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Overview

Distribution

Common garter snakes are native to the Nearctic region only. They occur throughout much of North America, although they are largely absent from the arid southwestern United States. Common garter snakes are found throughout eastern North America from Florida to coastal Quebec, west to British Columbia, south into southern California east of the Sierras, and throughout the less arid areas of the southwest. Isolated populations occur on mountain ranges in New Mexico and northern Mexico (New Mexico garter snakes, Thamnophis sirtalis dorsalis). They are found as far south as the Gulf of Mexico in the eastern United States.

Biogeographic Regions: nearctic (Native )

  • Conant, R., J. Collins. 1998. Peterson Field Guide to Reptiles and Amphibians of Eastern and Central North America. Boston: Houghton Mifflin.
  • Stebbins, R. 1985. Peterson Field Guide to Western Reptiles and Amphibians. Boston: Houghton Mifflin.
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Range Description

The species' 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 of Canada, to southern California, central Utah, northeastern Colorado, New Mexico, and Chihuahua (Mexico) (disjunct), Texas, Gulf Coast, and southern Florida (Conant and Collins 1991, Ernst and Ernst 2003, Stebbins 2003). There is a very small population in northwestern Chihuaha, Mexico.
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National Distribution

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

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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).

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Geographic Range

Common garter snakes are native to the Nearctic region only. They occur throughout much of North America, although they are largely absent from the arid southwestern United States. Common garter snakes are found throughout eastern North America from Florida to coastal Quebec, west to British Columbia, south into southern California east of the Sierras, and throughout the less arid areas of the southwest. Isolated populations occur on mountain ranges in New Mexico and northern Mexico (New Mexico garter snakes, Thamnophis_sirtalis_dorsalis). They are found as far south as the Gulf of Mexico in the eastern United States.

Biogeographic Regions: nearctic (Native )

  • Conant, R., J. Collins. 1998. Peterson Field Guide to Reptiles and Amphibians of Eastern and Central North America. Boston: Houghton Mifflin.
  • Stebbins, R. 1985. Peterson Field Guide to Western Reptiles and Amphibians. Boston: Houghton Mifflin.
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Continent: Middle-America Caribbean North-America
Distribution: S Canada (incl. Northwest Territories, Manitoba, Alberta, Saskatchewan, New Brunswick, Ontario, Prince Edward Island), USA (Alabama, Arkansas, California, Colorado, Connecticut, Delaware, Florida, Georgia, Idaho, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maine, Maryland, Massachusetts, Michigan, Minnesota, Mississippi, Missouri, Montana, Nebraska, NW Nevada, New Hampshire, New Jersey, New York, New Mexico, North Carolina, North-Dakota, Ohio, Oklahoma, Oregon, Pennsylvania, Rhode Island, South Carolina, South Dakota, Tennessee, Texas, N Utah, Vermont, Virginia, Washington, West-Virginia, Wisconsin, Wyoming), Mexico, Bahamas [Buckner & Franz 1998]  sirtalis: S Canada to Gulf of Mexico, west to Minnesota and E Texas.  pallidulus: S Quebec, from the eastern shore of James Bay to the Gulf of St. Lawrence and Nova Scotia, and south in New England to extreme NE Massachusetts.  parietalis: Kansas etc.  semifasciatus: NE Illinois, adjacent portions of Indiana and Wisconsin.  parietalis: EC British Columbia to Wisconsin, Oklahoma. Isolated population in SW Sask. (Canada)  dorsalis: USA (Rio Grand Valley from NC New Mexico south to vicinity of El Paso, Texas; disjunct populations in NE New Mexico); Mexico (Jalisco)  annectens: EC Texas; disjunct population in SW Kansas., adjacent Oklahoma, and Texas panhandle.  similis: W Florida from Wakulla Co. to the Tithlacoochee R.  
Type locality: “Canada”; Quebec County, Quebec [neotype]
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Physical Description

Morphology

Common garter snakes are highly variable in color pattern. They typically have three light stripes that run along the length of their body on a black, brown, gray, or olive background. The stripes can be white, yellow, blue, greenish, or brown. One stripe runs down the center of the snake's back, the other two stripes run alongside this central stripe. Sometimes the stripes are absent or poorly defined. Some garter snakes have alternating rows of dark spots that run along the stripes, making the stripes look more like checkerboard patterns of light, rather than lines. Common garter snakes have a head that is wider than the neck and is uniformly dark. Their tongues are red, tipped in black, and their scales are keeled (with a raised ridge along the length of the scale). The chin, throat and belly resemble the stripes in coloration, ranging from white to yellow, greenish, blue, or brown.

Common garter snakes grow to be 46 to 137 cm in total length. Males are generally smaller than females and have longer tails. Young common garter snakes are born at 12.5 to 23 cm long and are similar in appearance to the adults. There are many dozens of recognized regional populations of common garter snakes that have distinct color patterns. In some areas there are populations that have a high percentage of entirely black garter snakes. Common garter snakes are similar in appearance to their close relatives, ribbon snakes (Thamnophis sauritus) and Butler's garter snakes (Thamnophis butleri).

Range length: 46 to 137 cm.

Average length: 88.00 cm.

Other Physical Features: heterothermic ; polymorphic

Sexual Dimorphism: female larger; sexes shaped differently

Average mass: 150 g.

