Garter snake
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| Missing image Thamnophis_sirtalis_parietalis.jpg A Red-sided Garter Snake Red-sided Garter Snake Thamnophis sirtalis parietalis | ||||||||||||
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Many; see text. |
A garter snake, or garden snake, or gardner snake, is any species of North American snake within the genus Thamnophis.
There is no consensus exactly how many species there are, and disagreement among taxonomists and sources (such as field guides) over whether two types of snakes are separate species or subspecies of the same species is common. There is little variation within the pattern of scales among the different varieties of garter snakes, but coloration varies widely across varieties and geographic regions.
The pattern on these snakes consists of one or three longitudinal stripes on the back, typically red, yellow or white. The snake genus got its common name because people described the stripes as resembling a garter. In between the stripes on the pattern are rows with blotchy spots. Even within a single species the color in the stripes and spots and background can differ, much as humans across the world vary in hair and skin colors. In some species, the grass snakes, the stripes vary little in color from the adjacent bands or background and are not readily seen. Most garter snakes are under 60 cm (24 inches) long.
Garter snakes eat small creatures: insects, slugs (including banana slugs), snails, earthworms, leeches, mice, lizards and amphibians. The Western terrestrial garter snake will even eat carrion. When near the water, they will eat fish. Sometimes they will even eat baby birds. They are completely harmless to man, but will strike if disturbed. The ribbon snake in particular loves frogs (including tadpoles), readily eating them despite their strong chemical defenses. Food is swallowed whole. Although dining mostly upon live animals, they will sometimes swallow eggs as well.
Garter snakes began mating as soon as they emerge from hibernation. During mating season, the males will mate with several females. Males comes out of their dens and, as soon as the females begin coming out, will surround them. A male sends out pheromones, and the female will follow the pheromones to an attractive male and mate with him. Once impregnated, a female will retire from the mating ring and find food and a place to give birth. Female garter snakes are able to store the male's sperm before beginning the accouchement. The young are incubated in the lower abdomen, at about the midpoint of the length of the mother's body. Garter snakes are ovoviparous. Gestation is two to three months. As few as 3 or as many as 50 may be born in a single litter. The babies are independent upon birth, abandoning the mother.
Garter snakes of all species are gregarious (when not in hibernation or aestivation). They have complex systems of pheromonal communication. They can locate other snakes by following their pheromone-scented trails. Male and female skin pheromones are so different as to be immediately distinguishable. However, sometimes a male garter snake is born that has both male and female pheromones. During mating season, male snakes are often fooled into thinking these snakes are female by their pheromones, and will try to mate with them. These males with the female pheromone genetic variation are among the first to mate, attracting females while other males are still fooled into being attracted to them.
If disturbed, a garter snake may strike, and will often coil, but typically it will hide its head and flail its tail about. These snakes will also discharge a malodorous, musky-scented secretion from their anal gland, like a skunk spraying. They often use these techniques to escape when ensnared by a predator. They will also slither into the water to escape a predator on land. Hawks, crows, raccoons, crayfish and other snake species (such as the coral snake and king snake) will eat garter snakes, with even shrews and frogs eating the juveniles.
Being cold-blooded like all reptiles, garter snakes bask in the sun to keep their body temperature warm (at 28 to 32 degrees Celsius) during the morning. The temperature is lower during the evening. Garter snakes will often sleep together to keep their body temperature warm at night. They also sleep in large nests next to one another's body during hibernation. These snakes will migrate large distances to hibernate.
Garter snakes are extremely common across North America, from Canada to Central America, an everyday find in gardens. The single most widely distributed species of reptile in North America, in fact, is the common garter snake (T. sirtalis), which is the only species of snake to be found in Alaska. The genus' unparticular diet of small invertebrates makes it adaptable to different biomes and landforms, from marshes to hillsides to drainage ditches and even vacant lots. This genus is found in both dry and wet regions, with varying proximity to water and rivers, although as you approach the western portion of the continent the snakes are more water-loving than on the eastern portion. Northern populations hibernate in larger groups than southern ones. Despite the decline in their population from collection as pets (especially in the more northerly regions in which large groups are collected at hibernation), pollution of aquatic areas, and introduction of bullfrogs and bass, this is still a very common genus of snake. The San Francisco garter snake (Thamnophis sirtalis tetrataenia), however, is an endangered subspecies and has been on the endangered list since 1967. Predation by crayfish has also been responsible for the decline of the narrow-headed garter snake.
Species
- T. angustirostris
- T. atratus (Santa Cruz Garter Snake and Western Aquatic Garter Snake)
- T. brachystoma (Short-headed Garter Snake)
- T. butleri (Butler's Garter Snake)
- T. chrysocephalus
- T. couchii (Couch's Garter Snake)
- T. cyrtopsis (Black-necked Garter Snake)
- T. elegans (Western Terrestrial Garter Snake and Wandering Garter Snake)
- T. eques (Mexican Garter Snake)
- T. exsul
- T. fulvus
- T. gigas (Giant Garter Snake), listed as "vulnerable" on the IUCN Red List of Threatened Species
- T. godmani
- T. hammondii (Two-striped Garter Snake)
- T. marcianus (Checkered Garter Snake)
- T. melanogaster
- T. mendax
- T. ordinoides (Northwestern Garter Snake)
- T. proximus (Western Ribbon Snake)
- T. radix (Plains Garter Snake)
- T. rossmani
- T. rufipunctatus (Narrow-headed Garter Snake)
- T. sauritus (Eastern Ribbon Snake)
- T. scalaris
- T. scaliger
- T. sirtalis (Common Garter Snake)
- T. s. parietalis (Red-sided Garter Snake)
- T. sumichrasti
- T. validade:Strumpfbandnattern