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Eastern garter snake

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Eastern garter snake

Secure  (NatureServe)[1]
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Squamata
Suborder: Serpentes
Family: Colubridae
Genus: Thamnophis
Species:
T. sirtalis
Subspecies:
T. s. sirtalis
Trinomial name
Thamnophis sirtalis sirtalis
(Linnaeus, 1758)

The eastern garter snake (Thamnophis sirtalis sirtalis) is a medium-sized snake indigenous to North America.

Taxonomy

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Etymology

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The scientific name Thamnophis sirtalis sirtalis is a combination of Ancient Greek and New Latin that means "bush snake that looks like a garter strap". The generic name Thamnophis is derived from the Greek "thamnos" (bush) and "ophis" (snake) and the specific name sirtalis is derived from the New Latin "siratalis" (like a garter), a reference to the snake's color pattern resembling a striped garter strap.[2]

Anatomy and description

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Eastern garter snakes average between 46–66 cm (18–26 in) long. The largest recorded length was 124 cm (48.7 in) long. Females are typically larger than males. They are either a greenish, brown, or black color and have a distinct yellow or white stripe.

The eastern garter snake is broadly considered non-venomous. Garter snakes do have a Duvernoy's gland, and the secretion from the gland may be chewed into prey during bites. The secretion is noted to cause hemorrhaging in mice and has produced non-allergic symptoms in at least one bite on a human.[3][4][5]

Distribution and habitat

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The eastern garter snake has a wide range across eastern North America and as far north as southern Ontario and Quebec to the Gulf of Mexico in the south, along the eastern shores of America to the Mississippi River.[citation needed] Their distribution ranges all across America but tends not to be present in western deserts.[6] In New England, the snake is described as the "most widespread and ubiquitous" serpent, from wilderness to urban environments and from sea level to high elevations.[2]

The eastern garter snake will live in a variety of environments, with a preference for grassy or shrubby fields, including abandoned farmland, outbuildings and trash dumps.[2] In particular the snake likes to inhabit stone walls that separate the forest from fields. It is also found along moist habitats such as lakes, rivers, streams, swamps, bogs, ponds, drainage ditches, and quarries. Snakes are present in urban environments in habitats that include "city parks, cemeteries and suburban yards and gardens".[2] Eastern garter snakes like to conceal themselves under logs, stones and other debris that allow them to bask in the sunlight and quickly seek refuge from predators. Krulikowski notes that "old poultry farms with discarded sheet-metal incubation trays provide warm, moist hiding places."[2]

Colour variation in the eastern garter snake

Ecology and behavior

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Hunting and diet

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An eastern garter snake eating a northern leopard frog (Lithobates pipiens).

The majority of the eastern garter snake's diet (~80%) consists of earthworms, though they have a secondary preference (~15%) for amphibian prey (esp. frogs) as well.[7] As they mature, their preference in prey will undergo an ontogenetic shift. Younger eastern garter snakes (those under 40 cm (16 in) in length) prey almost exclusively upon earthworms (~88%) and smaller amphibians (~8%), such as spring peepers and northern cricket frogs, and generally avoid taking warm-blooded prey. Mature snakes rely more on amphibian prey (which now comprise ~19% of their diet), especially larger amphibians like green frogs and northern leopard frogs, though earthworms still make up the bulk of their diet (~76%).[8]

However, eastern garter snakes are opportunistic predators, and will readily consume almost any creature they can swallow. Other prey records for this subspecies include caterpillars,[7] leeches,[9] mudminnows,[9] the Jefferson salamander,[10] and the eastern meadow vole.[11] Large adults will even target small birds if the opportunity presents itself, such as song sparrows,[12] goldfinches,[12] and chipping sparrows.[13]

Predator avoidance

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The eastern garter snake is known to flatten its head and anterior body and strike forward if it is bothered. Juveniles have been observed to engage in this behavior and strike at such a force that they leave the ground entirely. Adults also will spray musk from glands in their tail, and sometimes defecate to discourage predators.[citation needed] Snakes with higher body temperatures are more likely to flee from predators.[14]

Reproduction

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Eastern garter snakes are ovoviviparous, giving birth to live young. Many males may try to mate with one female, resulting in a "snake orgy".[citation needed] The young are 13–23 cm (5–9 in) long at birth.

