GAP Analysis Predicted Distribution Map

Metadata (Data about data or how the map was made)

Legend:
= Core Habitat
= Marginal Habitat

Predicted Distribution
Reptiles do not migrate as some birds and mammals, so the colored areas depict the predicted range for the Western Terrestrial Garter Snake year-round. The habitats were identified using 1991 satellite imagery, other datasets and experts throughout the state, as part of the Washington Gap Analysis Project.

Other maps & Information: NatureMapping observations throughout the year Links to pictures and other information about this species

Distribution and Habitat Requirements
This species has been found rather infrequently and is regarded as one of the scarcer snakes in the Pacific Northwest. Although it is not the rare species previously supposed in California, it is not known if the Washington localities represent isolated populations. Its range, ecological distribution and behavior appear to be closely correlated with a highly utilized food resource: an introduced genus of slug in some areas. Eggs have been found in cracks in rock outcrops and in bunch grass roods on an unshaded, grass- covered southern slope with several small natural rock outcrops along a hillside in Oregon. In the Northwest, this species is apparently restricted to low elevations, in moist rotting logs or stable talus slopes, near streams or other moist habitats. This species has been found in numerous habitats where it can hide in cool and moist places, but is rarely encountered. Rocks and woody debris provide cover during periods when this snake is active, which is during cool, moist conditions. There is no evidence C. tenuis is associated with slugs in Washington State.

Models
The Columbia Basin, East Central and Southeast Cascades and Puget Trough ecoregions were selected. The Three-tip Sage, Klickitat Meadow Steppe, Bitterbrush, Central Arid Steppe, Ponderosa Pine, Interior Douglas-fir, Oak and Woodland/Prairie Mosaic zones were core. The Grand Fir zone was marginal. Good habitats were lakes, riparian areas (areas along streams and rivers) and all developmental stages of open and closed-canopy hardwood, hardwood/conifer and conifer forests. There is not much confidence in the model because so little is known of this snake. It is quite secretive and has even been found in basements and under rubbish piles in suburban areas. The scattered records are in such different ecological zones that they suggest this species can be found in a diverse area, which would normally be associated with a wider distribution. It is suspected that this species is more widespread than the model and records indicate.

Translated from the Washington Gap Analysis Amphibians and Reptiles Volume by Karen Dvornich

Webpage designed by Dave Lester.