Out of Eden An Odyssey of Ecological Invasion
By Alan Burdick
Farrar, Straus and Giroux Copyright © 2005 Alan Burdick
All right reserved. ISBN: 0-374-21973-7
The airport shuttle driver in Honolulu laughed when I told him where I was headed. "Watch out for snakes," he said.
Nine miles wide, thirty miles long, and a seven-hour flight across the date line from Hawaii, Guam is, for the moment, one of the world's more unusual cultural cauldrons. It is the most southern member of the Marianas archipelago, a five-hundred-mile string of islands that erupted from the ocean floor four million years ago and which, were it not for seven vertical miles of seawater, would comprise the highest mountain chain on Earth. The first inhabitants were the Chamorro, a group of South Asian lineage that flourished from thirty-five hundred years ago until shortly after the sixteenth century, with the simultaneous arrival of Spaniards, Catholicism, influenza, and smallpox. Today their descendants on Guam mostly occupy the southern third of the island, speaking a mixture of Spanish and ancient Chamorro, cruising through sleepy, palm-lined villages in lowrider pickup trucks, throwing Sunday fiestas for their patron saints, all in all presenting the appearance of East L.A. on an extended tropical vacation. In 1898 the United States acquired Guam, as well as Puerto Rico and the Philippines, from Spain under the Treaty of Paris. This tenure has been interrupted only once, on December 8, 1941-Pearl Harbor Day behind the date line-when the Japanese invaded from their outpost on the neighboring island of Saipan. The United States regained custody thirty-one months later, in one of the bloodiest battles of the Pacific. Since 1944, the northern third of Guam, a jungly limestone plateau, has been the almost exclusive purview of the U.S. military, which maintains a major air force base there and, until a decade ago, several hundred nuclear warheads. Complaints are muted: the military and the Guam government, known as GovGuam, together employ more than half the island's 150,000 residents. Officially, Guam is a U.S. territoty a privilege manifest in one nonvoting congressman and two tourist slogans: "The Gateway to Micronesia" and "Where America's Day Begins."
And what a beginning. The northern and southern thirds of Guam join in a narrow isthmus of common ground: strip malls, fast-food joints, high-rise resorts, an international airport, and a sleepless snarl of traffic. At what stoplight does the district of Tumon become entangled with Tamuning? Where does Tamuning let off and Agana begin? For most travelers from the U.S. mainland Guam is a tiresome stopover on the way to somewhere else: Palau, Pohnpei, somewhere quieter, more paradaisical. For international travelers however-particularly the burgeoning number of Japanese honeymooners, businessmen, vacationers, and bargain shoppers-Guam has become an end in itself. You can, for an immodest fee, discharge your choice of firearm (illegal in Japan) in any of several local shooting galleries, or dress in cowboy attire and ride a pony around a small ring in a back lot. You can shop tax free at the world's largest KMart, provided you can find a parking space: the lot is filled to capacity every night until the nine o'clock closing. You can stay in one of the many hotels that cater exclusively to Japanese guests. In 1972, Shoichi Yokoi, a sergeant in the Japanese army, emerged from the remote cave he had hidden in for the past twenty-eight years, unaware that the war had ended, and no doubt perplexed, on seeing so many Japanese billboards, as to which side had lost.
Into a world thus made, the brown tree snake somehow found itself. One local theory maintains that the American military set the snakes loose to get rid of the rats. No, another resident says: the snake swam from the Philippines, fifteen hundred miles away. Most biologists champion a cargo-based explanation: Boiga irregularis arrived some time around 1949 from a military base in the Admiralty Islands, near New Guinea, coiled in the dashboard of a jeep or in some other bit of wartime salvage. Until then, Guam had no proper snakes to speak of. What a novelty, then, to see one. SEVEN FOOT SNAKE SLAIN HERE, one headline exclaimed. Another announced: NAV MAG MEN FIND LARGEST SNAKE TO DATE-8.5 FT. LONG. And simply: SNAKES ALIVE! "Because they eat small pests and are not dangerous to man," the Guam Daily News reported in October 1965 alongside a photo of a seven-foot snake killed at the United Seamen's Service Center, "they may be considered beneficial to the island." Several equally large specimens were remarked upon in the local press in ensuing years, including a snake that one Mrs. Edith Smith found slipping across her neck at four o'clock one morning in June 1966.
