Four Wings and a Prayer.

Sue Halpern.

To Sophie Crane McKibben and her devoted scout, Barley, who brought me outside.

Chapter 1.

BILL CALVERT EASED his truck off Interstate 281 near McAllen, Texas, pulled into a mall parking lot, and drew a knife from his knapsack. It was late in the day, about eight o'clock, and he had been driving for the past five hours.

"What you want to do is make the cut like this," he said, unfastening his belt buckle and the top b.u.t.ton of his jeans. He peeled back the waistband to reveal the smallest of incisions. "Nothing too obvious."

Calvert pressed on the fabric, and it opened, exposing a tunnel the width of two fingers. He reached in and extracted a wad of cash that was folded to the size and shape of a stick of gum. Three hundred dollars, it looked like.

"You try," he said, handing over the knife.

I got out of the truck and began to slice at the inside of my jeans. People walked by, mothers and fathers towing small children, for the most part, but also the occasional solitary individual or couple, and if they found it odd to see a woman with a knife in her hand fiddling with her pants not two hundred yards from Montgomery Ward, they weren't saying.

"It's so uncomfortable to walk around with money in your shoes," Calvert was explaining. "It gets real damp. And smelly. This is much better."

We were ten miles from the Mexican border. I threaded my money into its hideaway and followed Calvert into the mall restaurant, a Luby's cafeteria. We were the only diners.

"I always come here before I go to Mexico," he said happily, sliding his tray along the steam table and overloading it with plates of green beans, broccoli, and peas, all of which looked like they had been through the wash. "These are the last green vegetables we'll see for two weeks." I couldn't say I was sorry.

BILL CALVERT is a biologist. Not the kind of biologist who wears a lab coat and not, especially, the kind who has a lab. He works out-of-doors most of the time, observing and cataloging and trying to come to terms with natural phenomena. Among people who study monarch b.u.t.terflies, which is what he himself has done for the past twenty-five years, Calvert is considered the best field researcher in the pack. This may have something to do with the fact that Bill Calvert isn't really part of a pack. He works by himself, getting grants here and there and leading trips for science teachers and wealthy ecotourists, just sc.r.a.ping by. Although he has a doctorate in zoology, academia doesn't interest him. A "real" job doesn't interest him. Calvert is fifty-eight years old. Going to Mexico to look for monarchs-what we were doing-interests him.

"I TOOK AN apt.i.tude test when I was in my thirties, and I scored two sigmas past a seventeen-year-old for 'desire for adventure,' " he said a couple of hours after we crossed the border at Reynosa, as he leapfrogged eighteen-wheelers along the rutted two-lane Mexican highway to Ciudad Victoria, where we planned to stop. It was close to midnight. We had just breezed through two military checkpoints with the words "Biologico" and "Mariposa monarca," and now ours was the only pa.s.senger vehicle on the road.

"I thought you weren't supposed to drive at night in Mexico," I said to Bill, who smiled at me and tugged on his mustache.

"Why not?" he asked thoughtfully, as if it were a real question.

"Bandits," I said.

"Maybe," he said, and smiled again. It was an enigmatic smile, nothing comforting.

I DIDN'T KNOW Bill Calvert. Or rather, I had known Bill Calvert for about ten hours, ever since he picked me up at the Austin airport earlier in the day. He was late, and I had begun to have my doubts, but then he'd rushed through the door and though I had never before laid eyes on him, I recognized him instantly and was rea.s.sured. He was a familiar type. Tall, thin, with a professorial mop of graying hair and an abundant white mustache, wearing stiff Wranglers, a plaid shirt, and scuffed brown shoes. Gla.s.ses. A sunburned neck. Mischievous eyes. Pens in his pocket. We had talked twice on the phone before that, too-I was interviewing him for an article I was writing-and it was during one of these conversations that he mentioned he would be driving to the International Conference on the Monarch b.u.t.terfly in Morelia, Mexico, the following month, looking for b.u.t.terflies along the way and doing some research, and invited me to come along.

This would be my second trip to Mexico to see monarchs. The first had been three years before, when my daughter was nine months old. That was how I would always remember the trip, with a certain amount of distance, as if I had been watching myself there: a woman in a foreign country with a small baby in her arms. We had been at a meeting, my husband and I, and at the end of it, as a kind of reward, we were to be taken into the mountains to a monarch b.u.t.terfly preserve. Those words, b.u.t.terfly preserve, meant nothing to me. I could not make them into a coherent image the way I could, say, Walt Disney World, where I had never been, either, or Glacier National Park, or Victoria Falls. What would a b.u.t.terfly preserve look like?

