The aquatic garter snake (''Thamnophis atratus'') 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 appropriate s ...

colubrid Colubridae (, commonly known as colubrids , from la, coluber, 'snake') is a family of snakes. With 249 genera, it is the largest snake family. The earliest species of the family date back to the Oligocene epoch. Colubrid snakes are found on ev ...

snake. Three subspecies are currently recognized.

Geographic range

It is found exclusively along the coast of

Oregon Oregon () is a state in the Pacific Northwest region of the Western United States. The Columbia River delineates much of Oregon's northern boundary with Washington, while the Snake River delineates much of its eastern boundary with Idaho. T ...

and

California California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the m ...

Description

The aquatic garter snake grows up to 18-40 inches (46–102 cm) long. Its dorsal coloration varies greatly. The different coloration patterns are: pale gray with alternating rows of darker blotches on the sides, dark brown with borders that are less distinct, or nearly all black. A long yellow stripe running down the back may be present or absent, only confined to the neck, or just very indistinct. The throat and underside of the snake are whitish to yellow. One

color morph In biology, polymorphism is the occurrence of two or more clearly different morphs or forms, also referred to as alternative ''phenotypes'', in the population of a species. To be classified as such, morphs must occupy the same habitat at the s ...

of the aquatic garter snake has a blue-gray background color with a faint olive-colored

dorsal Dorsal (from Latin ''dorsum'' ‘back’) may refer to: * Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism * Dorsal, positioned on top of an aircraft's fuselage * Dorsal c ...

stripe and white dots along its sides. Another color morph has a yellow dorsal stripe with black spots along its sides. The second color morph has the more classic

garter snake Garter snake is a common name for generally harmless, small to medium-sized snakes belonging to the genus ''Thamnophis'' in the family Colubridae. Native to North and Central America, species in the genus ''Thamnophis'' can be found from the ...

look; however, due to its behavior and scalation, it is grouped in this species.

Habitat

It can most commonly be found on the edges of bushlands, woodlands, grasslands, and forests near ponds, marshes, streams and lakes.

Behavior

When feeling threatened, this snake will seek shelter in a nearby water source. Occasionally, while the snake is hunting for food in a stream, it will flick its tongue above the water to mimic an

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 ...

that a small fish would usually eat, thus luring the

prey Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill ...

into its mouth.

Reproduction

The aquatic garter snake bears live young. Broods consist of three to 12 young.

Subspecies

* Santa Cruz garter snake, ''T. a. atratus'' ( Kennicott, 1860) * Oregon garter snake, ''T. a. hydrophilus'' Fitch, 1936 * Diablo Range garter snake, ''T. a. zaxanthus'' Boundy, 1999

References

*Peterson Field Guide - Western Reptiles and Amphibians - 3rd Edition Thamnophis Reptiles of the United States Fauna of California Biota of Oregon Fauna of the California chaparral and woodlands Fauna of the San Francisco Bay Area Reptiles described in 1860 Taxa named by Robert Kennicott {{Colubrids-stub