At first, sightings were limited to the area around the military seaport at Apra Harbor, several miles south of Agana. By 1970 the snake was making appearances island-wide. Other animals began disappearing: not just "small pests"-in a 1989 poll, more than half the respondents attested that the number of rats around their homes was definitely decreasing-but also chickens and eggs, domestic pigeons, guinea fowl, ducks, quail, geese, pet parakeets and finches, piglets, and cats. One day a chicken is in the cage; the next day, there is a snake too fat to escape. Gradually the snake began attempting larger prey. Between September 1989 and September 1991 the Guam Memorial Hospital recorded seventy-nine bites by brown tree snakes. Of those victims, sixty-three-80 percent-had been sleeping in their homes at the time; and of those, half were children under age five, including two infants who were bitten while sleeping between their parents. Yvonne Matson's experience typified a mother's terror. Early one morning she awoke to the screams of her infant son; racing to his room, she saw a five-toot brown tree snake entwining him from leg to neck and gnawing on his left hand. Months later, after her mother was bitten, Matson hired an exorcist.
As fast as the snake spread, word of it spread faster, to Hawaii, California, New York. A Wall Street Journal article claimed that the snakes "hang from trees like fat brown strands of cooked spaghetti." But I never saw that. None crawled in through my hotel sink. None lurked in the grass island of the Taco Bell parking lot. I drove around for two days after my arrival, asking after the snake.
"I think I saw one a couple of years ago on the road when I was driving, but it was night."
"My friend saw one a couple years ago when he was driving."
"I seen more snakes in Texas!"
A farmer described seeing a snake burrowing into the nose of his pet goat, which died a day later. "And you know, the color isn't brown. It's blue!"
In short, a dissonance has arisen on Guam, a discrepancy between the heard and the seen-a gap of uncertain size, yet wide enough to rankle. One evening I attended a cocktail gathering for guests of the Guam Hilton. The general manager, an amiable German transplant, assured me that he had encountered only one snake-"may it rest in peace"-on the hotel grounds during his six years there. He sounded sincere, so I was surprised a few weeks later to read an article in the Los Angeles Times in which an anonymous Hilton groundskeeper confessed to decapitating twenty snakes a month with his machete. I called to confirm. "I'm not at liberty to discuss that," said the hotel employee I'd been directed to. The line promptly went dead. Calling back, I was connected to a supervisor. He shouted into the phone: "Is everybody trying to sink the tourist industry? Everybody's got this twitch about the brown tree snake and how it's devouring Guam! I've lived here for three and a half years, and I've only seen two snakes. One was in a bottle-somebody caught it-and the other was squashed on the road. I tell you, I live in the boonies, and if I thought that brown tree snakes were dripping from the trees like spaghetti, I wouldn't have my children running around outside. All you people are making a mountain out of a molehill!"
So I'd come looking for a snake, a snake that clearly had no intention of showing itself anytime soon-indeed, a snake that had successfully navigated eons of evolution precisely by going about its business unseen.
"The snakes are extremely averse to light," Earl Campbell explained to me at his field site one evening. "During the day they take cover in places where people aren't likely to encounter them. Many of my friends have lived on Guam for years and never seen snakes."
Campbell, a young herpetologist from Ohio State University, suggested I might have some luck in his company. He worked under the auspices of the Brown Tree Snake Research Program, an array of federally financed research projects established in 1988 that aims to eliminate the brown tree snake population-or, more reasonably, to prevent its spread to Hawaii or anywhere else beyond Guam. Campbell's interest was snake barriers: real barriers, actual physical fences that would confine the snake to certain areas or, conversely, keep it out of other areas; and also figurative fences, general strategies of corralling the animal, reducing its numbers, slowing it down-barriers of human intelligence unsurmountable by any brown tree snake. To halt the enemy, however, one must first know something about how it operates; and until the brown tree snake appeared on Guam in profusion, virtually nothing was known about its basic biology. To learn that, a researcher first must find a brown tree snake.