We took a bus, and then a truck, and then we walked. At ninety-five hundred feet, where the climb began, the air was not so thin that you noticed, yet, how high you were. Other things were more obvious and would have taken your breath away even at sea level: the skinny little boys, for instance, who were selling things-recapped bottles of beer and snapshots of cl.u.s.tered monarchs and handkerchiefs embroidered by their mothers or grandmothers or sisters. The handkerchiefs cost a quarter, and though they were made by hand, all of them looked alike: a white cotton square with scalloped edges and an orange-and-black monarch b.u.t.terfly sewn into one of the corners. That was the other thing that brought me up short: the b.u.t.terflies. They were underfoot. I was used to seeing b.u.t.terflies in the air, or on flowers, but there, at the entrance to El Rosario, thousands of wings torn from their bodies lay in the dirt. They were like cairns in the forest, pointing upward, and so we climbed, my husband, our daughter, and I, and the little boys fell away, and I could hear myself breathing, and my heart in my ears, and when I looked up again, what I was seeing made so little sense that I turned it into something else, something I understood-autumn leaves, falling through the air. That was what it sounded like, too. Millions of leaves, ripped and ripping from their moorings. The sound was overwhelming. It woke the baby in my arms, who opened her eyes to this sight. The three of us stood there, looking and looking, and gradually it occurred to me, gradually it registered, that though there were millions of them, they were not leaves at all, they were b.u.t.terflies, monarch b.u.t.terflies, the b.u.t.terflies of my backyard. They were in the air, and so heavy on the branches of the pine trees that the branches bent toward the ground, supplicants to gravity and ma.s.s and sheer enthusiasm.

We moved on. As we hiked we saw even more b.u.t.terflies, more than would seem possible, twenty or thirty million. Every available place to roost was taken. Even the baby became a perch. There were b.u.t.terflies on her shoulder and shoes, b.u.t.terflies in her hair. Somehow she knew not to touch them, and not to be afraid. We found a rock at the edge of the forest, and the baby and I sat down. The clamor of b.u.t.terfly wings was as constant and irregular as surf cresting over rocks. I watched my daughter watching the b.u.t.terfly resting on her shoelace, watched her reach down and wait until the b.u.t.terfly crawled up the ladder of one of her fingers, climbed over the hump of knuckles, and rested on the back of her hand. She was completely silent, as if she had lost her voice. Her eyes were wide open, and so was her mouth, and for twenty minutes, maybe longer, the two of us just sat, eleven thousand feet up the side of a mountain, and paid attention. If I were a more religious person I would have called that place, and that moment, holy, or blessed. But my vocabulary did not typically include those words. Still, unbidden, they were the ones that came to mind.

AS A CHILD I collected rocks. Limestone, sandstone, mica, quartz-they all went in my box. Inside the box was a book with pictures of rocks, a field guide against which I would check my specimens, but what interested me most was how they felt in my hand, and their colors and consistency, not what they were called. The boy across the street collected b.u.t.terflies, which he would pin to a piece of foamcore. Although I didn't have this word for it then-I was eight or nine-I thought it was morbid, which is to say that when my grandfather died the next year and I looked at his body laid out in the casket, rigid and perfect, it reminded me of those b.u.t.terflies pinned to the board. The rocks, rattling around in my box, seemed more animate and full of possibility. Someday they would be dirt.

All these years later, I hardly remembered the difference between an igneous and a metamorphic rock. What I did remember was the single-mindedness with which I had picked through the woods behind my house, and the pure joy of finding something valuable enough to hold on to. It seemed reasonable to call this pa.s.sion, and to think of myself-and everyone else-as a collection of pa.s.sions. What this suggests is that it is not simply our ability to think, to be rational, that distinguishes humans from other species, but our ability to be irrational-to put stones in our pockets because we think they are beautiful.

All of us have experiences that could change our lives if we let them: love, offered suddenly, turning from the mantelpiece, as Delmore Schwartz put it. And that, oddly, was the way it was with me and the b.u.t.terflies. Not love, exactly, offered suddenly, but a similar quickening of heart and desire-in this case a desire to know, if knowledge was not only information and understanding but experience. I could feel those b.u.t.terflies tugging on my imagination as if it were a loose sleeve.

"YOU MEAN YOU agreed to spend a week in a car in a foreign country with a man you've never met?" my mother asked in disbelief the night before I left for Austin. She reminded me that I had a small child at home, and a husband. "Promise me you won't drive through Mexico at night," she said finally, and I did. I promised her up and down. And now it was near midnight and I was breaking that promise, doing something that only somebody who scored two sigmas more than a seventeen-year-old might find unremarkable.

"Are you worried?" Bill asked after a while, picking up, perhaps, on my body language, which spelled "tense" in marquee letters.

"Yes," I admitted. "Should I be?"

"I don't know," he said, but with conviction.

