Lizard scuttle and croak of raven, faint perfume of desert wildflowers, kiss of gentle sun: I stroll through a magical Mojave morning. This desert, always fickle, has decided to smile on me. Instead of the vicious, forty mile-an-hour westerlies of early spring, I am caressed me by a gentle breeze. I have shed the many layers of clothing that March demands and instead I wear a simple, hand-sewn dress of unbleached muslin, my standard field uniform. I wear clothes that protect my delicate Celtic skin with minimal restriction of air flow. As close as I can safely get to nudity, I luxuriate in 75 degrees. To mosey along on these rare, exquisite days, in the midst of a long season of field research, is joy. I am here to search for desert tortoises but I always find much more.
The rhythm of walking on such a pleasant morning lulls me. My mind drifts a bit- to thoughts of Kathy back home in Alaska, Iris at college in New York, to memories of a day in this very place, long ago, when I encountered eighteen tortoises in a single day. An old friend flickers across my memory, then the thought that I should get in tou…
A sizzling buzz shatters the morning calm, crackles across my eardrums, slices clean through my mammalian neocortex and buries itself in my reptilian brain. Response precedes thought. I become a survival machine. Adrenalin floods through me. Hair rises at my nape. Shallow breaths come in quick succession. I want to leap but I do not leap. A wrong move is worse than no move. Rooted to the spot, I sift furiously through a blizzard of sensory signals.
The sound is louder in my right ear than my left, so my head automatically snaps right. Muscles tense, ready to rocket me away. My eyes scan a hundred square feet of gravelly soil while my inner vision scours memory banks. A search image is stored somewhere in the three-pound hunk of organic circuitry housed in my skull - a generic picture of the highly venomous reptile that is somewhere very near. In the space before me I seek patterns that match the search image the threatening din has evoked. I am like any other mammal here- this automatic reaction would serve jackrabbit or badger, kit fox or bison just as well.
There! Mojave rattlesnake. In the space between those two creosote bushes: light, almost neon green loops dotted with olive hexagons; upraised neck bearing flared head; tail, held aloft, vibrating madly, displays its distinct pattern of wide white bands alternating with thin black ones. At the tip, the interlocking segments of dried keratin, the rattle, that gives the creature its name among the mammals that name everything. Snake faces me, taking my measure. Every ounce of my attention is on Snake. The space between us is sufficient to allow both of us to recover from the shock of this unrehearsed meeting. Having located the animal I realize that I am beyond its striking range and the andrenalin rush fades.
I have danced the mammal’s part in this ballet hundreds of times. Perhaps incongruously, I revel in the Zen purity of the time between the arrival of the virulent music in my ears and the settling of my eyes on its source. For a few brief moments I become reptilian, fully present in a moment of danger, a pure sensor and calculator. I am alive.
Crotalus scutulatus, the Mojave rattler, is a fearsome snake. Not because of its size- the western diamondback, for instance, gets much larger. An irascible snake, the Mojave announces its presence readily, rattling out fair warning at the approach of any large intruder. When other snakes flee this one stands its ground.
An encounter with any member of the genus Crotalus is memorable. By rattling, these snakes advertise their presence and so avoid being stepped on or attacked. The smallest of the desert rattlers, the sidewinder, will sound off as it flees but definitely emphasizes the get-away as a defensive strategy. The red diamond rattlesnake seems phlegmatic. It rattles a bit if really provoked but would rather just slither away from any unpleasantness. Despite their venom, many rattlers just want to put real estate between you and them. A big western diamondback, though, is a sight to see, rearing up and broadcasting a high decibel challenge. Of all the clan, though, the Mojave most radiates lethality, exuding a confidence borne of virulence. This animal is aware of its power: its boldness springs from what makes it a true hazard.