Athletic and prematurely graying, Campbell wore that grizzled look endemic to graduate students everywhere. His research site sat at the remote northern tip of Guam, on Northwest Field, a forested limestone plateau above the sea. During the Second World War the area held numerous military barracks, basketball courts, runways, and ammunition dumps. Afterward, it devolved into a scrub jungle of tangantangan trees-a gnarled, fast-growing Central American species that was planted en masse after the war to prevent erosion and has since come to provide abundant habitat for brown tree snakes. The snake is largely nocturnal; Campbell had become so too. One evening, well past dark, he arrived at the site for a few hours of research dressed in proper fieldwork attire: T-shirt, shorts, and sandals. A crescent moon hung low above the tree line; the humid tropical air resonated with the chirring of locusts. Campbell donned a helmet with a headlamp attached to it, flicked that oil, then headed down a path made narrow and low by dense foliage and dangling vines.
"Looking for a snake in the forest is sort of like being in a demented Where's Waldo? book," he said. He crept forward, turning his head from side to side, illuminating knotted boughs with the ray from his headlamp. "My average here is one an hour." He conceded that this number did not sound impressive. Nevertheless, he said, this patch of forest contained the highest concentration of brown tree snakes anywhere in the world. Some months earlier, Campbell had traveled with two colleagues to Australia to study the brown tree snake in its native range. In eighteen nights of looking, they together found just three snakes: one brown tree snake and two of another species. "It's incredible how well the brown tree snake does on Guam," Campbell said with a hint of admiration. Exactly how well it does, and why, are among the many things he and his colleagues would like to identify. This night's mission was part of what Campbell described as his "marker-recapture" work. Any brown tree snake he nabbed would be weighed, measured, tagged for identification and then set free, perhaps, he hoped, to be captured again days or weeks or months later. The cumulative data would shed light on the growth and movement habits of the snakes over time. "It turns out these snakes really migrate a lot," he said. "It's only when you get a barrier that you stop that movement."
Over the years, the proliferation of exotic species around the world has spawned its own field of scientific inquiry, known to its practitioners as invasion biology. The field marks its formal beginning with the 1958 publication of The Ecology of Invasions by Animals and Plants, by the English ecologist Charles Elton. Individual cases of biological introductions and invasions had been remarked upon in scientific journals for some time before that, but Elton was first to address such incidents as part of a large-scale, advancing phenomenon: "We must make no mistake: we are seeing one of the great historical convulsions in the world's fauna and flora." Elton covered a broad swath of history and territory-from the introduction, in 1890, of starlings into the United States (the man responsible, a Brooklynite named Eugene Schiefflin, intended to release into Central Park all the birds mentioned in the plays of William Shakespeare) to the blight wrought by Endothia parasitica, the Asian fungus that would eventually kill 75 percent of the nation's chestnut trees. At the time, ecology itself was a relatively new phenomenon, eager to be distinguished as a modern science apart from the gentlemanly, hunt-and-collect endeavor known for generations as natural history. So Elton strove to discern underlying patterns of invasion, to forge theories about the hidden structures of ecosystems and the manner of their unraveling. His treatise, The Ecology of Invasions, was as much a clarion call to his colleagues as it was to the public at large. Elton wrote, "We might say, with Professor Challenger, standing on Conan Doyle's 'Lost World,' with his black beard jutting out: 'We have been privileged to be present at one of the typical decisive battles of history-the battles which have determined the fate of the world.' But how will it be decisive? Will it be a Lost World? These are questions that ecologists ought to try to answer."
Ecologists are still at it-in greater numbers than in Elton's day, with more sophisticated instruments and analytic tools at their disposal and many more case studies to select from. To a degree, invasion biology can be thought of as evolutionary biology turned inside out. As Darwin recognized, the appearance of a new species is frequently the downwind result of an invasion-a finch blown off course, say-that occurred generations earlier. Contemporary evolutionary biologists are still working out the subtleties of Darwin's insight: the competitive tensions that ripple among species; the genetic mutations and recombinations at the heart of evolution; the isolative acts eons ago that set it off. The invasion biologist, in contrast, is drawn to those first critical moments of colonization under way right now, all around: the incidents of travel, the tooth-and-claw contests that unfold in the subsequent days, weeks, months, years.
Excerpted from Out of Eden by Alan Burdick Copyright © 2005 by Alan Burdick. Excerpted by permission.
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