  • Wechsler, D. 2001. Garter Snakes. New York: The Rosen Publishing Group, Inc.
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Physical Description

Common garter snakes are highly variable in color pattern. They typically have three light stripes that run along the length of their body on a black, brown, gray, or olive background. The stripes can be white, yellow, blue, greenish, or brown. One stripe runs down the center of the snake's back, the other two stripes run alongside this central stripe. Sometimes the stripes are absent or poorly defined. Some garter snakes have alternating rows of dark spots that run along the stripes, making the stripes look more like checkerboard patterns of light, rather than lines. Common garter snakes have a head that is wider than the neck and is uniformly dark. Their tongues are red, tipped in black, and their scales are keeled (with a raised ridge along the length of the scale). The chin, throat and belly resemble the stripes in coloration, ranging from white to yellow, greenish, blue, or brown.

Common garter snakes grow to be 46 to 137 cm in total length. Males are generally smaller than females and have longer tails. Young common garter snakes are born at 12.5 to 23 cm long and are similar in appearance to the adults. There are many dozens of recognized regional populations of common garter snakes that have distinct color patterns. In some areas there are populations that have a high percentage of entirely black garter snakes. Common garter snakes are similar in appearance to their close relatives, ribbon snakes (Thamnophis_sauritus) and Butler's garter snakes (Thamnophis_butleri).

Range length: 46 to 137 cm.

Average length: 88.00 cm.

Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry ; polymorphic

Sexual Dimorphism: female larger; sexes shaped differently

Average mass: 150 g.

  • Wechsler, D. 2001. Garter Snakes. New York: The Rosen Publishing Group, Inc.
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Size

Length: 66 cm

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Diagnostic Description

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.

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Type Information

Syntype for Thamnophis sirtalis
Catalog Number: USNM 974
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Amphibians & Reptiles
Preparation: Ethanol
Locality: Westport, Essex, New York, United States, North America
  • Syntype: Cope, E. D. 1875. Report upon Geographical and Geological Explorations and Surveys West of the Hundredth Meridian in Charge of First Lieutenant George M. Wheeler, Zoology. 546.
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Ecology

Habitat

Common garter snakes are very widespread, highly adaptable and can survive extreme environmental conditions. Common garter snakes are found in a wide variety of habitats, including meadows, marshes, woodlands, and hillsides. They tend to prefer moist, grassy environments. They are often found near water, such as near the edges of ponds, lakes, ditches, and streams, and are common in suburban and urban areas with plenty of cover (debris, boards, vegetation, logs, or rocks).

Habitat Regions: temperate ; terrestrial

Terrestrial Biomes: savanna or grassland ; forest

Wetlands: marsh ; swamp

Other Habitat Features: suburban ; agricultural ; riparian

  • Bartlett, R., P. Bartlett. 2001. Reptiles Keeper's Guide: Garter and Ribbon Snakes. New York: Barron's Educational Series, Inc.
  • Reynolds, M., F. Gould. date unknown. "Thamnophis" (On-line). Accessed April 3, 2002 at http://www.thamnophis.com/artic22.htm.
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Habitat and Ecology

Habitat and Ecology
Throughout the range, this species inhabits a very wide range of aquatic, wetland, and upland habitats; habitat preference exhibits rather pronounced regional differences (e.g., east vs. west). When inactive, it occurs underground, in or under surface cover, or in other secluded sites.

Systems
  • Terrestrial
  • Freshwater
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Central Pacific Coastal Forests Habitat

This taxon is found in the Central Pacific Coastal Forests ecoregion, as one of its North American ecoregions of occurrence. These mixed conifer rainforests stretch from stretch from southern Oregon in the USA to the northern tip of Vancouver Island, Canada. These forests are among the most productive in the world, characterized by large trees, substantial woody debris, luxuriant growths of mosses and lichens, and abundant ferns and herbs on the forest floor. The major forest complex consists of Douglas-fir (Pseudotsuga menziesii) and Western hemlock (Tsuga heterophylla), encompassing seral forests dominated by Douglas-fir and massive old-growth forests of Douglas-fir, Western hemlock, Western red cedar (Thuja plicata), and other species. These forests occur from sea level up to elevations of 700-1000 meters in the Coast Range and Olympic Mountains. Such forests occupy a gamut of environments with variable composition and structure and includes such other species as Grand fir (Abies grandis), Sitka spruce (Picea sitchensis), and Western white pine (Pinus monticola).

Characteristic mammalian fauna include Elk (Cervus elaphus), Black-tailed Deer (Odocoileus hemionus), Coyote (Canis latrans), Black Bear (Ursus americanus), Mink (Mustela vison), and Raccoon (Procyon lotor).

The following anuran species occur in the Central Pacific coastal forests: Coastal tailed frog (Ascaphus truei); Oregon spotted frog (Rana pretiosa VU); Northern red-legged frog (Rana pretiosa); Pacific chorus frog (Pseudacris regilla); Cascade frog (Rana cascadae NT), generally restricted to the Cascade Range from northern Washington to the California border; Foothill yellow-legged frog (Rana boylii) and the Western toad (Anaxyrus boreas NT).  A newt found in the ecoregion is the Rough skinned newt (Taricha granulosa).