The venom of all pit vipers, rattlesnakes among them, is generally formulated to break down tissue in the bite wound and, as the poison spreads, in the bloodstream. This hemotoxic fluid causes the agonizing pain and grotesque swelling of snake-bitten limbs and fingers. The bite delivers a burn beyond burning. The Mojave adds a jigger of neurotoxic proteins to its venomous cocktail. Injected deep into tissue by half-inch long fangs it not only attacks muscle and blood but nerve cells as well. The neurotoxin short-circuits the body’s phone system: although the autonomic system continues to send out the call for respiration the muscles of the diaphragm and chest cavity don’t get the message. The victim’s breathing apparatus remains intact but simply goes off-duty. Suffocation ensues. Mojave rattlers drop kangaroo rats and ground squirrels in their tracks. The fear of this bite works to repel larger mammals. Every rattlesnake bite is painful but few are deadly if attended medically. However, the Mojave’s bite can kill a healthy adult human being- a being like me.
Sounds dire, doesn’t it? It’s enough to make a guy fear to tread the desert sands. I know of a few hundred fieldworkers in the Mojave Desert and of all of them, for all their hundreds of thousands of miles of desert walking, I have heard of one case of snakebite, and that one was not accidental. My friend Dave picked up a sidewinder and held it at the back of the neck a little too loosely. Wriggling slightly free, it sank a fang in his thumb. The digit, and his arm, ballooned up dramatically and turned a vivid purple. After a shot of antivenin and a few days in the hospital he returned to work sorer, poorer and wiser.
Colorful though it is, snakebite, even for those walking daily through their habitat, is a minor threat. In contrast, three people I know have died in car wrecks. Paul, a fellow tortoise researcher and close friend, died when his decrepit truck rolled over and ejected him on a remote Nevada gravel road. There were undoubtedly Mojave rattlers quite close by as he perished. I’ve been in three smash-ups that could have ended my life, and had a dozen close automotive shaves. Dying in a car wreck is normal, though, and being bitten by a snake is exotic. Thus do we skew our calculation of hazards, mistakenly fearing snakes more than Impalas and Rams and Mustangs.
With the above knowledge swirling in my brain I face the snake across five meters of sandy soil. At a meter long it is large for its type. We are both still frozen- I in my tracks and the snake in its striking pose. The rear two-thirds of the body are held in a loose coil while the business end arches up off the ground. A rattlesnake prepares to strike by elevating the anterior portion of its body and throwing it into a tight curve. To strike, the snake straightens this curve with lightning speed. Mouth agape, it leads with the two elongated, hollow, and recurved teeth at the front of its mouth. These are attached via ductwork to paired sacs of venom stored in bulges behind its eyes. These hypodermic needles truly deserve the ominous sounding label “fangs”. The threatening body language of the creature before me, combined with the caudal sound effect, emphatically advises, “Don’t even think about it!”
Still rattling loudly, the serpent has certainly sussed me out as a large mammal- a potential threat. It probably anticipates one of two reactions to its percussion solo- flight or attack. In choosing a third way, non-action, I open a door. It is simple enough: I slowly lower myself and face the agitated snake. Stilling myself, I wait, squatting with heels flat on the soil, thighs folded against calves.
The snake’s eyes, set high on its head and angled laterally, monitor my movements through narrow vertical pupil slits. The snake sees forward to an extent but lacks the strong perception of depth I enjoy with my binocular vision. The rattler, both predator and prey, uses a split screen with a wider, shallower view. Its vision serves as an early warning system but the creature has other senses with which to gather data on the large mammal facing it.
Rattling on, it flicks its delicate forked tongue, testing the bubble of scent surrounding me. Shed skin cells, pheromones and aerosols of sweat adhere to the tongue’s surface. The tips, bearing these chemical messages, are inserted into twin pockets in the roof of its mouth, the Jacobson’s organs. Among the background scents of the desert the snake focuses on these traces of me with the high power olfactory cells lining the organs. A minutely higher concentration of scent molecules on the right tongue tip, for example, cues the snake that the source will be found to its right. Olfactory directionality is only one aspect of this exquisite sensory system. The snake assesses my nature and quite possibly my emotional state via chemical analysis. Compared to the snake’s abilities, my nose is a crude tool. Through my scent I am speaking to the snake in a language I myself can barely decode.
Tens of millions of years ago a legless, subterranean species of lizard, over thousands of generations, had its hearing reconfigured from sensing aerial sound waves to picking up vibrations through the ground. The bones of the middle ear were disconnected from the now useless eardrums and redeployed as elements of the jaw. The snake posed before me, a descendant of that lizard, is, paradoxically, deaf to its own rattle. With its head resting on the soil surface it can, however, feel the footfalls of a large mammal in its vicinity. Snakes quite literally keep their ears to the ground and the one before me may have felt my approach before seeing or smelling me.
