There’s no sound quite like it, or as viscerally terrifying: the ominous rattle of the timber rattlesnake. It’s a chilling shorthand for imminent danger, and a reminder of the countless ways that nature can suddenly snuff us out. Yet most of us have never seen a timber rattler. Though they’re found in thirty-one states, and near many major cities, in contemporary America timber rattlesnakes are creatures mostly of imagination and innate fear. Ted Levin aims to change that with America’s Snake, a portrait of the timber rattlesnake, its place in America’s pantheon of creatures and in our own frontier historyand of the heroic efforts to protect it against habitat loss, climate change, and the human tendency to kill what we fear. Taking us from labs where the secrets of the snake’s evolutionary history are being unlocked to far-flung habitats whose locations are fiercely protected by biologists and dedicated amateur herpetologists alike, Levin paints a picture of a fascinating creature: peaceable, social, long-lived, and, despite our phobias, not inclined to bite. The timber rattler emerges here as emblematic of America and also, unfortunately, of the complicated, painful struggles involved in protecting and preserving the natural world. A wonderful mix of natural history, travel writing, and exemplary journalism, America’s Snake is loaded with remarkable charactersnone more so than the snake at its heart: frightening, perhaps; endangered, certainly; and unquestionably unforgettable.
|Publisher:||University of Chicago Press|
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About the Author
A former Bronx Zoo zoologist, Ted Levin is the author of Blood Brook: A Naturalist’s Home Ground, Backtracking: The Way of the Naturalist, and Liquid Land: A Journey through the Everglades, which won the Burroughs Medal in 2004. He has written for Sports Illustrated, Audubon, National Wildlife, National Geographic Traveler, and other publications.
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The Rise and Fall of the Timber Rattlesnake
By Ted Levin, Alexandra Westrich
The University of Chicago PressCopyright © 2016 The University of Chicago
All rights reserved.
An Introduction to Crotalus horridus
She strongly resembles America in this, that she is beautiful in youth and her beauty increaseth with her age, her tongue also is blue and forked as the lightning, and her abode is among impenetrable rocks.
I have seen timber rattlesnakes before, mostly on the sun-baked talus of western Vermont — dark, with vague markings, or mustard-colored and distinctly banded to merge into the forest floor, but never an incandescent yellow one in the Northeast. The snake stretches out in the morning light, basking on the stone foundation of a building preempted by trees in a forested hillside in western New York. Chocolate-colored bands stain the yellow areas and loop its body from head to vent; the tail is as black as obsidian. And like most timber rattlesnakes I've seen, this one is content. No rattling. No threatening coil. No retreat. Not so much as a glance in my direction. Lidless eyes focus on the all or nothing of a New York morning, golden spheres each slashed by a vertical black pupil — eyes of the night.
At fifty-two inches and just over three and a half pounds, Hank is big. Of all the rattlesnakes I've encountered in the Northeast, only Travis, Hank's hillside neighbor, a black morph recumbent beneath the overhang of a bramble a quarter of a mile away, is bigger: fifty-two inches, four and a half pounds, and thick as the sweet spot on a baseball bat.
I'm in the field with Rulon Clark, a Utah native who completed his doctorate at Cornell University in nearby Ithaca with a dissertation on the communal habits of timber rattlesnakes and is now assistant professor in the biology department at San Diego State University. Although it was once widely believed that snakes led rudimentary lives of solitude, Clark discovered that timber rattlesnakes lead surprisingly rich social lives. Because they dwell in a different temporal realm than people, very slow and methodical, rattlesnakes live within a formerly unmapped wilderness of patience.
To understand timber rattlesnakes, you must learn to think like them, which means spending an inordinate amount of time on the ledges and in the woods. And you must also be a master of technology. According to Clark,
Rattlesnakes have adapted to live in such a way that they do things more slowly than we do. We're too quick for them in some ways; we don't recognize important things that could be going on. You really have to either be very patient or set up experiments in such a way that you see results regardless of your timescale.
During the six years that he studied rattlesnakes in Pennsylvania and New York, Clark unveiled a sisterhood of snakes, in which female timber rattlesnakes from the same litter entwined with each other more than with unrelated females, the first demonstration of kin recognition for any species of snake. In fact, Clark determined that female littermates separated for two years after birth immediately (in snake time) recognized each other.
