The Reptiles and Amphibians of Arizona

Online Field Guide to The Reptiles and Amphibians of Arizona

Thornscrub Hook-nosed Snake (Gyalopion quadrangulare) Arizona

Santa Cruz County, AZ

Santa Cruz Co., AZ	Santa Cruz Co., AZ	Santa Cruz Co., AZ

Santa Cruz Co., AZ	Santa Cruz Co., AZ	Santa Cruz Co., AZ

THORNSCRUB HOOK-NOSED SNAKE
Gyalopion quadrangulare

Non-Venomous

DESCRIPTION: A small (up to 300 mm or 12″ in total length) relatively stocky snake with a bold pattern of black saddles on a light cream to off-white background. Black saddles interrupt a wide, red to orange stripe on each side of the body. The black saddles are solid and rectangular on the dorsal surface and taper to a point on the lower sides. White spots mark the black saddles on the tapered lateral aspects. A black mask crosses the top of the head and covers the eyes. The ventral surface is pale cream. The pupils are round and the scales are smooth and shiny. The scale on the snout (rostral) is concave on top and noticeably upturned along the leading edge. The subcaudal scales are bifid (divided), distinguishing this snake from the Long-nosed Snake.

DISTRIBUTION: This snake only enters Arizona in a small portion of Santa Cruz County near the border with Mexico. In our state it is found at elevations between 3,500′ and 5,500′.

HABITAT: In Arizona this snake inhabits rolling mesquite-covered hills and oak-lined drainages within the Madrean Evergreen Woodland and Semidesert Grassland communities. It is usually encountered in areas with gravelly soil.

BEHAVIOR: This secretive ground-dweller spends most of it’s time burrowed underneath the soil. It is primarily nocturnal but occasionally encountered on the surface just before sunset. Encounters are often associated with recent rains.

DIET: It presumably uses its “hooked” snout to root through surface debris and under rocks and logs for prey which consists of scorpions, spiders, and a variety of insects.

REPRODUCTION: Reproductive behavior is poorly known. It lays clutches of up to 6 eggs.

By Thomas C. Brennan

Babb, R.D., G.L. Bradley, T.C. Brennan, A.T. Holycross. 2005. A preliminary assessment of the diet of Gyalopion quadrangulare. (Serpentes: Colubridae). Southwestern Naturalist 50(3).

Bartlett. 2000. Snakes of North America: Western Region. 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

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

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

Thornscrub Hook-nosed Snake (Gyalopion quadrangulare) Arizona Range Map

Visit Partners in Amphibian and Reptile Conservation:

If you make use of the textual contents of this site in reports, publications, etc. please cite and credit the author(s) and photographer(s). All photos on this website are copyrighted. However, those found in the species account section may be used for any noncommercial scientific, educational, or conservation purposes provided that photographs are not altered and continue to bear the copyright symbol and name of the photographer. Please contact the photographer regarding commercial use of copyrighted photographs.