Hold your hand half a foot over a candle and feel the heat. Now imagine sensing that candle’s heat from across the room and you will have an idea of the thermal sensitivity of a rattlesnake. The rattler I’m facing has an indentation in each cheek that gives its subfamily its name: the pit vipers. The lining of these pits is extremely sensitive to heat. Infrared photos or film give some idea of this sensory system. Warm-blooded mammals and birds are the main prey items and principal threats a rattlesnake faces. To the snake I appear as a large hot spot against a cooler background. This hot spot signals “threat” to the snake.
With all this equipment: laterally directed eyes; ear bones in its jaws; forked tongue and Jacobson’s organs; and infrared-sensing facial pits; the snake assesses me, the intruder before it. It has its own search images to which it compares me. As it monitors me it strives, as a matter of survival, to predict how I will behave. With much different equipment, I do the same.
The snake rattles at me for three solid minutes as I squat motionless. The frequency and volume declines, tailing off, gradually, to silence. After the commotion of our meeting both of us are now quiet and still, regarding each other across the short stretch of crusty soil between us. With the control of a yogi the snake holds its pose, statue-like. For five more minutes we wait, ready for any sudden move on the part of the other. Very, very gradually the snake lowers its head to the ground. Over the next two minutes it makes a fluid transition from striking pose to lying flat, its body a series of S-shaped curves.
We enter new territory. I have never before taken this tack with a snake, much less a Mojave. There is little doubt that among the large mammals it has encountered, the snake has never witnessed the behavior I display. I expect the serpent to make a gradual exit from the scene, to err on the side of caution. I am wrong. It is the snake’s turn to surprise me. It stretches itself into a line, pointed at me.
A Mojave rattlesnake has two modes of locomotion. In serpentine crawling the snake arranges its body in a series of curves and pushes against the soil with the lateral and posterior surfaces of the curves. This pressure, with subtle coordination, moves the snake forward. The other, odder looking and more rarely used, is called the rectilinear or caterpillar crawl. Here, the snake uses the belly scales, called scutes, spanning its undersides, as a set of hinged plates. Each swings forward, gains purchase on the soil and then folds back. The coordinated motion of several hundred scutes provides the thrust needed for slow forward motion. Viewed from the side, the coordinated motion of the scutes resembles the wave-like crawling of a caterpillar.
The odd thing about the caterpillar crawl is that the snake moves in a straight line. The motion of the scutes is difficult to see: the animal seems to progress effortlessly, almost miraculously. The Mojave rattler before me slowly straightens itself out, transforms itself into a dead-straight, slow motion projectile. There is no haste in the snake’s progress and this makes the experience all the stranger to me. Minutes flow by with this reptilian arrow approaching its target- a spot between my legs. With two meters between us I feel the first twinges of nervousness. Where is this interaction going? Half-formed questions of reptilian motivation dance on the edge of my consciousness. I still expect it to turn off and crawl away to safety. My attention, however, is riveted on this creature slowly, silently, steadily approaching me.
With a potent serpent crawling slowly, but inexorably, in my direction, I become aware of yet another anatomical contrast between the snake and me. The serpent’s sexual apparatus is tucked away within the rear portion of its tubular form. Mine is fully exposed and hangs a few inches from the ground- precisely in the snake’s path. I have now been squatting for about twenty minutes. My joints are stiffening and circulation to my legs is restricted. I wonder how long I can hold this pose. The snake shows no intention of veering off.
Oddly, there could not be a more vulnerable posture for the creature than the one it has adopted. The snake’s caterpillar crawl has the advantage of reducing the cross-sectional area it presents to me. By advancing in a straight line with no extraneous motion it minimizes the visual information it presents to me. The Mojave may be, in its own way, sneaking up on me. For all its chemical weaponry, though, my legless colleague is a fragile animal. The structural weak point on a snake is the occipital joint, where skull meets spinal column. This is especially true with heavy-bodied snakes like rattlers. A quick twist at this junction severs the snake’s spine. This is the target that a predator usually attacks; consequently the snake attempts to protect it above all others when threatened. To strike, the snake needs some slack in its pose, it has to coil the spring. Though able to quickly retract from the linear pose into striking position, the rattler presents me an opportunity to kill it with a quick strike to the back of the head. Whatever advantage the caterpillar pose provides the snake, advancing in a straight line renders the snake vulnerable. Of course, a similar statement could be made about my own situation. I am becoming more conscious of my own vulnerability with each passing moment.
