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Western Rattlesnake
Crotalus viridis oreganus

Western Rattlesnake
Western Rattlesnake

    Land Tenure - Western Rattlesnake Habitat
  • Other Name: Northern Pacific Rattlesnake
  • Length : adults 60 - 150 cm.
  • Rattle at end of tail produces buzzing sound to warn off intruders.
  • Dark blotches banded with light-coloured edges along center of back; dark stripe below eye to corner of jaw.


British Columbia Blue List

Special Significance

In British Columbia, the small population of Western Rattlesnakes is restricted to the dry valleys of the Southern Interior. Their exaggerated reputation for danger has resulted in needless killing of rattlesnakes, drastically reducing some local populations. Agricultural development and urban expansion have also destroyed rattlesnake dens and foraging areas.


  • Eight subspecies of the Western Rattlesnake are recognized, but only C. viridis oreganus occurs in British Columbia at the northern end of its range, extending from California.
  • British Columbia population is small and confined to dry grasslands in Bunchgrass, Ponderosa Pine zones of Okanagan-Similkameen, Thompson, Nicola and Kettle valleys, as well as the Lytton-Lillooet portion of the Fraser Canyon.


  • Found in rocky terrain or talus areas in forest or grassland habitats
  • Migration takes place in spring to favorite foraging and basking areas up to 1 km from den.
  • In summer, rattlesnakes are found in open grassland and areas with high rodent densities. They bask on sunny, rocky ledges with scattered shrubs for shade.
  • Snakes hibernate from September to April, returning to the same communal den each year (which may be shared with other species).
  • Hibernating dens are in rock fissures or caves; located on south facing rocky slopes or ridges at elevations of 500 to 625m.


  • Mating occurs in late summer; females store sperm over winter with ovulation and fertilization occurring the following spring.
  • Pregnant females stop feeding and stay close to the den during summer as embryos develop; 13 to 14 months after mating, 2-8 young are born live in mid-September to early October.
  • Immediately after birth, the emaciated females enter hibernation; while the newborns stay near the den for 2 weeks, shed their skins, then also enter the den to hibernate.
  • Females undergo a total fasting period of 19 months or more during pregnancy and hibernation; reproduction takes place every 3 years on average, since females need to double body weight before breeding again.
  • Delayed reproduction commonly occurs because of long hibernation period and limited energy stores; reproduction often begins when female rattlesnakes are 7-9 years old.
  • A rattlesnake's maximum known lifespan is 25 years.

Food Habits

  • Adults eat mainly voles and mice, ground-nesting birds, pocket gophers, wood rats, squirrels, chipmunks, muskrats, ground squirrels, young marmots, and young rabbits; young eat mainly newborn voles and shrews.
  • Foraging occurs from dusk to dawn.
  • A snake's body coils and strikes forward when attacking prey; one-half of body length is the normal striking distance.
  • Prey are stabbed and injected with venom from hollow fangs; venom glands are located behind and below each eye on upper jaw.
  • Venom is chemically complex, but primarily acts to break down proteins (e.g. blood vessel walls); also affects nervous system.


  • Rattlesnake bites are very uncommon and very rarely fatal, although they could be dangerous to young children.
  • Snakes will only become aggressive if chased or cornered; they are shy creatures which normally seek cover when approached, and usually give people a warning rattle.
  • Some rattlesnakes do not have rattles, including young snakes and those which have been damaged by vehicles.
  • If you see or hear a rattlesnake, freeze, then move away, giving the snake a wide berth.
  • If you feel a snake is a threat, it is much safer to carefully capture a rattlesnake in a garbage can than to try to kill it. Release the snake as soon as possible above the capture location, to ensure they are able to return to their den site.
  • Rattlesnakes are protected from killing or capture under the British Columbia Wildlife Act.


  • Their low reproductive rate means a slow recovery rate after disturbances; small populations are especially vulnerable.
  • Extensive land development in the Okanagan has eliminated or fragmented their habitat (including dens and feeding grounds).
  • Many rattlesnakes are intentionally killed by humans as well as being killed on roadways
  • Overgrazing by livestock has reduced their population by limiting prey and cover.

Management Considerations

  • Leave 1 km buffer zone around known den sites and critical habitats.
  • Avoid road and skid trail construction near potential den sites such as rock outcroppings and talus slopes, and around known snake dispersal routes.
  • Avoid disturbing rock and woody debris in potential snake habitat.
  • Maintain good range condition in grasslands for cover and prey species.
  • Contact your local British Columbia Ministry of Water, Land and Air Protection if a den site is located.


1. Blood, D.A. 1993. Western Rattlesnake; Wildlife at Risk in British Columbia. Brochure. Ministry of Water, Land and Air Protection. Victoria, British Columbia.
2. Gregory, P.T. and R.W. Campbell. 1984. The reptiles of British Columbia. British Columbia Provincial Museum Handbook No. 44. Victoria, BC.
3. Orchard, S.A. 1984. Amphibians and Reptiles of British Columbia; an Ecological Review. Ministry of Forests. Victoria, British Columbia.


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