Southwestern Field Herping Associates

RATTLESNAKES - Fact and Fiction

There is probably not a more recognizable serpent on our planet than the Rattlesnake, but as well known as this creature is, it is also one of the most misunderstood. Some ancient American cultures worshiped the Rattlesnake as a God, others revered it as a symbol of strength and fertility. Today, most so-called educated civilized people regard it as evil, and something that should be destroyed. It is true that Rattlesnakes are dangerous creatures, but so are lions and tigers and many other well known species, but because many of these other dangerous creatures are warm blooded and are closer kin to humans, we tend to admire their beauty and power, and strive to respect and protect them. Unfortunately the human psyche is not programmed the same way in regards to our cold-blooded fellow earthlings.  

Rattlesnakes are unique among all other serpents for the simple fact that they are the only snake species on the planet that has any sort of appendage on their tails. What is even more interesting is that this appendage is designed and used to make an audible sound. This, coming from a creature that is near totally deaf. Rattlesnakes are also native only to the Americas. They are not found on any other continent of the world. One can only imagine the excitement of the early European explorers and naturalists when they discovered this fascinating snake in the New World. There are approximately 64 known forms (species & subspecies) of Rattlesnakes, 32 of which reside in the USA, and most of them are found in the western part of our country. Arizona tops the list as the state with the most Rattlesnake types at 13, with California and Texas tied for second with 10 each.

Many people regard Rattlesnakes as being primitive relics of the ancient past. Nothing could be further from the truth. Rattlesnakes are modern predators, equipped with high-tech capabilities that human technology is just now learning how to master and use. Rattlesnakes are pit vipers. They get this name because they have deep pits, or orifices, in the front of their faces that are highly sensitive heat sensing organs. These heat sensing organs can detect warm blooded prey or predators in total darkness just by reading the heat image emitted from their bodies.

Like all pit vipers, Rattlesnakes have long, retractable, hollow fangs in the front of their upper jaw, which are connected to large venom producing glands located in their cheeks. Rattlesnakes are not constrictors, nor do they grasp prey with their teeth and hold onto it. The venom injection system is used to subdue prey, which the Rattlesnake does with a quick "stab" of its venom -filled "hypodermic needles". A Rattlesnake with no venom cannot kill prey, and therefore cannot survive.

Rattlesnake venom is composed primarily of tissue digestive and blood-targeted toxic enzymes, and nearly all species have some percentage of neurotoxin as part of their venom cocktail. All Rattlesnakes are potentially dangerous to humans and in some cases can be deadly, but as a rule, Rattlesnakes are not nearly as deadly as other snake species from other parts of the world. We in the Americas are lucky in that respect, because there are snake species in Africa, Asia and Australia that can inflict bites that are quite often fatal to humans. The percentage of Rattlesnake bite cases on humans that result in death are actually extremely low. According to reports by some American poison control organizations, the human death rate from the bites of Rattlesnakes is lower than .1%, or 1 death out of every 1,000 cases.

The question is often asked, which species of Rattlesnake is the deadliest? The answer is relative to what the intent of the question actually is. In other words, is the question, which Rattlesnake species is the most toxic? Or, which Rattlesnake species causes the most human deaths? Believe it or not, there is a big difference. How toxic, or how potent the venom of a particular species is, does not necessarily determine how deadly to humans the snakes bite is. In the case of venomous snakes, size matters.

According to a number of sources, the most deadly species of Rattlesnake in our country is the Eastern Diamondback Rattlesnake of the American Southeast. This snake is the largest of all species of Rattlesnakes and can deliver a large amount of venom, purely because of its size. Other Rattlesnake species that top the most deadly list are the Western Diamondback Rattlesnake, and the Mexican West Coast Rattlesnake. All of these snakes are large, and all are capable of delivering a large dose of venom with a single bite. It is mainly this fact that makes them so deadly.

Another factor that comes into play when you are talking about the "most deadly" species, is number of annual snake bites. It's possible that more people die from the bite of the Western Diamondback than do from the bite of the Eastern Diamondback simply because the Western Diamondback has a much larger distribution and more people are bitten by them each year than any other species of Rattlesnake. As with a lot of statistical information, it can be skewed in many different ways.

