| 1 | Texas’ most dangerous snake |
In the list of US snakebite deaths, there’s an ongoing debate as to which species tops the tally, and there’s only two real contenders: the east diamondback rattlesnake, and its close relative the west diamondback rattlesnake (Crotalus atrox).
This is the second longest and second heaviest venomous snake in America, easily outstripping the tiger rattlesnake or rock rattlesnake. West diamondbacks inhabit a huge unbroken stretch of the southern US, beginning in southeast California and covering Arizona, New Mexico, Texas, Oklahoma and more. They also inhabit a chunk of Mexico, down to Mexico City.
Western diamondbacks have no area of overlap with their eastern cousin. Their empire fizzles out in western Arkansas, whereas eastern diamondbacks only reach southeast Arkansas on their western flanks. Western diamondbacks are slightly shorter as well, with an all time-confirmed record of 233.7cm versus 251.5cm for the eastern.
However, west diamondbacks are considered to be more aggressive. They’re able to shake their rattle 40-60 times per second. The raw potency of its venom is just 2.72mg, weaker than a cottonmouth’s, but their brute size allows a generous splashing of venom, at 250-350mg per bite, potentially up to 800mg. Like the east diamondback, 10-20% of untreated bites are fatal.
| 2 | Appears in backgardens |
West diamondbacks are constantly sighted in the southern US, and one reason is their flexible habitats. They can pop up almost anywhere, from desert scrub, mesquite grassland, and pine-oak woods, to shrublands, grasslands and rocky limestone hills. They’re also comfortable about hanging out near buildings, resting against stone walls and wooden fences.
Don’t be surprised to find one roaming your backyard, whereas the likes of rock rattlesnakes or ridge-nosed rattlesnakes are never found in human zones. People have woken up in backgarden hammocks to the instant sound of a piercing rattle. One report found that west diamondbacks contributed 85.1% of callouts to professional reptile habitats in the city of Phoenix, Arizona.
West diamondbacks do have a few tendencies, as they’ll gravitate towards rocks if they can be found, and they prefer flatter, more open areas. For example, a study compared them to black-tailed rattlesnakes (Crotalus molossus) in the same desert location of Tucson, Arizona. West diamondbacks were found on steep slopes 20% of the time, versus 65% for west diamondbacks. But the latter appeared in creosote bush flats 10% of the time, versus 60% for west diamondbacks. West diamondbacks reach a maximum altitude of 2134 metres in New Mexico, and 2440 metres in San Luis Potosi, Mexico.
| 3 | Has learnt how to walk |
West diamondbacks have a classic rattlesnake strike posture. It’s pretty much the opposite of a cobra, which rears up its chest very straight, and stares at the aggressor menacingly. Crotalus atrox coils up into a bizarre shape, not a traditional S, but with its entire body contorted, and its neck actually held higher than its head, which faces the aggressor head on. See this video.
Sidewinding is the classic strategy of desert serpents, like the sidewinder itself, and the Namaqua dwarf adder in Namibia. West diamondback rattlesnakes use an even more bizarre strategy. They start by forming a complete body coil, which faces forward, possibly towards a human aggressor. Then they shift backwards using the left and right sides of this coil, alternating by pushing off, so that the centre never touches the floor, just these two small left-right points.
This was reported in 2003, and was like a complete coil wobbling backwards. It was supposedly the closest to a walking snake that had ever been observed. Why this happens (and how often) is a mystery. It might be a combination of two requirements: 1) minimising contact with the searing desert sands, and 2) facing forward to warn an aggressor, while slowly backing off. Unlike a coachwhip, Crotalus atrox isn’t fast enough to instantly blast off over the horizon, so they have to get inventive.
| 4 | No paralysis, lots of haemorrhaging |
The classic symptoms of a Crotalos atrox bite include swelling, myonecrosis, internal bleeding, organ damage, headaches, nausea, vomiting and abdominal pain. The speciality of this widespread serpent is undoubtedly haemorrhaging. Nearly 53% of its enzymes target the circulatory system, whether as anticoagulants that destroy clotting factors like fibrinogen, or toxins which physically degrade the linings of capillaries and venules, causing spontaneous bleeding. There’s also a mycardial depressant factor that weakens the beating of the heart.
