Thamnophis
HumboldtHerps.com
Thamnophis (2) I.D. Comparisons
Thamnophis (2) I.D. Comparisons
Information regarding sympatric colors and patterns of local Thamnophis cross-referenced using:
1. Pages 664-665, 667-668, 669, 674-675, and plates 504, 511, 512, 530, and 545, The Audubon
Society Field Guide to North American Reptiles and Amphibians. c. 1979.
2. Pages 68-69, 210-211, 216-217, 220-222, and 226, Reptiles of the Northwest. c. 2002
3. Pages 130-135, 375-380, 382-384, and 386-387, Western Reptiles and Amphibians (3rd ed.).
c. 2003.
Web7. http://www.californiaherps.com/identification/snakesid/gartersnakeskey.html (3 pages)
1. Pages 664-665, 667-668, 669, 674-675, and plates 504, 511, 512, 530, and 545, The Audubon
Society Field Guide to North American Reptiles and Amphibians. c. 1979.
2. Pages 68-69, 210-211, 216-217, 220-222, and 226, Reptiles of the Northwest. c. 2002
3. Pages 130-135, 375-380, 382-384, and 386-387, Western Reptiles and Amphibians (3rd ed.).
c. 2003.
Web7. http://www.californiaherps.com/identification/snakesid/gartersnakeskey.html (3 pages)
Complete
Species and Subspecies I.D. Comparisons
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Identifying garter snakes in the wild is often quite a challenging affair. And the jury is occasionally still undecided in
many of the cases where hybridization occurs. Sub-specific hybrids, where two individual subspecies intergrade, are
common (within the respective overlap). Inter-specific hybridization, where two separate species breed, is also
relatively common in some Thamnophis species. So one might ask, "What's in the cocktail?" Keep in mind that each
species usually has unique sympatric features (traits that adhere to the integrity of the species' known
chartacteristics without the effects of interbreeding with other species living in the same area): these include
dorso-lateral colors and patterns, labial scale counts, scale row counts, shapes of head and internasals, ventral
colors and blotching, size, etc. In turn, any existent subspecies within a group may also have additional features that
clearly identify it from other species and subspecies. On the other hand, there are individual species which exhibit a
wide variety of color and pattern phases and occasional scalation differences.
The following comparisons are based on descriptions from the three guides I regularly use; although the taxonomy
among the listed species and subspecies may have changed (The Audubon guide came out in 1979), the general
descriptions have not. We also referred to the garter identification keys from californiaherps.com. Some of the
photos may not be classic (sympatric) examples, as there appears to be a lot of interbreeding in this area. The
photographs that are pending will be my ongoing inspiration for putting on my hiking shoes and hitting the trails!
________________________________________________________________________________________________
Colors and Patterns
The Common Garter Snake (Thamnophis sirtalis): Well-defined wide dorsal and lateral stripes (white, yellow, orange, tan,
gray, green, or blue); small to large red spots or blotches with double row of alternating black spots between
stripes; head black or reddish; throat pale (cream); belly bluish-gray; tail dusky to black.
The California Red-sided Garter Snake (T. s. infernalis): Wide dorsal stripe (yellow, green-yellow, or blue-white);
equally wide or wider lateral stripes which often merge with ventral color (cream); reddish head; white lower
labials; throat pale (white to cream); ground color black with prominent red blotches between stripes.
The Valley Garter Snake (T. s. fitchi): Well-defined wide dorsal stripe (yellow or green-yellow) with paler lateral
stripes; ground color black or slate-gray with single series of red spots or blotches between stripes; head
usually black; belly is light with black only at the edge of the ventral scales.
The Northwestern Garter Snake (Thamnophis ordinoides): Often well-defined dorsal stripe (yellow, orange, red, blue, or
white), sometimes faint or absent at the neck; lateral stripe (tan, cream, white, or yellow) may be well-defined, faint,
or absent; ground color may vary (black, brown, olive, greenish to blueish gray) and is often speckled or spotted
with red or orange; head usually matches ground color; belly yellow or gray often flecked with red or orange.
Completely stripe-less red specimen found in Siskiyou Mountains in extreme NW California.