Salamanders within the ecoregion are: Del Norte salamander (Plethodon elongatus NT);  Van Dyke's salamander (Plethodon vandykei); Western redback salamander (Plethodon vehiculum); Northwestern salamander (Ambystoma gracile);  Olympic torrent salamander (Rhyacotriton olympicus VU), whose preferred habitat is along richly leafed stream edges; Long-toed salamander (Ambystoma macrodactylum), whose adults are always subterranean except during the breeding season; Dunn's salamander (Plethodon dunni), usually found in seeps and stream splash zones; Clouded salamander (Aneides ferreus NT), an aggressive insectivore; Monterey ensatina (Ensatina eschscholtzii), usually found in thermally insulated micro-habitats such as under logs and rocks; Pacific giant salamander (Dicamptodon tenebrosus), found in damp, dense forests near streams; and Cope's giant salamander (Dicamptodon copei), usually found in rapidly flowing waters on the Olympic Peninsula and Cascade Range.

There are a small number of reptilian taxa that are observed within this forested ecoregion, including: Pacific pond turtle (Emys marmorata); Common garter snake (Thamnophis sirtalis), an adaptable snake most often found near water; Northern alligator lizard (Elgaria coerulea); and the Western fence lizard.

Numerous avian species are found in the ecoregion, both resident and migratory. Example taxa occurring here are the Belted kingfisher (Megaceryle alcyon); Wild turkey (Meleagris gallopavo); and the White-headed woodpecker (Picoides albolarvatus) and the Trumpeter swan (Cygnus buccinator), the largest of the North American waterfowl.

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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.

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Common garter snakes are very widespread, highly adaptable and can survive extreme environmental conditions. Common garter snakes are found in a wide variety of habitats, including meadows, marshes, woodlands, and hillsides. They tend to prefer moist, grassy environments. They are often found near water, such as near the edges of ponds, lakes, ditches, and streams, and are common in suburban and urban areas with plenty of cover (debris, boards, vegetation, logs, or rocks).

Habitat Regions: temperate ; terrestrial

Terrestrial Biomes: savanna or grassland ; forest

Wetlands: marsh ; swamp

Other Habitat Features: suburban ; agricultural ; riparian

  • Bartlett, R., P. Bartlett. 2001. Reptiles Keeper's Guide: Garter and Ribbon Snakes. New York: Barron's Educational Series, Inc.
  • Reynolds, M., F. Gould. date unknown. "Thamnophis" (On-line). Accessed April 3, 2002 at http://www.thamnophis.com/artic22.htm.
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Migration

Non-Migrant: No. All populations of this species make significant seasonal migrations.

Locally Migrant: Yes. At least some 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.

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).

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Trophic Strategy

Common garter snakes typically eat earthworms, amphibians, leeches, slugs, snails, insects, crayfish, small fish and other snakes. They seem immune to the toxic skin secretions of toads and can eat them without harm. Occasionally small mammals, lizards, or baby birds are eaten as well. Common garter snakes find their prey using their excellent sense of smell and their vision. They use several different hunting methods, such as peering, craning, and ambushing to capture their prey. The different techniques describe the way the snakes move while they hunt. They immobilize their prey using their sharp teeth and quick reflexes. The saliva of common garter snakes may be slightly toxic to some of their small prey, making it easier to handle them while they are being eaten. Like other snakes, they swallow their food whole.

Animal Foods: birds; mammals; amphibians; reptiles; fish; insects; terrestrial non-insect arthropods; mollusks; terrestrial worms; aquatic crustaceans

Primary Diet: carnivore (Eats terrestrial vertebrates)

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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).

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Food Habits

Common garter snakes typically eat Oligochaeta, lissamphibia, Hirudinea, Stylommatophora, Stylommatophora, insecta, Decapoda, small actinopterygii and other serpentes. They seem immune to the toxic skin secretions of bufonidae and can eat them without harm. Occasionally small mammalia, sauria, or baby aves are eaten as well. Common garter snakes find their prey using their excellent sense of smell and their vision. They use several different hunting methods, such as peering, craning, and ambushing to capture their prey. The different techniques describe the way the snakes move while they hunt. They immobilize their prey using their sharp teeth and quick reflexes. The saliva of common garter snakes may be slightly toxic to some of their small prey, making it easier to handle them while they are being eaten. Like other snakes, they swallow their food whole.

Animal Foods: birds; mammals; amphibians; reptiles; fish; insects; terrestrial non-insect arthropods; mollusks; terrestrial worms; aquatic crustaceans

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Associations

Garter snakes are low-level predators, feeding on many small animals and in turn being eaten by other predators higher in the food web. These snakes are one of the few kinds of animals that can eat toads, newts, and other amphibians with strong chemical defenses.

Common garter snakes are infected by a parasitic nematode that lives in the tissues of their tail. Snakes with this condition often have shortened or stubby tails. The nematodes live part of their lifecycle in small aquatic crustaceans and in amphibian larvae. The snakes are infected when they eat the amphibian larvae.

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Common garter snakes are eaten by a wide variety of predators, which varies throughout their range. Large fish, bullfrogs, snapping turtles, milk snakes, American crows, hawks, great blue herons, raccoons, foxes, squirrels, and shrews are some of the animals that prey on common garter snakes. They rely on stealth and camouflage for protection, and will flee into water to escape predators on land. Their stripes make them difficult to see properly and capture in grassy areas. If unable to flee they coil to make themselves appear larger, and may strike and bite. If grabbed, these snakes writhe and release a foul-smelling secretion; they will also urinate on their attacker.

