Western Rattlesnake (specifically the Northern Pacific Rattlesnake)
Crotalus oreganus (subspecies C. o. oreganus) • Order: Squamata, Suborder: Serpentes, Family: Viperidae, Subfamily: Crotalinae, Genus: Crotalus, Species: oreganus
Western North America, ranging from British Columbia, Canada, south through Washington, Oregon, and California, and east into Idaho, Nevada, and Utah.
Look up Western Rattlesnake (specifically the Northern Pacific Rattlesnake) in the Snake Encyclopedia →Venomous Status
Highly Venomous. Possesses solenoglyphous fangs (long, hollow, retractable fangs at the front of the maxilla).
Danger Level
Extremely Dangerous. High risk of severe localized tissue damage, systemic effects, and potential mortality if untreated. While generally not aggressive, they defend themselves vigorously if threatened.
Family
Order: Squamata, Suborder: Serpentes, Family: Viperidae, Subfamily: Crotalinae, Genus: Crotalus, Species: oreganus
Conservation
IUCN Red List: Least Concern. Faces threats from habitat loss, road mortality, and intentional killing by humans.
Physical Description
Heavy-bodied with a triangular head distinct from the neck. Dorsal pattern consists of dark brown or olive blotches with light borders on a tan, grayish, or greenish ground color. Features heat-sensing pits between the eyes and nostrils, vertical pupils, and heavily keeled scales. A distinctive rattle is present at the tail tip.
Size & Dimensions
The specimen pictured appears to be a mid-sized adult, approximately 24-30 inches long. Adults typically range from 24 to 48 inches (60-120 cm), with rare individuals reaching 60 inches.
Habitat
Highly versatile, occurring in grasslands, brush, woodlands, and rocky hillsides. Often found near outcrops or human structures from sea level to over 8,000 feet in altitude.
Behavior & Temperament
Primarily crepuscular or nocturnal during hot weather; diurnal in spring/fall. Its primary defense is camouflage and its rattle. It will coil and strike if the flight distance is breached. It is generally reclusive but can be highly defensive if cornered.
Diet & Feeding
Generalist carnivore. Preys on small mammals (mice, rats, ground squirrels), birds, and occasionally lizards. Uses ambush 'sit-and-wait' strategy, striking and releasing prey before tracking the scent trail.
Reproduction
Viviparous (gives birth to live young). Typically breeds in spring or autumn with births occurring in late summer. Litter sizes range from 4 to 21 neonates.
Venom Profile
Complex mixture of enzymes and proteins including hemotoxins (tissue destruction), cytotoxins, and in some populations, neurotoxic components (notably 'M Mojave-like' toxins).
Look-alikes
Often confused with the Gopher Snake (Pituophis catenifer), which lacks a rattle, has a narrower head, and round pupils. Also resembles other members of the Crotalus viridis complex.
Conservation Status
IUCN Red List: Least Concern. Faces threats from habitat loss, road mortality, and intentional killing by humans.
Cultural Significance
Significant in Indigenous American cultures as a symbol of power and caution. Ecologically vital for controlling rodent populations and serving as prey for raptors and kingsnakes.
Notable Features
Equipped with sophisticated infrared loreal pits for detecting warm-blooded prey in total darkness and a keratinous rattle used as an acoustic warning system to avoid accidental tramplings.