Thamnophis sirtalis - (Linnaeus, 1766)
Common Gartersnake
Other English Common Names: Common Garter Snake, Red-sided Gartersnake, common gartersnake
Taxonomic Status: Accepted
Related ITIS Name(s): Thamnophis sirtalis (Linnaeus, 1758) (TSN 174136)
French Common Names: couleuvre rayée
Unique Identifier: ELEMENT_GLOBAL.2.101158
Element Code: ARADB36130
Informal Taxonomy: Animals, Vertebrates - Reptiles - Snakes
Image 11262

© Larry Master

Kingdom Phylum Class Order Family Genus
Animalia Craniata Reptilia Squamata Colubridae Thamnophis
Genus Size: D - Medium to large genus (21+ species)
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Concept Reference
Concept Reference: 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.
Concept Reference Code: B90COL01NAUS
Name Used in Concept Reference: Thamnophis sirtalis
Taxonomic Comments: Subspecies dorsalis was proposed as a distinct species by Collins (1991), but no supporting data were presented.

Boundy and Rossman (1995) pointed out some nomenclatural problems among Pacific coast populations and suggested that populations now known by the name Thamnophis sirtalis tetrataenia be referred to as T. s. infernalis and that populations recently known as T. s. infernalis be included within T. s. concinnus. ICZN (2000) rejected this change, designated a neotype for T. s. infernalis, and conserved the traditional subspecific taxonomy.
Conservation Status

NatureServe Status

Global Status: G5
Global Status Last Reviewed: 02Feb2016
Global Status Last Changed: 11Dec2001
Ranking Methodology Used: Ranked by inspection
Rounded Global Status: G5 - Secure
Nation: United States
National Status: N5 (05Oct1996)
Nation: Canada
National Status: N5 (02Feb2016)

U.S. & Canada State/Province Status
Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
United States Alabama (S5), Arkansas (S5), California (SNR), Colorado (S3), Connecticut (S5), Delaware (S5), District of Columbia (S4), Florida (SNR), Georgia (S5), Idaho (S3), Illinois (S5), Indiana (SNR), Iowa (S5), Kansas (S5), Kentucky (S5), Louisiana (S5), Maine (S5), Maryland (S5), Massachusetts (S5), Michigan (S5), Minnesota (S5), Mississippi (S5), Missouri (SNR), Montana (S4), Nebraska (S5), Nevada (S3), New Hampshire (S5), New Jersey (S5), New Mexico (S4), New York (S5), North Carolina (S5), North Dakota (SNR), Ohio (SNR), Oklahoma (S5), Oregon (S5), Pennsylvania (S5), Rhode Island (S5), South Carolina (SNR), South Dakota (S5), Tennessee (S5), Texas (S2), Utah (S4), Vermont (S5), Virginia (S5), Washington (S5), West Virginia (S5), Wisconsin (S4S5), Wyoming (S5)
Canada Alberta (S4), British Columbia (S5), Manitoba (S4), New Brunswick (S5), Northwest Territories (S2), Nova Scotia (S5), Nunavut (SNR), Ontario (S5), Prince Edward Island (S5), Quebec (S5), Saskatchewan (S5)

Other Statuses

Implied Status under the U.S. Endangered Species Act (USESA): PS
Comments on USESA: Subspecies tetrataenia of central California is listed by USFWS as Endangered.
Committee on the Status of Endangered Wildlife in Canada (COSEWIC): Candidate (Low) (10Jul2017)
IUCN Red List Category: LC - Least concern

NatureServe Global Conservation Status Factors

Range Extent: >2,500,000 square km (greater than 1,000,000 square miles)
Range Extent Comments: The wide range includes much of North America, from southeastern Alaska, British Columbia, southern Northwest Territories, northern Saskatchewan, central Manitoba, Ontario, central Quebec, and the Maritime Provinces to southern California, central Utah, northeastern Colorado, New Mexico and Chihuahua (disjunct), Texas, Gulf Coast, and southern Florida (Conant and Collins 1991, Ernst and Ernst 2003, Stebbins 2003).

Number of Occurrences: > 300
Number of Occurrences Comments: This species is represented by a very large number of occurrences (subpopulations) (Fitch 1980).

Population Size: >1,000,000 individuals
Population Size Comments: Total adult population size is unknown but likely exceeds 1,000,000.

Number of Occurrences with Good Viability/Integrity: Very many (>125)
Viability/Integrity Comments: Many occurrences have good viability.

Overall Threat Impact: Low
Overall Threat Impact Comments: No major threats have been identified.