As a child, Rulon Clark was attracted to non-fleeing predators (like rattlesnakes) and sponsored public feedings with his menagerie of reptiles and arthropods. "I had tolerant parents," he recalls. I had tolerant parents as well, but their level of tolerance was governed by the social codes of suburban Long Island. They accepted my boyhood passion for bringing home snakes, and would find me whenever anything unusual happened in a terrarium. Once my father prevented a garter snake from consuming its own young by tapping the snake on the head with the buckle on the dog's leash. My parents would likely have drawn the line against keeping a venomous pet, but since Long Island timber rattlesnakes had already been extirpated, this never became an issue.
Through the years, Clark's boyhood obsession grew. He examined eleven hundred timber rattlesnake museum specimens from collections all over the United States, and summarizing their dietary information made him an expert in the identification of half-digested mammal parts. "Don't let anyone tell you that you can't get practical skills out of a PhD."
Clark's audience also grew. The March 2005 issue of Natural History featured his essay "The Social Lives of Rattlesnakes," which was how I tracked him down. The week before I arrived in Ithaca, David Attenborough and a BBC film crew had visited Clark to film the hunting strategy of a wild timber rattlesnake (essentially waiting) for the final episode of the landmark two-part series Life in Cold Blood.
When I google "Rulon Clark" I find newspaper stories about pregnant rattlesnakes sun-bathing at a picnic area along a major highway in south-central New York. Clark advised the state to close the rest area until the snakes either give birth (sometime in late summer) or are relocated to an alternative basking site. When asked if the snakes pose a threat to travelers, Clark responded, "People are more likely to be killed by a drunken driver veering into the rest area than they are by a basking rattlesnake."
Radio-tracking enables Clark to eavesdrop on timber rattlesnakes during the four or five months when they're away from the den and fanning out for miles across the countryside. Earthly pulses and species-specific biorhythms, formerly understood only by the snakes themselves, govern the movement of these reptiles. Using a remote-sensor video, Clark films rattlesnakes as they wait hours, or even days, to ambush the small mammals that are their principal food. He learns where they eat, when they eat, what they eat, and how they eat, as well as what they do between meals (lounge and digest and eventually wander to their next ambush station). Clark's work dispels myths, confirms scientific speculation, and illuminates unknown aspects of rattlesnake behavior. It also adds a sense of wonder to the forested hillsides of the Northeast, a glimpse into the secret life of a reptile whose continued presence is a marvel of adaptation and concealment, for timber rattlesnakes are the very last of a short list of potentially dangerous pre-Columbian predators that still survive in the twenty-first century on the virtual (and sometimes real) doorstep of the urban Northeast.
* * *
Rattlesnakes belong to the subfamily Crotalinae, the pitvipers, of the family Viperidae, perhaps the most advanced family of reptiles in the world. Of the approximately three hundred species of viperids, one hundred ninety-nine are pitvipers, the most advanced of the vipers. And rattlesnakes, the most recently evolved of the pitvipers, sit alone on the pinnacle of serpentine evolution, cold-blooded "state of the art." The timber rattlesnake is one of thirty-eight species (and eighty recognized subspecies) of rattlesnakes, all restricted to the Western Hemisphere, as emblematic of the New World as maize and beans. Rattlesnakes evolved two to five million years ago on the grassy plains of north-central Mexico, still their epicenter of diversity, and have left their fossils — mostly vertebrae, but with occasional ribs, fangs, and skulls bones — in the gypsum and limestone caves of the Southwest and the tar pits of California. Thirty-six species belong to the genus Crotalus, the mailed rattlesnakes, the most recently evolved genus. Each has numerous small scales (as well as a few large ones) on the top of the head suggesting the overlapping rings or loops of chain mail worn by Elizabethan knights. The remaining two species, in the genus Sistrurus, sport nine large skull plates instead of tiny scales: the pygmy rattlesnake of the Southeast, and the massasauga, whose odd diagonal distribution runs from northern Mexico to the southern edge of the eastern Great Lakes, where they barely survive in wetlands outside Rochester and Syracuse, New York.
