Western Rattlesnake (Northern Pacific variant)
Crotalus oreganus • Order: Squamata, Suborder: Serpentes, Family: Viperidae, Subfamily: Crotalinae, Genus: Crotalus, Species: C. oreganus
Western North America from British Columbia, Canada, southward through the western United States to Baja California, Mexico.
Look up Western Rattlesnake (Northern Pacific variant) in the Snake Encyclopedia →Venomous Status
Venomous (Solenoglyphous fangs)
Danger Level
High Risk; bites are serious medical emergencies and can be life-threatening if untreated, though mortality is low with prompt antivenom treatment.
Family
Order: Squamata, Suborder: Serpentes, Family: Viperidae, Subfamily: Crotalinae, Genus: Crotalus, Species: C. oreganus
Conservation
IUCN Least Concern; threatened locally by habitat loss and human persecution.
Physical Description
Heavy-bodied with a distinct triangular head, vertical pupils, and a rattle at the end of the tail. Markings consist of dark brown or blackish blotches with light borders on a tan, gray, or olive background. Scales are heavily keeled.
Size & Dimensions
Specimen appears to be a medium adult (~60-90 cm); typical species range is 60 cm to 120 cm.
Habitat
Highly adaptable; found in grasslands, brush, rocky hillsides, and forest edges from sea level up to 2,500 meters. Often found in rocky outcrops or woodpiles.
Behavior & Temperament
Generally reclusive and avoids humans. If threatened, it will coil and rattle as a defensive warning. Most bites occur when the snake is stepped on or harassed.
Diet & Feeding
Generalist carnivore feeding primarily on small mammals (rodents, rabbits), birds, and occasionally lizards; uses a sit-and-wait ambush strategy.
Reproduction
Viviparous (gives birth to live young); typical litter size 4-21 neonates born in late summer or early autumn.
Venom Profile
Complex mixture of hemotoxins and cytotoxins causing tissue damage, swelling, and blood clotting interference; some populations exhibit neurotoxic components.
Look-alikes
Gopher Snake (Pituophis catenifer) which mimics the rattle's sound and pattern but lacks the triangular head, fangs, and heat-sensing pits.
Conservation Status
IUCN Least Concern; threatened locally by habitat loss and human persecution.
Cultural Significance
Ecologically vital for controlling rodent populations; culturally iconic as a symbol of the American West.
Notable Features
Equipped with heat-sensing loreal pits between the eye and nostril to detect warm-blooded prey in the dark, and a tail rattle made of keratin segments.