West diamondback venom usually doesn’t contain neurotoxins, unlike the notorious tiger and Mojave rattlesnakes. But a neurotoxin similar to Mojavetoxin has been detected in a few populations. The most lethal Crotalus atrox venoms are found in the southwest of its territory (California, western Arizona). These have the lowest protease activity, while northeasterly colonies (e.g. Arkansas) have the highest protease and lowest lethality.
Metalloproteases are the main toxin class, followed by cytotoxins and myotoxins. Permanent skin or tissue loss is possible after a west diamondback bite. Crotalus atrox is harsh on the kidneys, damaging their structure, whereas the black-banded sea krait it was compared to had no effect. A vial of west diamondback venom once lost little of its potency after 16-17 years of storage in the dark.
| 5 | Prefers mammals, but flexible |
With such a large territory in the Americas, the list of prey Crotalus atrox has to choose from is dizzying. Here’s a small sample of the meals they’re confirmed to eat…
Mammals: Ord’s kangaroo rat, eastern cottontail, black-tailed jackrabbit, prairie vole, fox squirrel.
Reptiles: lesser earless lizard, regal horned lizard, desert iguana, greater earless lizard, Texas banded gecko.
Birds: northern mockingbird, American mourning dove, laughing gull, caspian tern, northern bobwhite.
Mammals dominate, as a study involving 108 prey from 101 west diamondbacks found that 71.3% were mammals, followed by 9.3% reptiles, and the remainder being unidentified. A 1976 study was even more biased towards mammals, at 94.8% of prey by weight.
It’s extremely rare for western diamondbacks to eat fellow serpents. One exception was an adult Crotalus atrox which scavenged a rotting roadkill west diamondback, before regurgitating it. Snake-eating (ophiophagous) diets are rare in the rattlesnake family, and Crotalus atrox follows the rule. A rare exception is the Querétaro dusky rattlesnake of southern Mexico.
The reverse happens though. West diamondbacks are confirmed predators of the California kingsnake, which has innate resistance to rattlesnake venom, and middle American indigo snakes.
| 6 | An optimised starvation machine |
The likes of blood pythons can go over a year without eating, whereas corn snakes eat every 7 or 10 days. Western diamondbacks can go over 2 years without swallowing a meal. In 2006, a study gathered 16 west diamondbacks, and starved them for 168 days (5.5 months), while mimicking their natural climate.
Not only did the rattlers survive and thrive, relying on their stored fat reserves, but they managed to grow longer during their starvation period. They successfully reduced their resting metabolic demands by 80%, and they were experts at preserving the energy they had, once they’d begun “digesting” themselves.
Their bloodstream glucose fell, while their circulating ketones increased, a similar response to starved humans (e.g. the keto diet). They had physiological advantages for starvation, such as protecting spare free fatty acids from oxidation in the bloodstream. Over the 5.5 months, they gradually decreased their speed of movement.
It’s one thing to crawl around a desert becoming meaner and leaner, but west diamondbacks can add centimetres, after 4 months with no mice or gophers. Perhaps nature knows that they can’t afford to fall behind their fellow kind in length and mass, otherwise they’ll be at risk of being hunted.
| 7 | Subtly alters its rattle |
West diamondbacks are a fully evolved snake machine, and yet another trick is altering their rattle’s frequency, to create an illusion of close proximity. Researcher Boris Chagnaud first noticed this higher frequency when he entered an animal-holding facility. As he approached their enclosures, the rattlesnakes’ rattles noticeably changed in pitch. Chagnaud and his team then conducted an experiment where west diamondbacks were faced with two objects: a black disk, and a human-shaped torso, which rapidly approached them. Further away, the rattle’s frequency averaged at 40 hertz. When the objects reached close distances, it abruptly jumped to 60-100 hertz. The approach velocity of the object also affected the size of the jump.