Arguably the most novel appendage in the animal kingdom, the rattle evolved after gradual changes to the distal tail spine sparked the retention of the cone-shaped, terminal scale whenever the snake shed its skin. Made of keratin (like our fingernails and hair), the rattle is laterally flattened, thick and hard, hollow and musical when vibrated, and is so similar among rattlesnake species that biologists believe it arose just once from the common ancestor of the entire tribe. If you examine the shed skin of a rattlesnake, you'll see an opening at the tail tip where the terminal scale stayed behind with the snake to become the first rattle segment. In all other species, the shed terminal scale remains with the old skin. The base of the rattle — called the matrix — is the living end of the snake's tail. When a rattlesnake sheds, the skin of the old matrix pushes back to become the newest segment of the rattle, though the length of the rattle is not a precise indication of its of age. Each pagoda-shaped rattle segment, pinched into two- or three-tiered lobes, interlocks with its neighbor; the narrow end of one segment fit loosely into the wide base of the distal segment. The deep, transverse constrictions that create the lobes and the shallower, longitudinal grooves that run laterally along both sides of the rattle internally fasten the segments together. The entire rattle is referred to as the rattle string, which can be either complete or broken, tapered or untapered.
A newborn rattlesnake, or neonate, has a prebutton "rattle," a single, unconstricted lobe that covers the tail tip and is lost during the snakelet's first shed. Once that initial shed has been completed, the neonate is now a young-of-the-year, and its tiny rattle, or button, is a single constricted segment that looks like an itsy-bitsy replica of Abraham Lincoln's hat, and will remain the last segment of a complete string until broken off. As a snake grows, so too the matrix, and up to a point (about the tenth segment) each new rattle segment is slighter bigger than the one that preceded it. Because older snakes grow less dramatically than younger snakes and because rattles break, matriarchs and patriarchs sport untapered rattles. An ideal rattle length is approximately ten segments; many more would make the resonance of the rattle less efficient. The largest rattle string I've ever seen was eighteen segments, a broken, untapered rattle carried around by a big yellow male, but I've heard of wild snakes with more than twenty segments, which would be like lugging a tuba around when a bugle would be sufficient.
Like an asymmetric eight, a rattle is smaller and tilted forward above the longitudinal grooves, larger below, which prevents it from drooping, lessoning the opportunity for abrasion on rocky terrain. Instead, the rattle is held either parallel to the ground or tilted upward when the tail is lifted slightly, the standard crawling posture. In front of my keypad sits a ten-segment, complete rattle string, an inadvertent souvenir from a New York snake. The tiny button is top-hat obvious; the gradual increase in the size of successive segments, also obvious, echoes the growth of the snake. I see the asymmetry on either side of the longitudinal grooves; and when I hold the rattle right side up (the way the snake would), it extends straight out, parallel to the ground; when I turn it upside down, it droops like a flaccid hose when the water is shut off. Sound is produced in the larger, lower loop of the figure eight, where so much empty space amplifies rattling. Using my entire arm as a lever, no matter how vigorously I shake the rattle, it sounds no louder than an anemic cricket or a couple of pebbles bouncing around in a tin can.
The timber rattlesnake, of course, doesn't have this problem and is equipped to play the instrument. The muscle that shakes the rattle (the shaker muscle) is richly endowed with blood and oxygen and capable of sustained contraction as a human heart in fibrillation. The warmer the snake, the more rapidly the shaker muscle contracts. The faster the contractions, the faster the rattle vibrates. A rattlesnake warmed to ninety-five degrees Fahrenheit can vibrate its rattle eighty-six cycles per second, a visual blur capable of running uninterrupted for up to three hours; chill the snake to fifty-five degrees, however, and the vibrations slow to twenty cycles per second. According to a University of Washington physiologist, if human leg muscles were as efficient at using oxygen as a rattlesnake's shaker muscle, we could complete a twenty-six-mile marathon in less than nine minutes.
Hearing an unexpected rattlesnake is a full-body experience, and the chills that metastasize down our spines give significance and density to "the fear of God." One evening on the outskirts of Tucson, in the late eighties, when my son Casey was not yet three years old, I carried him upside down as I followed behind a squat, lumbering Gila monster that had just emerged from a pile of rust-colored rocks. The lizard was in no particular hurry. Consequently, neither were we. Where it went, we went. Over rocks, around cacti, across an arroyo. Suddenly, after the sky had darkened lumen by lumen from rose to violet, a chunk of reddish sandstone came alive beneath the lizard's feet. The delirious rattlesnake went crazy, buzzing. Never flinching, the Gila monster plodded on. I straightened as though I had touched an electric fence, and by the time I regained my composure, the lizard had vanished, and Casey, whose face had been a mere two feet or so above the ground, was totally jazzed as though I had planned the diversion. Driven by demonical fury, the snake held its ground, threatening to strike — its upper coil rising, its tail a wild blur. I stepped back instinctively, levering Casey into the upright position, and then followed the arroyo back down the canyon, accompanied by the sound of an acutely disturbed rattlesnake.
