Podcast interview with Harry W. Greene, author of Tracks and Shadows
Can snakes unhinge their jaws? Harry Greene debunks a popular snake myth.
Watch an interview with Harry Greene by the Museum of Vertebrate Zoology at UC Berkeley
Tracks and Shadows
A timely old quote sidles around the two entwined themes of this book, my eccentric meditation on natural history. Writing from 1849 about Sierra Nevada streams devastated by gold miners, journalist Bayard Taylor likened nature to "a princess, fallen into the hands of robbers, who cut off her fingers for the sake of the jewels she wears."1 His brutal imagery frames a modern dilemma, because although many people believe animals relocate when their habitats are destroyed, most organisms have nowhere to go. They will die rather than move. Worse yet, these losses are usually unseen and writ large all over the world, so we truly are thieves, pillaging the future. My first theme, coming to grips with this predicament, challenges everyone who cares about biodiversity-even if clarifying what we want turns out to be a philosophical snake in the grass, more nuanced and elusive than I long supposed.
Taylor's slashing tone also resonates with a second theme, the twists and turns of my personal quest for wildness. Early on, as a curious youngster with rural grandparents, I discovered the seductive joys of nature study. From horned lizards and livestock on a Texas farm to elephants and lions in zoos, I watched and wondered. How can they eat only ants or hay or meat? Why do cow patties look different from horse dung, and do insects poop? I picked up a box turtle, peered into scarlet eyes as the head craned out, and asked my mother, "Where are the ears?" In a child's naive but earnest way, I yearned to reveal their secrets, and later, as I read and traveled widely, grander questions caught my attention: Why are some animals similar and others different? Why are there so many species in the tropics? And as the human population climbs on past seven billion, will future generations still marvel over nature?
There has followed a lifetime of chasing serpents, mostly real but occasionally metaphorical. From earliest memories until age thirteen, I aspired to be a cowboy or an explorer. Then I met a zoology professor and vowed to become an academic. Soon I joined several organizations for herpetologists-folks interested in amphibians and reptiles, informally called herpers-and began publishing in their journals, obsessed with biology. In college, because my late-blooming, all-consuming social life required cash, I hired on at a local funeral parlor as a mortician's assistant and ambulance driver. Boy Scout training and vague notions of what the job would entail were my only qualifications, but I relished the excitement, so after graduation, having barely managed passing grades as a biology major, I enlisted as an army medic.
During my twenties I helped hundreds of ill and injured people, as well as watched a dozen or so die from shootings, stabbings, and accidents. I stitched up autopsied bodies, was bitten by an epileptic and squirted by severed arteries, had an assailant turn on me with a knife and listened uneasily to nearby gunfire. One night I tried to save a toddler with an allergic drug reaction, and forty-five years later, defenses softened by a good cabernet, I still suffer the agony in her mother's screams. There were happy endings, too-just days after that little girl died I placed a squirming newborn at the breast of another young woman. Through it all, field biology was a respite, and by the time thirty rolled around I was back on track for a Ph.D., studying snake evolution and utterly clueless as to how those experiences might illuminate the issues with which this book is concerned.2
A decade later and tenured at Berkeley, I'd lost an undergraduate advisor and a lover to murders, a heart attack had dropped my father, and several friends had died way too young. Their deaths provoked sensations of choking on explosions and desperate grappling, as if I might strangle reality back to the future, and at times these people seemed oddly still present, like phantoms of amputated limbs. Personal frailty intruded too, during those middle years, in episodes I'd gladly never repeat. Some were exhilarating yet over so fast they remained emotionally obscure, as when a high-speed collision spun our pickup truck through the rainy night into an Arizona pasture, or my foot bumped a Central American bushmaster, jolting the giant viper and me into mutually favorable defensive responses. Other threats loomed more ominous with every endless minute, like when we sat in speechless terror while our Aeroperú jet, one engine streaming flames, circled back to Lima, or were confronted by angry, armed men in Uganda.
Little wonder, given those brushes with mortality, that desert writer Ed Abbey's admonition to "throw metaphysics to the dogs, I never heard a mountain lion bawling over the fate of his soul" beckons like a Buddhist koan.3 And perhaps it's not surprising that natural born killers inspired me beyond scientific justification, as if confronting their deadly essence might solve more private riddles. The upshot has been rewards akin to those that motivate artists: animals are the focus of my teaching and research, but fieldwork has also been contemplative, inspiring me to pay attention and live more fully. The practice of natural history, I have learned, fosters peace of mind.