MONARCH b.u.t.tERFLIES never fly at night. They can't. Once the ambient temperature drops below fifty-five degrees, they become sluggish, unable to flap their wings. The wings, which are commonly-and erroneously-described as solar panels, don't store energy but instead absorb it directly from the sun and air. Pick a monarch off a tree in the early morning and put it on your palm and it will sit there as if it were tame. Until the sun warms the air, the monarch is stuck paralytically, making it breakfast for certain steel-gutted birds. This is crucial because every autumn, monarchs do something no other b.u.t.terflies do: they migrate unimaginably long distances. Monarchs born east of the Rockies typically go to Mexico. Those born to the west go for the most part to the California coast. They travel forty-four miles a day on average, but sometimes as many as two hundred, and all of it by day. Unlike songbirds, which often migrate in the dark to elude predators, monarchs are limited to flying out in the open when it is sunny enough for them, and warm enough, and not too windy.

"I THINK THEY are up there," Calvert speculated the next day, while the windshield wipers slapped at the morning drizzle as if it were something annoying, like bugs. The sky was gray, and Bill was narrating what we would have been looking at if we weren't looking at a thick curtain of clouds: big mountains, part of the Sierra Madre Oriental, mountains that rise eight and ten and twelve thousand feet into the air. In the foreground there were p.r.i.c.kly pear and century plants and scrub gra.s.s, beautiful in their own way but hardly majestic. Calvert was sure the monarchs were on the move, but up high, above the fog-an unprovable hypothesis.

"Keep your eyes open," he said. "If you ever see a b.u.t.terfly flying under these conditions-overcast, with no wind-it'll wreak havoc with all the existing theories." I understood implicitly that he would like this. Rules, even scientific rules, were anathema to him. But it wasn't going to happen; it was a biological impossibility. Thermoregulation was one of the few sure things that scientists knew about monarch migration. The rest-how the b.u.t.terflies knew when it was time to leave their summer breeding grounds for their overwintering sites thousands of miles away, and how, navigationally speaking, they got to those sites-had stymied them for decades. And so had this: how did monarch b.u.t.terflies from the eastern United States and Canada, millions of them, end up every year in the same unlikely spot, a remote and largely inhospitable fifty acres of oyamel fir forest ten thousand feet up the southwestern flank of Mexico's Transverse Neovolcanic Mountains?

This last question-how do monarchs find their way back to the same oyamel trees year after year?-remains one of the great unsolved mysteries of animal biology. Monarchs are not guided by memory, since no single b.u.t.terfly ever makes the round trip. Three or four generations separate those that spend one winter in Mexico from those that go there the next. A monarch b.u.t.terfly born in August where I live, in the Adirondack Mountains of New York State, for instance, will probably fly all the way to Mexico, spend the winter there, and leave in March. Then it will fly north, laying eggs (if it is female) on milkweed along the Gulf Coast in Texas and Florida before dying. The b.u.t.terflies born of those eggs will continue northward, breeding and laying more eggs along the way. So will their offspring. By August another monarch, four generations or so removed from the monarch that left my land for Mexico the previous summer, will emerge from its chrysalis hidden among the raspberry canes and do the same thing. It will head south, aiming for a place it's never been, an acre or two of forest on the steep slopes of the Neovolcanics.

All over the world-in the United States and Canada and Mexico, in Australia, in the United Kingdom, in Germany-people were puzzling this out. They were studying navigation, orientation, cellular structure, biogeology, ecology. All were doing science, and like much else in science, what they were doing was haphazard and unsystematic. Those of us who do not do science are often in awe of it, for it seems to possess a certain inherent power, the sort of power that comes from inalienable truths. For those of us who do not do science, science often seems to be the last bastion of unfuzzy logic, a place where the answers are clear-cut, a moral universe where there is a right and there is a wrong. But we fool ourselves-it's not like that at all. Science is ruled by human pa.s.sions and limitations and creativity. Science is the story we tell ourselves, or are told, to make sense of the world of atoms and cells, illness and beauty, ozone and oxygen, the world in which we-collections of atoms and cells-find ourselves.

Every fall monarchs pa.s.s through my yard, and though I know where they are going, no one can tell me for sure how they get there. Maybe it doesn't matter; so much of nature happens in the background, without most of us paying it any attention. But paying attention is part of our animal heritage, a link to deer and dolphin, owl and bear. And that, perhaps, is where the itch of curiosity begins, and the ongoing attempt to scratch it.

People have been paying attention to the monarch for hundreds of years, and most of them, unlike Bill Calvert, have not been professional scientists. They have been drawn to these insects because their behavior has seemed so unlikely, so amazing, so nearly heroic. The monarchs' presumed heroism, in fact, has been the subtext for much of the fascination. In the process, data have been collected and then organized into a narrative. Ultimately, that narrative didn't have to be true, but like all stories, it had to seem to be true.

Bill Calvert was one of the storytellers, as well as part of the story itself. As an undergraduate at the University of Texas he studied philosophy, and as a graduate student there, zoology. His dissertation was on b.u.t.terfly feet, how female b.u.t.terflies find their host plants. He started looking at monarchs on a lark because he was stuck in Ma.s.sachusetts one winter and wanted an excuse to go south. He went to a talk given by Lincoln Brower, then a professor at Amherst College and the world's leading monarch scientist. Brower needed b.u.t.terflies for his research, and he put Calvert up to flying down to Texas to collect some. It was the beginning of a loose collaboration that continues to this day.

