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Canadian Herpetological Society Société d'Herpétologie du Canada |
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Prairie Rattlesnake
Crotalus viridis
Family: Viperidae
COSEWIC status:- Special Concern
- Special Concern
- Least Concern
Description
The Prairie Rattlesnake is a moderately large, heavy-bodied snake that can reach adult lengths of 1.6 m. It has a distinctly triangular head, vertical pupils, heat-sensing facial pts and usually a rattle at the end of the blunt tail. The body colour is tan or light brown with darker brown dorsal blotches that turn into banding near the tail and smaller blotches along the sides. The blotches are often lighter in the centre, dark at the edges and bordered by whitish-yellow.
Similar Species
Although there are no other rattlesnake species in Saskatchewan or Alberta, the Bullsnake and Plains Hog-nosed Snake can be mistaken for rattlesnakes. However, neither of these species have vertical pupils and both have a tail that tapers to a fine point without a rattle. Further, Western Hog-nosed Snakes have a distinct upturned nose and large dark “ear spots” just behind the head.
Distribution
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In Canada, the Prairie Rattlesnake is found in southwestern Saskatchewan and southern Alberta. They are widely distributed throughout the central U.S. and their range extends into northern Mexico.
Habitat
The Prairie Rattlesnake inhabits prairie, scrubland, badlands, fields and rocky outcrops, and in Canada they are often associated with river valleys and coulees. Rocks, shrub cover and underground burrows are important microhabitat features. They overwinter communally in underground cavities and mammal burrows. Prairie Rattlesnakes will often occupy Prairie Dog towns where underground retreats and a quick meal are readily available. Cover objects, such as rocks, low-lying vegetation and dead wood, are important microhabitat features. Open habitats with adequate cover and retreat sites are used for gestation, and they are typically within close proximity to hibernacula.
Biology
In Canada, the Prairie Rattlesnake is only active for about four months of the year, from mid-May until mid-September. Females begin breeding at an age of four to seven years and reproduce every one to three years; males reach maturity in three to four years. Individuals of this species may live for as long as 30 years. Mating generally occurs in the late summer and an average of 10 live young are born in late summer of the following year. Prairie Rattlesnakes are most active in the morning and afternoons, but in hot weather they may shift to nocturnal behaviour. They primarily eat small mammals and, like all rattlesnakes, they have heat-sensing facial pits which helps them to locate their warm-blooded prey they. Rattlesnakes have venom, which they use to subdue their prey. They will also eat birds, lizards, frogs and other snakes. Since they prey largely on small mammals, rattlesnake populations help to control rodents and other pests and are an asset to farming communities. In spring and fall they can be found basking, often in high abundance, at the entrance to their hibernacula. Their primary defensive strategies are to rely on their cryptic camouflage to remain hidden, withdraw into a nearby retreat site or rattle to warn other animals to keep away; they generally bite only as a last resort. Anyone who is bitten by a rattlesnake should seek medical assistance.
Threats
The conversion of natural grasslands to agricultural uses reduces the available habitat for this species in Canada. Road mortality may contribute to population declines where roads bisect this species’ habitat, especially in areas where traffic volume is high. Human persecution is also a serious threat to this species because, unfortunately, many people are misinformed about the risks that rattlesnakes pose to humans and they kill them on sight. However, humans can live and work safely in areas where rattlesnakes exist.