In comparison, however, neither the Eastern Diamondback, Western Diamondback nor the Mexican West Coast Rattlesnake produce a venom as potent or toxic as several other lesser known species. In terms of which Rattlesnake produces the strongest or most toxic venom, the nod probably goes to the Tiger Rattlesnake of southern Arizona and northern Sonora.  Based on the venom toxicity testing method known as LD-50, when injected sub-cutaneously, the venom of the Tiger Rattlesnake is approximately 60% more potent than the venom of the dreaded Northern Mojave Rattlesnake, and approximately 680%, or 68 times more toxic than the venom of the Eastern Diamondback Rattlesnake. In the case of the Tiger Rattlesnake, however, it's a small snake in comparison, and has a disproportionately small head for the size of its body. The result is that the Tiger Rattlesnake is incapable of delivering as much venom to its prey, or to a human, as a large Eastern Diamondback, which may be why it is not known as one of the top deadliest Rattlesnakes.

As we have just seen, volume plays a big part in how dangerous the bite of certain species of venomous snakes can be. This is why the belief by some people that baby Rattlesnakes are more dangerous than big ones, is untrue. It is also not true that baby snakes don't know how to control their venom and large snakes do. To believe that you would have to believe that large snakes are capable solving mathematical equations involving how much venom to administer to a prey animal of a certain body weight, or some other such nonsense. It is true that in some species of Rattlesnakes, the newborn snakes sometimes posses a more toxic venom, but the amount of venom a small newborn Rattlesnake can deliver to a human is rarely enough to be fatal. When it comes to venomous snakes, size matters. Small venomous snakes are less dangerous than large venomous snakes of the same species - pure and simple.

In many cases of people being bitten by Rattlesnakes, as much as 35% of the time, the snake will deliver no venom, resulting in what is known as a dry bite. Why does this happen? Rattlesnakes have venom for one reason, and that is to kill prey. Rattlesnakes are not venomous for the purpose of killing people. Most of the time when a Rattlesnake bites a human, it's out of fear and self defense. The snake is not trying to kill you or eat you, it's simply trying to make you get away from it. Injecting venom is not one of the things the snake is intentionally trying to do.

Rattlesnakes from all regions of their range usually mate in the spring and give birth in the fall to live born young. The young snakes are perfect miniature clones of their parents in all respects including being fully equipped with fangs, and venom and the knowledge of how to use it. Some species are known to live in excess of twenty years. Despite what some people think, you cannot tell the age of a Rattlesnake by counting the number of rattle segments it has. A Rattlesnake gains one rattle segment every time it sheds its skin. It will shed its skin one, two, or even three times per year depending on how long the period of activity is in a particular region and how often the snake can acquire a meal. A well fed snake will grow at a very rapid rate and have a need to molt, or shed its skin quite often. Older snakes also lose the end of their rattles due to wear or maybe to a predator, so it's not at all possible to tell the age of a snake by the size of its rattle.

Much of what is printed on the internet and in newspapers about huge 10 and 12 foot-long Rattlesnakes is simply not true. The truth of the matter is that the Eastern Diamondback is the largest species of Rattlesnake, and it is extremely rare for it to reach a length in excess of 8 feet. In fact, it's rare to find one as long as 7 feet in the wild.

Rattlesnakes are important members of our natural ecological systems. They are predators that have a great influence on the control of potentially harmful rodent populations. Unlike rodents, snakes do not transmit deadly diseases like rabies, Hantavirus or the Bubonic plague to humans, but instead, kill, consume and control the rodents that do. For some unknown reason, in this day and age of conservation awareness and the awareness of the plight of much of our native wildlife due to human activity, the barbaric ritual of Rattlesnake round-ups is still practiced and condoned in some states. This practice of the senseless and reckless slaughter of one of our most important rodent controlling predators is reprehensible, and should be banned by our Federal and State governments.