Short-term Trend: Relatively Stable (<=10% change)
Short-term Trend Comments: Currently, extent of occurrence, area of occupancy, number of subpopulations, and population size probably are relatively stable or declining at a low rate.

Long-term Trend: Decline of <30% to increase of 25%
Long-term Trend Comments: Long-term extent of occurrence, area of occupancy, number of subpopulations, and population size probably have been relatively stable.

Other NatureServe Conservation Status Information

Global Range: (>2,500,000 square km (greater than 1,000,000 square miles)) The wide range includes much of North America, from southeastern Alaska, British Columbia, southern Northwest Territories, northern Saskatchewan, central Manitoba, Ontario, central Quebec, and the Maritime Provinces to southern California, central Utah, northeastern Colorado, New Mexico and Chihuahua (disjunct), Texas, Gulf Coast, and southern Florida (Conant and Collins 1991, Ernst and Ernst 2003, Stebbins 2003).

U.S. States and Canadian Provinces

Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
Color legend for Distribution Map
Endemism: occurs (regularly, as a native taxon) in multiple nations

U.S. & Canada State/Province Distribution
United States AL, AR, CA, CO, CT, DC, DE, FL, GA, IA, ID, IL, IN, KS, KY, LA, MA, MD, ME, MI, MN, MO, MS, MT, NC, ND, NE, NH, NJ, NM, NV, NY, OH, OK, OR, PA, RI, SC, SD, TN, TX, UT, VA, VT, WA, WI, WV, WY
Canada AB, BC, MB, NB, NS, NT, NU, ON, PE, QC, SK

Range Map
Note: Range depicted for New World only. The scale of the maps may cause narrow coastal ranges or ranges on small islands not to appear. Not all vagrant or small disjunct occurrences are depicted. For migratory birds, some individuals occur outside of the passage migrant range depicted.

