The common garter snake (''Thamnophis sirtalis'') is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriat ...

of thamnophis

snake Snakes are elongated, limbless, carnivorous reptiles of the suborder Serpentes . Like all other squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales. Many species of snakes have skulls with several more ...

, in the natricine subfamily, which is indigenous to

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and th ...

and found widely across the continent. Most common garter snakes have a pattern of yellow stripes on a black, brown or green background, and their average total length (including tail) is about , with a maximum total length of about . The average body mass is . Common garter snakes are the

state reptile Twenty-eight U.S. states have named an official state reptile. As with other state symbols, states compare admirable aspects of the reptile and of the state, within designating statutes. Schoolchildren often start campaigns promoting their fav ...

Massachusetts Massachusetts (Massachusett: ''Muhsachuweesut Massachusett_writing_systems.html" ;"title="nowiki/> məhswatʃəwiːsət.html" ;"title="Massachusett writing systems">məhswatʃəwiːsət">Massachusett writing systems">məhswatʃəwiːsət'' En ...

Description

Common garter snakes are thin snakes. Few grow over about long, and most stay smaller. Most have longitudinal stripes in many different colors. Common garter snakes come in a wide range of colors, including green, blue, yellow, gold, red, orange, brown, and black.

Life history

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.

Venom

The

saliva Saliva (commonly referred to as spit) is an extracellular fluid produced and secreted by salivary glands in the mouth. In humans, saliva is around 99% water, plus electrolytes, mucus, white blood cells, epithelial cells (from which DNA can ...

of a common garter snake may be

toxic Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a sub ...

to amphibians and other small animals. Garter snakes have a mild venom in their saliva. For humans, a bite is not dangerous, though it may cause slight itching, burning, and/or swelling. Common garter snakes may also secrete a foul-smelling fluid from postanal

gland In animals, a gland is a group of cells in an animal's body that synthesizes substances (such as hormones) for release into the bloodstream (endocrine gland) or into cavities inside the body or its outer surface (exocrine gland). Structure De ...

s when handled or harmed. Common garter snakes are resistant to naturally found poisons such as that of the American toad and

rough-skinned newt The rough-skinned newt or roughskin newt (''Taricha granulosa'') is a North American newt known for the strong toxin exuded from its skin. Appearance A stocky newt with rounded snout, it ranges from light brown to olive or brownish-black on ...

, the latter of which can kill a human if ingested. They have the ability to absorb the toxin from the newts into their bodies, making them poisonous, which can deter potential predators. The common garter snake uses toxicity for both offense and defense. On the offensive side, the snake's venom can be toxic to some of its smaller prey, such as mice and other rodents. On the defensive side, the snake uses its resistance to toxicity to provide an important antipredator capability. A study on the evolutionary development of resistance of

tetrodotoxin Tetrodotoxin (TTX) is a potent neurotoxin. Its name derives from Tetraodontiformes, an order that includes pufferfish, porcupinefish, ocean sunfish, and triggerfish; several of these species carry the toxin. Although tetrodotoxin was discovere ...

compared two populations of ''Thamnophis'' and then tested inside a population of ''T. sirtalis''. Those that were exposed to and lived in the same environment as the newts (''Taricha granulosa'') or rough-skinned newt, that produce tetrodotoxin when eaten were more immune to the toxin (see figure).It seems that the two species were in a evolutionary arms race. While resistance to tetrodotoxin is beneficial in acquiring newt prey, costs are associated with it as well. Consuming the toxin can lead to reduced speed and sometimes no movement for extended periods of time, along with impaired thermoregulation. The antipredator display that this species uses demonstrates the idea of an "arms race" between different species and their antipredator displays. Along the entire geographical interaction of ''T. granulosa'' and ''T. sirtalis'', patches occur that correspond to strong coevolution, as well as weak or absent coevolution. Populations of ''T. sirtalis'' that do not live in areas that contain ''T. granulosa'' contain the lowest levels of tetrodotoxin resistance, while those that do live in the same area have the highest levels of tetrodotoxin resistance. In populations where tetrodotoxin is absent in ''T. granulosa'', resistance in ''T. sirtalis'' is selected against because the mutation causes lower average population fitness. This helps maintain polymorphism within garter snake populations.

