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. The coloration varies from tan, yellowish, orange, and brown to gray and off-white. Patterns consist of dark blotches and small bands that give a geometrical “speckled” appearance that follows the dorsal surface to the sides. The color and patterns generally remain the same down the tail, with the last bands creating one large black band just before the rattle. Species lacks diagonal dark stripe across the eye. Adult range from 23-52 inches in length.

Habitat
Ranges throughout southeastern California from the eastern Sierra Nevada north of the Mojave River to the Nevada border. Inhabits desert mountains, canyons, foothills, buttes, and erosion gullies in rocky desert and scrub areas and less commonly in chaparral and pinyon-juniper woodland up to 8,000 feet in elevation.

Diet
Specializes in small mammals including mice, rats, 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
Most active from April through October. Typically crepuscular, mostly active from early evening until temperatures cool. Occasionally active during the day when temperatures are moderate. Uncommonly encountered by people due to the habitat and elevations it inhabits. Ambush predator, but may seek out prey by following scent trails. Typically unaggressive. Prefers to remain motionless as first line of defense, but may rattle and strike if threatened.

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. Females give birth to 2-12 live between July and August. Neonates measure approximately 10 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. An ovoviviparous species requires considerable energy from the female, fertilized eggs are retained and prior to birth the young pierce the egg membranes and are born live.

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. Panamint rattlesnake bites are uncommon primarily due to the landscapes it inhabits which are away from urban interfaces. 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
Inyo, Kern, Los Angeles*, Mono*, and San Bernardino* counties.

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