Range Map Compilers: NatureServe, 2005

U.S. Distribution by County Help
State County Name (FIPS Code)
CA San Diego (06073), San Mateo (06081), Santa Cruz (06087), Ventura (06111)
ID Ada (16001), Adams (16003), Bannock (16005), Bear Lake (16007), Benewah (16009), Bingham (16011), Blaine (16013), Boise (16015), Bonner (16017), Bonneville (16019), Boundary (16021), Canyon (16027), Caribou (16029), Clark (16033), Clearwater (16035), Elmore (16039), Franklin (16041), Fremont (16043), Gooding (16047), Idaho (16049), Kootenai (16055), Latah (16057), Lemhi (16059), Lewis (16061), Madison (16065), Nez Perce (16069), Owyhee (16073), Shoshone (16079), Valley (16085), Washington (16087)
OH Erie (39043), Lucas (39095), Ottawa (39123), Sandusky (39143)
OK Atoka (40005), Cherokee (40021), Cleveland (40027), Ellis (40045), Le Flore (40079), Muskogee (40101), Roger Mills (40129)
TX Atascosa (48013), Austin (48015)*, Bastrop (48021), Bell (48027), Bexar (48029), Brazoria (48039)*, Burnet (48053), Dallas (48113)*, Denton (48121), Hays (48209)*, Hill (48217)*, Hutchinson (48233), Limestone (48293)*, Llano (48299), Matagorda (48321)*, McLennan (48309)*, Motley (48345), Randall (48381), Tarrant (48439)*, Taylor (48441)*, Travis (48453)*, Williamson (48491)*
UT Box Elder (49003)*, Cache (49005), Davis (49011)*, Juab (49023), Rich (49033)*, Salt Lake (49035), Sanpete (49039), Summit (49043)*, Tooele (49045), Uintah (49047), Utah (49049), Wasatch (49051), Weber (49057)*
WY Albany (56001), Big Horn (56003), Campbell (56005), Carbon (56007), Crook (56011), Fremont (56013), Goshen (56015), Hot Springs (56017), Johnson (56019), Laramie (56021), Lincoln (56023), Natrona (56025), Niobrara (56027), Park (56029), Platte (56031), Sheridan (56033), Sublette (56035), Sweetwater (56037), Teton (56039), Uinta (56041), Washakie (56043), Weston (56045)
* Extirpated/possibly extirpated
U.S. Distribution by Watershed Help
Watershed Region Help Watershed Name (Watershed Code)
04 Cedar-Portage (04100010)+, Sandusky (04100011)+, Huron-Vermilion (04100012)+
10 Clarks Fork Yellowstone (10070006)+, Upper Wind (10080001)+, Little Wind (10080002)+, Popo Agie (10080003)+, Muskrat (10080004)+, Lower Wind (10080005)+, Badwater (10080006)+, Upper Bighorn (10080007)+, Nowood (10080008)+, Big Horn Lake (10080010)+, Dry (10080011)+, North Fork Shoshone (10080012)+, South Fork Shoshone (10080013)+, Shoshone (10080014)+, Little Bighorn (10080016)+, Middle Fork Powder (10090201)+, Upper Powder (10090202)+, South Fork Powder (10090203)+, Crazy Woman (10090205)+, Clear (10090206)+, Middle Powder (10090207)+, Little Powder (10090208)+, Upper Little Missouri (10110201)+, Lance (10120104)+, Beaver (10120107)+, Upper Belle Fourche (10120201)+, Redwater (10120203)+, Upper North Platte (10180002)+, Pathfinder-Seminoe Reservoirs (10180003)+, Medicine Bow (10180004)+, Sweetwater (10180006)+, Middle North Platte-Casper (10180007)+, Glendo Reservoir (10180008)+, Middle North Platte-Scotts Bluff (10180009)+, Upper Laramie (10180010)+, Lower Laramie (10180011)+, Horse (10180012)+, Cache La Poudre (10190007)+, Lone Tree-Owl (10190008)+, Crow (10190009)+
11 Middle Canadian-Spring (11090106)+, Lower Canadian-Deer (11090201)+, Little (11090203)+, Dirty-Greenleaf (11110102)+, Illinois (11110103)+, Robert S. Kerr Reservoir (11110104)+, Poteau (11110105)+, Tierra Blanca (11120101)+, Palo Duro (11120102)+*, North Pease (11130103)+, Muddy Boggy (11140103)+, Kiamichi (11140105)+
12 Lower West Fork Trinity (12030102)+*, Elm Fork Trinity (12030103)+, Upper Trinity (12030105)+*, Austin-Oyster (12040205)+*, Upper Clear Fork Brazos (12060102)+*, Middle Brazos-Lake Whitney (12060202)+*, Bosque (12060203)+*, North Bosque (12060204)+*, Lower Brazos (12070104)+*, Leon (12070201)+, San Gabriel (12070205)+*, Middle Colorado-Elm (12090101)+*, Jim Ned (12090108)+*, Buchanan-Lyndon B (12090201)+, Llano (12090204)+, Austin-Travis Lakes (12090205)+*, Lower Colorado-Cummins (12090301)+, East Matagorda Bay (12090402)+*, San Marcos (12100203)+*, Medina (12100302)+, Atascosa (12110110)+
14 New Fork (14040102)+, Upper Green-Slate (14040103)+, Big Sandy (14040104)+, Bitter (14040105)+, Upper Green-Flaming Gorge Reservoir (14040106)+, Blacks Fork (14040107)+, Muddy (14040108)+, Vermilion (14040109)+, Little Snake (14050003)+, Muddy (14050004)+, Ashley-Brush (14060002)+, Strawberry (14060004)+
16 Upper Bear (16010101)+, Central Bear (16010102)+, Bear Lake (16010201)+, Middle Bear (16010202)+, Little Bear-Logan (16010203)+, Lower Bear-Malad (16010204)+*, Lower Weber (16020102)+*, Utah Lake (16020201)+, Spanish Fork (16020202)+, Provo (16020203)+, Jordan (16020204)+, Rush-Tooele Valleys (16020304)+, Great Salt Lake (16020310)+*, San Pitch (16030004)+, Lower Sevier (16030005)+
