Online Field Guide to The Reptiles and Amphibians of Arizona

Chihuahuan Nightsnake (Hypsiglena jani) Arizona
County, AZ

Chihuahuan Nightsnake (Hypsiglena jani) Arizona
Orange phase, Coconino Co., AZ

DESCRIPTION: A small (up to about 600 mm or 23″ in total length) gray, or orange-tan snake with a row of small, dark, gray-brown blotches on the back (dorsal blotches). The dorsal blotches are usually in a single row but are sometimes offset at the midline of the back creating two rows of small, alternating blotches. A dark collar consisting of three united gray-brown blotches marks the neck. The central collar-blotch is a dark, narrow stripe that extends forward to the parietal scales (posterior-most large head plates). The two lateral components of the collar are larger than the central blotch and their edges fuse with those of the central blotch. A dark gray-brown bar extends back from each eye to the collar. The underside is plain pale gray. The head is relatively flat. The pupils are vertically elliptical and the scales are smooth.

DISTRIBUTION: This snake is distributed across the southern portion of the Colorado Plateau in northeastern Arizona and in sub-Mogollon Rim southeastern Arizona. It is found at elevations ranging from about 3,000′ to about 8,500′.

HABITAT: The Chihuahuan Nightsnake inhabits a wide variety of biotic communities ranging from Sonoran Desertscrub and Chihuahuan Desertscrub, through grasslands, and woodlands, and into cool Petran Montane Conifer Forest. It is found in an equally wide variety of terrain types ranging from the flat, open deserts to steep, rocky, wooded slopes. It seems to be most abundant in moderate terrain within desertscrub and grassland communities.

BEHAVIOR: This strictly nocturnal snake hibernates during the cold months of late fall and winter. When persistently harassed it often coils into a tight, spiraled shield or cone with the head tucked tightly against the center of the spiral. It is often encountered on remote roadways at night. It is mildly venomous but rarely bites when captured and its venom is not considered to be dangerous to humans.

DIET: The Chihuahuan Nightsnake uses mild venom injected by enlarged teeth in the rear upper jaw to subdue lizards and small snakes. It also eats reptile eggs, frogs, and a variety of insects.

REPRODUCTION: Mating probably takes place in spring and a clutch of up to 9 eggs is laid in spring or summer.

By Thomas C. Brennan

Bartlett. 2000. Snakes of North America: Western
Gulf Publishing Co. Houston, TX

Brennan, T. C., and A. T. Holycross. 2006. A Field Guide to Amphibians and Reptiles in Arizona. Arizona Game and Fish Department. Phoenix, AZ

Brennan, T. C., and A. T. Holycross. 2005. A Field Guide to Amphibians and Reptiles of Maricopa County. Arizona Game and Fish Department. Phoenix, AZ

Degenhardt, W. G., Painter, C. W., and Price, A. H.. 1996. Amphibians and Reptiles of New Mexico. University of New Mexico Press. Albuquerque.

Fowlie. 1965. The Snakes of Arizona. Azul Quinta Press, Fallbrook, California

Lowe, Schwalbe, Johnson. 1986. The Venomous Reptiles of Arizona. Nongame Branch
Arizona Game and Fish Department. Phoenix, AZ

Mulcahy, D.G. 2008. Phylogeography and species boundaries of the western North American Nightsnake (Hypsiglena torquata): Revisiting the species concept. Molecular Phylogenetics and Evolution. 46 1095-1115.

Stebbins. 1985. Western Reptiles and Amphibians. Houghton Mifflin. New York,

Chihuahuan Nightsnake (Hypsiglena jani) Arizona Range Map


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