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Once upon a Diamondback

Learning Lessons about the Fragility of Desert Life

Life is both remarkably resilient and at the same time scarily fragile. It persists in its numerous forms in the most hostile environments, yet its constituent components are often extraordinarily sensitive to even minor disruption of their habitats. Individuals in many environments live life on the edge, precariously balancing the physiological limits that govern their raw survival with the equally strong drive to gather the resources needed to ensure reproduction to pass their genes on to the next generation. In extreme environments, this balancing act can be precarious enough for even very minor chance events to make the difference between life and death.

Intellectually, messages on the fragility of life are easy to understand. We are bombarded with messages on the delicate nature of the intricate ecosystems surrounding us and their vulnerability to disturbance. For those interested in reptiles and amphibians in nature, field herpetology Facebook groups are full of reminders that disturbing animals can have profound consequences for their survival and that of their populations. However, while these reminders are easily read, they are even more easily forgotten, without triggering deeper assimilation or reconsideration of one’s own field methods and ethics. All too often, it takes the personal experience of witnessing this fragility and the consequences of seemingly minor events to develop a deeper consciousness of this vulnerability.

One of my moments of epiphany on these issues came from a chance encounter with a Western Diamondback Rattlesnake (Crotalus atrox) in Cochise County, Arizona, on a fine morning in September 2018. After turning northeast off Highway 80 in the San Simon Valley toward the majestic Chiricahua Mountains, illuminated by the early morning sun that was now behind me, I kept scanning the dirt road ahead for signs of life, especially snakes, while heading toward the mountains for a photographic project. As is common in this part of the world, I soon spotted an average-sized adult Western Diamondback Rattlesnake emerging from the roadside vegetation on the right-hand side of the road, seemingly from a rocky outcrop located a few meters from the road. As the snake slowly progressed across the road, without taking much notice of either the four-wheeled creature now stationary a few meters away or the delighted bipedal synapsid it had disgorged, I had a remarkable view of the snake in the foreground gliding across the road with the majesty of the Chiricahuas behind it. I seized the opportunity to lie flat on the road at a respectful distance and got some photos of the scene. Apart from a few brief stops and tongue flicks, the snake paid no heed to my presence and continued to cross the road until it disappeared into some bushes bordering fenced-off pasture to my left.

Western Diamondbacks are extremely abundant snakes in many parts of the southwestern United States, and chance encounters like this are almost daily occurrences. Nevertheless, I never tire of the majestic sight of one of these creatures crossing a road. Delighted with the impromptu encounter, I continued on my journey toward my intended photographic project, which went off without a hitch. Thus satisfied, I started my return drive back toward Highway 80, this time driving against the sun. As I passed the location of the diamondback sighting approximately two hours after the initial encounter, the backlighting brought out in spectacular fashion the tracks left by the snake earlier that morning. I stopped and took a few shots, showing the tracks’ origin in the rocky outcrop in the background and its rectilinear progress across the dust and gravel of the road.

It was only while photographing these tracks that I noticed, somewhat to my surprise, that their author had emerged from the bushes a few meters away from me and was heading back onto the road, presumably toward the outcrop from where it had emerged earlier that morning. However, something was strikingly different: the snake now contained an enormous bulge, and was moving slowly and with obvious effort. Waddling is not among the commonly accepted forms of snake locomotion, yet it seems the most apt description for the gait displayed by rattlesnakes after eating very large meals—not unlike that of herpetologists after a late-night visit to a Denny’s. That certainly applied to this particular diamondback.

As I watched the snake and its bulge, several thoughts shot through my mind. That snake had headed out to a clump of bushes with an empty stomach and was now attempting the return journey a mere 90 minutes later with a full stomach. Ninety minutes! Barely the time required to find, kill, and eat the kind of large meal this snake clearly contained. Some of my own shopping trips to the local supermarket, carefully planned to minimize the time spent in an environment that I consider an antechamber to hell, take almost as long. Did that snake really plan its gastronomic foray with this level of foresight and strategy? Can predation success really be this predictable? Did the snake know what it was doing and plan the timing of this outing? After I related the experience on social media, suggestions included that the snake was following a prey item it had previously struck and released. However, the photos of the snake tracks across the road revealed no evidence of a large prey mammal having preceded the snake on that journey. Similarly, in the absence of traffic, it seems unlikely that it was aiming for a roadkill, even though rattlesnakes are known to sometimes consume these. Yet, if this was really a planned foraging outing, that raises questions on the nature of ambush versus actively foraging snakes. What would I have given to have observed the full sequence of events that unfolded after my earlier morning encounter with that snake… . I found myself wishing that I had scrapped my photo project and followed that snake instead earlier that morning! But that’s hindsight for you.

