Rattlesnakes are members of the subfamily Crotalinae (pit vipers), named for the two infrared (heat-sensing) pits located between the eye and nostril. They include the rattlesnakes, massasaugas, water moccasins (cottonmouths), and copperheads. There are approximately 155 species of Crotalines in the Americas and 30 recognized rattlesnake species. California is home to seven species and Arizona tops the rattlesnake diversity list with 13.
Rattlesnakes are heavy-bodied snakes with large triangular heads, keeled scales, front-hinged fangs, and a rattle consisting of interlocking hollow segments that is used as a warning to predators and those that wander too close for comfort. The pupils of rattlesnakes are vertical slits which not only allow more light to enter during nocturnal slitherabouts, but it also improves the resolution of shapes and enhances their depth of field. This allows for better detection capabilities of horizontal movements typical of their prey by keeping them in sharp focus which is important for an animal that hunts close to the ground.
Although their coloration and patterns are distinct, they vary wildly to match their environment; even individuals of the same species may exhibit high variability in both patterns and coloration. Patterns range from triangular markings, to dark brown or black blotches, and dark to light lined borders on both the back and sides. The undersides are shiny silver and gold and as soft as velvet…No they’re Not! Really, who writes this stuff??? The tails are often distinctly colored in alternating light and dark bands of uniform width with a joyful little rattle at the end. There is often a diagonal stripe that crosses the eye from the corner of the mouth.
There are seven rattlesnake species in California and ten subspecies. Aside from the yellow-bellied sea snake which occurs infrequently along the Pacific Coast shoreline south of Ventura, rattlesnakes are the only venomous snakes in the state that poses a threat to humans (those bipedal creatures that walk around poking things with sticks while babbling loudly). Adults reach lengths of 33-65 inches with the exception of the western diamond-backed rattlesnake that can reach lengths up to 90 inches. Now, that’s a big rattlesnake! The young, referred to as neonates, are born live unlike most snakes which lay eggs. Neonates average approximately 10 inches in length and can fit through an opening greater than ¼ inch, which is why exclusion fencing should be chosen with care and properly installed. Hey! We know experts who do that!!!
So…what’s the deal with venom?
I’m so glad you asked. Venom is a complex mix of proteins that have evolved over the millennia to target various organs and cells as a way of subjugating prey. Snakes, if you haven’t noticed, do not have arms and legs and had to innovate, by way of complex evolutionary magic, ways in which to survive in a world that moves around quite easily on leg, wing, and flipper. Snakes have developed two means of tackling this challenge: constricting and envenomation. Constricting refers to wrapping their body around an object, let’s say an elephant shrew for this example…they’re cute, Google it. The snake quickly grabs the prey with its mouth and coils its body around it. It then squeezes tightly preventing the prey from breathing until subjugated then consumed. I’m now regretting now using the adorable elephant shrew in this horrific example.
Envenomation, on the other hand, is injecting prey with toxic venom and for rattlesnakes that’s through specialized hypodermic-like teeth. The venom is also the reason for the rattlesnake’s characteristic triangular head which supports a venom gland behind each eye. Snakes in the Viperidae family have front-hinged fangs that allow for the development of longer, specialized teeth nightmares are made of. Other families such as the elapids (cobras, mambas, sea snakes, and coral snakes), have short, front-fixed fangs that do not hinge or fold, but are otherwise just as adept at delivering venom. Still other families including those of the Colubridae, Homalopsidae, and Lamprophiidae, have rear fangs but generally lack the enlarged venom glands and supporting musculature that aids in its delivery. They, instead, have a Duvernoy’s gland, a mucosecretory, supralabial gland (yeah, heavy words, man) that secretes venom down grooved, and sometimes ungrooved, enlarged rear maxillary teeth. The venom is often chewed into its prey as it is subdued. Still there are other species such as gartersnakes that have mildly toxic saliva which isn’t good if you’re an amphibian, but is harmless to humans other than causing mild skin irritation in some cases.
With front-fanged snakes, venom is injected by contracting muscles around the venom glands which forces venom down a duct and into hollow fangs. Injecting venom is a process controlled by the snake which can choose to release venom and the quantity that is releases. Most rattlesnakes are passive and will chose to stay motionless and silent as a first means of defense rather than rattle or strike. Rattling and coiling to strike is a secondary defense and a warning. They will strike if necessary or provoked, but do not always inject venom when defensively striking. Additionally, rattlesnakes may also strike without rattling so it’s important to be aware of your surroundings.
How many people are bitten by rattlesnakes?
An estimated 7,000-8,000 people are bitten by venomous snakes each year in the U.S. Of those, only one in 50 million are fatal resulting in 5-6 deaths per year. To put this in perspective, more people die each year from dog bites, bee stings, lightning strikes, and forklift accidents (yup…around 85 forklift deaths per year) than from snake bites. So even though the thought of being struck by a snake is terrifying, the chances of it happening are relatively slim. Our advice, keep your distance and be aware of your surroundings. And please do not try to get close or pick up a rattlesnake. This is the primary reason people get bit. Also, rattlesnakes strike in as little as ½-second. That’s quite fast and we’re willing to bet that’s faster than you can swat it on the head and say “No! Bad snake!” On the contrary, data on how many snakes are bitten by humans each year is less clear, but we’ll look into it.
What is a dry bite?
It’s when you take a bite of a green banana and it sucks all the moisture from your mouth. Am I the only one? Fine…a dry bite refers to being bitten without venom injected into the site of the bite. It’s estimated that approximately 20-40% of rattlesnake bites and 50% of coral snake bites are dry bites. Much like a soufflé, venom requires a lot of energy to make and snakes are wary about throwing it around with abandon. Snakes eat on average once every two weeks (or once a week for baby rattlesnakes) and some as few as 5-6 times per year. That’s not a lot of energy to make their witchy concoction of venom. It’s far better to use it wisely and sparingly like that tasty vermin you’ve been eyeing near the old tree stump.
Seeing red…well, infrared.
The infrared receptors, or pits, are membrane lined much like that of our eardrum, which has a stereo effect of detecting prey, other organisms, and the immediate environment. Rattlesnakes can use these sensors to identify the direction, size, and distance of prey crossing their field of view and can discriminate temperature differences of 0.2°C from ambient background.