Thamnophis hammondii 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Reptilia Squamata Natricidae

Scientific Name: Thamnophis hammondii (Kennicott, 1860)
Common Name(s):
English Two-striped Gartersnake, Two-striped Garter Snake
French Serpent-jarretiere À Deux Raies
Spanish Serpiente Jarretera
Taxonomic Notes: Formerly included in Thamnophis couchii. Includes T. digueti Mocquuard, 1899 of Baja California. The specific name in IUCN Red Lists prior to 2007 was incorrectly spelt as hammondi.

Assessment Information [top]

Red List Category & Criteria: Least Concern ver 3.1
Year Published: 2007
Date Assessed: 2007-03-01
Assessor(s): Frost, D.R., Hammerson, G.A. & Hollingsworth, B.
Reviewer(s): Cox, N., Chanson, J.S. & Stuart, S.N. (Global Reptile Assessment Coordinating Team)
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 threatened category. However, if loss of suitable habitat continues, it could qualify for listing as Near Threatened.
Previously published Red List assessments:

Geographic Range [top]

Range Description:The range of this species extends from coastal California (United States) in the vicinity of Salinas, Monterey County, south to the vicinity of El Rosario in northern Baja California (Mexico) and disjunctly south as isolated populations to the La Presa region of southern Baja California. It occurs at elevations from sea level to around 2,450 m asl (8,000 feet) (McGuire and Grismer 1993, Jennings and Hayes 1994, Rossman et al. 1996, Grismer 2002, Stebbins 2003).
Countries occurrence:
Mexico (Baja California, Baja California Sur); United States (California)
Additional data:
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:This species is represented by at least several dozen extant occurrences or subpopulations (Jennings and Hayes 1994, Grismer 2002). The total population size is unknown but surely is at least several thousand. This snake is common in suitable habitat in northwestern Baja California (Grismer 2002). A decline has occurred primarily in urbanized areas of California. The species has disappeared from about 40% of the historical range in California, mostly since 1945 (Jennings and Hayes 1994), who mapped dozens of locations with presumed extirpated populations. However, it is probably the most common snake in southern California away from urban areas, and it is not unusual to see several individuals at a time in a given spot. Some populations in Baja California appear to be relatively stable, but others are decreasing, and it might be extirpated in San Ignacio and San Fernando Velicata. Overall, its extent of occurrence, area of occupancy, number of subpopulations, and population size currently may be declining but probably not at a rate greater than 10% over 10 years or three generations.
Current Population Trend:Decreasing
Additional data:

Habitat and Ecology [top]

Habitat and Ecology:This highly aquatic and amphibious snake is generally found in or near permanent fresh water, often along streams with rocky beds bordered by willows and other riparian vegetation, including mountain slopes and desert oases (Jennings and Hayes 1994, Rossman et al. 1996, Grismer 2002, Stebbins 2003). In the southern part of its range it is restricted to palm oases.
Systems:Terrestrial; Freshwater

Threats [top]

Major Threat(s): In California, this species has declined due to loss and degradation of habitat by urbanization and flood control, excessive livestock grazing, predation by introduced animals, loss of food resources, drought, and direct killing by increasing numbers of humans in the habitat (Jennings and Hayes 1994). Predators include introduced bullfrogs (Lithobates catesbeianus) (Hovey and Bergen 2003), but the level of threat posed by these amphibians is uncertain. In northern Baja California the species is impacted by changes to aquatic systems due to urbanization and agriculture. In southern Baja California, it is being affected by human disturbance, the introduction of alien species, and the impact of dams in its palm oasis habitat.

Conservation Actions [top]

Conservation Actions: At least a few and probably several occurrences are protected.

Citation: Frost, D.R., Hammerson, G.A. & Hollingsworth, B. 2007. Thamnophis hammondii. The IUCN Red List of Threatened Species 2007: e.T21707A9311793. . Downloaded on 26 May 2018.
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