Known Predators:

Anti-predator Adaptations: cryptic

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Ecosystem Roles

Garter snakes are low-level predators, feeding on many small animals and in turn being eaten by other predators higher in the food web. These snakes are one of the few kinds of animals that can eat bufonidae, Salamandridae, and other amphibians with strong chemical defenses.

Common garter snakes are infected by a parasitic Nematoda that lives in the tissues of their tail. Snakes with this condition often have shortened or stubby tails. The nematodes live part of their lifecycle in small aquatic crustacea and in lissamphibia larvae. The snakes are infected when they eat the amphibian larvae.

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Predation

Common garter snakes are eaten by a wide variety of predators, which varies throughout their range. Large actinopterygii, Rana catesbeiana, Chelydridae, Lampropeltis, Corvus brachyrhynchos, accipitridae, Ardea herodias, procyon lotor, canidae, sciuridae, and soricidae are some of the animals that prey on common garter snakes. They rely on stealth and camouflage for protection, and will flee into water to escape predators on land. Their stripes make them difficult to see properly and capture in grassy areas. If unable to flee they coil to make themselves appear larger, and may strike and bite. If grabbed, these snakes writhe and release a foul-smelling secretion; they will also urinate on their attacker.

Known Predators:

  • hawks (Accipitridae)
  • American crows (Corvus_brachyrhynchos)
  • raccoons (Procyon_lotor)
  • shrews (Soricidae)
  • milk snakes and king snakes (Lampropeltis)
  • coral snakes (Elapidae)
  • large fish (Actinopterygii)
  • bullfrogs (Rana_catesbeiana)
  • snapping turtles (Chelydridae)
  • great blue herons (Ardea_herodias)
  • foxes (Canidae)
  • squirrels (Sciuridae)

Anti-predator Adaptations: cryptic

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Known predators

Thamnophis sirtalis is prey of:
Accipitridae
Soricidae
Lampropeltis
Micrurus fulvius
Procyon lotor

This list may not be complete but is based on published studies.
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Known prey organisms

Thamnophis sirtalis preys on:
Actinopterygii
Annelida
Amphibia
Reptilia
Aves
Mammalia
Dendroica petechia

This list may not be complete but is based on published studies.
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Population Biology

Number of Occurrences

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: > 300

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

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Global Abundance

>1,000,000 individuals

Comments: Total adult population size is unknown but likely exceeds 1,000,000.

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General Ecology

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.

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Life History and Behavior

Behavior

Common garter snakes communicate with each other primarily through touch and smell, especially for breeding. Outside of the breeding season they do not interact much with other snakes. They use their forked tongues to collect chemicals from the air and insert these forks into a special organ in the roof of their mouth, which interprets these chemical signals, called pheromones. Pheromones can be used as a tracking device for garter snakes. Using their acute sense of smell, common garter snakes can locate other snakes or trails left behind by other snakes through the pheromones given off by their skin. After they are born, baby snakes follow the same pheromone trails to feed and locate other common garter snakes. Snakes are also sensitive to vibrations and have reasonably good vision.

During the breeding season, common garter snakes use complex systems of chemical communication. Male common garter snakes use skin lipids as pheromonal cues for sex recognition because female and male skin pheromones are extremely different. However, some males are occasionally born with both female and male skin pheromones. During mating season these males with female pheromones are courted by other males. The confusion often allows the males with female pheromones to mate first because the other males are courting the wrong sex. Shine et al. (2000) hypothesized that the behavior could provided a mating advantage to the genetically altered males.

Communication Channels: tactile ; chemical

Other Communication Modes: pheromones

Perception Channels: visual ; infrared/heat ; tactile ; vibrations ; chemical

  • LeMaster, M., I. Moore, R. Mason. 2001. Conspecific trailing behavior of red-sided garter snakes, *Thamnophis sirtalis parietalis*, in the natural environment. Animal Behavior, 61: 827-833.
  • Shine, R., P. Harlow, M. LeMaster, I. Moore, R. Mason. 2000. The transvestite serpent: Why do male garter snakes court (some) other males?. Animal Behavior, 59: 349-359.
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Communication and Perception

Common garter snakes communicate with each other primarily through touch and smell, especially for breeding. Outside of the breeding season they do not interact much with other snakes. They use their forked tongues to collect chemicals from the air and insert these forks into a special organ in the roof of their mouth, which interprets these chemical signals, called pheromones. Pheromones can be used as a tracking device for garter snakes. Using their acute sense of smell, common garter snakes can locate other snakes or trails left behind by other snakes through the pheromones given off by their skin. After they are born, baby snakes follow the same pheromone trails to feed and locate other common garter snakes. Snakes are also sensitive to vibrations and have reasonably good vision.

Communication Channels: tactile ; chemical

Other Communication Modes: pheromones

Perception Channels: visual ; infrared/heat ; tactile ; vibrations ; chemical

  • LeMaster, M., I. Moore, R. Mason. 2001. Conspecific trailing behavior of red-sided garter snakes, *Thamnophis sirtalis parietalis*, in the natural environment. Animal Behavior, 61: 827-833.
  • Shine, R., P. Harlow, M. LeMaster, I. Moore, R. Mason. 2000. The transvestite serpent: Why do male garter snakes court (some) other males?. Animal Behavior, 59: 349-359.
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Cyclicity

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.

