Description
A medium-sized 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. Species lacks diagonal dark stripe across the eye. The head appears gray on the sides and brownish on the top. Coloration of the rest of the body harmonizes with its habitat ranges from off-white, yellowish, gray, tan, and pinkish to pale orange and brown. Patterns consist of dark speckled banded markings across the entirety of the body, with black and ash-gray rings surrounding the tail near the rattle. Adult range from 23-52 inches in length, averaging 2-3.5 feet.

Habitat
Commonly found throughout southern and southeastern California. Inhabits mostly arid areas alongside buttes, mesas, and desert outcroppings that are vegetated by sagebrush, creosote, thorn scrub, chaparral, pinon-juniper woodland, and succulent desert. Den sites are characterized by rocky outcrops. Home range size averages 9-25 hectares with males almost double the size of females.

Diet
Specializes in small mammals including mice, rats, rabbits, and gophers with a preference for squirrels and pocket mice. Secondary prey includes ground dwelling birds, lizards, and other small animals. Juveniles feed more on ectotherms, e.g. lizards and other small snakes, transitioning predominantly to mammals and birds as they become adults. Feeding frequency drops significantly during mating season in the spring.

Behavior
Typically unaggressive. Prefers to remain motionless and quiet as first line of defense, but will coil and rattle if threatened or move away from threats. May strike and bite if provoked or startled. Active from late-March through early November depending on local environmental conditions. Primarily nocturnal during periods of excessive high heat in the summer, but active in the early daytime hours when the temperatures are cooler and moderate. Tends to be diurnal during the spring and fall especially in areas where their range overlaps with sidewinders which are primarily nocturnal. Overwinters in subterranean dens, rock crevices, caves, and under houses, outbuildings, wood piles, and debris. Denning occurs individually or in small groups of 10 or less. Species migrate seasonally between overwintering sites and summer ranges and have been reported moving up to 1.5 km between sites. Movement is strongly correlated to temperature and is most pronounced during the mating season in both frequency of movement and distance traveled. Species typically use the same pathways when traveling between overwintering sites and summer ranges. Home ranges vary in size from 9-29 acres. Species occupy habitat within 1,600 feet from denning sites for females and 3,600 feet for males. Movement between sites generally occurs infrequently, where individuals stay at a site for several days before relocating.

Reproduction
Mating occurs from late-April to early June within 3-6 weeks after emergence from overwintering sites. Species does not breed again in the fall like other pit vipers in North America. Reproduction in females likely occurs biennially (once every other year) at most and some may reproduce every 3-4 years. The female stores sperm until the following year and gives birth to 2-12 live young between July and August. Neonates measure 8.5-10.5 inches at birth and 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. Males reach sexual maturity between the ages of 3 and 5 and females from 5 to 7. Females eat sparingly or not at all while gravid (with young) and forgo eating after giving birth until they emerge the following spring emaciated. It generally takes 2-3 years to rebuild fat reserves before repeating the breeding cycle.

Venom Profile
Venom in a mixture of hemotoxic and neurotoxic chemicals. Hemotoxic proteins target the circulatory system by interfering with blood pressure, platelets and clotting factors, causing hemorrhaging through weakening of the blood vessel walls. Neurotoxins can cause paralysis, weakness, respiratory failure and muscular twitching. Venom from this species is known to cause blood plasma coagulation and rapid hydrolysis, but completely lacks hemorrhagic activity. Speckled rattlesnake bites are uncommon. 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, Kern*, Los Angeles, Orange, Riverside, San Bernardino, and San Diego counties.

*Indicates counties where the species’ range extends only into a minor portion of the county.