Predators are linked in our psyches with wildness, perhaps all the more so for those who study them. In Costa Rica fleeting shadows and strange sounds intrigued me, and because we found tracks and scats of jaguars I always hoped but never expected to see one of those great hunters. Instead I poked through droppings and identified the drab remnants of lives briefly met, puzzled over little cloven hooves of collared peccaries and scythelike claws of three-toed sloths, the scaly feet and parchment-shelled eggs of green iguanas.4 Once a botanist led me to the bloody husk of a nine-banded armadillo, all that was left of a fresh kill. And late at night, deep in the black woods, I thought about skull-piercing canines and meat-rasping tongues, tried to imagine the prey's fine-tuned senses and gut-twitching anxieties. Do those wild-pig relatives squeal in their final moments, and would the lizards know what hit them? Could I empathize with armadillos at the expense of an empty belly or hungry youngsters back in the den?
When a local entomologist grumbled, "Everybody wants to meet el tigre," I chimed in about ecotourists seeking a quick nature fix, as if they were rushing through the Louvre for a peek at Mona Lisa. Better be content with turds and pugmarks, I mused, yearn for a glimpse of the great rainforest carnivore but settle for heightened awareness. Then, during one among countless nights searching for snakes, a companion exclaimed, "Hey, a cat!"-it had bounded across the trail in front of him-and our lights swung into the forest. The jaguar squinted from thirty feet away, all round head and broad shoulders, rosettes and long tail; just as suddenly, with not so much as a whispered paw on leaves, there were only small palms and saplings in the headlamp beams. No more cat, as if it had evaporated, and in those few seconds we more easily empathized with the Mayans, Olmecs, and others who have imbued forest creatures with mystical qualities.
Years later the memory of that animal surfaced when, with my wife, Kelly, and two Mexican friends, I backpacked from pine-oak forest that rims the four-thousand-foot-deep Barranca del Cobre down into sweltering tropical thorn scrub along the Rio Urique. Fox scats and other carnivore sign were common along the canyon's narrow game trails, so on the third day, when we sought permission to drink from a Tarahumara family's spring, I inquired about predators. A grizzled elder told us black bears raid their crops and they see tracks of mountain lions and jaguars. The mammals themselves are rarely visible, he added, and, as if by way of explanation, "Esos gatos caminan muy escondidos"-those cats walk really hidden. Asked about rattlesnakes, the old man volunteered only that they're common and bite people, leaving me wondering if his people regard las cascabeles as even more inscrutable than felids, if, like me, they find dangerous snakes charismatic.
During my travels, focused on predators, I've come to believe nature's most profound lessons, like god and the devil, lurk in hard-won details. As a youth I'd envied George Schaller's landmark studies of Serengeti lions but couldn't conceive of similar research on the smaller, more secretive creatures that captivated me. By the 1980s, though, I was collaborating with Tucson physician David Hardy, and technology made it possible for us to implant tiny radio transmitters in fifty black-tailed rattlesnakes. Over the course of nearly five thousand encounters, we tracked those lovely black and yellow serpents in Arizona's Chiricahua Mountains, chronicling their hunting tactics and spying on their social lives. And throughout that experience, we kept asking ourselves a question that motivates many naturalists: What is it like to be a blacktail, or for that matter a house wren or my dog Riley?
Almost six hundred observations of our most scrutinized rattler began in the fall of 1994, when we located her coiled with male 18 under the leaves of a yucca. While new female 21 was anesthetized Dave detected a meal by palpating her abdomen, and weeks later a substantial midbody bulge indicated she ate again before entering a winter refuge in November. That next March she moved to an abandoned rock squirrel burrow and in July delivered six babies. Female 21 remained there ten days, until the youngsters shed their natal skins and dispersed, then crawled forty yards to a white-throated woodrat's nest and hunted for the first time in nine months. She was courted by three males over the next two years, mated with male 27 prior to her 1998 litter, mated with male 26 prior to birthing in 2000, and then skipped three years before her fourth litter.5
We especially relished familiarity with individuals. Male 3 courted females but never mated, whereas male 26, at about four feet long and three pounds our largest blacktail, had an enormous range and successfully courted several females. Superfemale 21, as I later called my all-time favorite snake, was an excellent hunter and good mother, plus she stayed out of trouble; over the course of twelve years she showed more meal bulges than any of the others, guarded four litters through their vulnerable first days, and never betrayed her camouflage by rattling. Woodrats and rock squirrels are staple prey for this species, but one morning our star gal struck a desert cottontail, followed the wounded rabbit's chemical trail for more than two hours, and consumed it ninety yards from the ambush site.