Subspecies

Current scientific classification recognizes 13

subspecies In biological classification, subspecies is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics ( morphology), but that can successfully interbreed. Not all specie ...

(ordered by date): A trinomial authority in parentheses indicates that the subspecies was originally described in a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

other than ''Thamnophis''.

Etymology

The

subspecific name In zoological nomenclature, a subspecific name is the third part of a trinomen. In zoology there is only one rank below that of species, namely "subspecies". In botanical nomenclature, there are several levels of subspecific names, such as ''var ...

''fitchi'' is in honor of the

American American(s) may refer to: * American, something of, from, or related to the United States of America, commonly known as the "United States" or "America" ** Americans, citizens and nationals of the United States of America ** American ancestry, pe ...

herpetologist Herpetology (from Greek ἑρπετόν ''herpetón'', meaning "reptile" or "creeping animal") is the branch of zoology concerned with the study of amphibians (including frogs, toads, salamanders, newts, and caecilians ( gymnophiona)) and rep ...

Henry Sheldon Fitch Henry Sheldon Fitch (December 25, 1909 – September 8, 2009) was an American herpetologist. Fitch was born in Utica, New York. When he was a year old, the family moved to Medford in the Rogue Valley in Oregon. Growing up, he had a keen interest i ...

. The subspecific name ''lowei'' is in honor of the American herpetologist Charles Herbert Lowe. The subspecific name ''pickeringii'' is in honor of the American naturalist Charles E. Pickering.

Reproduction

Generally, populations include far more males than females, so during mating season, they form "mating balls", in which one or two females are completely swamped by ten or more males. Sometimes a male snake mates with a female before hibernation, and the female stores the sperm internally until spring, when she allows her eggs to be fertilized. If she mates again in the spring, the fall sperm degenerate and the spring sperm fertilize her eggs. The females may give birth ovoviviparously to 12 to 40 young from July through October. In the early part of sex, when snakes are coming out of hibernation, the males generally emerge first to be ready when the females wake up. Some males assume the role of a female and lead other males away from the burrow, luring them with a fake female

pheromone A pheromone () is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting like hormones outside the body of the secreting individual, to affect the behavio ...

. 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. This method also serves to help warm males by tricking other males into surrounding and heating up the male, and is particularly useful to subspecies in colder climates (such as those inhabited by ''T. s. parietalis''); this type of

mimicry In evolutionary biology, mimicry is an evolved resemblance between an organism and another object, often an organism of another species. Mimicry may evolve between different species, or between individuals of the same species. Often, mimicry f ...

is primarily found in that subspecies. These deceptive males have been found to mate with females significantly more often than males that do not exhibit this mimicry.

Habitat

The

habitat In ecology, the term habitat summarises the array of resources, physical and biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species habitat can be seen as the physical ...

of the common garter snake ranges from forests, fields, and prairies to streams, wetlands, meadows, marshes, and ponds, and it is often found near water. Depending on the subspecies, the common garter snake can be found as far south the southernmost tip of

Florida Florida is a state located in the Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Bahamas and Atlantic Ocean, and ...

in the United States and as far north as the southernmost tip of the

Northwest Territories The Northwest Territories (abbreviated ''NT'' or ''NWT''; french: Territoires du Nord-Ouest, formerly ''North-Western Territory'' and ''North-West Territories'' and namely shortened as ''Northwest Territory'') is a federal territory of Canada. ...

in Canada. It is found at altitudes from sea level to mountains.

