Western Diamondback Rattlesnake

Description: The western diamondback is one of the largest of the rattlesnakes, occasionally measuring over six feet in length. It is heavy-bodied, and like all rattlesnakes, it has keeled scales and a sensory pit located on each side of its upper jaw, between the nostril and the eye. These pits detect heat, acting almost like a pair of infrared eyes. The diamond pattern on the snake's back is the source of its name, however similar patterns are common among rattlesnakes, as is the western diamondback's raccoon-striped tail.

A rattlesnake's rattle is a series of modified scales, linked loosely together; newborn snakes have only one segment, called a button, and therefore cannot produce a rattling sound until after their first shed, when a new segment is exposed. The snake will add one segment each time it sheds, which may be only a few times a year, or as often as every month, depending on how quickly it grows. A western diamondback's rattle may measure a few inches in length and nearly an inch wide on larger specimens, but over time, segments of the rattle are usually damaged and fall off, preventing it from becoming especially long. Like all reptiles, rattlesnakes continue to grow throughout their lives, in contrast with mammals and birds, which reach a maximum size and stop growing.

The western diamondback rattlesnake is venomous, possessing hollow fangs for injecting venom into its prey. Being a viper, the rattlesnake's fangs are not fixed, but instead fold against the roof of its mouth when not in use. Fangs regularly fall out and are replaced; it is not uncommon for the new set of fangs to grow in before the old ones have dropped out, resulting in the presence of three or four fangs instead of two. The venom is highly hemotoxic, meaning that it breaks down blood and tissue; this enables rattlesnakes and other vipers to begin digesting their prey before they have swallowed it, and the action of their venom speeds the digestion process after the prey has been consumed.

Habitat: Western diamondbacks typically inhabit dry, rocky terrain with low-growing shrubs for cover, or grasslands. They favor areas with crevices and rodent burrows where they can hide from predators, escape the heat of the day, or conserve their body heat on cold nights. They do not require a water supply, as they are capable of deriving the water they need from their prey, or from drinking dew droplets from the foliage of plants and from their own skin, and thus they may be found deep in the desert, well away from streambeds or natural springs. Around human settlement, piles of debris like old tires or corrugated metal often attract snakes and the animals they eat.

Distribution: Western diamondbacks are found from southeastern California east through southern Arizona and most of New Mexico, southern Oklahoma, most of Texas, into western Arkansas, and south to northern Sinaloa on the west coast of Mexico, and Veracruz on the Gulf coast. It is possible that the snakes might also be found in the southern tip of Nevada, and an isolated population may occur in southeastern Colorado.

Behavior: The western diamondback's optimum body temperature is around 85°F, meaning that its activities throughout the day are generally aimed at keeping its body as close to that temperature as possible. Snakes may bask in the sun in the morning, and retire to a rodent burrow to escape the afternoon heat. Early evening is an ideal time for hunting rodents, rabbits, and birds; as the air cools, prey species become more active, and the snakes are still warm from the heat of the day.

The rattlesnake uses a combination of senses to locate prey. Its eyesight is fairly poor, but it makes up for it with its other modes of perception. It has two senses of smell: the 'standard' sense afforded by its nostrils, which is somewhat weak, and the stronger sense achieved with a chemoreceptor organ in the roof of its mouth called the Jacobson's organ. The snake flicks its tongue, picking up minute, airborne, chemical compounds, which are then deposited on the Jacobson's organ when the tongue reenters the mouth. The sensory pits on the rattlesnake's upper jaws detect body heat from small mammals and birds. Its body is sensitive to vibration, such as those caused by a mouse running along a fallen tree branch. Although they have no external ears, snakes may not be completely deaf, as they do possess underdeveloped, internal ears. It is unknown whether or not these ears are functional.

Using all of its senses in concert, a rattlesnake can locate its prey with a good degree of accuracy; it crawls slowly to within striking distance, which is generally around a third of its body length, and bites the prey, injecting a lethal dose of venom. The snake then backs away quickly to avoid being injured, and waits for the prey animal to die. This may take minutes or hours, depending on the amount of venom injected, the size of the prey, and its resistance to the venom. As the prey animal retreats, the rattlesnake follows it at a safe distance, using its senses of smell and heat perception to track it. Once the dead prey is located, it is consumed, usually head first. The snake's jaws disarticulate, or spread apart, to accommodate prey items that are larger than its own head. Large prey like rabbits may take a few hours to swallow, and the rattlesnake becomes vulnerable to predators while feeding, unable to strike defensively with food in its mouth. While they usually eat prey that they have killed themselves, at least one western diamondback rattlesnake has been observed consuming carrion.

Western diamondback rattlesnakes mate in the spring; males often engage in ritualized combat in competition for a female. The two males approach each other and raise their heads as high as they are able, then make contact, spiraling around one another, each one trying to force his opponent's head to the ground. The victor wins the right to mate with the female, if a third male doesn't steal her away while the other two are preoccupied with combat. Rattlesnakes are ovoviviparous, meaning the young hatch from their eggs while still inside their mothers; a female western diamondback may give live birth to as many as 25 young. The newborn snakes are fully self-sufficient, leaving their mother within a few hours of birth. Most do not survive their first winter, due to predation and freezing temperatures.

