need for maternal affection can be shown by enclosing it in a wire cage with a bottle of milk and a terry-cloth-covered sculpture. But a creature’s drive to migrate can’t be so easily re-created in a box or cage. And scientists had few techniques by which to observe it in the wild.
Many of the billions of birds that migrate21 across seas and continents every year fly under cover of darkness. They can be glimpsed by observers only when in the right place at the right time. At Point Pelee in Ontario, where a narrow spit of marshland extends into Lake Erie, millions of monarchs can be briefly sighted flying south. Along the coasts of the Panama Canal, over half a million raptors can be seen migrating overhead. Along the five-kilometer-long reef in Falsterbo, Sweden, observers can catch nearly 2 million migrating birds from twenty-five different species aloft. In certain secret places, if one looks up into the night sky, tens of millions of migrant birds can be seen flying across the face of the moon; in a single night, 50 million migrants may pass overhead, traveling in a two-hundred-kilometer front.
Most of these spectacles, in which the peculiarities of geography force migrants to briefly merge into dense concentrations, remain as hidden as a tropical beach on the far side of a cave. Given the conventional worldview of an immobile world, few even thought to look.
That started to change when British engineers figured out how to send radio waves into the atmosphere and analyze the echoes they made on passing objects. By installing the technology—nicknamed “radar” for “radio detection and ranging”—they could track all manner of once-hidden movements. During the Second World War, British radar stations installed up and down the coast tracked the movements of enemy planes and ships.
One evening in March 1941, as bombs rained down on London, a radar operator picked up a massive formation of flying objects moving slowly across the English Channel. Presuming the formation indicated an onslaught of invading Germans, military authorities put the Royal Air Force on red alert. The blips continued to approach. When they arrived within forty miles of the Dorset coast, British pilots climbed into their cockpits and flew out over the darkened channel, under orders to intercept and shoot down the intruders.
But when the pilots arrived at the spot from which the radar signals originated, the only sound above the rippling waters was that of their own engines. The night sky was clear, with not an enemy plane in sight.
The confused pilots returned to their base to learn that the blips had mysteriously splintered into single echoes and then faded away.
As the war progressed, the strange signals continued to plague radar installations. Military units would be sent into high alert, only for the signals to inexplicably expand into rings and concentric rings and slowly vanish into nothingness. Whatever created the signals “defied all the known laws of aerodynamics,” the New York Times reported. The signals arrived day and night. They moved against the wind. Sometimes they moved even faster than the wind.
The ornithologist David Lack had a theory22 about the strange signals. Lack and Elton both had studied under Julian Huxley and had ascended to the top of neighboring research institutes at Oxford. But the two scientists worked and lived alongside each other like two parallel lines, never intersecting. While Lack was a devout Christian and a music-loving bird-watcher who puttered around in a poorly maintained moss-covered car, Elton zoomed around on motorcycles and in airplanes. Their respective research institutes were situated next door to each other, and their personal residences were separated by just one hundred yards, but despite their professional and geographic proximity, the Lacks and the Eltons never socialized. At Oxford, they always kept the door between their adjoining institutes locked. Their ideas about migration and its role in nature would be similarly distant.
Like other scientists, Lack had been drafted into the war effort, serving in a special unit working on radar technology. He brought his ornithological expertise to bear on the problems he encountered. He’d been watching birds for years. As a student, he’d sit on his bed playing guitar and eating boiled eggs whole, with the shell, for the extra calcium. As a research scientist at Oxford, he spent much of his time in a long, shabby raincoat, hiding among trees to furtively observe his favorite creatures. Thanks to his long hours of bird observation, he knew that birds in groups could fly at speeds similar to those of a fast-moving ship. Even a flock of starlings could cause echoes that might confuse radar operators; large seabirds and shorebirds such as gulls and gray geese could, too.
Lack was not afraid of upsetting the conventional wisdom in order to stick up for his scientific findings. Once he’d suffered the wrath of an elderly bird-watcher who insisted that the same robin had been living in her back garden for seventeen years. When he explained that that couldn’t be true because robins didn’t live that long, she beat him on the head with her umbrella.
But military officials scoffed at Lack’s suggestion that the strange radar signals could be caused by flying birds. Like most people, they believed that birds couldn’t fly much at night, because they’d collide into trees and other objects. Plus, birds were small and delicate, nothing like the German fighter jets with 1,200-horsepower Daimler-Benz engines that radars tracked. How could such tiny and insignificant creatures compare to the miracles of wartime engineering?
