by Sue Halpern
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 passions 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 pass 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 butterfly feet, how female butterflies find their host plants. He started looking at monarchs on a lark because he was stuck in Massachusetts 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 butterflies 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 butterflies 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 butterfly colonies were at ten thousand feet and that they were in the state of Michoacán. 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 butterfly, and when he showed it to the mayor of the town, the mayor became very excited and began to talk about a butterfly 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 butterflies 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—“butterfly”—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 butterflies 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 butterfly before, as if it wasn’t the most common and best-known butterfly 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 compass, and his global positioning unit.
“One at six feet at two-oh-five degrees,” he said into the tape recorder after holding up the compass to take the vanishing bearings of the butterflies 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 passing 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 pass 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 t
ravel—big, imposing mountains that rippled like an inland sea, all the way to the horizon. We waited. Butterflies passed 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, passing 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, glassine 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 butterflies 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 butterfly, 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 butterflies; 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 butterflies 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 butterflies 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 butterflies, 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 butterfly found its way from Canada to Mexico, or the answers to the hundreds of questions raised by its flight.
THE BUTTERFLIES at this particular roost were fifteen, twenty feet up—too high to grab with a regular butterfly 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 butterflies, 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, sex, and condition. Bill sat cross-legged on the ground, pulling butterflies from the net one by one, measuring their wingspan, and noting how tattered or not they were and which sex. While I wrote all this down in the log, Calvert would fold, then stuff, the monarch into a two-inch glassine 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 butterflies 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 butterfly’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 anticipation 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 butterflies 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 butterfly 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 butterflies and assessing 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 passions, I thought, and though it sounded good, Bill Calvert seemed to contradi
ct 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 classic 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 passage 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 butterflies 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 pass 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 faggot,” he said.