The Western Terrestrial Garter Snake (Thamnophis elegans): Dorsal stripe is well-defined or faint, straight or irregular
(yellow, orange, cream, or white); lateral stripes may be equal, lighter, or irregular; ground color varies (black, olive,
brown, greenish or bluish gray); head usually matches ground color; space between stripes marked with dark
spots or scattered light specks; belly is pale, dark, or bluish gray, greenish ,or brown and is mottled with black or
reddish flecks.
The Mountain Garter Snake (T. e. elegans): Well-defined (sometimes irregular) dorsal and lateral stripes (yellow,
orange-yellow, or white); no red pigments; ground color is velvet-black to brown-gray with occasional
white flecks; belly pale, dark, or bluish gray with light dusting of black spots; some of the irregularly striped
variants' lateral stripes are replaced by merged belly color and intermittent black spots (like interlocking
building blocks).
The Coast Garter Snake (T. e. terrestris): Well-defined dorsal stripe (cream to yellow) and well-defined duller
laterals; ground color is olive or brown suffused with rusty red above the laterals and covered with a
doubled series of dark spots; lateral stripes and belly often awash with reddish flecks.
The Wandering Garter Snake (T. e. vagrans): Irregular dorsal stripe (dull yellow ) may be a well-defined "zig-zag",
or it may be so faint it can only be seen near the neck; irregular laterals are a duller color and may be
defined or virtually non-existent; irregular striping appears to be caused by an interference of the double
series of large or small spots in the dorso-lateral field; ground color is usually light gray to greenish brown;
belly may have scattered black markings at the vent or may be a uniform black except for at the throat or
vent.
The Pacific Coast Aquatic Garter Snake (Thamnophis atratus): Only the two variants of the one subspecies in our area will
be discussed. Sub-specific intergrades with the Santa Cruz Garter (Thamnophis atratus atratus) occur south of
our field of exploration. Inter-specific hybrids with the Sierra Garter Snake (Thamnophis couchii) occur further east.
The Oregon Garter Snake (T. a. hydrophilus): Spotted variant - Dorsal stripe dull, thin, and/or faint (pale yellow to
barely visible except at the neck); lateral stripes less pronounced than dorsals, some non-existent;
ground color pale gray, light gray-green, or olive-brown marked with two alternating rows of large or small
black or dark olive-gray squares or spots; head usually matches ground color; throat is usually white
turning light gray towards the belly, then grading towards salmon-orange or pinkish-purple towards the
vent; occasional black flecks often present on edges of ventral scales.
Striped variant - Lateral stripes are often wider, brighter (yellow), and more defined than the dorsal stripe
(dull yellow); ground color dark gray or olive-brown with two rows of alternating black spots or blotches that
are often barely discernible; head usually matches ground color; throat is white to lemon yellow; belly is
light gray grading towards salmon-orange or pinkish-purple towards the vent.
many of the cases where hybridization occurs. Sub-specific hybrids, where two individual subspecies intergrade, are
common (within the respective overlap). Inter-specific hybridization, where two separate species breed, is also
relatively common in some Thamnophis species. So one might ask, "What's in the cocktail?" Keep in mind that each
species usually has unique sympatric features (traits that adhere to the integrity of the species' known
chartacteristics without the effects of interbreeding with other species living in the same area): these include
dorso-lateral colors and patterns, labial scale counts, scale row counts, shapes of head and internasals, ventral
colors and blotching, size, etc. In turn, any existent subspecies within a group may also have additional features that
clearly identify it from other species and subspecies. On the other hand, there are individual species which exhibit a
wide variety of color and pattern phases and occasional scalation differences.
The following comparisons are based on descriptions from the three guides I regularly use; although the taxonomy
among the listed species and subspecies may have changed (The Audubon guide came out in 1979), the general
descriptions have not. We also referred to the garter identification keys from californiaherps.com. Some of the
photos may not be classic (sympatric) examples, as there appears to be a lot of interbreeding in this area. The
photographs that are pending will be my ongoing inspiration for putting on my hiking shoes and hitting the trails!
________________________________________________________________________________________________
Colors and Patterns
The Common Garter Snake (Thamnophis sirtalis): Well-defined wide dorsal and lateral stripes (white, yellow, orange, tan,
gray, green, or blue); small to large red spots or blotches with double row of alternating black spots between
stripes; head black or reddish; throat pale (cream); belly bluish-gray; tail dusky to black.