In the winter, the snakes retreat to communal dens, where several hibernate together. In cooler areas, these are typically rodent burrows, which have good insulative properties, but in warmer climates, the dens may merely be rock piles or debris from human settlements. The hibernation is not a true dormancy, but simply a metabolic slow-down that may be interrupted by brief periods of warm weather.

Rattlesnakes do not attack human beings; biting anything other than its next meal comes at a great cost to a rattlesnake, as it takes a good deal of energy to replace the venom it has used. Bites to humans occur only when the snake feels threatened, and in most cases, such incidents are totally avoidable. When confronted by a human, the snake's first instinct is to flee. If no escape route is available, a western diamondback will hold its ground, assuming a defensive posture; the snake gathers itself into a tight coil and elevates the front portion of its body into an S-shaped-curve. Its tail will remain erect, shaking its rattle at up to 60 cycles per second. Biting is a last resort, although a surprised snake may bite without rattling first. Not all bites inject venom, but those that do are immediately painful. If medical treatment is not received, the venom will continue to move through the recipient's living tissue, digesting it. Blood and muscle typically sustain the most damage, making the heart and other organs vulnerable. Western diamondback bites can result in necrosis, the loss of limbs, and death in human beings.

Human Impact: The western diamondback's communal denning behavior has made it vulnerable to snake hunters. Rattlesnake roundups are illegal in most states, but they still occur in Texas, Oklahoma, New Mexico, and several other states outside the snake's home range. Snake hunters capture thousands of rattlesnakes for each roundup, often with the use of gasoline or other toxic chemicals pumped into their hibernation burrows. These chemicals pollute the environment and kill non-target species, like tortoises and prairie dogs. Once captured, the snakes are taken to a central facility, where they are used to entertain the public with cruel games that violate their basic welfare, after which they are slaughtered for meat and the production of gruesome souvenirs.

Roundups severely deplete rattlesnake populations, which contributes to overpopulation of rodents in agricultural areas. They also serve to spread misinformation about rattlesnakes; roundup participants go to great lengths to sway public opinion, portraying the snakes as aggressive killers, and an imminent threat to human safety. Framed as safety demonstrations, these 'educational' activities typically convey unsafe practices that audience members may later attempt to duplicate. Conditions at the roundups are anything but safe; snake handlers may be bitten and snakes are not always properly secured away from the general public.

Rattlesnake roundup personnel regularly attempt to legitimize their activities by claiming that they extract venom for the production of antivenin, used to save the lives of snakebite recipients; however, the venom collection methods used at roundups do not meet FDA guidelines, and no antivenin producer in the United States would knowingly purchase venom from rattlesnake roundups. Legitimate venom collectors observe high standards of animal husbandry, cleanliness, and safety, and they do not butcher their snakes.

Rattlesnakes have also grown in popularity in the reptile trade; many hobbyists purchase rattlesnakes in the interest of having a dangerous pet to show off to their friends, or to satisfy their morbid fascination with the way they kill their prey. The end result is often a snakebite, an escaped rattlesnake, or a snake that receives poor care because its owner is afraid to remove it from its cage for routine cleaning, water changes, etc. Few hobbyists have adequate access to antivenin, or even the legal permits to keep venomous snakes.

Western diamondback rattlesnakes are legally protected in some states insomuch as they are not considered game species and cannot be legally hunted, and that a collection permit is required for their capture. Laws preventing the keeping of venomous snakes also afford them some degree of protection, however they receive no status specific to their species from any government entity. They may be exported without permits, transported across state lines, and bought and sold at will. It is crucial that western diamondbacks and other rattlesnakes be given the protection that a mammal or bird species in a similar state of vulnerability would receive. These animals must not be vilified for the fact that they happen to produce venom; the benefits of a healthy rattlesnake population far outweigh the minimal risks they pose. Rattlesnakes must simply be treated with the same respect due to all living things, and be left alone.

This western diamondback rattlesnake's sensory pits are clearly visible; the pits are larger than the nostrils, and are located below and to the rear of them. Gerald and Buff Corsi; © California Academy of Sciences

A typical western diamondback, showing the dorsal pattern for which the snake is named, and the raccoon-stripe markings on its tail

The characteristic facial stripes of the western diamondback are clearly visible in this snake; Jens V. Vindum; © California Academy of Sciences

A western diamondback skull, demonstrating the formation of the new fangs that would have eventually replaced the older ones.

A baby rattlesnake's button; the next link in the snake's rattle will be revealed after it sheds its skin. This individual is a timber rattlesnake, Crotalus horridus.

A typical defensive posture, with rattle humming

Two male western diamondbacks engage in ritual combat.

Aberrant color morphs, like this albino, have increased the popularity of western diamondbacks in captivity.

While 'designer snakes' like this colorless morph are visually appealing, they are no less venomous than their more typical-looking brothers and sisters.

At a rattlesnake roundup in Texas, a man lies still while a snake handler puts twenty live rattlesnakes into his sleeping bag; stunts like this are the staple of roundup entertainment, and besides being wholly unnecessary, they cause undue stress to the animals and put humans in pointless danger of being bitten.

In their circus-like atmosphere, rattlesnake roundups are sometimes the stage for the exploitation of other wild animals, like this capuchin monkey (Cebus capucinus).

In another dangerous and unnecessary stunt, a snake handler at the roundup kisses the head of a monocled cobra, Naja kaouthia, a venomous species from India and Southeast Asia that is common in the exotic reptile trade.