Regularity: Regularly occurring
Type of Residency: Year-round
Global Range: (200,000 to >2,500,000 square km (about 80,000 to >1,000,000 square miles)) The range extends from southern Colorado and Utah south through Arizona, New Mexico, western and central Texas, 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.
Distribution: SW USA (S Colorado, Utah, Arizona, Texas, New Mexico), Mexico (Aguascalientes, Tamaulipas), Guatemala ocellatus: Edwards Plateau of SC Texas west to the Big Bend. postremus: Mexico (Michoacan) vicinus: Mexico (Michoacan)
Length: 109 cm
Colorado Plateau Shrublands Habitat
This taxon can be found in the Colorado Plateau shrublands, as one of its North American ecoregions of occurrence. The Plateau is an elevated, northward-tilted saucer landform, characterized by its high elevation and arid to semi-arid climate. Known for the Grand Canyon, it exhibits dramatic topographic relief through the erosive action of high-gradient, swift-flowing rivers that have downcut and incised the plateau. Approximately 90 percent of the plateau is drained by the Colorado River and its tributaries, notably the lower catchment of the Green River.
A pinyon-juniper zone is extensive, dominated by a pygmy forest of Pinyon pine (Pinus edulis) and several species of juniper (Juniperus spp). Between the trees the ground is sparsely covered by grama, other grasses, herbs, and various shrubs, such as Big sagebrush (Artemisia tridentata) and Alder-leaf cercocarpus (Cercocarpus montanus).
A montane zone extends over large areas on the high plateaus and mountains, but is much smaller than the pinyon-juniper zone. The montane vegetation varies considerably, from Ponderosa pine in the south to Lodgepole pine and Aspen further north. Northern Arizona contains four distinct Douglas-fir habitat types. The lowest zone has arid grasslands but with many bare areas, as well as xeric shrubs and sagebrush. Several species of cacti and yucca are common at low elevations in the south.
Numerous mammalian species are found within the Colorado Plateau shrublands ecoregion, including the Black-tailed prairie dog (Cynomys ludovicianus); Long-eared chipmunk (Tamias quadrimaculatus); Utah prairie dog (Cynomys parvidens EN); Yellow-bellied marmot (Marmota flaviventris); and the Uinta chipmunk (Tamias umbrinus), a burrowing omnivore.
A large number of birds are seen in the ecoregion, with representative taxa: Chestnut-collared longspur (Calcarius ornatus NT); Greater sage grouse (Centrocercus urophasianus NT); Northern pygmy owl (Glaucidium gnoma); Cactus wren (Campylorhynchus brunneicapillus).
There are various snakes occurring within the Colorado Plateau, including: Black-necked garter snake (Thamnophis cyrtopsis), usually found in riparian zones; Plains Blackhead snake (Tantilla nigriceps); Black-tailed rattlesnake (Crotalus molossus), who seeks inactivity refuge in rock crevices, animal burrows and even woodrat houses. Other reptiles found here include the Common checkered whiptail (Cnemidophorus tesselatus).
There are only a limited number of anuran taxa on the Colorado Plateau; in fact, the comprehensive occcurrence list for the ecoregion is: Red-spotted toad (Anaxyrus punctatus); Canyon treefrog (Hyla arenicolor); Woodhouse's toad (Anaxyrus woodhousii); Couch's spadefoot toad (Scaphiopus couchii); Northern leopard frog (Lithobates pipiens); Plains spadefoot toad (Spea bombifrons); and Southwestern toad (Anaxyrus microscaphus). The Tiger salamander (Ambystoma tigrinum) is the sole salamander found on the Colorado Plateau shrublands.
The Colorado River fish fauna display distinctive adaptive radiations. The Humpback chub (Gila cypha), for example, is a highly specialized minnow that lives in the upper Colorado. It adapted to the water’s fast current and its extremes of temperature and flow rate. Dams and water diversion, however, have created a series of placid, stillwater lakes and side streams, and the Humpback chub may not be able to adapt to these altered conditions. The species, along with other native Colorado River fishes including the Bonytail (Gila elegans), Squawfish (Ptychocheilus lucius), and the Flannelmouth sucker (Catostomus latipinnis), may not survive much further in time.
- C. Michael Hogan & World Wildlife Fund. 2014."Colorado Plateau shrublands". Encyclopedia of Earth, National Council for Science and the Environment, Washington DC ed.Mark McGinley.
- Michael G. Barbour and William Dwight Billings. 2000. North American Terrestrial Vegetation. Cambridge University Press. ISBN 0-521-55986-3.