Diet

The diet of ''T. sirtalis'' consists mainly of

amphibian Amphibians are four-limbed and ectothermic vertebrates of the class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terrestrial, fossorial, arbo ...

s and

earthworm An earthworm is a terrestrial invertebrate that belongs to the phylum Annelida. They exhibit a tube-within-a-tube body plan; they are externally segmented with corresponding internal segmentation; and they usually have setae on all segments. T ...

s, but also

leech Leeches are segmented parasitism, parasitic or Predation, predatory worms that comprise the Class (biology), subclass Hirudinea within the phylum Annelida. They are closely related to the Oligochaeta, oligochaetes, which include the earthwor ...

es,

slug Slug, or land slug, is a common name for any apparently shell-less terrestrial gastropod mollusc. The word ''slug'' is also often used as part of the common name of any gastropod mollusc that has no shell, a very reduced shell, or only a ...

snail A snail is, in loose terms, a shelled gastropod. The name is most often applied to land snails, terrestrial pulmonate gastropod molluscs. However, the common name ''snail'' is also used for most of the members of the molluscan class ...

insect Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three pa ...

crayfish Crayfish are freshwater crustaceans belonging to the clade Astacidea, which also contains lobsters. In some locations, they are also known as crawfish, craydids, crawdaddies, crawdads, freshwater lobsters, mountain lobsters, rock lobsters, m ...

fish Fish are Aquatic animal, aquatic, craniate, gill-bearing animals that lack Limb (anatomy), limbs with Digit (anatomy), digits. Included in this definition are the living hagfish, lampreys, and Chondrichthyes, cartilaginous and bony fish as we ...

lizard Lizards are a widespread group of squamate reptiles, with over 7,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The group is paraphyletic since it excludes the snakes and Amphisbaenia altho ...

s, other snakes, small

bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweig ...

s, and

rodent Rodents (from Latin , 'to gnaw') are mammals of the order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are rodents. They are n ...

s. Common garter snakes are effective at catching fast-moving creatures such as fish and tadpoles.

As prey

Animals that prey on the common garter snake include large fish (such as

bass Bass or Basses may refer to: Fish * Bass (fish), various saltwater and freshwater species Music * Bass (sound), describing low-frequency sound or one of several instruments in the bass range: ** Bass (instrument), including: ** Acoustic bass gui ...

and

catfish Catfish (or catfishes; order Siluriformes or Nematognathi) are a diverse group of ray-finned fish. Named for their prominent barbels, which resemble a cat's whiskers, catfish range in size and behavior from the three largest species alive, ...

American bullfrog The American bullfrog (''Lithobates catesbeianus''), often simply known as the bullfrog in Canada and the United States, is a large true frog native to eastern North America. It typically inhabits large permanent water bodies such as swamps, p ...

common snapping turtle The common snapping turtle (''Chelydra serpentina'') is a species of large freshwater turtle in the family Chelydridae. Its natural range extends from southeastern Canada, southwest to the edge of the Rocky Mountains, as far east as Nova Scotia ...

s, larger snakes,

hawk Hawks are birds of prey of the family Accipitridae. They are widely distributed and are found on all continents except Antarctica. * The subfamily Accipitrinae includes goshawks, sparrowhawks, sharp-shinned hawks and others. This subfa ...

raccoon The raccoon ( or , ''Procyon lotor''), sometimes called the common raccoon to distinguish it from other species, is a mammal native to North America. It is the largest of the procyonid family, having a body length of , and a body weight of ...

s, foxes,

wild turkey The wild turkey (''Meleagris gallopavo'') is an upland ground bird native to North America, one of two extant species of turkey and the heaviest member of the order Galliformes. It is the ancestor to the domestic turkey, which was originally d ...

s, and domestic cats and dogs.

Conservation

Water contamination, urban expansion, and residential and industrial development are all threats to the common garter snake. The

San Francisco garter snake The San Francisco garter snake (''Thamnophis sirtalis tetrataenia'') is a slender multi-colored subspecies of the common garter snake. Designated as an endangered subspecies since the year 1967, it is endemic to San Mateo County and the extrem ...