The spooky signals, they decided, must be ghostly echoes from fallen soldiers, temporarily revived from the beyond. They called them “radar angels.”
Years passed before Lack confirmed that the radar angels were, in fact, birds on the wing. One night he and his colleagues rushed out to investigate some radar angel signals and discovered a stand of trees covered in starlings. As they watched, the birds suddenly rose as one and landed on another stand of trees, in a concentric circle around the first—exactly as the unexplained radar signals had recorded.
Lack went on to revolutionize the study of birds, using radar technology to reveal their long-hidden movements. But sometimes all it took to catch a glimpse of the migratory world all around was a willingness to look.
One afternoon after the war ended, Lack and his wife set off for a hike into one of the rare high passes through the Pyrenees, which separate France and Spain. They did not expect to see many flying migrants. Creatures such as songbirds avoid mountain passes, and weak flyers like butterflies can hardly withstand the winds whipping around the peaks.
It took four hours for the couple to reach 2,300 meters. Some years earlier Lack had been struck with Bell’s palsy, paralyzing one side of his face. Critics described his face as bent into a permanent sneer, but it undoubtedly transformed into something else that afternoon. As the two rested at the high pass, they saw a mass moving toward them in the sky. As they watched in shock and delight, thousands of butterflies and hundreds of songbirds rushed by.
They were flying against the wind and over the mountains. Even Lack, with all his knowledge of and appreciation for migrants and migration, had underestimated the physical capacities and drive of creatures on the move.
Before the war, Elton’s concerns about the ecological threat posed by migrants had been tempered by his sense that most species stayed put. But as armies of soldiers crisscrossed Europe, aided by new transportation technologies, he started to suspect otherwise.
During the war, he’d been enlisted to help protect Britain’s dwindling food supply from rodents. Wartime propaganda cast such rodents as “practically in league with the Nazis,”23 as a modern critic put it. As the creatures he once studied became the subject of extermination campaigns, his assessment of the threat posed by animals on the move took on a new tenor. Everywhere he looked, he saw wild creatures migrating into new places, and precipitating disaster.
In the United States, he noted, the arrival of Asian chestnut trees24 had introduced a parasitic fungus called Endothia parasitica, causing “chestnut blight,” which nearly wiped out eastern American chestnut trees. In Europe, a landowner in Czechoslovakia had introduced five North American muskrats. They grew into a population of millions, rampaging through croplands and burrowing into the banks of rivers and streams. In the midwestern United States, the construction of canals introduced the blood-sucking sea lamprey into the Great Lakes. The local lake trout population collapsed. Elton called it “one of the great historical convulsions in the world’s fauna and flora.”
In his postwar books, radio addresses, and papers,25 Elton enlisted the language of war to sound the alarm. “It is not just nuclear bombs and war that threaten us,” he proclaimed. Wild migrant “invasions” caused “explosive violence.” They launched “surprise attacks,” with “attack[s] and counterattack[s].” And their goal was the same as that of the Nazi invaders his fellow Britons had fought during the war: complete domination or, as he put it, “the eventual expansion and occupation of territory from which they are unlikely to be ousted again.”
Even if newly arrived species26 seemed benign, he said, their arrival presaged danger. They might just be lying in wait, ready to “rapidly spread to become pests of major proportion.” In time, the invaders would take over, displace original inhabitants, and leave the entire ecosystem diminished. Wild invaders, he warned, would “eventually reduce the rich continental faunas to a zoned world fauna consisting of the toughest species.” They’d trigger a “zoological catastrophe.”
To depict species on the move as “invaders”27 and their impact as catastrophic, Elton cherry-picked only the most disruptive of introduced species. He also considered only the costs that introduced species exacted, and none of the benefits they rendered, of which there were many obvious ones—the harvests from corn, soybeans, wheat, and cotton, to name just a few, all of which derived from plants that had been introduced from one continent into others.
As GPS technology would later allow biologists to document, wild species, like peoples, move around all the time, whether through their own locomotion or by being carried on the winds, currents, or backs of other moving creatures. Inserting themselves into continuously shifting landscapes, most either fail, struggle, or incorporate themselves inconspicuously in temporary assemblages that themselves assort and reassort dynamically. (Which is why biologists would also find that the introduction of a species from one landscape into another generally increases biodiversity.) It is true that predators and pathogens introduced into relatively closed ecosystems, such as lakes and islands, can drive already-resident species to extinction. But most ecosystems do not have closed borders around them.