In monarch circles, which are bigger than one might suppose, Bill Calvert is something of a legend. It's not just his reputation as a cowboy entomologist, a guy who sleeps in his truck in pursuit of monarch b.u.t.terflies and has more field notes and more data than he'll ever be able to write up-though these are part of it. What makes him a legend is that almost twenty-five years ago Bill Calvert figured out, based on a couple of clues in a National Geographic article whose authors were trying to keep it secret, where monarchs from the eastern United States and Canada spend the winter.

"I had a friend who was a librarian," Calvert said, "and she gave me a bunch of maps. There were two clues in the National Geographic article, that the b.u.t.terfly colonies were at ten thousand feet and that they were in the state of Michoacn. When you put those two features on a map, there were not very many choices."

Calvert and three friends borrowed a truck and drove to Angangueo, a mountain town that was home to a silver-mining company once owned by the Guggenheim family. He was carrying a picture of a monarch b.u.t.terfly, and when he showed it to the mayor of the town, the mayor became very excited and began to talk about a b.u.t.terfly roost high in the mountains, a place called Chincua. It was the last day of 1976. Bill Calvert called Lincoln Brower and told him this. The next day Calvert and his companions found the b.u.t.terflies on a ridge above Zapatero Canyon.

Bill Calvert gave up his postdoc on tent caterpillars. He bought lots of maps and started looking for place-names with the word paloma-"b.u.t.terfly"-in them. He mounted expedition after expedition, discovering seven more colonies, roaming around Mexico on National Science Foundation money. Nearly twenty-five years later he was still roaming. He had a wife and a son back near Austin, but the marriage was breaking up. He was too restless-or she wasn't restless enough. "You pretty much have to be retired to do this research, wandering around, looking at things," Bill Calvert said. "You can spend all your time traveling around and not getting conclusive answers. So that leaves people like me to do it."

IT WAS NOVEMBER 6. According to the biological clock that unwittingly winds us all, the b.u.t.terflies would be approaching their winter home. The door would be ajar, and they would be streaming over the threshold, marathoners tired from their long journey, eager for a patch of bark, or the branch of a tree on which to rest. Where Bill and I were, not far past the enormous concrete globe with a black line girdling the twenty-third parallel that marks the beginning of the Tropic of Cancer, there were pecan groves, row after row of them, and a carpet of yellow flowers. The rain had stopped, and though the day was bright, it was hazy. We hadn't seen a single monarch all day.

"If we're going to see monarchs today, this is the place," Bill said, stopping on the side of the road by an irrigation ditch. This is the kind of place they love." He pointed to the trees, which were bowed over the stream. "They just love these." We got out of the truck and began looking, searching the sky and the tree limbs and the water itself. We stayed maybe five minutes, as hopeful and enthusiastic as if we had never seen a monarch b.u.t.terfly before, as if it wasn't the most common and best-known b.u.t.terfly in North America. There is something self-preserving about the natural world-its ultimate adaptation-so that what is familiar and expected often seems new, over and over again: snow in winter, robins in spring, leaves turning in the fall. Bill Calvert has probably seen more monarchs than any other person on earth, twelve or fifteen or twenty million in a single frame, yet here he was, excited to maybe see one, right now, in this place. But he didn't. There weren't any. And he was disappointed.

"Let's go catch up with them," he said, so we got back in the truck and continued along Route 101. There were tapes on the dashboard-Gordon Lightfoot, Vivaldi, Bach fugues-but we drove in silence, looking, looking, looking, until it hurt to look so purposefully, at least for me.

"Over there," he said fifteen miles later, when we had begun the climb out of the lowlands into the mountains, and there it was, a single monarch, flapping its wings athletically, flying across the road. And, "There," again. Three more monarchs coming off the ridge to our right, heading southeast. And then more coming right over the truck, crossing the highway, sinking down toward the valley below, disappearing. Calvert stopped the truck and gathered up his binoculars, his tape recorder, his compa.s.s, and his global positioning unit.

"One at six feet at two-oh-five degrees," he said into the tape recorder after holding up the compa.s.s to take the vanishing bearings of the b.u.t.terflies as they dropped to the valley. "Powered flight," he recorded, meaning that they were not gliding but were flapping their wings. "One traveling at ten feet at two-oh-five," Calvert called out. The number 205 referred to the monarch's azimuth, its direction with respect to magnetic north. In this case the monarchs appeared to be flying south-southwest. Calvert unsheathed the global positioning device and placed it flat on the ground, aiming it upward to beam a signal to a satellite pa.s.sing overhead. "Let's find out where in the world we are," Bill said, turning it on.

The answer didn't come immediately. It reminded me of one of those Magic Eight Ball toys to which you direct a life-defining question ("Will I pa.s.s the math test?" "Will I find true happiness?") and wait expectantly while the answer floats into view ("It is too early to tell"; "Try again later").

