Pit Vipers--Rattlesnakes and Sidewinders
Rattlesnakes belong to a group of snakes classified as vipers. Vipers are characterized by having large, hollow fangs in the front of the upper jaw that they use to inject venom into their prey. Rattlesnakes and sidewinders are members of a viper sub-group called pit vipers because they have a heat-sensitive pit on each side of the head between the eye and the nostril. Once the snake has detected prey by means of its tongue, it will turn the side of its head toward the victim in order to pick up heat waves being emitted by the body of the animal. Once it has a precise sense of where the animal is, it will strike accurately and rapidly, injecting its venom into its prey. This advanced system of prey detection makes these snakes especially dangerous, and the photo below shows how well their pattern works as camouflage in their habitat. Watch where you step when you're in rattlesnake country!
Western Diamondback Rattlesnake, USFWS photo by Luther C. Goldman
Western Diamondback Rattlesnakes are more likely than most snakes to live near human populations, perhaps because of the number of rodents that are also found in greater numbers in our cities. These large, heavy-bodied snakes can reach up to 6 feet in length, and will stand their ground when threatened. While rattling a loud warning, they raise their head and upper body in preparation for a strike. Though they can be seen during the day time they will generally be most active in summer during evening and night-time hours. Their peak hunting efficiency is at temperatures between 68 and 80 degrees Fahrenheit. There are many varieties of rattlesnakes and sidewinders. (Arizona is home to eleven species of rattlesnake.)
The Mohave rattlesnake (shown below) is one of the most dangerous venomous snakes in the Sonoran Desert and is probably responsible for a recent trend of increased severity of snake bites in the Cochise County area. Having a neurotoxin that is not typically found in other venomous snakes, bites delivered by the Mohave rattler are extremely toxic and can be lethal. The three most common types of rattlesnakes in Cochise County are the Mohave, the western diamondback and the blacktail.
Pit vipers, including both rattlesnakes and sidewinders, can be from two-and-a-half to six feet in length and are found in most desert environments from sand dunes to rocky foothills and mountainous areas. We tend to think all rattlers look like the western diamondback, but the appearance of many of the lesser known rattlesnakes may be quite different.
Sidewinders have potent venom, and often match the surrounding soil in the area where they are found. Their name comes from their unique method of locomotion. They thrust their body forward until it's at the side of their head, then move the head forward, and repeat the movement. This makes it easy to identify their tracks in the sand after they have passed. They also have an interesting facial feature--over each eye is a triangular "horn" shown in the close-up below.
Although the main function of venom is in killing prey and beginning the process of digestion, all of these snakes will strike to protect themselves if they feel threatened. The key to preventing injury is to avoid these situations. If you do receive a snake bite know that most of the folk remedies such as sucking on the wound or using a tourniquet may do more harm than good. THE ONLY TREATMENT FOR A SNAKE BITE IS ANTIVENOM ADMINISTERED AT A HOSPITAL. Do not give the victim any drugs or alcohol to control the pain, since this may cause complications.
Speckled rattlesnakes (pictured at right) have an appearance that blends very well with their surroundings, so they may not be noticed if you are not watching your step carefully. They like rocky outcroppings and rock piles, emerging to hunt small rodents, lizards, and birds in the evening when temperatures are hot and during the day when it is cool.
Ridgenose rattlesnakes are a protected species because they are at risk for extinction. They are currently limited to small areas in Arizona and New Mexico. These small (1.5 to 2 feet in length) snakes are often found near water and become more active during a rainy season or after a rainstorm. Their diet consists of lizards and small rodents. Some subspecies have the white "flash marks" on the side of the face as shown in the close-up photo. Their name refers to the ridge along the edge of the snout.
Ridgenose rattlesnake, USFWS photo by Jeff Servoss
A final word of caution from Peggy Larson, author of The Deserts of the Southwest:
John Russell Bartlett, on his journey with the Boundary Commission in 1850, describes an incident in which a horse was bitten by a rattlesnake:
In his book, Life Among the Apaches, John Cremony relates the Apache lore that tells of a rattlesnake sharing the same den with a prairie dog family and a ground owl. Read it here.
If you wish to identify a particular specimen of rattlesnake, it is advisable to consult a guide such as Amphibians and Reptiles of Western North America by Robert Stebbins.
A number of different rattlesnakes are pictured on the reptiles section of the image library of the Arizona Ecological Field Services Office of the U.S. Fish and Wildlife Services.
Brennan, Thomas C. and Andrew T. Holycross. A Field Guide to Amphibians and Reptiles in Arizona. Phoenix: Arizona Game and Fish Department, 2006.
Hare, Trevor. Poisonous Dwellers of the Desert: Description, Habitat, Prevention, Treatment Tucson: Southwest Parks and Monuments Association, 1995. A short, reasonably priced guide to venomous desert life--how to avoid getting bit and what to do if you do, illustrated by Barbara Terkanian.
Larson, Peggy Pickering. A Sierra Club Naturalist's Guide to the Deserts of the Southwest. San Francisco: Sierra Club Books, 1977.