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Home/Species/ Two-striped Gartersnake

Thamnophis hammondii

(Kennicott, 1860)

Two-striped Gartersnake

G4Apparently Secure Found in 59 roadless areas NatureServe Explorer →
G4Apparently SecureGlobal Rank
Least concernIUCN
HighThreat Impact
Identity
Unique IDELEMENT_GLOBAL.2.105900
Element CodeARADB36160
Record TypeSPECIES
ClassificationSpecies
Classification StatusStandard
Name CategoryVertebrate Animal
IUCNLeast concern
Endemicoccurs (regularly, as a native taxon) in multiple nations
KingdomAnimalia
PhylumCraniata
ClassReptilia
OrderSquamata
FamilyColubridae
GenusThamnophis
Synonyms
Thamnophis couchii hammondii(Kennicott)
Other Common Names
Two-striped Garter Snake (EN)
Concept Reference
McGuire, J. A., and L. L. Grismer. 1993. The taxonomy and biogeography of Thamnophis hammondii and T. digueti (Reptilia: Squamata: Colubridae) in Baja California, Mexico. Herpetologica 49:354-365.
Taxonomic Comments
Formerly included in Thamnophis couchii. Includes T. digueti of Baja California Sur; McGuire and Grismer (1993) examined variation in squamation and color and concluded that digueti is an invalid taxon and placed it in the synonymy of T. hammondii.
Conservation Status
Review Date2014-04-25
Change Date2014-04-25
Edition Date2005-12-16
Edition AuthorsHammerson, G.
Threat ImpactHigh
Range Extent20,000-2,500,000 square km (about 8000-1,000,000 square miles)
Number of Occurrences21 - 300
Rank Reasons
Range is restricted essentially to stream courses in portions of southern California and Baja California; has disappeared from about 40% of historical range in California but has not declined significantly in Baja California; common in Baja California and in eastern San Diego County, California; decline is due to effects of urbanization, flood control, exotic species, livestock grazing, direct mortality from humans, and drought; still declining.
Range Extent Comments
The range extends from coastal California in the vicinity of Salinas, Monterey County, south to the vicinity of El Rosario in northern Baja California and disjunctly south as isolated populations to the La Presa region of southern Baja California, at elevations from sea level to around 2,450 meters (8,000 feet) (McGuire and Grismer 1993, Jennings and Hayes 1994, Rossman et al. 1996, Grismer 2002, Stebbins 2003 ). See Ely (1992, Herpetol. Rev. 23:124-125) for recent records from Fresno County.
Occurrences Comments
This species is represented by at least several dozen extant occurrences or subpopulations (Jennings and Hayes 1994, Grismer 2002).
Threat Impact Comments
In Baja California, this species appears not to be significantly threatened. 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 (Hovey and Bergen 2003), but the level of threat posed by these amphibians is uncertain.
Ecology & Habitat

Description

Middorsal stripe absent or reduced to a spot on the neck; in the U.S., dorsum is olive, brown, or brownish-gray, with 4 rows of small dark spots or spots confined to the lower sides; venter yellowish to reddish, unmarked or slightly marked with dusky; melanistic specimens have been found along the coast from Monterey County to San Luis Obispo County; subspecies DIGEUTI of Baja California Sur is nearly uniform olive to dusky above, with vague stripes at most; adult total length usually 60-90 cm (Stebbins 1985).

Diagnostic Characteristics

Differs from other sympatric garter snakes in lacking a middorsal stripe.

Habitat

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).

Reproduction

Captive gave birth to 25 young on October 30 (Stebbins 1985).
Palustrine Habitats
Riparian
Other Nations (1)
United StatesN2
ProvinceRankNative
CaliforniaS3Yes
Threat Assessments
ThreatScopeSeverityTiming
1 - Residential & commercial development——High (continuing)
1.1 - Housing & urban areas——High (continuing)
1.2 - Commercial & industrial areas——High (continuing)
2 - Agriculture & aquaculture——High (continuing)
2.1 - Annual & perennial non-timber crops——High (continuing)
2.3 - Livestock farming & ranching——High (continuing)
5 - Biological resource use——High (continuing)
5.1 - Hunting & collecting terrestrial animals——High (continuing)
6 - Human intrusions & disturbance——High (continuing)
6.1 - Recreational activities——High (continuing)
7 - Natural system modifications——High (continuing)
7.2 - Dams & water management/use——High (continuing)
8 - Invasive & other problematic species, genes & diseases——High (continuing)
8.1 - Invasive non-native/alien species/diseases——High (continuing)
11 - Climate change & severe weather——High (continuing)
11.2 - Droughts——High (continuing)