The numbers started to drift in: 23 degrees, 23.25 N; 99 degrees 29.37 H. 4704 feet. To me they were less telling than what I could see: mountains as far as the eye could travel-big, imposing mountains that rippled like an inland sea, all the way to the horizon. We waited. b.u.t.terflies pa.s.sed close by. Thirty monarchs in fifteen minutes.

"They're very patchy," Bill said when we were back in the truck. "I suspect ridges have something to do with it. I suspect that wind currents do, too. But it's hard for us to read the wind." Another two monarchs worked their way over us and dropped out of sight in the valley. Then three more. Then nothing. We had caught up with the monarchs, but we couldn't follow them. There was no road where they were going, so we moved on, scanning the sky, focusing on the foreground and the middle distance, but we saw none. We had lost them.

More than that sense of loss, I don't remember what I was thinking. We were coming to a town, Tula, where I hoped to find a phone to call home, so maybe it was that. But suddenly the brakes were on and we were making a dusty U-turn, and Bill Calvert was pointing to a stand of willows ten yards from the road, encircling a muddy pond. "Whoa," he said. "There's a roost. Probably two thousand monarchs in there." We picked our way over a barbed-wire fence for a better look, pa.s.sing a great blue heron arrayed in its winter whites, and paused to admire a vermilion flycatcher, a bird so radiant I had to fight the urge to squint. Compared to this, the monarchs' orange and black markings, and especially their dried-leaf appearance when their wings were folded as they roosted, might have seemed drab. But the monarch itself did not. I had sometimes heard lepidopterists refer to the monarch's charisma, to its character, and as I stood in that swamp, looking up at the monarchs resting in the branches overhead, I knew exactly what they meant. These less-than-a-gram creatures had flown, most of them, nearly two thousand miles. They had almost made it. They seemed ... admirable. Bill Calvert got out his equipment: a ruler, gla.s.sine envelopes, a digital balance, a tattered net, extension poles, duct tape. His subjects had arrived: he was going to do science.

WHEN BIRDS MIGRATE, they do so primarily because of food. Winter comes, and mosquitoes and berries and other food sources dwindle or become less accessible. Birds fly south, and the landscape becomes one big commissary. This is oversimplified, of course, but even schematically, what birds do is nothing like what b.u.t.terflies do. Monarchs do not leave their northern breeding grounds because the flowers have withered. They leave for the same reason the flowers wither: the climate changes. The monarch b.u.t.terfly, which is, genetically, a tropical species, cannot survive sub-freezing temperatures. And when monarchs are wet, they are even more vulnerable. If they are going to reproduce, they have to move to a more hospitable place-or, as is really the case, a less inhospitable place. At ten thousand feet, the Neovolcanics are not the Bahamas for b.u.t.terflies; the overwintering sites are not warm. Rather, they have the right microclimate for monarch survival, warm enough so the monarchs don't freeze and cool enough so they don't drain their finite supply of energy, the lipids stored in their bellies. Monarchs spend an average of 135 days at the overwintering colonies, days of entropy when food may be sought but is not much available.

But they need food; they need energy, both to fly long distances and to survive the winter. Intuitively one might expect the b.u.t.terflies to bulk up in the north, the way we might fill up the gas tank before driving cross-country. The problem is that a loaded gullet may actually require more energy to transport. And it may cause drag. So the question of when a monarch obtains its winter food supply is an important one, both because it may suggest how the b.u.t.terflies find their way to Mexico (do they, for instance, follow the asters and the black-eyed Susans?) and because it may have implications for conservation (what happens if wildflowers are replaced by roads or subdivisions or wheat fields?). Besides, it is just plain interesting: science for science' sake.

This last, more than the others, appealed to Bill Calvert: the questions, one begetting another-no; begetting many others. We would drive, and I would ask Calvert, who has devoted his life to studying monarch b.u.t.terflies, how high monarchs flew, and if they followed corridors of wildflowers when they headed south, and if predation was greater during migration or remigration, and invariably he would smile and tell me that I had asked a good question and say, "But that's the thing, no one knows the answer." In my knapsack I was carrying around a book called The End of Science, about how scientists were closing in on a unifying theory to explain everything, and it seemed pretty clear to me, in talking with Bill Calvert, that the physicists were going to be able to tell us how the world worked, and we still wouldn't know how a single monarch b.u.t.terfly found its way from Canada to Mexico, or the answers to the hundreds of questions raised by its flight.

THE b.u.t.tERFLIES at this particular roost were fifteen, twenty feet up-too high to grab with a regular b.u.t.terfly net. Calvert rooted around and found a long stick, which he taped to his extension pole. Then he taped this gangly arm to the handle of his net. It almost reached-he was going to have to jump. The monarchs, meanwhile, were sitting ducks. A few were milling about in the air, but most were lined up, thorax to proboscis, along the branches. Calvert made one practiced swipe and nabbed about thirty b.u.t.terflies, who seemed astonished to find themselves suddenly crowded into a green mesh funnel and who tried frantically to escape. But it was impossible. Calvert had deftly tossed the bag over itself, effectively sealing it. Nothing could fly out.