Watching the blacktails, besides yielding generalizations about their biology, sometimes left us grinning and shaking our heads in disbelief. One morning male 41 crawled over the cobbles and dry leaves of a shady ravine, stopped abruptly, and for thirteen minutes meticulously tongue-flicked a cliff chipmunk's runway. Then he coiled, pointed at the little squirrel's path. Because hunting site selection had rarely been seen, we lingered, observing with binoculars from a few yards away. A dry fern was centered eight inches into the rattler's strike zone, and after two minutes he extended the crooked neck posture with which males fight over females, crushed the obstructing plant, and reformed his ambush coil. I shot Dave a skeptical glance and was reassured by his whispered, "He bent down that fern!" Later, after I published those observations,6 Alberta naturalist Jonathan Wright wrote me of his astonishment at seeing a prairie rattlesnake tamp down grass around rodent burrows before setting up its ambush.
The surprisingly crafty responses of those snakes challenge clichés about minimal intelligence in reptiles, as well as pose questions some researchers believe are unanswerable, even silly: Could male 41 have conceptualized how a plant might thwart his quest for prey, even if the problem manifested itself hours or even days later? Did he employ inferential reasoning and a move usually reserved for vanquishing rivals to solve what experimental psychologists call a barrier problem? What would a naive young male without combat experience have done, and, since rattlers of the opposite sex don't fight, how would superfemale 21 have dealt with that fern? I am among those lucky folks for whom such puzzles keep us headed outdoors, into the lives of others.
Nature has blessed me with many moments when my rumpled soul was naked and yet I felt unafraid. As we walked those cactus-studded ravines, gathering data and imagining the lives of blacktails, I turned from buried grief and self-absorption to more humble notions of our place in the cosmos. Studying predators, I contemplated violence without evil, death without tragedy, as if when their fangs pierced another creature I might accept my own simmering losses. Other memories drift in too, of frogs singing and friends talking softly while high mountain mist enveloped our camp and dusk fell on an African swamp. I recall afternoon shadows in the Mohave and how in that perfect stillness my students were mesmerized by bone fragments protruding from an old owl pellet, then shortly thereafter by the backlit, oversized ears of a kit fox napping by its burrow. Accompanied by kindred souls in such magical places, I've sometimes imagined us lions in the grass, tails twitching and joy overwhelming even the most powerful sadness.
The essays that follow address my twin themes: first, by portraying how natural historians transform curiosity into science and thence help save species from extinction. More than that, though, I aim to push into the poetry of field biology, to emphasize the second, more personal theme and explore how nature eases our existential quandaries. I'll begin by introducing the great explorers Charles Darwin and Alfred Russel Wallace, then bring in a venerable institution and another, less well known but also extraordinarily accomplished naturalist. Since early in the last century Berkeley's Museum of Vertebrate Zoology has played leadership roles in research, education, and conservation, and Henry Fitch, my most influential teenage mentor, got his Ph.D. there in 1937. I've enjoyed a life in some ways parallel to Henry's and for twenty years was employed by the M.V.Z., so Part I combines our stories to illustrate how childhood passions, chance, and opportunity shape adult trajectories.
Part II moves from youthful obsessions to academic jobs, and thence into deserts and rainforests, looking for snakes and other creatures. We'll get acquainted with the nuts and bolts of field research and teaching, contrast the emotional impact of hot dry places with hot wet ones; we'll learn some basics of serpent biology and examine ways in which fear plays into relationships with limbless reptiles. Part III begins with reflections on friendship and happiness, then delves into how an eighteenth-century philosopher's aesthetics and Darwin's theory of "descent with modification" can enhance appreciation for biodiversity. We'll also tackle troublesome notions like anthropomorphism and wilderness, and finally, backpacks brimming with questions, hit the trail after answers. My overarching claims are that organisms remain the core of biology, science plays key roles in conservation, and natural history offers an enlightened form of contentment.
With this book I've set out to praise sweeping dry plateaus and soggy tropical floodplains, as well as the black-tailed rattlesnakes, jaguars, and other creatures that enliven them. More privately, though, right from the start, I wanted to thank my heroes and explain some things to friends and loved ones; I knew there would be disturbing undercurrents and thought they'd be straightforward. Instead, Tracks and Shadows has unfolded as a complex, rewarding journey during which, after decades of studying predators, I became one myself. Along the way, problems that seemed easy proved intractable. Nonetheless, by sharing my search for solutions, I aim to persuade others to get out there and learn more about themselves. By portraying field biology as art, I hope to add another brief in defense of the wild.
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