17 Lower Kootenai (17010104)+, Moyie (17010105)+, Pend Oreille Lake (17010214)+, Priest (17010215)+, Upper Coeur D'alene (17010301)+, South Fork Coeur D'alene (17010302)+, Coeur D'alene Lake (17010303)+, St. Joe (17010304)+, Upper Spokane (17010305)+, Snake headwaters (17040101)+, Gros Ventre (17040102)+, Greys-Hobock (17040103)+, Upper Henrys (17040202)+, Lower Henrys (17040203)+, Teton (17040204)+, Willow (17040205)+, American Falls (17040206)+, Blackfoot (17040207)+, Portneuf (17040208)+, Upper Snake-Rock (17040212)+, Beaver-Camas (17040214)+, Big Wood (17040219)+, Little Wood (17040221)+, Bruneau (17050102)+, Boise-Mores (17050112)+, Lower Boise (17050114)+, Payette (17050122)+, North Fork Payette (17050123)+, Brownlee Reservoir (17050201)+, Lower Snake-Asotin (17060103)+, Palouse (17060108)+, Middle Salmon-Panther (17060203)+, Middle Salmon-Chamberlain (17060207)+, South Fork Salmon (17060208)+, Lower Salmon (17060209)+, Little Salmon (17060210)+, Lochsa (17060303)+, South Fork Clearwater (17060305)+, Clearwater (17060306)+, Upper North Fork Clearwater (17060307)+, Lower North Fork Clearwater (17060308)+
18 Coyote (18050003)+, San Francisco Bay (18050004)+, San Francisco Coastal South (18050006)+, San Lorenzo-Soquel (18060001)+, Santa Clara (18070102)+, San Luis Rey-Escondido (18070303)+
+ Natural heritage record(s) exist for this watershed
* Extirpated/possibly extirpated
Ecology & Life History
General Description: The coloration varies geographically and is difficult to characterize succinctly. These snakes have 19 dorsal scale rows at mid-body, a pale lateral stripe on each side on the 2nd and 3rd scale rows (also on row 4 in subspecies annectans of Texas-Oklahoma), 7 scales on each upper lip, 1 preocular (scale in front of eye), 3 postoculars (scales behind eye), keeled scales on the back, and an undivided anal scale (covers vent). Adult total length is usually 16-26 inches (41-66 cm), with the maximum around 52 inches) (131 cm). Newborns are around 5-7 inches (12-23 cm) in total length (Conant and Collins 1991, Smith and Brodie 1982).
Diagnostic Characteristics: This species differs from other sympatric garter snakes by the following combination of characteristics: lateral stripe confined to 2nd and 3rd scale rows (except in annectans), seven scales along each upper lip; tail less than 27% of total length, and 19 scale rows at mid-body.
Reproduction Comments: In much of the range, mating occurs primarily in spring, just after emergence from hibernation, though possibly to a limited extent also in late summer. Adult females give birth usually in July or August but earlier in the south and as late as early October in the north. Litter size averages about 13-26 but varies geographically (generally larger in the east than in the west); the largest females tend to produce the largest litters. Individuals become sexually mature in 1-2 years. In Northwest Territories, Canada, females evidently rarely gave birth in successive years (Larsen et al. 1993). See Cover and Boyer (1988) for information on captive breeding.
Ecology Comments: Home range size variously reported as 0.8 ha to 14 ha (DeGraaf and Rudis 1983). In the far northern part of the range, thousands may aggregate at hibernacula. Population density estimates in different areas range from about 10/ha to 100/ha.
Non-Migrant: N
Locally Migrant: Y
Long Distance Migrant: N
Mobility and Migration Comments: In some areas in the northern part of the range, common gartersnakes make long migrations between winter hibernacula and summer range (up to at least 16 km between winter hibernaculum and summer range in at least some northern localities; Fitch 1980). In Manitoba, females dispersed from a communal den in all directions, rather than following distinct migration corridors (Shine et al. 2001).
Estuarine Habitat(s): Herbaceous wetland
Riverine Habitat(s): BIG RIVER, CREEK, Low gradient, MEDIUM RIVER, Moderate gradient, Pool, SPRING/SPRING BROOK
Lacustrine Habitat(s): Shallow water
Terrestrial Habitat(s): Bare rock/talus/scree, Cropland/hedgerow, Forest - Conifer, Forest - Hardwood, Forest - Mixed, Grassland/herbaceous, Old field, Suburban/orchard, Woodland - Conifer, Woodland - Hardwood, Woodland - Mixed
Special Habitat Factors: Burrowing in or using soil, Fallen log/debris
Habitat Comments: Throughout the range, common gartersnakes inhabit a very wide range of aquatic, wetland, and upland habitats; habitat preference exhibits rather pronounced regional differences (e.g., east vs. west). In some regions, such as much of eastern North America, these snakes are decidedly terrestrial and range far from water. In other areas, such as the Rocky Mountain region, they are mostly confined to riparian corridors. When inactive, they occur underground, in or under surface cover, or in other secluded sites.