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Life Cycle

The young grow quickly and become mature in their second or third year, when they reach about 55 cm in length. Growth continues throughout the lifespan of these snakes.

Development - Life Cycle: indeterminate growth

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Development

The young grow quickly and become mature in their second or third year, when they reach about 55 cm in length. Growth continues throughout the lifespan of these snakes.

Development - Life Cycle: indeterminate growth

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Life Expectancy

The average lifespan of wild common garter snakes is approximately two years. Most common garter snakes probably die in their first year of life. Common garter snakes reach sexual maturity, and maximum size, at 3 to 4 years of age. The lifespan of common garter snakes kept in captivity is longer, between 6 and 10 years. One captive common garter snake lived to be 20 years old, but few wild snakes live this long.

Average lifespan

Status: wild:
2 years.

Range lifespan

Status: captivity:
20 (high) years.

Average lifespan

Status: captivity:
6-10 years.

Typical lifespan

Status: captivity:
6 to 20 years.

  • Harding, J. 1997. Amphibians and Reptiles of the Great Lakes Region. Ann Arbor, Michigan: University of Michigan Press.
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Lifespan/Longevity

The average lifespan of wild common garter snakes is approximately two years. Most common garter snakes probably die in their first year of life. Common garter snakes reach sexual maturity, and maximum size, at 3 to 4 years of age. The lifespan of common garter snakes kept in captivity is longer, between 6 and 10 years. One captive common garter snake lived to be 20 years old, but few wild snakes live this long.

Average lifespan

Status: wild:
2 years.

Range lifespan

Status: captivity:
20 (high) years.

Average lifespan

Status: captivity:
6-10 years.

Typical lifespan

Status: captivity:
6 to 20 years.

  • Harding, J. 1997. Amphibians and Reptiles of the Great Lakes Region. Ann Arbor, Michigan: University of Michigan Press.
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Lifespan, longevity, and ageing

Maximum longevity: 14 years (captivity)
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Reproduction

These snakes begin mating in the spring as soon as they emerge from hibernation. The males leave the den first and wait for the females to exit. Once the females leave the den the males surround them. The males give off pheromones that attract the females. After the female has chosen her mate and mated, she returns to her summer habitat to feed and to find a proper birth place. However, the males stay to re-mate with other available females. The females have the ability to store the male's sperm until it is needed and thus a female may not mate if she does not find a proper partner.

Mating System: polygynandrous (promiscuous)

Common garter snakes are ovoviviparous (bearing live young). The young are incubated in the lower abdomen, about half way down from the snake's body. Gestation is usually two to three months. Most females in the northern parts of their range give birth to from 4 to 80 young between late July and October. Most litters range from 10 to 40 young and litter size depends on the size of the female, with larger females giving birth to larger litters. Upon birth, baby garter snakes are independent and must find food on their own.

Common garter snakes become sexually mature at 1.5 years (males) or two years (females).

Breeding interval: Common garter snakes breed once each year.

Breeding season: Common garter snakes breed in the spring and give birth to their young in late summer.

Range number of offspring: 4 to 80.

Average number of offspring: 10 to 40.

Range gestation period: 2 to 3 months.

Average age at sexual or reproductive maturity (female): 2 years.

Average age at sexual or reproductive maturity (male): 1.5 years.

Key Reproductive Features: iteroparous ; seasonal breeding ; sexual ; fertilization ; ovoviviparous ; sperm-storing

Average age at sexual or reproductive maturity (male)

Sex: male:
730 days.

Average age at sexual or reproductive maturity (female)

Sex: female:
730 days.

Female common garter snakes nurture their young in their bodies until they are born. The mother gives birth to live young, she doesn't lay eggs. Newly born snakes tend to stay around their mother for several hours or days but she provides no parental care or protection after they are born.

Parental Investment: pre-hatching/birth (Provisioning: Female, Protecting: Female)

  • Bartlett, R., P. Bartlett. 2001. Reptiles Keeper's Guide: Garter and Ribbon Snakes. New York: Barron's Educational Series, Inc.
  • Wechsler, D. 2001. Garter Snakes. New York: The Rosen Publishing Group, Inc.
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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.

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These snakes begin mating in the spring as soon as they emerge from hibernation. The males leave the den first and wait for the females to exit. Once the females leave the den the males surround them. The males give off pheromones that attract the females. After the female has chosen her mate and mated, she returns to her summer habitat to feed and to find a proper birth place. However, the males stay to re-mate with other available females. The females have the ability to store the male's sperm until it is needed and thus a female may not mate if she does not find a proper partner.

Mating System: polygynandrous (promiscuous)

Common garter snakes are ovoviviparous (bearing live young). The young are incubated in the lower abdomen, about half way down from the snake's body. Gestation is usually two to three months. Most females in the northern parts of their range give birth to from 4 to 80 young between late July and October. Most litters range from 10 to 40 young and litter size depends on the size of the female, with larger females giving birth to larger litters. Upon birth, baby garter snakes are independent and must find food on their own.

Common garter snakes become sexually mature at 1.5 years (males) or two years (females).

Breeding interval: Common garter snakes breed once each year.

Breeding season: Common garter snakes breed in the spring and give birth to their young in late summer.

Range number of offspring: 4 to 80.