Conservation status

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Melanistic eastern garter snake

As of 2024, the eastern garter snake has not been assessed by the IUCN Red List, nor has it been assessed by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC).[15] Its parent species, the common garter snake (Thamnophis sirtalis), was last assessed by the IUCN in 2007 and determined to be of least-concern due its wide geographic distribution, (presumed) large population, and lack of significant threats to its survival.[16] In 2016, NatureServe assessed the eastern garter snake to be a secure subspecies (G5T5) globally, and nationally secure (N5) in Canada.[1]

References

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Citations

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  1. ^ a b NatureServe 2016.
  2. ^ a b c d e Krulikowski 2004.
  3. ^ Hayes & Hayes 1985.
  4. ^ Vest 1981.
  5. ^ Gomez et al. 1994.
  6. ^ Shine et al. 2004.
  7. ^ a b Carpenter 1952, p. 239: "The Common Garter Snake, while showing a preference for earthworms (80%), also has a secondary preference for amphibians (15%) and consumed a much greater variety of foods, including mammals, fish, caterpillars and leeches (Fig. 4)."
  8. ^ Carpenter 1952, p. 239: "Common Garter Snakes exceeding 40 cm in length capture more amphibians and take more warm blooded prey than the smaller snakes: earthworms 76% and 88%, amphibians 19% and 8%, mammals 2% and 0%, others 3% and 4%, respectively. The amphibians eaten by the small snakes were all small forms (two Hyla crucifer, one Pseudacris nigrita, one Acris crepitans, and a metamorphosing Rana clamitans). Large Rana clamitans and Rana pipiens, made up 65% of the amphibians eaten by the larger snakes, suggesting that they choose these larger frogs."
  9. ^ a b Carpenter 1952, p. 241: "Six other individuals contained two or three types of food at one time in combinations of earthworms and mammal, earthworm and frog and another had eaten five mudminnows (Umbra limi), a tadpole and a leech."
  10. ^ Carpenter 1952, p. 241: "A third disgorged an earthworm and a Jefferson Salamander (Ambystoma Jeffersonianum), one month later a Green Frog, and a little over one year later, three earthworms."
  11. ^ Carpenter 1952, p. 242: "All of the mammals eaten were Microtus pennsylvanicus. Two were represented by the skull and fur, one by fur only, and the other by fur and newly born young."
  12. ^ a b Carpenter 1952, p. 242: "The first record [from the Common Garter Snake] for a bird was an adult Song Sparrow (Melospiza melodia) taken at the Fleming Creek area. There is no evidence to show whether it was dead or alive when taken. The other record was for four Goldfinch nestlings (Spinus tristis) taken in the field just east of the Cherry Hill area, but the Goldfinches may have been alive, as indicated by adult activity near the nest, though the condition of the nest led me to believe they were dead when eaten."
  13. ^ Carpenter 1952, p. 242: "Walkinshow (1943) reports this species eating Chipping Sparrows (Spizella passerina)."
  14. ^ Passek & Gillingham 1997.
  15. ^ Ontario Nature 2024: "Neither the Committee on the Status of Species at Risk in Ontario nor the Committee on the Status of Endangered Wildlife in Canada has assessed the status of the eastern gartersnake. [...] The International Union for Conservation of Nature has not yet assessed the global status of the eastern gartersnake, but lists the common gartersnake (of which the eastern gartersnake is a subspecies) as Least Concern."
  16. ^ Frost, Hammerson & Santos-Barrera 2007: "Listed as Least Concern in view of its extremely wide distribution, presumed large population, and because populations are unlikely to be declining."

Bibliography

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  • Carpenter, Charles C. (October 1952). "Comparative Ecology of the Common Garter Snake (Thamnophis s. sirtalis), the Ribbon Snake (Thamnophis s. sauritus), and Butler's Garter Snake (Thamnophis butleri) in Mixed Populations". Ecological Monographs. 22 (4). Wiley: 235–258. doi:10.2307/1948469. JSTOR 1948469.
  • Krulikowski, Linda (2004). Snakes of New England / Photographic and Natural History Study. Luvlife Publishing. pp. 72–84. ISBN 978-0976431602.
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