Elton delivered his warnings about invasive species28 in a series of BBC broadcasts, straightforwardly titled The Invaders. Then he wrote a short book on the subject. The book was “written hurriedly,” writes the historian Matthew Chew, and “less coherently and deeply considered” than his other works. Elton knew it, admitting to one of his students that he’d pounded out the book on the basis of the radio addresses in a matter of weeks. “I did the broadcasts,” he wrote, “am now turning that stuff into a 45,000-word heavily illustrated book … which I shall have written in nine weeks.”
His 1958 book, The Ecology of Invasions by Animals and Plants, would inform the management of national parks and programs protecting wildlife around the world. It launched a whole new field of inquiry dedicated to documenting the negative impact of species on the move, a field known as “invasion biology,” which would take off in the 1980s. The book would be hailed for decades to come as “one of the central scientific books of our century,”29 as the science writer David Quammen called it in 2000.
The spectacle of the suicidal migration of the lemmings embedded itself into public consciousness in 1958, the same year The Ecology of Invasions came out.
Produced by Walt Disney studios,30 the nation’s most powerful and celebrated production company, White Wilderness31 showcased the eerie, rarely seen world of the frozen Arctic, using the most cutting-edge cinematic techniques of the day. Nine photographers had “roamed the snow-sheeted wastes,” covering “thousands of miles of tundra, lakeland, mountains and icy rivers” to make the film, the New York Times reported. The documentary, one of the most anticipated of the year, was the thirteenth in a series showcasing the strange and mysterious phenomena of the natural world, with stunning, never-before-seen footage from some of the most remote places on earth, from the islands of the Bering Sea to the plains of the Serengeti. In White Wilderness, audience members would be treated to “one of the most ambitious sagas in the annals of nature photography,” one of the film’s consultants told the Times.
Filmgoers settled into the Normandie Theatre’s plush, mohair-velvet-upholstered seats one stormy August afternoon in New York to watch the premiere. They’d be talking about the documentary’s most shocking images for years to come. The six-minute scene depicted one of “nature’s strangest phenomena,” as Disney put it.
In it, the camera pans across an icy landscape where lemmings congregate. With their long whiskers and lush fur, they look like round, fluffy hamsters. At first they meander, delicately sniffing the ground and each other. But then they slowly start to move across the frozen tundra, their tiny paws flicking bits of snow behind them as they gain momentum.
The narrator explains that a cliff—not pictured in the scene—lies in their path. “Ahead lies the Arctic shore and beyond, the sea,” the baritone voice-over says, as the furry horde continues its determined march. “And still the little animals surge forward.”
The camera follows along. “They reach the final precipice,” the narrator says. “This is the last chance to turn back.”
Few in the audience could boast any special expertise in lemming behavior. Still, every schoolchild knew that the guiding principle of animal behavior, as for human behavior, is self-preservation. On screen, the lemmings reach the brink of the rocky cliff, their sharp claws gripping the edge. They pause.
One by one, they leap.
The next image is of furry balls aloft, little feet scrambling in the air.
The camera then moves to the gray, featureless expanse of the sea below the cliff, as it’s punctured by a rapid fusillade of falling lemming bodies, plunging into the icy depths to their deaths.
It’s a ghastly scene. Did they lemmings fall by mistake? Was their plunge the result of some kind of bizarre navigational error? viewers likely wondered. No. The lemmings’ “eerie death march” stems from a “blind, instinctive impulse,” the filmmakers explained. Their mass suicide is no anomaly or accident. Flinging themselves from cliffs is what the lemmings are supposed to do. “It is not given to man,” the narrator says, “to understand all of nature’s mysteries.”
Elton is remembered today as the “founding father”32 of animal ecology and a “towering figure” in biology, as the Royal Society put it. But though he circled back to his story of lemmings again and again, neither he nor any of his colleagues had ever seen a lemming migration into the sea. After decades of attempts to observe the phenomenon, scientists could boast just a single blurry photograph, picturing a lemming in transit. In 1935 one of Elton’s students, Dennis Chitty, ventured into the Canadian Arctic with plans to study lemming migrations, expecting to find the land “overrun with lemmings” as he put it. He traveled aboard a ship up the Hudson Bay, around Baffin Island, north to Ellesmere Island, then west to the Northwest Passage. For seven weeks, they sailed through the blustery cold, covering thousands of miles. They saw “masses of ancient lemming droppings” but not a single lemming. Fifty years later, Chitty tried again, in Finse, Norway. He’d heard reports that lemmings had boomed that year. By the time he arrived, they’d vanished.