I was awoken from my musings by the fact that, unfortunately, my presence disturbed the rattlesnake and dissuaded it from continuing its journey: it turned around and headed back into the bushes from which it had just emerged rather than continuing toward its intended destination on the opposite side of the road, the rocks from where it had come this morning. Very slowly, because of the size of its bulge, it waddled back into the bushes.

At this time, midmorning, the sun was already high in the sky and temperatures were rising rapidly. The snake was clearly keen to get back to its rocks, but I had gotten in the way. I felt the first pangs of conscience about the entirely unintended impact of my presence on its plans for the day and immediately decided to retreat to allow the snake to resume its journey toward its intended destination. I got back in the car and parked several tens of meters away from the snake and the morning’s crossing point and waited to see if the snake would try crossing the road again. Concern mounted that it might end up spending too much time in the sun owing to the burden of its meal and risk overheating on the shelterless road. However, after approximately 30 minutes, the snake had not re-emerged from the bushes.

A quick look under the bush confirmed that the snake was still there, now loosely coiled in the dappled shade of one of the bushes. I considered my options. Leaving the snake alone, to make its own decisions, was one. The other was capturing it and returning it to its rock outcrop. The latter would have involved significant additional stress, and the risk that the snake would regurgitate its large meal, a significant loss of energy. Moreover, there was no way of knowing where among the rocks that snake had started its journey or the thermal qualities of the various available shelters in the outcrop. Capturing and returning the snake without a clear destination seemed risky.

Leaving the snake in place also carried risks. However, after due consideration, in terms of temperature, the situation seemed manageable. Daytime temperature maxima in the San Simon Valley at that time of year are usually in the low–mid 30s (°C)—well within the envelope of survivable temperatures for a Western Diamondback. Moreover, the snake had access to the dark shade of a very dense bush right next to the one it was sheltering under at the time. Consequently, I felt confident that the snake would be able to sit out the heat of the day under that bush and decided against capturing it and carrying it back to the rock outcrop. But, of course, that was still a suboptimal solution: in the bushes, the snake was at a considerably increased risk of exposure to predators, and there was the possibility that the snake might become a victim of road traffic during its next crossing attempt. With some anxiety, I left the snake to its own devices under its bush.

Through the rest of the day, my thoughts returned frequently to that diamondback, with concern for its welfare. That concern continued through the night, when, as so often, the imagination ran riot during moments of early morning wakefulness, conjuring up the worst possible scenarios. Since thoughts of that diamondback and my impact on its day never fully left my mind, I sought closure the next morning and returned to the scene. Words cannot describe my relief at finding a second, new set of rattlesnake tracks across the road. This new track headed from the bushes under which my waddling snake had been sheltering back into the rocky area by the side of the road. The space under the bushes was devoid of any sign of the snake as well as any signs of a struggle or regurgitation: the snake had made it back home!

So this chance encounter had a happy ending for everyone. And yet, the outcome could so easily have been different. Had the bush under which the snake sought refuge not been dense enough, or the day that little bit hotter, my inadvertent disturbance that stopped that snake from reaching its intended shelter could have been a death sentence. The same encounter in the lower-lying areas of the Sonoran Desert, where daytime temperatures often exceed the lethal maximum temperature of a rattlesnake, would have ended fatally if the snake had not found a sufficiently deep refuge that it could reach and fit into despite its meal. Equally, left in the open rather than the shelter of the rock outcrop, the diamondback, slowed down by the bulk of its prey, would have been easy prey for any passing predator. My simple presence and unintended disturbance of that snake, without any deliberate interference, much less actual contact, could easily have made the difference between its survival and its demise. Good fortune rather than design prevented my mere presence from spelling the end of that beautiful diamondback’s existence.

The take-home message? Small disturbances can have big effects. Desert snakes need to balance the need to forage, the need to avoid dehydration, and especially the need to avoid overheating in the daytime. Small disturbances that seem trivial to the casual observer could tip a snake past the point of no return, by causing it to overheat directly or by preventing it from returning to safety. Those warnings offered by keen field herpers on Facebook and elsewhere of the impact of seemingly minor disturbances are right—small actions can have big consequences. So my own take-home message from the episode was to reflect more on the fragility of the life I so admire, and my impact upon it, however unintentional it may be. By sheer stroke of luck, I can remember this encounter as a lesson learned without harm to anyone and with a smile on my face. But I will never forget how easily it could have turned into a moment of shame that would have stayed with me for life.