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Thamnophis atratus 

Scope: Global
Language: English
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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Reptilia Squamata Natricidae

Scientific Name: Thamnophis atratus (Kennicott, 1860)
Common Name(s):
English Aquatic Gartersnake, Pacific Coast Aquatic Garter Snake, Santa Cruz Garter Snake, Western Aquatic Garter Snake
Taxonomic Notes: Rossman and Stewart (1987) recognized Thamnophis atratus and T. couchii as distinct species. They recommended that T. a. aquaticus not be recognized as a valid taxon (atratus, hydrophilus, and aquaticus formerly were recognized as subspecies of T. couchii). Rossman et al. (1996) and Boundy (1999) also did not recognize aquaticus as valid.

Assessment Information [top]

Red List Category & Criteria: Least Concern ver 3.1
Year Published: 2007
Date Assessed: 2007-03-01
Assessor(s): Hammerson, G.A.
Reviewer(s): Cox, N., Chanson, J.S. & Stuart, S.N. (Global Reptile Assessment Coordinating Team)
Justification:
Listed as Least Concern in view of its wide distribution, presumed large population, and because it is unlikely to be declining fast enough to qualify for listing in a more threatened category.

Geographic Range [top]

Range Description:This species is endemic to the west of the United States. Its range includes southwestern Oregon and western California north of Point Concepcion, at elevations from sea level to around 1,920 m (Nussbaum et al. 1983, Brown et al. 1995, Rossman et al. 1996, Stebbins 2003).
Countries occurrence:
Native:
United States
Additional data:
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:This species is represented by a large number of occurrences (subpopulations). The adult population size is unknown but presumably exceeds 100,000. This snake is common in many parts of its range. The extent of occurrence, area of occupancy, number of subpopulations, and population size are probably relatively stable.
Current Population Trend:Stable
Additional data:

Habitat and Ecology [top]

Habitat and Ecology:Habitats include rocky fast-flowing streams, sluggish streams with soft bottoms, ponds, small lakes, and the adjacent riparian zone, in areas surrounded by woodlands, woodland-grass ecotones, or chaparral (Nussbaum et al. 1983, Rossman et al. 1996, Ernst and Ernst 2003, Stebbins 2003). This snake basks on boulders and vegetation along banks and in mid-stream; it seeks cover under water under rocks or among exposed tree roots. In most areas this snake is closely tied to water, but individuals sometimes travel on land away from water.
Systems:Freshwater

Threats [top]

Major Threat(s): No major threats are known. Predation by introduced bullfrogs (Lithobates catesbeianus) may be a concern in some areas.

Conservation Actions [top]

Conservation Actions: Many occurrences are in protected areas.

Citation: Hammerson, G.A. 2007. Thamnophis atratus. The IUCN Red List of Threatened Species 2007: e.T63970A12732165. . Downloaded on 19 January 2018.
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