Northwestern Garter Snake

Contents:
 
Links:
Taxon, Status, and Ranks Habitat Photos
General Description State Status Comments
Identification Tips Inventory & Research Needs Key Features
Phenology Threats & Mgmt Concerns
Range References Distribution Map

Taxon, Status, and Rank

Species Thamnophis ordinoides     (Baird and Girard, 1852)
Family Colubridae
(Colubrids)
Status none
State Rank S5
Global Rank G5

Our three garter snake species are similar in general appearance and have coloration and patterns that vary regionally and by individual. All traits, especially scale counts, color and pattern, must be examined to correctly identify a garter snake to species. Although little appreciated, these are beautiful snakes with many stunning color variations.

General Description

This is a small to medium-sized, brown or black snake with stripes. Spots may also be present. Typically three stripes are present; a thin vertebral stripe and two thin lateral stripes. The vertebral and/or lateral stripes may be absent. Adults rarely exceed 600 mm (23.6 in.) total length. The pupil is round. The scales are keeled and there are usually 17 (occasionally 19) rows at mid-body. The upper jaw has 7 scales (upper labials) and the lower jaw has 8-9 scales (lower labial scales).

Coloration and patterns are highly variable. The dorsal color is brown, dark brown, slate gray or black. The vertebral stripe is white, yellow, orange, red, green, turquoise, or blue. The lateral stripes are white, yellow, green, turquoise, or blue. Small dark spots may be present between the vertebral stripe and the lateral stripes. White flecks are present on the edges of the dorsal scales. The ventral coloration is usually white or yellow at the chin with increasing bluish or black pigmentation toward the tail. Red, orange or salmon colored blotches are usually present on the ventral surface of individuals with red vertebral stripes.

The following three variations are commonly seen in Washington: 1) A dark dorsal color with yellow, green, turquoise or blue vertebral and lateral stripes; 2) A brown dorsal color with dull yellow vertebral and lateral stripes and two rows of alternating small dark spots above the lateral stripes and adjacent to the vertebral stripe; and 3) A dark dorsal color with a red vertebral stripe and bright yellow lateral stripes. In some individuals, the red pigment is only present in part of the vertebral stripe or appears more orange than red. See Photos Page.

Identification Tips

Depending on stripe color and pattern, Northwestern Garter Snake can be easily mistaken for either the Common Garter Snake or Western Terrestrial Garter Snake. Northwestern Garter Snakes differ in having 17 scales (occasionally 19) at mid-body, 7 upper labial scales and 8-9 lower labial scales. Also, the head is relatively small in proportion to the body. When Northwestern Garter Snakes have dark spots, the spots do not invade the dorsal stripe. Northwestern Garter Snakes do not have red spots or bars along the sides of the body although some red pigmentation may be present along the sides of individuals with a red stripe. Northwestern Garter Snakes have white specks on the edges of the dorsal scales, a trait our Common Garter Snakes do not have. In Washington, only Northwestern Garter Snakes will have a red vertebral stripe (locally called “red racers”), but this is one of the less common vertebral stripe color variations.

Striped Whipsnakes differ in being larger (adults greater than 1 meter in length), having smooth scales, 15 dorsal scale rows and they have a distinct pattern of dark and light colored stripes on the sides of the body. See Key Features Page.

Phenology

At low elevations, activity starts in March and continues into early November. After emergence from winter dens, snakes may remain in the vicinity of the overwintering site for two or more weeks until mating is complete and weather conditions are appropriate for dispersal. Northwestern Garter Snakes typically breed in spring after emergence in late March to early April and again in late September and early October. After mating, snakes disperse to summer foraging areas. In the lower Puget Sound area, female garter snakes of all three species are commonly found clustered in open grassy areas. Northwestern Garter Snakes give birth to their young rather than lay eggs. The young are born in late summer and early fall depending on location. In the lowland Puget Sound area, newborns (neonates) start to appear in late August and early September.

Range

Northwestern Garter Snakes occur primarily west of the Cascades Mountain crest in the Northwest Coast, Puget Trough and West Cascades ecoregions. Occurrences in the East Cascades Ecoregion are from the Cle Elum area in Kittitas County, northwestern Yakima County and western Klickitat County. The species may also cross into the Northern Cascade Ecoregion near Deming. See Distribution Map.

For information on the complete range of this species, see NatureServe Explorer.

Habitat and Habits

Northwestern Garter Snakes are the smallest and most terrestrial of our three garter snake species. They occur in open grassy areas, in forest openings and edges of coniferous forest. They are also common near water bodies. This species is a specialist on slugs and earthworms.

Garter snakes defend themselves by releasing the contents of their cloaca and musk glands then smearing this pungent foul smelling mixture over themselves and their attacker. Some will also regurgitate the content of their stomach and most will bite.

State Status Comments

This is a common species in western Washington. No declines have been reported at this time.

Inventory and Research Needs

Observations can be submitted to the Washington Department of Fish and Wildlife WSDM database by contacting Lori Salzer by E-mail salzeljs@dfw.wa.gov. Photo vouchers highlighting the labial scales, as well as dorsal and ventral views are preferred.

Current or Recent Research in Washington

The authors know of no current research on this species.

Threats and Management Concerns

Over hunting or collecting, wanton killing, and destruction of overwintering sites can result in local declines. Road mortality is also a threat in areas where the snakes must cross to access overwintering or foraging habitat.

References

Fitch (1941), Nussbaum, et al. (1983), Rossman et al. (1996)


Hallock, L.A. and McAllister, K.R. 2009. Northwestern Garter Snake. Washington Herp Atlas. http://www1.dnr.wa.gov/nhp/refdesk/herp/

Last updated: June 2009


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