- Taylor H. Ricketts. 1999. Terrestrial ecoregions of North America: a conservation assessment. 485 pages
Habitat and Ecology
Comments: 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).
Non-Migrant: No. All populations of this species make significant seasonal migrations.
Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).
Locally Migrant: No. No populations of this species make annual migrations of over 200 km.
Comments: Eats frogs, toads, tadpoles, salamanders, lizards, and crustaceans (Stebbins 1985, Tennant 1984). Opportunistic forager. Forages mainly along stream banks and at pools, and at or near the water's surface (Jones 1990).
Number of Occurrences
Note: For many non-migratory species, occurrences are roughly equivalent to populations.
Estimated Number of Occurrences: 81 to >300
Comments: This species is represented by many occurrences or subpopulations. Webb (1980) mapped over 200 collection sites across the entire range.
10,000 - 1,000,000 individuals
Comments: 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).
Life History and Behavior
Comments: Active from April to October in north (Hammerson 1982).
Lifespan, longevity, and ageing
Gives birth to 3-25 young (usually less than 10), June- August.
Molecular Biology and Genetics
Barcode data: Thamnophis cyrtopsis
Below is the sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.
See the BOLD taxonomy browser for more complete information about this specimen.
Other sequences that do not yet meet barcode criteria may also be available.
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Download FASTA File
Statistics of barcoding coverage: Thamnophis cyrtopsis
Public Records: 1
Specimens with Barcodes: 3
Species With Barcodes: 1
IUCN Red List Assessment
Red List Category
Red List Criteria
- 2007Least Concern
National NatureServe Conservation Status
Rounded National Status Rank: N5 - Secure
NatureServe Conservation Status
Rounded Global Status Rank: G5 - Secure
Global Short Term Trend: Relatively stable (=10% change)
Comments: Extent of occurrence, area of occupancy, number of subpopulations, and population size probably are relatively stable. Possible declines have been recorded at the extreme northern limit of the range in southwestern Colorado (Hammerson 1999).
Global Long Term Trend: Increase of 10-25% to decline of 30%
Degree of Threat: Medium
Comments: 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. The pet trade is a potential threat to this species.
Global Protection: Several to many (4-40) occurrences appropriately protected and managed
Comments: At least several occurrences are in protected areas.
Blackneck garter snake
|This article needs attention from an expert on the subject. (July 2009)|
- Common names: blackneck garter snake, black-neck garter snake
Thamnophis cyrtopsis, the blackneck garter snake, is a species of garter snake of the genus Thamnophis. It is native to the southwestern United States, Mexico and Guatemala, and can be found in a wide range of different habitats, often near water sources.
Western blackneck garter snake
The western blackneck garter snake may attain 107 cm (42 inches) in total length. The snake is colored dark olive with an orange-yellow stripe that is displayed on the middle of the body from the top while the underside is usually a cream or light shade of gray. The western blackneck is a water snake that lives near rivers, swims, and eats small fish and tadpoles.
Eastern blackneck garter snake
The eastern blackneck garter snake is smaller than the western blackneck garter snake, with an average total length of less than 51 cm (20 inches). It is frequently found on dry land near a water source rather than in water. It displays three light stripes on a dark-colored body with uniform orange and orange-yellow spreading throughout.
Found near water in desertscrub, grasslands, chaparral, woodland environments.
It is active during the day and during twilight activities, and occasionally at night, hibernating from late fall to winter and mating in late spring or summer.
Hunts in rivers for small fish, amnphibians, other snakes, and invertebrates, such as earthworms.
- Hammerson, G.A. (2013). "Thamnophis cyrtopsis". IUCN Red List of Threatened Species. Version 2013.2. International Union for Conservation of Nature. Retrieved 29 December 2013.
- "Blackneck Garter Snake". Colorado State University. Retrieved 2009-06-09.
- "Black-necked Garter Snake". Nearartica.com. Retrieved 2009-06-06.
- "BLACK-NECKED GARTERSNAKE Thamnophis cyrtopsis". Thomas C. Brennan. Retrieved 2011-08-05.
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Names and Taxonomy
Comments: Thamnophis cyrtopsis was for many years referred to as T. eques (see Rossman et al. 1996 for a discussion of the complicated taxonomic history of T. cyrtopsis). Thamnophis cyrtopsis includes "Thamnophis vicinus," formerly regarded as a distinct species but now regarded as a localized color pattern morph of T. cyrtopsis occurring in Michoacan, Mexico (Rossman 1996, Proc. Biol. Soc. Washington 109:10-16).