Thamnophis cyrtopsis 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Reptilia Squamata Natricidae

Scientific Name: Thamnophis cyrtopsis (Kennicott, 1860)
Common Name(s):
English Black-necked Gartersnake, Blackneck Garter Snake

Assessment Information [top]

Red List Category & Criteria: Least Concern ver 3.1
Year Published: 2013
Date Assessed: 2012-05-10
Assessor(s): Hammerson, G.A.
Reviewer(s): Bowles, P.
Listed as Least Concern in view of the large and probably relatively stable extent of occurrence, area of occupancy, number of subpopulations, and population size. No major threats are known.
Previously published Red List assessments:

Geographic Range [top]

Range Description:Range extends from southern Colorado and Utah south through Arizona, New Mexico, western and central Texas in the United States, and much of Mexico to Guatemala, at elevations from near sea level to around 2,700 meters (8,700 feet) (Webb 1980, Rossman et al. 1996, Stebbins 2003). The distribution is spotty in many areas.
Countries occurrence:
Guatemala; Mexico; United States
Additional data:
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:This species is represented by many occurrences or subpopulations. Webb (1980) mapped over 200 collection sites across the entire range. The total adult population size is unknown but certainly exceeds 10,000 and probably exceeds 100,000. This snake is often common in suitable habitat (Woodin 1953, Minton 1959, Tennant 1984). Its extent of occurrence, area of occupancy, number of subpopulations, and population size are probably relatively stable. Possible declines have been recorded at the extreme northern limit of the range in southwestern Colorado (Hammerson 1999).
Current Population Trend:Stable
Additional data:

Habitat and Ecology [top]

Habitat and Ecology:This snake occurs in a wide range of habitats, from desert flats, dry grasslands, and tropical lowlands to pine-oak habitats and cloud forest in mountains; in the southwestern United States it is often in the vicinity of permanent and intermittent streams, spring seepages, and irrigation canals, usually in canyons, foothills, or mountains (Stebbins 2003). It inhabits rocky hillsides and limestone ledges, and wooded ravines and cedar brakes, in the Texas Hill Country (Tennant 1984). In Mexico, habitats include tropical barrancas, thorny scrub forest, tropical deciduous forest, and upper arid or mixed boreal-tropical cloud forest (Rossman et al. 1996). This snake wanders far from water into adjacent grassland, desert, woodland, and shrubland, but mostly it is restricted to the vicinity of consistent water sources in the arid southwest (Jones 1990).
Systems:Terrestrial; Freshwater
Movement patterns:Not a Migrant

Use and Trade [top]

Use and Trade: This species is little used in the pet trade.

Threats [top]

Major Threat(s): No major threats are known. In some areas, habitat has been lost or degraded as a result of urbanization, deforestation, or conversion to intensive agricultural uses. In some areas, this species may be collected for the pet trade, but this is not a significant threat.

Conservation Actions [top]

Conservation Actions: Currently, this species is of relatively low conservation concern and does not require significant additional protection or major management, monitoring, or research action. At least several occurrences of this species are in protected areas.

Classifications [top]

1. Forest -> 1.4. Forest - Temperate
1. Forest -> 1.5. Forest - Subtropical/Tropical Dry
1. Forest -> 1.6. Forest - Subtropical/Tropical Moist Lowland
1. Forest -> 1.9. Forest - Subtropical/Tropical Moist Montane
3. Shrubland -> 3.4. Shrubland - Temperate
3. Shrubland -> 3.5. Shrubland - Subtropical/Tropical Dry
3. Shrubland -> 3.6. Shrubland - Subtropical/Tropical Moist
4. Grassland -> 4.4. Grassland - Temperate
5. Wetlands (inland) -> 5.1. Wetlands (inland) - Permanent Rivers/Streams/Creeks (includes waterfalls)
5. Wetlands (inland) -> 5.2. Wetlands (inland) - Seasonal/Intermittent/Irregular Rivers/Streams/Creeks
5. Wetlands (inland) -> 5.4. Wetlands (inland) - Bogs, Marshes, Swamps, Fens, Peatlands
5. Wetlands (inland) -> 5.5. Wetlands (inland) - Permanent Freshwater Lakes (over 8ha)
5. Wetlands (inland) -> 5.6. Wetlands (inland) - Seasonal/Intermittent Freshwater Lakes (over 8ha)
5. Wetlands (inland) -> 5.7. Wetlands (inland) - Permanent Freshwater Marshes/Pools (under 8ha)
5. Wetlands (inland) -> 5.8. Wetlands (inland) - Seasonal/Intermittent Freshwater Marshes/Pools (under 8ha)
5. Wetlands (inland) -> 5.9. Wetlands (inland) - Freshwater Springs and Oases
8. Desert -> 8.2. Desert - Temperate

In-Place Research, Monitoring and Planning
In-Place Land/Water Protection and Management
  Occur in at least one PA:Yes
In-Place Species Management
In-Place Education

♦  Pets/display animals, horticulture

Bibliography [top]

Hammerson, G.A. 1999. Amphibians and reptiles in Colorado. Second edition. University Press of Colorado, Boulder, Colorado.

IUCN. 2013. IUCN Red List of Threatened Species (ver. 2013.2). Available at: (Accessed: 13 November 2013).

Jones, K.B. 1990. Habitat use and predatory behavior of Thamnosis cyrtopsis (Serpentes: Colubridae) in a seasonally variable aquatic environment. Southwestern Naturalist 35: 115-122.

Köhler, G. 2003. Reptiles of Central America. Herpeton, Germany.

Minton, S.A. 1959. Observations on amphibians and reptiles of the Big Bend region of Texas. Southwestern Naturalist 3: 28-54.

Rossman, D.A., Ford, N.B. and Seigel, R.A. 1996. The Garter Snakes. University of Oklahoma Press, Norman, Oklahoma and London, UK.

Stebbins, R.C. 2003. A Field Guide to Western Reptiles and Amphibians. Third Edition. Houghton Mifflin Company, Boston, Massachusetts.

Tennant, A. 1984. The Snakes of Texas. Texas Monthly Press, Austin, Texas. 561 pp.

Webb, R.G. 1980. Thamnophis cyrtopsis (Kennicott) Black-necked garter snake. Catalogue of American Amphibians and Reptiles 245: 1-4.

Wilson, L.D., Townsend, J.H. and Johnson, J.D. (eds). 2010. Conservation of Mesoamerican Amphibians and Reptiles. pp. 816. Eagle Mountain Publishing, Eagle Mountain, Utah.

Woodin III, W.H. 1953. Notes on some reptiles from the Huachuca area of southeastern Arizona. Bulletin of the Chicago Academy of Science 9: 285-296.

Citation: Hammerson, G.A. 2013. Thamnophis cyrtopsis. The IUCN Red List of Threatened Species 2013: e.T63975A3132338. . Downloaded on 24 June 2018.
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