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Canadian Amphibian and Reptile Conservation Network - Réseau Canadien de 
Conservation des Amphibiens et des Reptiles

Crotalus oreganus
Northern Pacific Rattlesnake / Crotale de l'Ouest


Northern Pacific Rattlesnake

Description
The Northern Pacific Rattlesnake is a moderately large, heavy-bodied snake with a distinctly triangular head and a rattle at the end of the tail. The eyes have vertical pupils. It is a tan or brownish snake with large brownish irregular blotches down the back and smaller blotches along the sides. The blotches are often lighter in the centre, dark at the edges but surrounded with a light border. Maximum adult size is over 1.6 m.

Confusing Species
Although there are no other species of rattlesnake in British Columbia, there are other blotched snakes which are commonly mistaken for rattlesnakes. The Great Basin Gophersnake tends to have a more regular checkered pattern to the blotches. Night Snakes, found in British Columbia, also have vertical pupils but are much smaller and more slender than Northern Pacific Rattlesnakes. Neither of these species has the typical triangular head and rattle of a rattlesnake.

Distribution
Northern Pacific Rattlesnakes are found in interior British Columbia and adjacent states as far south as central California.

Habitat
The Northern Pacific Rattlesnake is found in desert, short grass prairie and dry open scrubland. It is often seen near rock piles or boulders in areas with sandy soil but may also be found near farms and fields. This snake may also be found on rocky outcrops and talus slopes and in association with Prairie Dog towns.

Reproduction
Females begin breeding at an age of 6-8 years and probably do not breed every year. They are live bearing and produce 4-21 young up to 30 cm long. Young are born in late summer or fall.

Natural History
Rattlesnakes have heat sensing facial pits which allow them to locate warm blooded prey such as small mammals and birds. Farmers value them in reducing pests. They also eat reptiles and amphibians. They often hibernate communally in rock crevices or caves or individually in mammal burrows. In spring they may be seen basking at the entrance to a communal hibernaculum. They are an aggressive snake and when disturbed will coil, vibrate the rattle and strike. Although bites are rarely fatal Northern Pacific Rattlesnakes are venomous and should be treated with caution.

Conservation Concerns
Their communal denning habit makes this snake particularly vulnerable to persecution by people. The Northern Pacific Rattlesnake has been designated Threatened by COSEWIC because of its limited distribution in Canada, and the rapid loss of its habitat through urbanization and agriculture.