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Canadian Herpetological Society Société d'Herpétologie du Canada |
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Desert Nightsnake
Hypsiglena chlorophaea
Family: Colubridae
The subspecies of Desert Nightsnake that occurs in Canada is the Northern Desert Nightsnake (Hypsiglena chlorophaea deserticola).
COSEWIC status:- Endangered
- Endangered
- Not Assessed
Description
The Desert Nightsnake is beige, grey or brown with dark blotches on the back and sides and smooth scales. It has a large dark blotch extending back from each eye, another extending from the back of the head and one on each side of the neck. The belly is white to cream coloured and the pupils of the eyes are vertical. This is a small snake and adults only grow to about 60 cm in length.
Similar Species
The other blotched snakes in B.C., the Great Basin Gophersnake and the Western Rattlesnake, are much larger than Desert Nightsnakes, but juveniles of these species as well as the patterned juveniles of Western Yellow-bellied Racers may be confused with Desert Nightsnakes. The gophersnake has keeled scales and both gophersnake and racer have a round pupil. The rattlesnake can be distinguished by a more robust body, heat sensing facial pits, keeled scales and usually the presence of a rattle.
Distribution
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In Canada, the Desert Nightsnake appears to be limited to the southern portion of British Columbia’s Okanagan Valley, although it was only first discovered in Canada in 1980 and its range may be more extensive in southern BC. This species has a large North American range, which extends through the western U.S. and into Mexico.
Habitat
In Canada, the Desert Nightsnake occurs in arid grasslands and sagebrush habitats and is often associated with rocky areas and talus slopes. Rocks, logs and other cover objects are important microhabitat features, which this species uses for shelter. Desert Nightsnakes hibernate in rock crevices, talus slopes or mammal burrows.
Biology
Females lay an average of four eggs in late spring to early summer, which hatch in the late summer. Hatchlings range in size from 10–19 cm in length. Males of this species reach maturity in one or two years and age of maturity of females is not known. Individuals can live for more than 10 years, although little is known about maximum longevity. Nightsnakes are mainly nocturnal and most of the day is spent under cover. The nightsnake has mild venom, produced by the Duvernoy’s gland, and enlarged grooved teeth at the back of the upper jaw which pierce the prey and allow the venom to immobilize it. Desert Nightsnakes primarily consume lizards, frogs, salamanders and small snakes including juvenile rattlesnakes, although earthworms and insects will sometimes be eaten. This species is not considered harmful to people.
Threats
The rapid conversion of lowland habitats into agricultural and urban areas in the Okanagan Valley presents a significant threat to this species. Due to its very restricted range, this habitat loss has the potential to cause the extirpation of this species from Canada. Road mortality and human persecution are also threats in areas where roads and human settlements occur.