(''T. s. tetrataenia''), which is extremely scarce and occurs only in the vicinity of ponds and reservoirs in

San Mateo County, California San Mateo County ( ), officially the County of San Mateo, is a county located in the U.S. state of California. As of the 2020 census, the population was 764,442. Redwood City is the county seat, and the third most populated city following Dal ...

, has been listed as an

endangered species An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching and inv ...

by the U.S. Fish and Wildlife Service since 1967.

Antipredatory displays

Garter snakes exhibit many different behaviors to ward off predators. Garter snakes exhibit a greater variety of body postures than other snakes. Under selection by predation, these snakes have developed postural responses that are highly variable and heritable. These are highly variable even within a single population. Different postures indicate whether the snake is preparing to flee, fight, or protect itself. Different biological factors such as body temperature and sex also influence whether the snake exhibits certain antipredatory behaviors. The warmer the temperature of a garter snake, the more likely the snake is to flee a predator; a snake with a cooler body temperature is more likely to remain stationary or attack. Male garter snakes are also more likely to flee. Garter snakes that exhibit more aggressive antipredatory displays tend to also be fast and have high stamina. However, the reason for this correlation is unknown. The first response of the snake to a predator is often a bluff. When the snake was teased with a finger under laboratory conditions, the snake reacted aggressively, but once touched, it became passive. This may be because the snake is disinclined to attack an organism it sees as larger than itself. Garter snakes do not exhibit

or aposematic coloration; relying on

cryptic Cryptic may refer to: In science: * Cryptic species complex, a group of species that are very difficult to distinguish from one another * Crypsis, the ability of animals to blend in to avoid observation * Cryptic era, earliest period of the Earth ...

coloration for protection, they will freeze until they know they are spotted, then attempt a stealthy departure. The decision of a juvenile garter snake to attack a predator can be affected by whether the snake has just eaten or not. Snakes that have just eaten are more likely to strike a predator or stimulus than snakes that do not have a full stomach. Snakes that have just eaten a large animal are less mobile. Another factor that controls the antipredatory response of the garter snake is where on its body the snake is attacked. Many birds and mammals prefer to attack the head of the snake. Garter snakes are more likely to hide their heads and move their tails back and forth when being attacked close to the head. Snakes that are attacked in the middles of their bodies are more likely to flee or exhibit open-mouthed warning reactions. Age may be another factor that contributes to antipredatory responses. As garter snakes mature, the length of time for which they can engage in physical activity at 25 °C increases. Juvenile snakes can only be physically active for 3–5 minutes. Adult snakes can be physically active for up to 25 minutes. This is mostly due to aerobic energy production;

pulmonary The lungs are the primary organs of the respiratory system in humans and most other animals, including some snails and a small number of fish. In mammals and most other vertebrates, two lungs are located near the backbone on either side of ...

aeration increases up to three times in adult garter snakes when compared to juveniles. The quick fatigue of the juveniles limits the habitats they can live in, as well as their food sources. It also affects the antipredator response of both juvenile and adult garter snakes; without sufficient energy production, the snake cannot effect an antipredatory response. File:Eastern_Garter_Snake.jpg, ''T. s. sirtalis'' (Ontario specimen) File:Couleuvres-rayees-magog-quebec.jpg, ''T. s. sirtalis'' (Quebec, Canada) File:Thamnophis sirtalis sirtalis Florida specimen.JPG, ''T. s. sirtalis'' (Florida specimen) File:Thamnophis sirtalis.JPG, ''T. s. pallidulus''

References

Bibliography

*Beolens, Bo; Watkins, Michael; Grayson, Michael (2011). ''The Eponym Dictionary of Reptiles''. Baltimore: Johns Hopkins University Press. xiii + 296 pp. .

External links

*
Care of Garter SnakesGarter Snake Information
* .
Eastern Garter Snake
at Ontario Nature.
Red-sided Garter Snake
at Ontario Nature.