The truth about lemmings emerged33 when biologists peered under the snow in lemming territory. It turned out that they didn’t disappear into the icy depths of the Arctic Sea. They dug holes and hid under the snow, feeding on moss and breeding their young in the little gap created by the warm ground melting the layer of snow directly above it known as the “subnivean space.” For years, biologists hadn’t thought to look, because breeding under the snow had been considered biologically impossible.
During snowy years, unknown to anyone34 scanning the landscape, their numbers build up under the snow cover. When the snow melts, their tunnels and holes fill with meltwater, forcing them to leave abruptly. Suddenly, they appear in great numbers as if out of nowhere and their tracks speckle the sea ice. Then as winter approaches and snow blankets the land, they burrow back under the snow, seeming to mysteriously vanish.
Collett’s book, which Elton had relied on, was like Linnaeus’s source material, an amalgam of myths, legends, and “cock-and-bull stories from Norwegian sailors,”35 the historian of ecology Peder Anker explains. Elton might have realized it if he hadn’t relied on his crude translation of the book.
But while scientific evidence for the suicidal lemming migration had materialized out of a series of misunderstandings, its popularization was the result of a purposeful deception. In 1982, the Canadian Broadcasting Corporation aired a documentary called Cruel Camera, about animal abuse in film. It recounted how the lemming migration in White Wilderness had been filmed.
The lemming suicide march had been staged.36 The Disney filmmakers used an animal trainer who built little studios and sets for their wildlife documentaries. He had created scenes of geese flying, for example, by positioning captive geese in front of wind machines. The animal trainer and his team hired local kids to capture lemmings for twenty-five cents per lemming. Then they shipped the lemmings one thousand miles away to a set they’d built outside Calgary, replete with a painted Arctic sky. They herded the lemmings onto a turntable, then filmed them running around it. This created the appearance of a horde of lemmings running in a straight line.
Then they gathered the lemmings, loaded them onto a truck, and with the cameras rolling, tipped them out over a riverbank. The lemmings hadn’t committed suicide. They’d been murdered.
White Wilderness infiltrated the public mind for decades before the exposé came out. The scene of the lemming suicide helped make White Wilderness a critically acclaimed hit. In 1959 the film won the Academy Award for best documentary feature. It would be shown in public schools across the country for years, bringing to the masses Elton’s bleak vision of the ecological necessity of migrant deaths.
I learned about the lemmings’ mass suicide in a fluorescent-lit classroom of a suburban Connecticut middle school in the late 1970s. Like everyone else, I found the story darkly fascinating. I remember being struck by how much the driven lemmings looked like my own pet hamster, Hammy, whose reputation as a simple-minded creature driven by immediate needs seemed suddenly and thrillingly suspect.
The lemmings’ macabre migration captivated the nation.37 Their mass suicide quickly became a cultural shorthand for self-destructive behavior of all kinds. A musical group from Berkeley, California, dubbed themselves The Lemmings and published an image of a line of cars driving off a cliff into the sea on the cover of their album. The New Yorker cartoonist James Thurber imagined a conversation between a lemming and a scientist in his “Interview with a Lemming.” “I don’t understand,” says the scientist, “why you lemmings all rush down to the sea and drown yourselves.” “How curious,” says the lemming. “The one thing I don’t understand is why you human beings don’t.” The English poet Patricia Beer waxed darkly about the lemmings’ “hot blood” pouring into the “cold sea.” During the war, millions had marched to their deaths38 “like lemmings,” as the psychologist Bruno Bettelheim put it. “War,” the biologist Richard A. Watson wrote, “is the ultimate manifestation of the lemming-like madness that grips large populations of men in great need.”
In the late 1950s, when the film first came out, the notion that suicidal migrations occurred in nature helped make sense of the still-raw trauma of the Second World War. By sacrificing themselves, the soldiers and others who died had helped maintain a balance in nature just as the migrant lemmings did by flinging themselves into the sea. The appropriate conclusion to the migratory act, in other words, was death.
With the borders around countries such as the United States firmly closed, no one had cause to ponder the political and ecological dilemmas that might arise if migrants didn’t martyr themselves.
That would change.