We got to work. The scale was set up and calibrated, and I started a log sheet, with columns for time, weight, s.e.x, and condition. Bill sat cross-legged on the ground, pulling b.u.t.terflies from the net one by one, measuring their wingspan, and noting how tattered or not they were and which s.e.x. While I wrote all this down in the log, Calvert would fold, then stuff, the monarch into a two-inch gla.s.sine envelope and lay it on the scale. "The envelope is so it won't hurt itself," he explained. It prevented the monarch from flapping wildly. Once it was in the envelope, he could lay it down on the scale and get its weight. I recorded that, too.

"These b.u.t.terflies are very heavy," Bill observed. "You'd think they would have a harder time with a heavier load."

"Maybe the load supplies extra energy," I suggested. It seemed as good a theory as any.

Bill Calvert considered this for a second. "There are many trade-offs in a b.u.t.terfly's life," he said, smiling.

Calvert had once thought that monarchs started their journey south as lightweights and didn't begin to add weight until they reached Texas. They would lose some crossing the desert and then begin to nectar heavily once they were in Mexico, in antic.i.p.ation of the winter to come.

"But now I'm not so sure," Bill said. "I contracted with a woman in Milwaukee to capture monarchs and send them to me overnight, and I weighed them, and they weighed a lot less than the b.u.t.terflies I was capturing in Texas. But then I had her weigh them before she sent them from Milwaukee, and I weighed them the next day-they were sent FedEx-and they were considerably lighter. I think the definitive paper on the use of nectar during migration remains to be written."

TWO BURROS WERE tethered to the fence opposite us, and there were two women there, too, waiting for a bus. But the bus was nowhere in sight, and before long the women asked us what we were doing, and we said the words "Biologico" and "Mariposa monarca," and they grunted and shook their heads and smiled at us and kept watching. Watching and smiling and pointing and laughing. We were pretty entertaining, especially when a b.u.t.terfly would push its way out of an envelope and we'd flop after it, trying to get it back.

As the women watched us, I watched Bill Calvert sitting Indian-style in the dirt, measuring and weighing the b.u.t.terflies and a.s.sessing their condition on a scale of one to five. Most of the monarchs were in good shape, all things considered, fresh and untattered. Focused as Bill was, I noticed that his affect was that of a child-happy, engaged, fully present. He reminded me of my daughter at the edge of our pond, sorting rocks, digging for turtles, catching newts. Children have enthusiasms and adults have pa.s.sions, I thought, and though it sounded good, Bill Calvert seemed to contradict it. The answers mattered to him-that was a given-but getting at them mattered even more.

"The need of the age gives its shape to scientific progress as a whole," I read months later, in Jacob Bronowski's cla.s.sic meditation Science and Human Values. "But it is not the need of the age which gives the individual scientist his sense of pleasure and of adventure.... He is personally involved in his work, as the poet is in his and artist is in the painting. Paints and painting too must have been made for useful ends; and language was developed from whatever beginnings, for practical communication. Yet you cannot have a man handle paints or language or the symbolic concepts of physics, you cannot even have him stain a microscope slide, without instantly waking in him a pleasure in the very language, a sense of exploring his own activity." It was an old book. I had underlined the pa.s.sage twenty years before. But it described precisely what I was seeing while I was watching Bill Calvert.

THE BUS CAME, and the women waved and turned and got on it. It shambled on, dust rising behind it. The heron paced the bank; our log list grew longer. The b.u.t.terflies were healthy and fat. Their trip appeared not to have taken a toll. A young man rode by on a bicycle, doubled back, looked at us, rode by, and doubled back again-like a yoyo. Cheered by the bonhomie of our encounter with the two women, I decided to clue him in on what we were doing on his next pa.s.s by. "Mariposo," I shouted loudly as he rolled past. "Mariposo!" Bill Calvert looked up at me and smiled. I smiled back, happy to have explained our mission with such ease and precision.

"You'd better hope he doesn't come back this way again," Bill drawled as he casually stuffed a monarch into an envelope. I looked at him curiously. "You just called him a f.a.ggot," he said.

THAT NIGHT WE WERE stopped by the police. Or maybe it was the army; it wasn't obvious which. There were sixteen of them, in knee-high black paratrooper boots and black pants and black sweatshirts, and they had AK-47s and Uzis. It was dark. We were in the desert and it was late. We had gotten cavalier about where we went, and when. We had been taking our time all afternoon, inching our way along the side of the road just past Tula, looking for roosts. Every couple of trees Bill would say, "Over there" or "A thousand on that one," and "That will grow by a factor of ten by nightfall." He said this so confidently that I wrote it down in my notebook as if it were fact, not prediction.

