The Red Diamond Rattlesnake

(Crotalus ruber)

by Jay Sharp

The red diamond rattlesnake's "size and beauty," said the San Diego Natural History Museum, "make it a very impressive animal, especially when seen in the wild." It is one of the three species of rattlesnakes commonly called "diamondbacks." (The other two are the western and the eastern diamondbacks.) The red diamond rattlesnake occupies a range that extends from the southwestern corner of California southward through most of Mexico's Baja peninsula. Its territory generally overlaps that of the southern Pacific rattlesnake. (See "Southern Pacific Rattlesnake,") Equipped with loreal pits – heat-sensing organs on each side of its face – the red diamond rattlesnake belongs to the subfamily commonly called "pit vipers," which includes the rattlers as well as the water moccasins and copperheads.

The snake's triangular-shaped head spans about twice the width of its neck.

Characteristics of the Red Diamond Rattlesnake

Heavy bodied with a stout tail and typically light to dark reddish brown in hue, the red diamond rattlesnake's distinguishing features include:

• Adult Size and Weight: Typically, the snake measures about 2 ½ to 3 ½ feet in length, although rarely, it may reach 5 feet in length. A large one may weigh several pounds. The male's tail is thicker than the female's tail, according to the U. S. Geological Survey.
• Color and Pattern: Born grayish in color, the snake develops a more reddish color as it matures. Classically, its back bears diamond-shaped blotches framed with light edges. Like the other diamondbacks, its tail is encircled with black and white rings.
• Head and Face: The snake's triangular-shaped head spans about twice the width of its neck. It eyes have vertical, elliptically-shaped pupils. They are bracketed with light stripes that extend diagonally down the face. Its loreal pits lie just below and behind the nostrils.
• Fangs: The adult has a matched pair of hollow fangs, each about ½-inch in length, that unfold from the roof of the mouth to deliver a bite. The fangs serve as hypodermic syringes to inject venom from glands, located behind the eyes, into a victim's tissue. Lost fangs are rapidly replaced by new fangs.
• Rattles: The snake's rattles comprise nested modified scales. A new rattle is added with each molt. Old rattles sometimes break off. The total number of rattles varies during the year.
• Senses: The snake has acute senses of smell and heat detection, a good sense of vision, and high awareness of vibrations (which helps compensate for its lack of hearing). Most notably, the snake, usually a hunter of the night, smells prey by using its forked tongue to collect minute odor particles from its surrounding environment and delivering them to the highly sensitive specialized smelling organ – the Jacobson's organ – in the roof of its mouth. It can effectively "see" and strike its prey, even in absolute darkness, by using its loreal pits to form a "heat image" in the brain. After a strike, it can then use its tongue and Jacobson's organ to track a dying prey trying to escape through the darkness, even in a pitch-black den.
• Communication: Like its close kin, the snake rattles and may hiss to warn an intruder of its presence. The female leaves scent marks in the fall to guide offspring to the family communal denning site, where several members may gather for the winter.
• Strike and Bite: Usually the snake, with a flash of swiftness, strikes its prey from ambush. As it strikes, according to the Arizona-Sonora Desert Museum, it unfolds the fangs "to an erect position, somewhat perpendicular to the jaw line" then drives them into the flesh of the victim, sending its poison home. Even a newborn arrives with fangs and toxin, fully prepared for hunting and defense.
• The Venom and Its Effects: Although the red diamond rattlesnake's venom is less toxic than that of other rattlers, said the U. S. Geological Survey's Southwest Biological Science Center, the fully mature adult can deliver a large amount of venom—indeed, more than three times the dose that could kill a human. The venom produces intense localized pain, massive swelling, discoloration and blood degeneration as well as nausea, vomiting and various other symptoms. The venom, dried and stored, retains almost its full toxicity for well over two decades. Fortunately, red diamond rattlesnake bites occur infrequently.

The snake's rattles comprise nested modified scales.
A new rattle is added with each molt. Old rattles sometimes break off.

Distribution and Habitat

Within its range, from southwestern California to Cabo San Lucas as well as some offshore islands, the red diamond rattlesnake, says the U. S. Geological Survey, prefers "coastal sage scrub, rocky hillsides, and outcrops." It also occupies the lower woodlands as well as cultivated fields. It usually avoids the lower flats on the desert floor and elevations above 5000 feet, according to the San Diego Natural History Museum. While usually a snake of the ground, it sometimes climbs into low-growing vegetation such as sage, shrubs and even cacti. If threatened, said the California Department of Fish and Game, it may retreat "into rodent burrows, into cracks in rocks or under surface cover objects." Evidently – based on research by the San Diego Zoo – the red diamond rattlesnake never travels more than a couple of miles in its entire lifetime, and like other snakes, it creates a mental map of its immediate surroundings, allowing "an individual to return to the same bush or rock year after year."

Diet

According to the California Department of Fish and Game, the red diamond rattlesnake feeds on small mammals such as rabbits, ground squirrels and wood rats and on reptiles such as lizards and other snakes. Given the opportunity, it may feed on a bird. If the snake feeds on substantial prey, it may wait a couple of weeks before feeding again.

Behavior and Life Cycle

With the warming of the days in the spring, the snake emerges from the darkness of its communal winter den, ready for the breeding season as well as sunlight and a meal. Two males may battle for the right to mate with a receptive female. About four months later, in a sequestered place such as an abandoned animal burrow or within a rock crevice, she will deliver perhaps 5 to 15 offspring, each measuring approximately 12 or 13 inches in length. Prepared at birth to feed and defend themselves, the young soon scatter to take up independent lives. The red diamond rattler may live for 15 or 16 years in the wild and as much as 19 years in captivity.

Perils

The snake may be preyed on by kingsnakes, roadrunners and possibly owls, said California's Department of Fish and Game, and it has lost habitat as human developments expand into its range. Nevertheless, it is ranked as a species of "least concern" by theInternational Union for Conservation of Nature and Natural Resources. However, the species' population trend is down, and it may face long-term threats. In fact, said the San Diego Natural History Museum, it is listed as a "Special Concern species" by both the Federal and California state governments.

Interesting Facts

The red diamond rattlesnakes venom increases in toxicity at the animal matures. "Tissue damaging properties of venom," said the University of California at Davis, "are 6 – 15 times greater in adults than juveniles.

Severe as the effects of the red diamond rattler's bite may be, it causes fewer deaths each year than bee stings.

Rattlesnake rattles, said authority Anders Nielsen, likely evolved on the Great Plains – according to one theory – as a means for the snakes to warn bison not to step on them.

Following an old tradition, some states hold "rattlesnake roundups" in an organized effort to kill large numbers of the snakes.

For tips for avoiding rattlesnake bites

For tips for dealing with a rattlesnake bite

Read more about rattlesnakes:
- Rattlesnakes
- The Sidewinder
- Western Diamondback

Video on Rattlesnakes

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