Next, they tested people’s perceptions of the rattle. The study entered a high tech phase, as they sent human volunteers into a virtual reality grassland populated with west diamondbacks. Whenever they encountered a piercing rattle, they were asked to estimate the distance. When the lower frequency rattle sounded (40 hertz), the volunteers estimated the snake’s distance away with decent accuracy. But when this was switched to higher frequencies of 70 hertz, at 4 metres away, the volunteers almost always underestimated the distance, believing the rattler to be 1 metre away, right on their toes, when it was actually much further.
West diamondbacks are a deceiver snake – in a bushy desert flat, they could trick you into thinking they’re closer than they really are, sending you fleeing back to your car, and achieving their goals of avoiding a fight simply by shaking their tail. Crotalus atrox’s rattle isn’t a simple shaky sound like a kid’s toy, but much more complex.
| 8 | Strikes faster than other vipers |
A 2002 study compared the west diamondback’s predatory and defensive strikes. The first was stimulated using live mice, and the second using a Pikachu toy. The results showed that defensive strikes were launched from twice the distance of predatory strikes on average. Predatory strikes kicked off at 0.75-15cm away, while defensive lunges began 2-17cm away. The ranges were similar, but the averages were 4.09cm versus 9.43cm.
Likewise, defensive strikes reached higher speeds, achieving a maximum velocity of 5.5 metres per second, versus 4.28 m/s for predatory strikes.
Meanwhile, the average maximum velocity for the 13 predatory strikes was 2.61 m/s. This was higher than two deadly Eurasian vipers, the nose-horned viper (1.47 m/s) and gaboon adder (1.55m/s). The same was true for the maximum velocities, which were roughly twice as fast. Again, this was 4.28m/s for the west diamondback, while nose-horned vipers and gaboon adders achieved maximums of just 2.2 and 1.9 m/s respectively. The strikes for those species were also predatory strikes, so this was a direct comparison.
| 9 | The annual rattler festival |
The southern US is home to an annual tradition, the tradition of the “rattlesnake roundup”, where men, women, and children enter the countryside and kidnap as many rattlesnakes as they can, then gather in the town centre in joyous scenes of celebration and music. Beginning in the 1950s, the original goal was pest extermination, with some rattlesnakes gruesomely beheaded. These days, most are paraded around for educational purposes, or simple spectacle. Dozens of writhing serpents are poured into a colossal snake pit using a bucket, and children are allowed to stroke the snakes in awe while handlers grip their menacing heads. The events crown a “Miss snake charmer”, and awards for the heaviest rattlesnake collected are handed out. It’s a free-for-all of snake madness.
While timbre and prairie rattlesnakes are captured and dunked in the pit, west diamondbacks are undoubtedly the most popular species, partially because of their conspicuous jumbo size. Whether the roundups are harming wild populations are unknown. Timbre rattlesnakes have been hurt by these festivals in the northeast USA, but it’s assumed that west diamondbacks are so dominant that the roundups make a dent at best.
The largest roundup happens in Sweetwater, Texas, and supposedly, this results in the annual capture of 1% of the state’s total rattlesnake population (some believe this is nonsense). Texas is the main host to this madness overall.
| 10 | Doesn’t require a body |
Killing a west diamondback is always sad, but if you’re cornered in a supermarket aisle, you might have no choice. But never let your guard down, as happened in May 2018, when a Texas man found a 1.25 metre west diamondback slithering around his backyard. According to Jennifer Sutcliffe, her husband grabbed his trusty shovel and decapitated the rattlesnake. He bent over to pick up the severed head, thinking the threat was over, but felt two sharp fangs embed themselves in his hand.
Immediately, he began to have seizures. He was airlifted to hospital, where he was given CroFab, the standard US rattlesnake antivenom. The man required 26 vials of antivenom, versus the usual 4. For 24 hours, the doctors warned that he might not make it. The man survived, though continued to suffer from weak kidney function.
The incident happened while the couple were weeding their flowerbed, in the town of Corpus Christi. West diamondbacks join an illustrious club, also occupied by the red-belled black snake of Australia, whose severed head once bit a graveyard worker 45 minutes after he killed it in 2010, amidst spooky graves and tombs (he survived).