The land outside Tula was arid; rain seemed a memory. The ground was cracked and it curled like smoke when the wind blew. The wind was blowing. Monarchs were dropping out of the sky. Those that were flying at tree height were being tossed around like falling leaves. They were fighting back, treading the air by pumping their wings, but often blowing backward. "Golly," Bill said to me, "there are a lot of them." And then, to his tape recorder: "The last five-mile segment there were at least one hundred b.u.t.terflies."

We drove due south. When the wind let up, the monarchs escorted us, flying straight along the edge of the road as if they were pedestrians on a sidewalk. But then, as if there were a sign, or a crossing guard, or a traffic light, they all turned at the same spot and went to the other side of the road. We stopped the truck and got out and looked up. The trees were teeming with monarchs. I followed Bill across the road and saw him enter a grove of huisache trees and drop to his knees. There was little understory here, but enough to get my legs full of cactus thorns. Bill was rooting around the leaves at the base of one of the trees. "Mouse cache," he said as I walked up behind him. He pointed to the pile of leaves, only they weren't leaves, they were monarch wings-hind wings, forewings, left wings, right wings. Wings, no bodies. "The mice eat the bodies and leave the wings," Bill said. I poked around with the tip of my boot. There were hundreds of them.

When we crossed the road again to walk back to the truck, the sun was going down. Not one to pa.s.s up an opportunity, Bill got out his net and his scale and his ruler, and I started a new page in the logbook, sitting on the hood of the truck.

So we were late, and crossing the chaparral in darkness. Not late for anything in particular, though I guessed there were chicken mole and Dos Equis and a marginal hotel room not far ahead. The road had turned b.u.mpy, and then there was a detour sign, and we followed it, though it took us off the pavement and through dried streambeds and gullies that the truck strained to climb. The truck, which was already low to the ground, bounced on its shocks like a pogo stick. Bill gripped the wheel and fought to keep us upright. All of the things in the truck bed, Calvert's carapace, really-the sleeping bags, gallon jugs of water, the Random House Dictionary, a Spanish dictionary, woven mats, nets, our gear, his boots-crashed into one another and into the windows. They were timpani to the engine's tuneless melody. We were gaining alt.i.tude, little by little. Outside of the narrow band of the high beams, everything was black. It was as if the night were a well and we were submerged in its ink.

They must have seen us, then, long before we crested the last hill. They must have seen us dipping into each ravine and heard us pulling out. Their lights were riveting, like klieg lights when you're standing on a stage, and there was no choice but to stop. They made a ring around the truck, each one pointing a gun. One of them opened the door and motioned to Bill, with a wave of the barrel, to step out. I was like a monarch in the morning, unable to move. A gun, though, can motivate you. The handle of the door on my side turned, and when I looked to see what it was, I saw the midsection of a man with a gun trained on me.

We showed them our papers-first our pa.s.sports, then the ones that said we were going to a conference on monarch b.u.t.terflies. I was careful not to say the word mariposo. I was careful not to say anything. The men with the guns handed back the papers and opened the hood and peered inside with flashlights. They took off the hubcaps and looked in there. They dumped out our trash and rifled through our books. Bill and I didn't talk. I knew what he was thinking: if they found the gla.s.sine envelopes and the digital scale, we were in big trouble. It occurred to me that we had picked the perfect cover for running drugs.

The men with guns thought so, too. They checked out our field gla.s.ses, the tape recorder, our cameras. They looked behind the heating vents. They pulled up the floor mats. The lights of a city, maybe two miles away, winked as if they were in on a joke. One of the policemen was wearing a U.S. Army surplus jacket that had once belonged to a soldier named Olson. They started in on our duffel bags, feeling them up and down as if frisking bodies. The scale was back there, too, in a knapsack stored inside a backpack. The backpack had many pockets. It was freezing outside.

"Basta," said one of the men. How long had it been? Forty minutes? Fifteen? The others lowered their guns. The one with the army surplus jacket nodded at us.

"Mariposa monarca," he said.

Back in the truck, driving again, the heat was on, but I couldn't stop shivering.

"Bet you didn't know studying b.u.t.terflies was such a dangerous occupation," Bill said.

Chapter 2.

OF COURSE we kept driving at night. There was no time during the day. We'd go three miles and stop to scan the sky or poke around for roost sites or evidence of roost sites (disembodied wings, half-eaten thoraxes), go another few miles, hop out of the cab, do it again.

We were in dry, poor country. The houses were made of concrete and tin, or sticks and mud. Smoke rose thinly from makeshift chimneys, and threadbare clothes hung from wash lines. Water was carried in. The word that came to mind was abject. But the word poverty, which is typically twinned with abject in such circ.u.mstances, seemed far too modern. This place was preindustrial, sixteenth-century, with not a power line or a phone cable or a car in the yard to be seen. The yards, in any case, were scars of earth where nothing grew. Hunched old women with bundles of spindly logs slung on their backs walked the roads, bringing home cooking fuel. Rib-skinny dogs trotted alongside them, scavenging for anything remotely edible, while turkey vultures patroled the sky, scavenging the dogs. This was not the Mexico of the off-the-beaten-track tourist guides. There was no track.

