Western Rattlesnake (specifically the Great Basin or Prairie Rattlesnake)
Crotalus oreganus (cf. Crotalus viridis) • Order: Squamata, Suborder: Serpentes, Family: Viperidae, Subfamily: Crotalinae, Genus: Crotalus, Species: Crotalus oreganus
Broadly distributed across Western North America, from Southwestern Canada through the Western United States to Northern Mexico.
Look up Western Rattlesnake (specifically the Great Basin or Prairie Rattlesnake) in the Snake Encyclopedia →Venomous Status
Venomous; Solenoglyphous (possesses long, retractable fangs in the front of the upper jaw).
Danger Level
Extremely Dangerous; potential for medically significant bites that require antivenom. While rarely fatal with modern medical care, it can cause severe tissue damage.
Family
Order: Squamata, Suborder: Serpentes, Family: Viperidae, Subfamily: Crotalinae, Genus: Crotalus, Species: Crotalus oreganus
Conservation
Least Concern (IUCN); however, populations face threats from habitat fragmentation, road mortality, and intentional killing by humans.
Physical Description
Heavy-bodied with a triangular, distinct head. Coloration is typically tan, olive, or gray with large dark brown or black dorsal blotches surrounded by light halos. It features a visible rattle on the tail, vertical pupils, and heat-sensing pits between the eye and nostril.
Size & Dimensions
The specimen in the photo appears to be a smaller individual, likely 12-18 inches in length. Adults typically range from 24 to 48 inches (max recorded approx. 60 inches).
Habitat
Extremely versatile, occupying sagebrush plains, grasslands, rocky hillsides, ponderosa pine forests, and agricultural edges. It ranges from sea level to over 11,000 feet in elevation.
Behavior & Temperament
Generally shy and retiring. When threatened, it will coil and rattle its tail as a defensive warning. They are crepuscular or nocturnal during hot summer months and diurnal in spring and fall.
Diet & Feeding
Active foragers and ambush predators. Diet consists mainly of small mammals (voles, mice, ground squirrels), birds, and occasionally lizards or amphibians.
Reproduction
Viviparous (gives birth to live young). Litters typically range from 4 to 12 young, born in late summer or early fall. Females may only breed every 2 to 3 years.
Venom Profile
Primarily hemotoxic and cytotoxic, causing tissue necrosis, swelling, and blood clotting interference. Some populations of Crotalus oreganus also contain neurotoxic components.
Look-alikes
Gopher snake/Bullsnake (Pituophis catenifer), which lacks the rattle and heat pits, and has round pupils. Juvenile racers or kingsnakes may also have similar blotched patterns.
Conservation Status
Least Concern (IUCN); however, populations face threats from habitat fragmentation, road mortality, and intentional killing by humans.
Cultural Significance
Iconic symbol of the American West. Ecosystem service provider by controlling rodent populations and preventing the spread of zoonotic diseases like Lyme disease.
Notable Features
The rattle is composed of modified keratin scales that produce a high-frequency buzz. Heat-sensing pits allow the snake to 'see' the infrared signatures of warm-blooded prey in total darkness.