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Roadless Areas (59)
California (59)
AreaForestAcres
Arroyo SecoAngeles National Forest4,703
Barker ValleyCleveland National Forest11,940
Bear MountainLos Padres National Forest913
Black ButteLos Padres National Forest5,116
Cahuilla MountainSan Bernardino National Forest6,952
CajonSan Bernardino National Forest7,548
CalienteCleveland National Forest5,953
CamuesaLos Padres National Forest8,209
Chalk PeakLos Padres National Forest7,472
City CreekSan Bernardino National Forest9,997
ColdwaterCleveland National Forest8,402
Crystal CreekSan Bernardino National Forest6,783
Cucamonga AAngeles National Forest1,249
Cucamonga CSan Bernardino National Forest4,106
Cutca ValleyCleveland National Forest14,530
De La GuerraLos Padres National Forest5,418
Deep CreekSan Bernardino National Forest23,869
DiableLos Padres National Forest19,597
Dry LakesLos Padres National Forest17,043
Eagle PeakCleveland National Forest6,481
Fish CanyonAngeles National Forest29,886
Fox MountainLos Padres National Forest52,072
Garcia MountainLos Padres National Forest7,850
Hixon FlatSan Bernardino National Forest8,095
Horse Creek RidgeSan Bernardino National Forest8,969
JuncalLos Padres National Forest12,289
La BreaLos Padres National Forest14,031
LaddCleveland National Forest5,300
Little PineLos Padres National Forest1,315
Lpoor CanyonLos Padres National Forest13,762
Machesna MountainLos Padres National Forest12,271
Magic MountainAngeles National Forest15,542
Malduce BuckhornLos Padres National Forest14,177
ManzanaLos Padres National Forest2,101
MatilijaLos Padres National Forest5,218
Mill PeakSan Bernardino National Forest7,884
MonoLos Padres National Forest28,141
No NameCleveland National Forest4,897
NordhoffLos Padres National Forest12,031
Pine CreekCleveland National Forest503
Pleasant ViewAngeles National Forest26,395
Pyramid Peak BSan Bernardino National Forest7,194
Rouse HillSan Bernardino National Forest13,745
Salt CreekAngeles National Forest11,022
San DimasAngeles National Forest7,160
San Gabriel AddAngeles National Forest2,527
Santa CruzLos Padres National Forest21,182
Sawmill - BadlandsLos Padres National Forest51,362
Sespe - FrazierLos Padres National Forest106,910
Sheep MountainAngeles National Forest21,098
Sill HillCleveland National Forest5,294
Strawberry PeakAngeles National Forest7,245
TequepisLos Padres National Forest9,080
TrabucoCleveland National Forest23,341
TuleAngeles National Forest9,861
West ForkAngeles National Forest1,169
WestforkAngeles National Forest4,407
White LedgeLos Padres National Forest18,632
WildhorseCleveland National Forest1,483
References (12)
  1. Collins, J. T. 1990. Standard common and current scientific names for North American amphibians and reptiles. 3rd ed. Society for the Study of Amphibians and Reptiles. Herpetological Circular No. 19. 41 pp.
  2. Crother, B. I. (editor). 2008. Scientific and standard English names of amphibians and reptiles of North America north of Mexico, with comments regarding confidence in our understanding. Sixth edition. Society for the Study of Amphibians and Reptiles Herpetological Circular 37:1-84. Online with updates at: http://www.ssarherps.org/pages/comm_names/Index.php
  3. Crother, B. I. (editor). 2012. Scientific and standard English names of amphibians and reptiles of North America north of Mexico, with comments regarding confidence in our understanding. 7th edition. SSAR Herpetological Circular 39:1-92.
  4. Crother, B. I. (editor). 2017. Scientific and standard English names of amphibians and reptiles of North America north of Mexico, with comments regarding confidence in our understanding. 8th edition. SSAR Herpetological Circular 43:1-104. [Updates in SSAR North American Species Names Database at: https://ssarherps.org/cndb]
  5. Ernst, C. H., and E. M. Ernst. 2003. Snakes of the United States and Canada. Smithsonian Books, Washington, D.C.
  6. Grismer, L. L. 2002. Amphibians and reptiles of Baja California including its Pacific islands and islands in the Sea of Cortes. University of California Press, Berkeley. xiii + 399 pp.
  7. Hovey, T. E.and D. R. Bergen. 2003. <i>Rana catesbeiana</i> (bullfrog). Predation. Herpetological Review 34:360-361.
  8. Jennings, M. R., and M. P. Hayes. 1994. Amphibian and reptile species of special concern in California. Final Report submitted to the California Department of Fish and Game, Inland Fisheries Division. Contract No. 8023. 255 pp.
  9. McGuire, J. A., and L. L. Grismer. 1993. The taxonomy and biogeography of <i>Thamnophis hammondii</i> and <i>T. digueti</i> (Reptilia: Squamata: Colubridae) in Baja California, Mexico. Herpetologica 49:354-365.
  10. Rossman, D. A., N. B. Ford, and R. A. Seigel. 1996. The garter snakes: evolution and ecology. University of Oklahoma Press, Norman. xx + 332 pp.
  11. Stebbins, R. C. 1985a. A field guide to western reptiles and amphibians. Second edition. Houghton Mifflin Company, Boston, Massachusetts. xiv + 336 pp.
  12. Stebbins, R. C. 2003. A field guide to western reptiles and amphibians. Third edition. Houghton Mifflin Company, Boston.