Rattlesnakes of Southern California
Text and photos by Michael D. Cardwell
Loma Linda University is located midway between Los Angeles and Palm Springs, near the edge of the great deserts of the southwestern United States and northern Mexico where rattlesnakes are believed to have originated and great species diversity still exists. In addition to two taxa found in the immediate vicinity of the campus (red diamond and southern Pacific rattlesnakes), several other desert species live within a couple hours' drive. As a Level I regional trauma center with a well-established reputation for snakebite expertise, the emergency medicine department at LLU Medical Center receives many rattlesnake bite cases each year from both coastal and desert species.
Here, we briefly describe each of the six species of rattlesnake that occur in Southern California.
Red Diamond Rattlesnake (Crotalus ruber)
This large, brick red snake is primarily a Baja California species, including several islands, and extends only into the corner of the United States, with Loma Linda representing just about the northern limit of its range. It is common in the low hills within a kilometer of the campus. Red diamond rattlesnakes can exceed 1.5 m in length but tend to have a rather passive disposition compared to many other rattlesnake species.
Southern pacific rattlesnake (Crotalus helleri)
Found throughout Southern California's densely populated coastal valleys and foothills, this dangerous snake is responsible for most of the rattlesnake bites in the greater Los Angeles basin. It was considered a subspecies of Crotalus viridis for many years, but recent genetic analyses have led to systematic revisions of these taxa, with some researchers classifying helleri as part of the Crotalus oreganus group while others elevate it to full species status. It can exceed 1.5 m in length.
Western diamondback rattlesnake (Crotalus atrox)
This snake can be found about 100 km east of LLU. It inhabits a large portion of the arid southwestern United States and northern México, including the southeastern corner of California. Adults can exceed 2.0 m in length and are the largest rattlesnake species in the western United States. They are notoriously nervous and quick to rattle, often assuming a dramatic defensive pose when bothered by creatures as large as humans. The western diamondback's range in California encompasses sparsely populated areas where they encounter few people.
Mohave rattlesnake (Crotalus scutulatus)
This rattlesnake is common around many high-desert communities north of Loma Linda. It produces one of the most toxic venoms of any North American rattlesnake. Called "Mohave Greens" by the locals, they seem to have achieved "urban legend" status with a greatly exaggerated reputation for aggressiveness. Like other rattlesnakes, they prefer to remain still in hopes of going unnoticed. But if bothered, they will defend themselves enthusiastically. Length rarely exceeds 1 m in this area.
Sidewinder (Crotalus cerastes)
California's smallest rattlesnake species, this elegant snake rarely reaches 0.75 m in length. Famous for their specialized method of moving efficiently over loose sand by pushing straight down in only two places at a time, they can also be common on firmer substrates. Due to their small size (and, therefore, low venom yield) and comparatively low venom potency, their bites are usually not as serious as bites by other species. Two subspecies occur nearby, the Mohave Desert sidewinder (C. c. cerastes) and the Colorado Desert sidewinder (C. c. laterorepens).
Southwestern speckled rattlesnake (Crotalus mitchelli pyrrhus)
This snake is a rocky hillside specialist in the deserts north and east of Loma Linda. South towards San Diego, however, this species inhabits coastal hills and valleys. Probably due to their habitat preferences, they seem to suffer fewer encounters with people than other species that inhabit flatter terrain. The dorsal coloration of speckled rattlesnakes can vary greatly from gray to tan and even burnt orange. They are relatively small but occasionally exceed 1.25 m in length.