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Plains Black-headed Snake (Tantilla nigriceps)

[/vc_column_text][gap size=”12px” id=”” class=”” style=””][/vc_column][/vc_row][vc_row][vc_column width=”1/2″][vc_single_image image=”2111″ img_size=”large” alignment=”center” style=”vc_box_rounded”][vc_column_text]Plains Black-headed Snake, Cochise County, AZ. Photo by Jim Rorabaugh[/vc_column_text][/vc_column][vc_column width=”1/2″][vc_row_inner][vc_column_inner width=”1/2″][vc_single_image image=”2410″ img_size=”medium” alignment=”center” onclick=”img_link_large”][vc_column_text]Plains Black-headed Snake, Cochise County, AZ. Photo by Jim Rorabaugh[/vc_column_text][gap size=”12px” id=”” class=”” style=””][/vc_column_inner][/vc_row_inner][/vc_column][/vc_row][vc_row][vc_column width=”1/6″][/vc_column][vc_column width=”2/3″][vc_column_text]

Description

The Plains Black-headed Snake (Tantilla nigriceps) is a small (< 423 mm TL, although most are < 250 mm) and slender, secretive species.  The head is not distinct from the neck.  It is tan, yellowish-brown, or cream dorsally with a dark gray-brown or black head cap that extends 2-6 (mostly 3-4 in Arizona) scales behind the furrow between the parietal scales. The posterior edge of the head cap tapers to a point or is convex, sometimes irregularly so.  There is no light neck collar posterior to the head cap.  Dorsal scales only rarely exhibit minute dark spots or maculations.  The venter is white or cream with a broad red, pink, or orange stripe (Cole and Hardy 1981, Degenhardt et al. 1996, Ernst and Ernst 2003, Painter et al. 2003, Wilson and Mata-Silva 2014).

The loreal scale is absent and the anterior infralabials are usually in contact.  Gular scale counts in Arizona specimens range from 16-29, but most (79%) have 21 or more.  The dorsal scales are smooth, without pits, and are arranged in 15 rows throughout the length of the body.  Males and females have 123-153 and 135-168 ventrals and 43-66 and 21-58 subcaudals, respectively (Wilson and Mata-Silva 2014).  The anal plate and subcaudals are divided (Ernst and Ernst 2003).  A pair of slightly enlarged, grooved teeth are present in the rear of the upper jaw that may serve to deliver toxins from a Duvernoy’s gland to prey.  No subspecies are currently recognized (Crother 2012).

Within its range in Arizona and the 100-Mile Circle, the Plains Black-headed Snake is most likely to be confused with the other three Arizona Tantilla.  It is readily distinguished from the Chihuahuan (T. wilcoxi) and Yaqui (T. yaquia) Black-headed Snakes by the absence of a light neck collar.  Those other two species always have a bold light collar.  Distinguishing Smith’s Black-headed Snake (T. hobartsmithi) from the Plains Black-headed Snake can, at times, be difficult.  Refer to the account for that species for diagnostic characters.  However, some specimens, particularly from the San Pedro River Valley, defy categorization to one species or the other.

Arizona Tantilla specimens in museums have frequently been misidentified.  In southeastern Arizona, many T. hobartsmithi specimens have been misidentified as Plains Black-headed Snakes, obscuring the actual distribution of the latter species.  Based on examination of available specimens by the author and others, the distribution of the Plains Black-headed Snake in Arizona appears to be limited to the Sulphur Springs Valley (from about Bonita to Elfrida), around the southern base of the Chiricahua and Pedregosa mountains,  a site near Thatcher, and Texas Canyon between the Dragoon and Little Dragoon Mountains.  Some Tantilla from the San Pedro River Valley are difficult to categorize as either T. nigriceps or T. hobartsmithi; however, no clearly diagnosable specimens of T. nigriceps are known from that valley, except for the west side of Texas Canyon. Range wide, the species is known from southeastern Arizona and portions of New Mexico, Colorado, Nebraska, Kansas, Oklahoma, and western and central Texas south into the Mexican states of Chihuahua, Coahuila, Nuevo Leon, Tamaulipas, and Durango (Ernst and Ernst 2003, Wilson and Mata-Silva 2014).  It is not known from Sonora, but may occur in the northeastern valleys of the state.

In Arizona, the Plains Black-headed Snake is found in valleys or bajadas, most often in semi-desert grassland.  Elevational range in Arizona is 670-1675 m.  Rosen et al. (1996) considered it a species of the grassland biome, whereas Smith’s Black-headed Snake, where it occurred in close proximity, was typically a species of Chihuahuan desertscrub.  That said, the Plains Black-headed Snake has been found in Chihuahuan desertscrub near Portal and around the base of the Chiricahua Mountains.  In Texas Canyon it has been found in oak savanna. It is found in a variety of vegetation communities and terrain in New Mexico (Degenhardt et al. 1996).  The species was not uncommonly encountered in riparian thickets on the Rio Grande in New Mexico and Texas, where it was taken in funnel and pitfall traps (Chung-MacCoubrey and Bateman 2006, Bateman et al. 2009).  It should be looked for in similar habitats within its range in Arizona.

This species is surface active at night when it can be found on roads, but it hides under rocks, logs, and other surface debris during the day.  It has been collected from February into September in Arizona, but most are found in August.  It is susceptible to desiccation and unlikely to be found surface active or under surface debris in dry periods or seasons.