Outside Ahuacataln, in the dusty heat, we saw monarchs high in the sky and stopped to watch. I was conscious of our binoculars, and global positioning device, and tape recorder, and cameras-of how absolutely rich we were, in relative terms. As if reading my mind, a drunken young man in black jeans and a cowboy hat came reeling up the road, mumbling to himself, carrying an unsheathed machete that he twirled absently in his hand. He stopped nearby and stood at the edge of the road, peering into the same distance we were peering into, trying to see what we were seeing. The machete impressed me into silence, and I stood staring skyward, as if I could will myself up there, away from that blade. And maybe I did. After a few minutes the man wandered off, though I dared not lower my field gla.s.ses to see where he'd gone.

"I guess we'd better get going," Bill said finally, when he had seen enough, and then he proceeded to walk past the truck and continue down the road as if he'd forgotten where he'd parked his vehicle.

"It occurred to me that we might find a roost," he said when I caught up with him, fifty yards later.

But we didn't, not then-not until the next morning, when, driving out of Tequisquiapn, we took a wrong turn down Avenida Cinco de Mayo, which dead-ended at a stream decked with cypress trees. "This is perfect for monarchs," Bill said, pointing to the water and the trees. He moved his finger two degrees to the left. "And there they are."

And there they were-a pair of monarchs chasing each other five feet above the middle of the streambed. We trailed them like spies, hanging back a few feet, trying to stay out of sight as we picked our way along the water's edge and were led unseen to one roost site, and then another, till we counted four of them in all, each with about a hundred b.u.t.terflies.

WHEN PEOPLE FOLLOW the laws of a nation-when they pay their taxes and stop at red lights and respect others' privacy-the infrastructure that lets us live together is transparent, and no one really notices it. The laws of nature are different. When the natural world conforms to them, or at least when it conforms to certain patterns, one glimpses, and understands-if understanding is a feeling-the origin of magic.

That morning was magic, even when, an hour later, we had progressed no more than two miles and stood on the side of a busy road, and not a single monarch of the dozens we were seeing was going in what was supposed to be the "right" direction-that is, the direction that would lead it to its winter habitat. (The wrong direction, meanwhile, would ultimately send it back to the United States.) Calvert was unperturbed.

"It seems to me that I've run into this before," he said, more to himself than to me. "Their initial behavior in the early morning is east, toward the sun, and then they warm up and head southwest."

Then we were heading southwest ourselves. At most, the b.u.t.terflies were intermittent. We stopped near San Juan del Rio at Comercial Mexicana-a Mexican version of Kmart-to stock up on bottled water, but we never made it into the store. Calvert sensed that there were monarchs overhead, sensed them the way a dowser smells water, and though I couldn't see them myself, I wasn't surprised when I looked through a pair of binoculars and saw them skipping across the very top of the optical range. They were like stars in a cloudy night sky, only vaguer. "Let's take some azimuths," he said, so we did. The b.u.t.terflies were going the "right" way, and so were we. That was the day when, at long last, we entered Michoacn, the state where most of the monarchs overwinter and where the North American Monarch b.u.t.terfly Conference would begin in Morelia, the capital city, the next day. It was an uneventful crossing through a scorched and scrubby desert, but it meant we were in range of the monarchs' winter home. Flat though it was where we were, we could see tall, rugged mountains in the distance and began to gain alt.i.tude ourselves.

"I think the b.u.t.terflies may use those mountains as beacons, to guide them in," Bill Calvert said casually, as though that thought had just popped into his head. But I had heard it before, in different versions, all of them his. We were taking the high road ourselves, on the spine of the Sierra Madre Oriental, then dropping into the valleys, because of this very notion-the idea that monarch b.u.t.terflies might use these mountains as a focusing mechanism to set them on a narrow path leading to the preserves.

"A b.u.t.terfly born in Minnesota and one born in New York State end up in the same intermontane valley because of this focusing device," he said. "When they start out they're spread two thousand miles across the continent, but when they get into Mexico they're condensed into just fifty miles. Wherever they join the mountain ranges of the Sierra Madre Oriental, they turn and follow it."

That was the theory-the only one, Calvert said, that accounted for longitude in a monarch's migration. The problem was that the hypothesis was basically unprovable. Calvert ticked off a list of questions that could be answered, it seemed, only by radio telemetry: "Where do monarchs. .h.i.t the Neovolcanics? How accurate are these creatures, anyhow? How do they know when to stop? Are they really directional? There's some evidence that suggests that they're not." But so far, sticking a radio transmitter on a monarch b.u.t.terfly had not been an option-the devices didn't come in that microdot size, and even if they did, using them would probably feel like cheating to an inveterate field biologist like Bill Calvert, a guy who made his own furniture, poured his own concrete, raised his own bees.