In the Northeast, rattlesnakes are just as easy to overlook, though more equanimous, often not as quick to rattle. The first time Alcott Smith scrambled up a rockslide in search of a den, he had followed the directions of an armed acquaintance, who, for fear of snakes, proceeded no further than the base of the slide. Scrambling around the rocks, Alcott stumbled on to the threshold of Vermont's largest den, setting off a chorus of half a dozen snakes before he had laid eyes on one. He froze, stone stiff for some time until he figured where the snakes were, half hidden in rocky alcoves. Hearing one is a bit unnerving the first time. And the second ... the third ... and so on and so forth, which, of course, is why the rattle evolved in the first place. It's a sound you never fully get used to, a sound that demands attention, like an unexpected blast of thunder or the roar of a hidden lion.
Timber rattlesnakes that live on hard rock granite of the Adirondack foothills tend to have shorter rattles than those that live on soft sandy loam of the New Jersey Pine Barrens. No matter where the snake lives, however, rattles are fragile. They wear and tear and pop off like snap-on beads. Alcott Smith once knocked the rattle off a snake he was examining and snapped it back on. When Smith realized the drooping rattle was upside down, he quickly caught the snake and made the necessary adjustment. And, one hot July afternoon, in lower New York State, Randy Stechert, who monitors rattlesnakes for the state's Department of Environmental Conservation (DEC), drove past a thirty-nine-inch snake with an eight-segment, complete rattle string. Since Stechert hadn't planned on marking snakes and didn't have a snake bag, he caught the rattlesnake and held it out the open window of his car, pinching its head between his thumb and forefinger, wedging its flagellating body under his left arm, and drove home past houses, farms, and fields. En route, the rattle broke off, temporarily vanishing in the darkness beneath the front seat. Stechert eventually recovered the rattle and, a year later, the snake, which he brought back home, again; then, like the fitting of Cinderella's glass slipper, he snapped the lost rattle back in place.
The more a snake eats, the more it sheds, and a timber rattlesnake, honed in the boom or bust cycles of the deciduous forest, can depress its metabolism and go without food for more than a year or can gorge on rodents, feeding every four or five days. I once watched a well-fed western diamondback on exhibit in the Arizona-Sonora Desert Museum molt its skin (ecdysis), a delicate process that took hours (snake time). Bearing witness to the event was more interesting than watching my laundry dry, but still required downtime for both the observer and the observed. The scales of a snake and the scales of a fish are not homologous. Snake scales originate in the epidermis (the outer layer of skin) and form a seamless covering (a sleeve) of textured folds; whereas fish scales are individual outgrowths of the dermis (the inner layer of skin) and can be removed one at a time. (Snake scales do not come off on your fingers as fish scales do.) Chafing against a rock, the diamondback split the skin around his snout and lips, and then moved about his enclosure. Whenever he snagged the loose flap on something rough he crept forward, literally oozing out of his skin one micrometer at a time. Hours later, when the snake had finished, he left behind a perfect grayish casting of himself, an inverted replica.
Excerpted from America's Snake by Ted Levin, Alexandra Westrich. Copyright © 2016 The University of Chicago. Excerpted by permission of The University of Chicago Press.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
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Table of Contents
1 An Introduction to Crotalus horridus
Part One Egress: The Dangers of Leaving Home
2 A Quirky Subculture
3 Quasimodo in the Blue Hills
4 Live Free or Die
5 Zero at the Bone
6 A Long, Muscular Tube
Interlude: High Summer: On the Trail with Timber Rattlesnakes
7 The Dangers of Being Male
8 The Dangers of Being Female
9 A Commodity of Rattlesnakes: Snakes Today, Bibles Tomorrow
Part Two Ingress: The Dangers of Coming Home
10 Chaos of Rocks
11 Among Rattlesnakes
12 Into the Abyss
13 The Very Last Rattlesnake
Epilogue: The Ambiguous World of the Timber Rattlesnake