About a meter away, the highly venomous creature still shows no sign of altering its course or speed. In the theater of my mind a lurid, worst-case scenario runs: snake arrives beneath me and, betrayed by unsteady legs and a failure of nerve, I topple onto it. In the process, I present the serpent with a particularly prominent and, to me, precious, set of organs. A considerable writhing ensues: by the entangled and panicked snake to position itself to bite and by me after the delivery of the venom to a particularly well-vascularized portion of my anatomy.
It strikes me that I am all alone, a long way from help. This cautious side of me wants to get old with genitalia intact, wishes to avoid being the punch line of a crude joke. The dispassionate biologist within me, in contrast, remains spellbound. The snake closes the gap, now not even pausing to flick its tongue. What is going on in that creature’s head? What is going to happen? This side of me aches to stay still and watch even as the cautious me prepares evacuation plans.
Half its length away from me, the snake is now within striking distance. The faint murmur of scutes sliding over soil is the only sound. I can see every scale, the cat’s-eye pupils, the pits on the side of its face, the tiny nostrils. It is an exquisite creature. Still it advances. Caution, a modest caution, overcomes curiosity- but barely. Hands hang between my knees and I give the merest flick of my right fingers, once. At this tiny gesture the snake halts, gives a single flick of its forked tongue. Sun strikes scales and skin alike. Silence. Stillness. Another minute crawls by with motionless snake and motionless mammal close together and each, in its own way, voluntarily and profoundly vulnerable.
The serpent makes the decision. Curving its head left, it executes a graceful, unhurried one-eighty, heading slowly back whence it has come. A meter along it resumes its serpentine crawl, proceeding with reptilian aplomb. Keeping my part of the truce, I remain still for the next five minutes. Only after the snake crawls out of sight around a creosote bush do I rise. In the silence I begin to breathe again. As blood returns to my tingling legs, I dwell in quiet exhilaration. I have seen more deeply into the world I inhabit.
Years later the question hangs in my mind: what would the snake have done had I not waved it off with that little hand motion? I don’t entirely regret the caution I displayed, though the odds of a serious mistake on my part were quite low. My daughter was eight years old- I was more curious to see how she would turn out than to see what the serpent would ultimately do.
The encounter is etched in my memory. I still cherish that half-hour squatting in the desert, staring in wonder. Why did the serpent not simply retreat when given the opportunity? What did the snake take away from the encounter? Was it gathering data on mammalian behavior that might be of future use? What memories did it retain of me? How did it use the information it derived from our slow-motion dance? Was some curiosity within it satisfied? The snake and I had faced the same decisions: to invite or avoid a risky encounter, and, having initiated the contact, how and when to break it off. For each of us a moment came when caution won out over curiosity. We were a pair of biologists doing researching on one another.
I now think of the caution-tempered inquisitveness that the snake and I shared as a potent survival tool. Rattlesnakes, like humans, are long-lived animals. For both of us, continued well-being depended on a thorough knowledge of the environment and the creatures we might encounter. The snake and I came to our meeting with a drive to understand the alien other. Both of us were there to learn: this is the only reason I can envision to explain the snake’s inherently risky behavior. Admittedly, it applies to my own as well. After surprising one another, each of us then took our time investigating the other. In the end we separated peacefully under a warm Mojave sun, each of us changed by the experience.
Now I am a middle-aged biologist. My daughter is grown. I have reached the point that the time that remains to me is less than that which I have already spent. My knees are a little stiff: squatting is not quite so easy as it once was. Despite that, the thought occurs to me to run the experiment again, to seek another snake in hopes that it will make the same choice that beautiful Mojave rattler did.
Next time, I may just stay still as the arrow of fate approaches.