B.C. Reptiles & Amphibians

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Credit: Charles R. Peterson

Desert Nightsnake

Hypsiglena chlorophaea deserticola

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Description

The Desert Nightsnake is a small, slender snake that typically reaches sizes of 25 – 53 cm; larger individuals up to 60 cm are sometimes encountered, although they appear to be most common in the northern extent of the range. The have a relatively flat head that is slightly triangular, vertical pupils for night vision, and smooth scales. Their colouration is well adapted for camouflage in arid environments, consisting of a tan, grey, or light brown background colour with dark brown slightly square-shaped blotching. One of the best identifiers for Nightsnakes is the presence of black eye ‘mask’ that runs through each eye sometimes connecting to a dark ‘collar’ that forms around the neck at the base of the head.

Listen to the Indigenous words for “snake” here!

Similar Species

The Desert Nightsnake is very rare in British Columbia, and superficially resembles the Western Rattlesnake and Great Basin Gophersnake. Upon closer inspection, Nightsnakes can be easily differentiated from rattlesnakes with a few characteristics. First, Nightsnakes do not possess a rattle. They also have smaller markings, a less distinct neck, a slimmer head, and smooth scales (as opposed to keeled). Night Snakes also have a dark band through each eye and a dark collar-like neck marking that often blends with the eye bands. This neck marking is unique to Nightsnakes in British Columbia and can also be used as an identifier between Nightsnakes and Gophersnakes. Nightsnakes also possess a vertical pupil, like rattlesnakes, whereas Gophersnakes have a round pupil.

Western Rattlesnake

Great Basin Gophersnake

Desert Nightsnake

Distribution

The Desert Nightsnake is the rarest species of snake in British Columbia with very few observations per year. According to these few observations, their Canadian range appears to be heavily restricted to the south Okanagan and the southern Similkameen, which comprise the northern-most limit of the species. Further south in the United States, they appear to be much more common and range along the Pacific Coast from southern British Columbia to California and inland to northern Idaho in the North, south to Colorado and New Mexico.
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Habitat

Desert Nightsnakes are incredibly secretive and are rarely seen even when they are known to be in the area, due to their nocturnal nature. They spend the winter in hibernacula that may be shared with other snake species like Western Rattlesnakes, although they have never been documented at dens together in British Columbia. In British Columbia, they are associated with shrub-steppe habitat in the arid southern interior valleys, particularly in desert-like habitats. The few observational records of Nightsnakes in British Columbia have associated them with talus slopes and rock outcrops. In Idaho, Nightsnakes have been documented using old rodent burrows, suggesting these may also be important microhabitat features.

Reproduction

Next to nothing is known about the life history of Desert Nightsnakes in British Columbia, and there is little information for them in the United States. Night Snakes are oviparous and will lay 3 – 6 eggs in late spring or early summer. Nest sites have never been observed in British Columbia, but eggs are likely to be laid on south-facing slopes with adequate cover. The age of sexual maturity and longevity is not known, but it is assumed that these snakes live for 5 – 10 years.

Diet

Desert Nightsnakes are generalist predators of amphibians and reptiles, and their favourite foods are small lizards, lizard eggs, juvenile snakes, frogs, and toads. The main hunting strategy of the Desert Nightsnake is to ambush their prey by burrowing beneath the sand, using their colouration to camouflage them. They have slightly upturned eyes that help them to view the world, and approaching prey, from their hiding spots.

Conservation Status

Global: G5 (2016)

COSEWIC: E

SARA:1-E (2003)

Provincial: S2 (2018)

BC List: Red

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Threats

In addition to being the rarest snake in British Columbia, its range also coincides with one of the fastest developing areas in B.C. Human activities like urbanization, expansion of vineyards and orchards, rock removal for construction, and landscaping may impact habitat availability and connectivity for Desert Nightsnakes. The combination of these threats, the rarity of the species, and their restricted range has led to the Desert Nightsnake being federally listed as Endangered.

Little is known about the range, habitat, or behaviour of Desert Nightsnakes in B.C. If you see a Desert Nightsnake, please submit an observation report to the Ministry of Environment and Climate Change.
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Did You Know?

The Desert Nightsnake is the only rear-fanged snake in Canada. They have enlarged, grooved teeth in the back of their mouths that they use to inject a mild venom from a modified saliva gland into their prey.

Species Account Author: Marcus Atkins

References

B.C. Conservation Data Centre. 2009. Species Summary: Hypsiglena chlorophaea. B.C. Minist. of Environment. Available: https://a100.gov.bc.ca/pub/eswp/ (accessed Jun 16, 2021). 
B.C. Conservation Data Centre. 2018. Conservation Status Report: Hypsiglena chlorophaea. B.C. Minist. of Environment. Available: https://a100.gov.bc.ca/pub/eswp/ (accessed Jun 16, 2021). 
B.C. Conservation Data Centre. 2021. BC Species and Ecosystems Explorer. B.C. Minist. of Environ. Victoria, B.C. Available: https://a100.gov.bc.ca/pub/eswp/ (accessed Jun 16, 2021). 
COSEWIC. 2011g. COSEWIC status appraisal summary on the Desert Nightsnake Hypsiglena chlorophaea in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. xiii pp. 
Environment and Climate Change Canada. 2019e. Recovery Strategy for the Western Rattlesnake (Crotalus oreganus), the Great Basin Gophersnake (Pituophis catenifer deserticola) and the Desert Nightsnake (Hypsiglena chlorophaea) in Canada. Species at Risk Act Recovery Strategy Series. Environment and Climate Change Canada, Ottawa. Part 1, 28 pp., Part 2, A. 37 pp., B. 36 pp., C. 28 pp. 
Goldberg, S.R. 2001. Reproduction in the Night Snake, Hypsiglena torquata (Serpentes: Colubridae), from Arizona. Texas J. Sci. 53(2): 107-114. 
Lacey, H., C.H. Shewchuck, P.T. Gregory, M.J. Sarell, and L.P. Gregory. 1996. The occurrence of the Night Snake, Hypsiglena torquata, in British Columbia, with comments on its bodysize and diet. Can. Field-Nat. 110:620-625. 
Southern Interior Reptile and Amphibian Working Group. 2016d. Recovery plan for the Desert Nightsnake (Hypsiglena chlorophaea) in British Columbia. Prepared for the B.C. Ministry of Environment, Victoria, BC. 28 pp. 
https://www.bcreptiles.ca/snakes/night.htm 
http://www.canadianherpetology.ca/species/species_page.html?cname=Desert%20Nightsnake 
http://linnet.geog.ubc.ca/efauna/Atlas/Atlas.aspx?sciname=Hypsiglena%20chlorophaea&ilifeform=42