It was about this time of year three years ago, as the desert slowly cooled toward autumn, that my girlfriend Annette and I went on one of our first dates, hiking in a desert wilderness in Nevada. We slow-walked through the Joshua trees, watching cactus wrens and leopard lizards and Audubon's cottontails, and getting to know each other a little bit. After an hour or two we started getting low on water, despite the cool temperatures, and decided to turn back toward the trailhead and my Jeep, hiking in a wash cut into the desert by the summer's monsoons.
Rounding a bend in the wash, we heard a sound that sent an involuntary thrill up my spine. It took me less than a second to find the source of the insistent rattling: there in mid-wash maybe twenty yards ahead of us, peering at us around a clump of creosote, was a very agitated individual of the species Crotalus scutulatus. "That's a Mojave green rattlesnake," I told Annette; "the most dangerous snake in North America." "I really didn't need to know that," she replied.
The Mojave green is dangerous, but I may have overstated matters a bit. The Eastern timber rattler is bigger, produces more venom, and has relatively long fangs, and thus often has the title "North America's Most Dangerous Snake" bestowed on it, despite its relatively retiring disposition. What puts the Mojave green in the running is its venom. Unlike the six or so other rattler species in the California deserts, which possess the standard rattlesnake toxin that causes widespread internal hemorrhaging, the Mojave green adds a neurotoxin to the mix, which can cause problems with coordination and vision, overall muscular weakness, and even asphyxiation.
Of course the snake has to bite you in order to deliver that venom cocktail, and even Mojave greens -- which have a reputation for aggressiveness -- would really prefer not to bite anything larger than a rabbit, given the choice. The vast majority of rattlesnake bites occur in situations in which a person is deliberately handling the snake, or trying to. Left to their own devices, they tend to leave us to ours. I suspect the Mojave green's "aggressive" reputation stems from its occasional decision to stand its ground, not to slither away at the first sight of human beings.
Which is certainly what the snake Annette and I saw had decided to do. It was robust, looking about four feet long (though it was probably three at most) and pretty hefty looking, and it had staked out its spot in the wash, and it was telling us in plain language that it was unwilling to share its patch of desert with the likes of us.
We went around.
I don't remember whether I mentioned it to Annette at the time, but for all of my calculated nonchalance, that Mojave green was the first full-on, classic rattlesnake experience I'd had in decades of exploring the desert. I had seen one or two before, sunning themselves in parking lots or snoozing under chollas, but this was the very first time I'd seen one venturing abroad in the desert, active and wary and rattling angrily.
It's not that they're uncommon in the desert: they aren't. There are seven species of rattlesnake in the California deserts, depending on which taxonomist you ask, and they occupy almost every kind of landscape aside from the barrenest of playas -- sidewinders in the sand dunes, Pacific rattlesnakes in the chaparral mountains at the desert edges, Mojave greens in the creosote and yucca and Great Basin rattlers in the sagebrush, from below sea level to eight or nine thousand feet in elevation, rattlensakes are near-ubiquitous in the desert. They're just really good at not being seen.
This makes sense when you think about it. Most smaller rattlesnakes are ambush predators. They have to be good at hiding or they don't eat. Larger rattlers sometimes hunt actively, foraging for prey, but they take advantage of ambush tactics as well. Typically a hidden snake will strike at its prey and envenomate it, retreat, then follow their fleeing target's scent trail at a safe distance. When the venom has immobilized or killed the prey, the snake will then swallow it whole. This strategy is safer for the snake: a bitten woodrat or rabbit could inflict serious damage on a snake before it succumbed.
Rattlers will eat pretty much anything that is 1) smaller than them and 2) susceptible to their venom. Small snakes will subsist on lizards, frogs, large insects and the occasional litter of mice or clutch of baby birds. Their larger cousins will take down animals as large as black-tailed jackrabbits on occasion, but smaller -- and slower -- mammals like ground squirrels are a much more likely meal. Some ground squirrels, the eastern Mojave's resident rock squirrel being an example, have evolved the ability to at least partially neutralize rattlesnake venom. Studies suggest that at least in some places, rattlers and ground squirrels might be engaging in an evolutionary arms race, each squirrelly innovation in venom neutralization spurring the evolution of new and different venoms. Even within the same species of rattler, there are often regional variations in venom, and coevolution with local ground squirrels may be one reason.
At any rate, those of us who don't look like snake food can walk right past a spot where a hidden rattlesnake waits for a ground squirrel to walk by and never know the snake is there. The vast majority of human-rattlesnake encounters take pace without the human ever knowing it happened.
But if you're going to notice rattlesnakes in the desert, now's the time. The desert is cooling, and the snakes (and their prey) are shaking off their summer mid-day torpor, becoming more active during daylight hours. Young snakes born this summer are venturing out; most of them will have been eaten by roadrunners and other predators by this time next year, but for now they swell the desert's snake population.
More to the point, you're more likely to be out wandering around in the desert during daylight hours. Be careful where you put your hands and feet while poking around, stay moderately aware of your surroundings, and if you do see a rattlesnake stay calm and admire it from a respectful distance. They are powerful, evocative, and beautiful creatures, and after you see one the whole desert comes alive for the next few miles of hiking.
But if that makes you too nervous, you can always just go around.
Chris Clarke is an environmental writer of two decades standing. Author of Walking With Zeke, he writes regularly at his acclaimed blog Coyote Crossing and comments on desert issues here. He lives in Palm Springs.
TrackBack URL: http://www.kcet.org/cgi-bin/mt/mt-tb.cgi/10854