In some areas, common gartersnakes spend the cold winter months completely submerged in water. Submerged snakes retain more body water and conserve more stored energy than do snakes in dry sites. At the low temperatures of hibernation, the snake's metabolic rate is very low, so oxygen needs can be met even while the snake is submerged and unable to breathe air.

Adult Food Habits: Carnivore, Invertivore, Piscivore
Immature Food Habits: Carnivore, Invertivore, Piscivore
Food Comments: Preys chiefly on earthworms, frogs, toads, salamanders, and fishes; less regularly on slugs, leeches, small mammals and birds; rarely on insects, spiders, and small snakes (Fitch 1980).
Adult Phenology: Circadian, Hibernates/aestivates
Immature Phenology: Circadian, Hibernates/aestivates
Phenology Comments: Most activity occurs from about March or April through October in the north and at higher elevations; the active season is longer in the south (year-around in Florida). Common gartersnakes are active both day and night in most of the range; nocturnal activity often occurs during hot weather.

Length: 66 centimeters
Economic Attributes Not yet assessed
Management Summary Not yet assessed
Population/Occurrence Delineation
Group Name: Medium And Large Colubrid Snakes

Use Class: Not applicable
Minimum Criteria for an Occurrence: Occurrences are based on evidence of historical presence, or current and likely recurring presence, at a given location. Such evidence minimally includes collection or reliable observation and documentation of one or more individuals (including eggs) in or near appropriate habitat where the species is presumed to be established and breeding.
Separation Barriers: Busy highway or highway with obstructions such that snakes rarely if ever cross successfully; major river, lake, pond, or deep marsh (this barrier pertains only to upland species and does not apply to aquatic or wetland snakes); densely urbanized area dominated by buildings and pavement.
Separation Distance for Unsuitable Habitat: 1 km
Separation Distance for Suitable Habitat: 10 km
Separation Justification: Available information on movements of colubrid snakes is limited to a small minority of species. These data indicate that nearly all species have home ranges smaller or much smaller than 25 ha (e.g., less than 3 ha, Pituophis catenifer in California, Rodriguez-Robles 2003), with some up to about 75 ha (Heterodon platirhinos, average 50 ha, Plummer and Mills 2000), and the largest up to 225 ha in the biggest colubrids (Drymarchon, summer mean 50-100 ha, USFWS 1998).

Radiotelemetry data for Pantherophis indicate that residents of hibernacula that are 1-2 km apart (with suitable intervening habitat) probably interbreed (Prior et al. 1997, Blouin-Demers and Weatherhead 2002). However, "evidence of genetic structure even over short distances (e.g., 2-20 km) implies that gene flow among rat snake populations can be easily disrupted" (Prior et al. 1997). Loughheed et al. (1999) found evidence of substantial genetic exchange among local hibernacula (< 6 km apart), but gene flow over distances of 10s of km appears to be substantially less. Based on extensive radio-tracking data, Blouin-Demers and Weatherhead (2002) found that home range size of Pantherophis averaged 18.5 ha and ranged up to 93 ha; based on the most mobile individuals, Pantherophis from hibernacula up to 8 km apart can come together for mating. Pantherophis and probably other colubrids exhibit high fidelity to hibernacula and shift even to nearby sites only rarely (Prior et al. 2001).

Many of the several studies that report small home ranges for colubrids did not employ methods (e.g., radio telemetry) suitable for detecting full annual or multi-annual home range size, dispersal, or other long-distance movements, so these may have yielded underestimates of home ranges or activity areas.

At least some colubrids, including medium-sized species such as garter snakes, not uncommonly move between areas up to a few kilometers apart, and several species make extensive movements of up to several kilometers, so separation distances of 1-2 km for suitable habitat are too small for medium-sized and large colubrids.

A separation distance of 10 km for suitable habitat was selected as most appropriate for snakes assigned to this Specs Group because it seems generally unlikely that two locations separated by less than 10 km of suitable habitat would represent distinct occurrences.

For the purposes of these occurrence specifications, upland habitat is regarded as unsuitable habitat for aquatic and wetland snakes. For upland snakes, shallow or patchy wetlands are treated as unsuitable habitat whereas large deepwater habitats (subjective determination) are barriers.

Inferred Minimum Extent of Habitat Use (when actual extent is unknown): .5 km
Date: 12Feb2013
Author: Hammerson, G.
Notes: Separation distance for suitable habitat was changed from 5 km to 10 km based on comments from Dale Jackson (12 Feb 2013).
Population/Occurrence Viability
U.S. Invasive Species Impact Rank (I-Rank) Not yet assessed
NatureServe Conservation Status Factors Edition Date: 22Aug2006
NatureServe Conservation Status Factors Author: Hammerson, G.
Element Ecology & Life History Edition Date: 28Jan2010
Element Ecology & Life History Author(s): Hammerson, G.

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