Common Garter Snake
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|Common Garter Snake|
|Thamnophis sirtalis sirtalis|
13 sspp., see text
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). The average body mass is 150 g (5.3 oz).
Current scientific classification recognizes thirteen subspecies (ordered by date):
- T. s. sirtalis (Linnaeus, 1758) – Eastern Garter Snake
- T. s. parietalis (Say, 1823) – Red-sided Garter Snake (has also been introduced to northern Halland in Sweden)
- T. s. infernalis (Blainville, 1835) – California Red-sided Garter Snake
- T. s. concinnus (Hallowell, 1852) – Red-spotted Garter Snake
- T. s. dorsalis (Baird & Girard, 1853) – New Mexico Garter Snake
- T. s. pickeringii (Baird & Girard, 1853) – Puget Sound Garter Snake
- T. s. tetrataenia (Cope, 1875) – San Francisco Garter Snake (endangered)
- T. s. semifasciatus (Cope, 1892) – Chicago Garter Snake
- T. s. pallidulus Allen, 1899 – Maritime Garter Snake
- T. s. annectens B.C. Brown, 1950 – Texas Garter Snake
- T. s. fitchi Fox, 1951 – Valley Garter Snake
- T. s. similis Rossman, 1965 – Blue-striped Garter Snake
- T. s. lowei W. Tanner, 1988
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.
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. Also, Garter Snakes are resistant to most naturally found poisons such as that of the American Toad and Rough-Skinned Newt, the latter able to kill over five adult humans.
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.
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.
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.
See also 
- Narcisse Snake Pits
- Inger, R. F. (1946) Restriction of the type locality of Thamnophis sirtalis. Copeia 1946:254.
- "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.
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