Average number of offspring: 10 to 40.

Range gestation period: 2 to 3 months.

Average age at sexual or reproductive maturity (female): 2 years.

Average age at sexual or reproductive maturity (male): 1.5 years.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization ; ovoviviparous ; sperm-storing

Average age at sexual or reproductive maturity (male)

Sex: male:
730 days.

Average age at sexual or reproductive maturity (female)

Sex: female:
730 days.

Female common garter snakes nurture their young in their bodies until they are born. The mother gives birth to live young, she doesn't lay eggs. Newly born snakes tend to stay around their mother for several hours or days but she provides no parental care or protection after they are born.

Parental Investment: pre-hatching/birth (Provisioning: Female, Protecting: Female)

  • Bartlett, R., P. Bartlett. 2001. Reptiles Keeper's Guide: Garter and Ribbon Snakes. New York: Barron's Educational Series, Inc.
  • Wechsler, D. 2001. Garter Snakes. New York: The Rosen Publishing Group, Inc.
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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage: Thamnophis sirtalis

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 17
Species With Barcodes: 1
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Conservation

Conservation Status

Common garter snakes are some of the most common and abundant snakes throughout the eastern United States, at least partly because they do well in urban and suburban areas. Despite the fact that they are harmless snakes, they are often persecuted by humans. Pesticide use in some areas has significantly reduced common garter snake populations. Habitat destruction and over-collection for the commercial pet trade have also led to a decline in the number of garter snakes in the wild. Water pollution is a problem for this species, because so much of its food is aquatic. Northern populations are more vulnerable than southern ones, because they hibernate in larger groups (which are easily harvested) and produce smaller numbers of young each year. It is important to continue to monitor populations of 'common' species as declines in their populations can tell us a great deal about environmental health.

One subspecies, the San Francisco garter snake, Thamnophis sirtalis tetrataenia, is considered endangered, and placed on the US and California Endangered Species list in 1967. Other subspecies may be protected by state laws.

US Migratory Bird Act: no special status

US Federal List: no special status

CITES: no special status

State of Michigan List: no special status

IUCN Red List of Threatened Species: least concern

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IUCN Red List Assessment


Red List Category
LC
Least Concern

Red List Criteria

Version
3.1

Year Assessed
2007

Assessor/s
Frost, D.R., Hammerson, G.A. & Santos-Barrera, G.

Reviewer/s
Cox, N., Chanson, J.S. & Stuart, S.N. (Global Reptile Assessment Coordinating Team)

Contributor/s

Justification
Listed as Least Concern in view of its extremely wide distribution, presumed large population, and because populations are unlikely to be declining.
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National NatureServe Conservation Status

Canada

Rounded National Status Rank: N5 - Secure

United States

Rounded National Status Rank: N5 - Secure

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NatureServe Conservation Status

Rounded Global Status Rank: G5 - Secure

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Common garter snakes are some of the most common and abundant snakes throughout the eastern United States, at least partly because they do well in urban and suburban areas. Despite the fact that they are harmless snakes, they are often persecuted by humans. Pesticide use in some areas has significantly reduced common garter snake populations. Habitat destruction and over-collection for the commercial pet trade have also led to a decline in the number of garter snakes in the wild. Water pollution is a problem for this species, because so much of its food is aquatic. Northern populations are more vulnerable than southern ones, because they hibernate in larger groups (which are easily harvested) and produce smaller numbers of young each year. It is important to continue to monitor populations of 'common' species as declines in their populations can tell us a great deal about environmental health.

One subspecies, the San Francisco garter snake, Thamnophis sirtalis tetrataenia, is considered endangered, and placed on the US and California Endangered Species list in 1967. Other subspecies may be protected by state laws.

IUCN Red List of Threatened Species: least concern

US Migratory Bird Act: no special status

US Federal List: no special status

CITES: no special status

State of Michigan List: no special status

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Population

Population
This species is represented by a very large number of occurrences (subpopulations) (Fitch 1980). Many occurrences have good viability. The total adult population size is unknown but probably exceeds 1,000,000. Long-term extent of occurrence, area of occupancy, number of subpopulations, and population size have probably been relatively stable. Currently, extent of occurrence, area of occupancy, number of subpopulations, and population size are probably relatively stable or declining at a low rate.

Population Trend
Stable
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Global Short Term Trend: Relatively stable (=10% change)

Comments: Currently, extent of occurrence, area of occupancy, number of subpopulations, and population size probably are relatively stable or declining at a low rate.

Global Long Term Trend: Increase of 10-25% to decline of 30%

Comments: Long-term extent of occurrence, area of occupancy, number of subpopulations, and population size probably have been relatively stable.

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Threats

Major Threats
No major threats have been identified. The Mexican population is vulnerable to changes in hydrology.
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Degree of Threat: Low

Comments: No major threats have been identified.

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Management

Conservation Actions

Conservation Actions
Many occurrences of this species are in areas that afford adequate protection.
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Global Protection: Very many (>40) occurrences appropriately protected and managed

Comments: Many occurrences are in areas that afford adequate protection.

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Relevance to Humans and Ecosystems

Benefits

On very rare occasions people have been known to have allergic reactions to common garter snake saliva after handling one and being bitten. These are extremely rare, though, and their reputation as harmless snakes is well deserved.