The California Red-sided Garter Snake (T. s. infernalis): Wide dorsal stripe (yellow, green-yellow, or blue-white);
equally wide or wider lateral stripes which often merge with ventral color (cream); reddish head; white lower
labials; throat pale (white to cream); ground color black with prominent red blotches between stripes.
The Valley Garter Snake (T. s. fitchi): Well-defined wide dorsal stripe (yellow or green-yellow) with paler lateral
stripes; ground color black or slate-gray with single series of red spots or blotches between stripes; head
usually black; belly is light with black only at the edge of the ventral scales.
The Northwestern Garter Snake (Thamnophis ordinoides): Often well-defined dorsal stripe (yellow, orange, red, blue, or
white), sometimes faint or absent at the neck; lateral stripe (tan, cream, white, or yellow) may be well-defined, faint,
or absent; ground color may vary (black, brown, olive, greenish to blueish gray) and is often speckled or spotted
with red or orange; head usually matches ground color; belly yellow or gray often flecked with red or orange.
Completely stripe-less red specimen found in Siskiyou Mountains in extreme NW California.
The Western Terrestrial Garter Snake (Thamnophis elegans): Dorsal stripe is well-defined or faint, straight or irregular
(yellow, orange, cream, or white); lateral stripes may be equal, lighter, or irregular; ground color varies (black, olive,
brown, greenish or bluish gray); head usually matches ground color; space between stripes marked with dark
spots or scattered light specks; belly is pale, dark, or bluish gray, greenish ,or brown and is mottled with black or
reddish flecks.
The Mountain Garter Snake (T. e. elegans): Well-defined (sometimes irregular) dorsal and lateral stripes (yellow,
orange-yellow, or white); no red pigments; ground color is velvet-black to brown-gray with occasional
white flecks; belly pale, dark, or bluish gray with light dusting of black spots; some of the irregularly striped
variants' lateral stripes are replaced by merged belly color and intermittent black spots (like interlocking
building blocks).
The Coast Garter Snake (T. e. terrestris): Well-defined dorsal stripe (cream to yellow) and well-defined duller
laterals; ground color is olive or brown suffused with rusty red above the laterals and covered with a
doubled series of dark spots; lateral stripes and belly often awash with reddish flecks.
The Wandering Garter Snake (T. e. vagrans): Irregular dorsal stripe (dull yellow ) may be a well-defined "zig-zag",
or it may be so faint it can only be seen near the neck; irregular laterals are a duller color and may be
defined or virtually non-existent; irregular striping appears to be caused by an interference of the double
series of large or small spots in the dorso-lateral field; ground color is usually light gray to greenish brown;
belly may have scattered black markings at the vent or may be a uniform black except for at the throat or
vent.
The Pacific Coast Aquatic Garter Snake (Thamnophis atratus): Only the two variants of the one subspecies in our area will
be discussed. Sub-specific intergrades with the Santa Cruz Garter (Thamnophis atratus atratus) occur south of
our field of exploration. Inter-specific hybrids with the Sierra Garter Snake (Thamnophis couchii) occur further east.
The Oregon Garter Snake (T. a. hydrophilus): Spotted variant - Dorsal stripe dull, thin, and/or faint (pale yellow to
barely visible except at the neck); lateral stripes less pronounced than dorsals, some non-existent;
ground color pale gray, light gray-green, or olive-brown marked with two alternating rows of large or small
black or dark olive-gray squares or spots; head usually matches ground color; throat is usually white
turning light gray towards the belly, then grading towards salmon-orange or pinkish-purple towards the
vent; occasional black flecks often present on edges of ventral scales.
Striped variant - Lateral stripes are often wider, brighter (yellow), and more defined than the dorsal stripe
(dull yellow); ground color dark gray or olive-brown with two rows of alternating black spots or blotches that
are often barely discernible; head usually matches ground color; throat is white to lemon yellow; belly is
light gray grading towards salmon-orange or pinkish-purple towards the vent.
ventrals pending
pictures pending
striped variant - no definitive spots
striped variant - visible spots
spotted variant - very faint dorsal stripe
(pattern often resembles a zipper)
(pattern often resembles a zipper)
