Description
California’s largest and most aggressive rattlesnake. A heavy-bodied pit viper with keeled scales, elliptical eyes, spade-shaped head, infrared pits on either side of the head between their eye and nostril, and a distinctive rattle at the tip of its tail. A dark stripe extends from the upper lip behind the eye diagonally upward across the eye. Coloration varies from gray, tan, brown, and olive-green to yellowish. Patterns consist of diamond shaped blotches on the dorsal surface that are brown or black with light edges. Blotches and patterns can be indefinite resulting in an overall dusty appearance. Patterns transition to distinct black and white rings, equal in size, near the tail with a black ring adjacent to the rattle. Due to the resemblance of a raccoon tail, they are often referred to as “coontail” rattlesnakes. This is the largest rattlesnake in California with adults ranging from 30-90 inches in length. Males are generally larger than females.

Habitat
Range is limited to the southeastern corner of California. Inhabits arid and semiarid areas including plains, mountains, woodlands, pine-oak forests, mesquite-grasslands, deserts, canyons and rocky vegetated foothills.

May also be found in areas of the desert that have been modified by urban development and agriculture. Prefers areas with dense brushy cover. Habitat overlaps with that of the Mojave rattlesnake.

Diet
Considered a dietary generalist, species preys on a variety of small mammals including mice, rats, rabbits, squirrels, and gophers. Secondary prey includes ground dwelling birds, lizards, and even carrion on occasion. Juveniles occasionally eat large insects and frogs. Can survive without feeding for two years but generally feeds every 2-3 weeks. Feeding frequency varies depending on temperature ranges. In the mild temperatures of spring (March-May) this species can be more active during the day, and during period of the higher temperatures of summer (June-August) activity is greatest during dusk and nights. An ambush predator, the species awaits along areas trafficked by prey, strikes, releases and then tracks the prey, where the envenomated mammal is then consumed whole.

Behavior
Typically quick to act defensively if startled and will aggressively hold their ground by raising their head high in a striking coil with the tail elevated and rattling, while hissing loudly. May strike and bite if provoked. Primarily active during early daytime hours when temperatures are cool to moderate, often basking in open areas; and seeking shelter in excessive daytime heat. May stay active into the evenings past midnight on warm nights and are not active during cooler periods of winter. Species is most active in mid-March through October. Winter hibernation occurs in debris piles, artificial and natural rock formations, rock crevasses and mammal burrows. Migration to communal dens occurs during spring and fall, aggregating in large numbers and often with other snake species. A combat dance is observed between males during mating season, entwining bodies until the weaker male retreats.

Reproduction
Sexual mature at 3 years, Mating occurs in the spring; 4-25 live young are born between August and October. Neonates measure approximately 10 inches at birth, but can range anywhere from 6-12 inches. They are born with a single button at the end of the tail that doesn’t produce the rattle sound until additional segments are added during successive shedding events. Males and females mate via copulation lasting several hours. The gestation period is 165 days. Females give birth to 10-20 neonates in the late summer or early fall. An ovoviviparous species, fertilized eggs are retained and prior to birth the young pierce the egg membranes and are born live. Birthing process can take 3-5 hours. Neonates leave the female within hours of birth and are heavily predated upon with a low survival rate.

Venom Profile
Venom consists of hemotoxic, myotoxic, cytotoxic, and hemorrhagic toxins. Cytotoxins destroy cells and tissue. Hemotoxins destroy red blood cells and target the circulatory system by interfering with blood pressure, platelets and clotting factors. Myotoxic causes paralysis and destroys skeletal muscle tissue. Hemorrhagic effects cause persistent bleeding. Antivenin treatment may require multiple doses over several days to neutralize the venom, which may cause permanent damage and disfigurement even when administered shortly after envenomation.

Range
Imperial, Riverside, San Bernardino, and San Diego counties.