Negative Impacts: injures humans (bites or stings)

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Common garter snakes act to control populations of insect and mollusk pests. They are a common and welcome sight to many gardeners. They also tame easily and are sometimes kept as pets.

Positive Impacts: pet trade ; controls pest population

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Economic Importance for Humans: Negative

On very rare occasions people have been known to have allergic reactions to common garter snake saliva after handling one and being bitten. These are extremely rare, though, and their reputation as harmless snakes is well deserved.

Negative Impacts: injures humans (bites or stings)

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Economic Importance for Humans: Positive

Common garter snakes act to control populations of insect and mollusk pests. They are a common and welcome sight to many gardeners. They also tame easily and are sometimes kept as pets.

Positive Impacts: pet trade ; controls pest population

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Wikipedia

Common Garter Snake

The Common Garter Snake (Thamnophis sirtalis) is an indigenous North American snake found widely across the continent. Most garter snakes have a pattern of yellow stripes on a brown or green background and their average length is about 55 cm (22 in), with a maximum length of about 137 cm (54 in).[1][2] The average body mass is 150 g (5.3 oz).[3]

Subspecies[edit]

Current scientific classification recognizes thirteen subspecies (ordered by date):[4]

Description[edit]

Garter snakes are very thin snakes. None grow over about 4 feet long and most stay smaller. Most have longitudinal stripes in many different colors. Garters come in a wide range of colors including: green, blue, yellow, gold, red, orange, brown, and black

Life history[edit]

The Common Garter Snake is a diurnal snake. In summer, it is most active in the morning and late afternoon; in cooler seasons or climates, it restricts its activity to the warm afternoons.

In warmer southern areas, the snake is active year-round; otherwise, it sleeps in common dens, sometimes in great numbers. On warm winter afternoons, some snakes have been observed emerging from their hibernacula to bask in the sun.

Toxicity[edit]

The saliva of a garter snake may be toxic to amphibians and other small animals. For humans, a bite is not dangerous, though it may cause slight itching, burning, and/or swelling. Most garter snakes also secrete a foul-smelling fluid from postanal glands when handled or harmed.

Garter Snakes are resistant to most naturally found poisons such as that of the American Toad and Rough-Skinned Newt, the latter of which can kill a human if ingested. Garter snakes have the ability to absorb the toxin from the newts into their body making them poisonous, which can deter potential predators.[5]

Reproduction[edit]

In the early part of spring, when snakes are coming out of hibernation the males generally emerge first to be ready when the females wake up. Some males will assume the role of a female and lead other males away from the burrow, luring them with a fake female pheromone. After such a male has led rivals away, he "turns" back into a male and races back to the den, just as the females emerge. He is then the first to mate with all the females he can catch. There are generally far more males than females and that is why, during mating season, they form "mating balls," where one or two females will be completely swamped by ten or more males. Sometimes a male snake will mate with a female before hibernation and the female will store the sperm internally until spring, when she will allow her eggs to be fertilized. If she mates again in the spring, the fall sperm will degenerate, and the spring sperm will fertilize her eggs. The females may give birth ovoviviparously to 12 to 40 young from July through October.

Habitat[edit]

The habitat of the garter snake ranges from forests, fields, and prairies to streams, wetlands, meadows, marshes, and ponds, and it is often found near water. It is found at altitudes from sea level to mountain locations. Their diet consists mainly of amphibians and earthworms, but also fish, small birds, and rodents. Garter snakes are effective at catching fast-moving creatures like fish and tadpoles. Animals that eat the Common Garter Snake include large fish (such as bass and catfish), bullfrogs, snapping turtles, larger snakes, hawks, raccoons, foxes, wild turkeys and domestic cats and dogs.

Conservation[edit]

Water contamination, urban expansion, and residential and industrial development are all threats to the garter snake. The San Francisco Garter Snake (T. s. tetrataenia), which is extremely scarce and occurs only in the vicinity of ponds and reservoirs in San Mateo County, California, has been listed as an endangered species by the U.S. Fish and Wildlife Service since 1967.

Anti-predatory displays[edit]

Garter snakes exhibit many different anti-predatory behaviors, or behaviors that ward off predators. Morphology refers to the shape that the snake’s body makes in response to the environment, predatory defense, mating, etc. The term body geometry may also be used to describe the shape a snake's body makes. Garter snakes exhibit a higher variation of morphology when compared to other snakes. Predation has been such an intense selection pressure throughout evolution; these snakes have developed body geometries that are highly variable and heritable.[6] These morphologies have been concluded to be highly variable even within a single population.[7] Different geometries indicate whether the snake is preparing to flee, fight, or protect itself. Since the traits are heritable, there must be some evolutionary benefit such as warding off predators. Additional research also shows that different biological factors such as body temperature and sex influence whether the snake will exhibit certain anti-predatory behaviors.[8]

Studies show that the warmer the temperature of a Garter snake, the more likely the snake is to flee a predator. While a snake with a cooler body temperature remains stationary or attacks. Male garter snakes are also more likely to flee.[9] Garter Snakes that exhibit more aggressive anti-predatory displays tend to also be fast and have high stamina. However the cause for correlation is unknown.[10]

Aposematism, or warning coloration, is another factor that influences anti-predator behavior. For example, the coral snake exhibits aposematic coloration that can be mimicked.[11] While garter snakes do not exhibit mimicry or aposematic coloration, it has been found that garter snakes with striped patterns are more likely to slowly, successively crawl away, while spotted and not striped snakes were more likely to deceptively flee from predators.[12]