Snakes likely mate in the spring and 1-3 eggs are laid in June or July, which hatch 2-3 months later (Degenhardt et al. 1996, Ballinger et al. 2010, Goldberg 2016).  Hatchlings are 100-128 mm TL and resemble the adults, and the smallest adults of the western form of T. nigriceps are about 225mm TL (Wright and Wright 1957, Degenhardt et al. 1984, Ernst and Ernst 2003).

The diet includes mostly small invertebrates such as tenebrionid beetle larvae, snails, centipedes, millipedes, worms, spiders, and insect larvae (Ernst and Ernst 2003, Tennant 1998).  They will also take relatively large Scolopendra centipedes (LaDuc et al. 1996), and have eaten beetle and termite larvae, small brown centipedes, and small slugs in captivity (Tennant 1998).

The Plains Black-headed Snake is listed as a species of least concern on the 2014 IUCN Red List.  With a valid Arizona hunting license, four can be captured per year or held in possession.  For a variety of reasons, grasslands in Arizona have been in decline for many decades (Bahre 1995, Bodner et al. 2012).  It is possible that desertification of grasslands could adversely affect the Plains Black-headed Snake, although there is as yet no evidence of that (see Mendelson and Jennings 1992).

Acknowledgments: Andy Holycross, Tom Brennan, and Randy Babb assisted with the examination of specimens upon which Arizona T. nigriceps and T. hobartsmithi scalation counts and characterizations are based.

Suggested Reading:

Bahre, C.J. 1995. Human impacts on the grasslands of southeastern Arizona. Pages 230-264 in M.P. McClaran and T.R. Van Devender (editors), The Desert Grassland. University of Arizona Press, Tucson.

Ballinger, R.E., J.D. Lynch, and G.R. Smith. 2010. Amphibians and reptiles of Nebraska. Rusty Lizard Press, Oro Valley, AZ.

Bateman, H.L., A. Chung-MacCoubrey, H.W. Snell, and D.M. Finch. Abundance and species richness of snakes along the middle Rio Grande riparian forest in New Mexico. Herpetological Conservation and Biology 4(1):1-8.

Bodner, G.S., P. Warren, D. Gori, K. Sartor, and S. Bassett. 2012. Sustaining the grasslands sea: Regional perspectives on identifying, protecting and restoring the sky island region’s most intact grassland valley landscapes. Pages 399-409 in G.J. Gottfried, P.F. Ffolliott, B.S. Gebow, L.G. Eskew, L.C. Collins (compilers), Proceedings: Merging science and management in a rapidly changing world: Biodiversity and management of the Madrean Archipelago III and 7th Conference on Research and Resource Management in the Southwestern Deserts. May 1-5 2012. Tucson, AZ. RMRS-P-67. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station.

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

Chung-MacCoubrey, A.L., and H.L. Bateman. 2006. Herpetological communities of the middle Rio Grande bosque: What do we know, what should we know, and why? Pp. 57-66 in USDA Forest Service Proceedings RMRS-P-42CD, CO.

Cole, C.J., and L.M. Hardy. 1981. Systematics of North American colubrid snakes related to Tantilla planiceps (Blainville).  Bulletin of the American Museum of Natural History 171(3):199-284.

Crother, B.I. 2012. Scientific and standard English names of amphibians and reptiles of North America north of Mexico, with comments regarding confidence in our understanding, seventh edition. Society for the Study of Amphibians and Reptiles, Herpetological Circular (39):1-92.

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

Ernst, C.H., and E.M. Ernst. 2003. Snakes of the United States and Canada. Smithsonian Books, Washington, D.C.

Goldberg, S.R. 2016. Reproduction in the Plains Black-headed Snake, Tantilla nigriceps (Serpentes, Colubridae) from New Mexico. Sonoran Herpetologist 29(4):47-50.

LaDuc, T.J., D.I. Lannutti, M.K. Ross, and D. Beamer. 1996. Lampropeltis getulus splendida (desert kingsnake). Diet. Herpetological Review 27:25.

Mendelson, J.R. III, and W. B. Jennings. 1992. Shifts in the relative abundance of snakes in a desert grassland. Journal of Herpetology 26(1):38-45.

Painter, C.W., D.S. Sias, D. Salceies, and P.E. Humphrey. 2003. Tantilla nigriceps (Plains Black-headed Snake). Maximum Size. Herpetological Review 34(2):157.

Rosen, P.C., S.S. Sartorius, C.R. Schwalbe, P.A. Holm, and C.H. Lowe. 1996. Draft annotated checklist of the amphibians and reptiles of the Sulphur Springs Valley, Cochise County, Arizona. Final report, part 1, to the Arizona Game and Fish Department, Phoenix.  Heritage Program, IIPAM Project No. I92052.

Tennant, A. 1998. A Field Guide to the Snakes of Texas. Gulf Publishing Company, Houston, TX.

Wilson, L.D., and V. Mata-Silva. 2014. Snakes of the genus Tantilla (Squamata: Colubridae) in Mexico: taxonomy, distribution, and conservation. Mesoamerican Herpetology 1(1):5-95.

Wright, A.H., and A.A. Wright. 1957. Handbook of Snakes of the United States and Canada.  Volumes I and II. Comstock Publishing Associates, Cornell University Press, New York, NY.

Author: Jim Rorabaugh

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