The decision of a juvenile garter snake to attack a predator can be affected by whether the snake has just eaten or not.[13] Snakes that have just eaten are more likely to strike a predator or stimuli than snakes that do not have a full stomach. Snakes are more likely to flee a threatening situation if their stomachs are empty.[14] Snakes that have just eaten a large animal are less mobile. Feeding positively affects endurance as opposed to speed.[15]

Another factor that controls the anti-predatory response of the garter snake is where the snake attacked. Many birds and mammals prefer to attack the head of the snake.[16] In a research study, it was found that garter snakes are more likely to hide their head and move their tail back and forth when being attacked close to the head.[17] The same study concluded that snakes that were attacked in the middle of their body were more likely to flee or exhibit open-mouthed warning reactions.[18]

Time may be another factor that contributes to anti-predatory responses. Garter snakes are affected by maturation time.[19] As snakes mature, the length of time at which garter snakes can display physical activity at 25°C increases. Juvenile snakes can only be physically active for three to five minutes. Adult snakes can be physically active for up to 25 minutes.[20] This is mostly due to aerobic energy production; pulmonary aeration increases up to three times in adult garter snakes when compared to juveniles.[21] The quick fatigue of the juveniles most certainly limits the habitats they can live in as well as their food source.[22] It absolutely affects the anti-predator response of both juvenile and adult garter snakes; without sufficient energy production the snake cannot exhibit any anti-predatory response.

Female garter snakes produce a specific pheromone. Studies show that some males of various species of garter snake exhibit female behavior as well as morphology.[23] This type of mimicry is primarily found in the red-sided garter snake. A portion of the males that exhibit female mimicry also secrete the sex-specific hormone to attract other males.[24] In a study these “she-males” mated with females significantly more often than males that did not exhibit this mimicry.[25] A male pretending to be a female around other males increases his chances of reproduction as well as protects against stronger, more aggressive males.

See also[edit]

References[edit]

  1. ^ Conant, Roger. 1975. A Field Guide to Reptiles and Amphibians of Eastern and Central North America. Houghton Mifflin. Boston.
  2. ^ [1]
  3. ^ [2]
  4. ^ Thamnophis sirtalis , Reptile Database
  5. ^ Williams BL, Brodie ED Jr,Brodie ED 3rd. (2004). A resistant predator and its toxic prey: Persistence of newt toxin leads to poisonous (not venomous) snakes. J Chem Ecol 30(10):1901-19.
  6. ^ Garland, 1988. pp. 335-350.
  7. ^ Garland, 1988. pp. 335-350.
  8. ^ Shine, 1999. pp. 239-245.
  9. ^ Shine, 1999. pp. 239-245.
  10. ^ Brodie, 1992. pp. 1284-1298.
  11. ^ Greene, 1981. pp. 1207-1212.
  12. ^ Arnold, 1984. pp. 1108-1118.
  13. ^ Herzog, 1987. pp. 387-389.
  14. ^ Herzog, 1987. pp. 387-389.
  15. ^ Herzog, 1987. pp. 387-389.
  16. ^ Langkilde, 2004. pp. 937-947.
  17. ^ Langkilde, 2004. pp. 937-947.
  18. ^ Langkilde, 2004. pp. 937-947.
  19. ^ Pough, 1977. pp. 337-345.
  20. ^ Pough, 1977. pp. 337-345.
  21. ^ Pough, 1977. pp. 337-345.
  22. ^ Pough, 1977. pp. 337-345.
  23. ^ Mason, 1985. pp. 59-60.
  24. ^ Mason, 1985. pp. 59-60.
  25. ^ Mason, 1985. pp. 59-60.
  • "Thamnophis sirtalis". Integrated Taxonomic Information System. Retrieved 6 February 2006. 
  • Care of Garter Snakes
  • Garter Snake Information
  • Caring for Your Garter Snake
  • "IUCN Red List of Threatened Species". Retrieved 2008-09-06. 
  • Shine, R., M.M. Olsson, M.P. Lesmaster, I.T. Moore and R.T. Mason. (1999). Effects of Sex, Body, Size, Temperature & Location on the Antipredator Tactics of Free-Ranging Gartner Snakes (Thamnophis sirtalis, Colubridae). Oxford Journal 11 (3), 239 -245
  • Garland, T. (1988). Genetic Basis of Activity Metabolism. I. Inheritance of Speed, Stamina & Antipredator Display in the Garter Snake, Thamnophis sirtalis. Evolution 42(2), 335-350
  • Brodie III, E.D. (1992). Correlational Selection For Color Pattern & Antipredator Behavior In The Garter Snake. Evolution 46(5), 1284-1298.
  • Greene, H.W. and R.W. McDiarmid. (1981). Coral Snake Mimicry: Does It Occur? Science 213, 1207-1212.
  • Arnold, S.J., & A.F Bennett. (1984). Behavioural Variation in Natural Population III: Antipredator Display in the Garter Snake Thamnophis Radix. Animal Behavior 32, 1108-1118.
  • Mason, Robert T., and David Crews. "Female Mimicry in Garter Snakes." Nature 316 (1985): 59-60.
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Names and Taxonomy

Taxonomy

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.

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