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Overview

Brief Summary

Thamnophis proximus, Western Ribbon Snake, is a species prominent in North and South America. Although abundant in some areas, it is registered as an endangered species in Wisconsin and New Mexico, where it is uncommon (Rossman et al. 1996). It is found in a variety of different climates and environments; however, it is reliant on aquatic habitats for food. 

  • Rossman, D.A., N.B. Ford, and R.A. Seigel. 1996. Garter snakes: evolution and ecology. University of Oklahoma Press, Norman, OK.
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Distribution

Range Description

Distribution extends from southern Wisconsin and Ohio, in the central United States, southward on the Atlantic versant to Belize and then discontinuously to northern Costa Rica, and on the Pacific versant from Guerrero to Chiapas, Mexico, and from El Salvador southward to central Costa Rica. Elevational range of this species extends from sea level to 2,500 meters (Wilson and Johnson 2010).
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occurs (regularly, as a native taxon) in multiple nations

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National Distribution

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

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Global Range: (200,000 to >2,500,000 square km (about 80,000 to >1,000,000 square miles)) The range extends from southeastern Colorado (at least historically; Hammerson 1999), eastern Nebraska, Iowa, southern Wisconsin, and Indiana southward to eastern New Mexico, Texas, Louisiana, and Mississippi, and through eastern Mexico to the Isthmus of Tehuantepec, then discontinuously through southern Mexico, Belize, Guatemala, El Salvador, Honduras, and Nicaragua to Costa Rica, at elevations from sea level to 2,438 meters (8,000 feet) (Rossman et al. 1996).

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Continent: Middle-America North-America
Distribution: C USA (incl. Illinois, Indiana, Oklahoma, Wisconsin, Kansas, Louisiana, Mississippi),  E Mexico, Guatemala, Belize, El Salvador, Honduras, Nicaragua, Costa Rica  rutiloris: Costa Rica  
Type locality: stone quarry on west side of Missouri three miles above the mouth of Boyer's River.
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Physical Description

Morphology

            Thamnophis proximus, the Western Ribbon snake, has a total body length (TBL) of approximately 510-760 mm (Ernst and Ernst 2003). The maximum recorded TBL is 1263 mm (Ernst and Ernst 2003). The tail accounts for no more than one-third of the body length (Ernst and Ernst 2003). Typically, all six subspecies of these snakes are characterized by a uniformly colored dorsum, though the color of that uniform dorsum varies between subspecies from black to dark brown to olive gray. Typically, there are yellow lateral stripes on scale rows three and four (Ernst and Ernst 2003; Rossman et al. 1996). Like Thamnophis sauritus, T. proximus lack the black markings on the labials and ventrals that are seen in garter snakes (Ernst and Ernst 2003). A dark ventrolateral stripe that is either absent or very narrow, distinguishes T. proximus from T. sauritus (Ernst and Ernst 2003; Rossman 1962). Vertebral stripe color on the dorsum varies with geographical location and typically between subspecies, ranging from grayish-tan to gold to orange to red (Rossman et al. 1996). Dorsal scales are pitless and keeled (Ernst and Ernst 2003).  The dorsal scale row formula for more than 96% of T. proximus is 19-19-17: that is, scales typically occur, when counting around the body, in 19 rows towards the anterior part of the body, in 19 rows at midbody, and 17 rows towards the tail ((Rossman et al. 1996; Ernst and Ernst 2003).  All Thamnophis have a single, undivided anal plate, which is considered one of the distinguishing external characteristics of the genus (Rossman et al. 1996). Thamnophis proximus has 141-181 ventral and 82-131 subcaudal scales (Ernst and Ernst 2003). About 27-34 teeth are located on each maxilla (Ernst and Ernst 2003). The organs, including the heart, gall bladder, liver, pancreas, and kidneys, of T. proximus are present more posteriorly in the body than almost all other Thamnophis species (Rossman et al. 1996).

            Within the genus, T. proximus and T. sauritus have the shortest head to total body length ratio (3.9%) (Rossman et al. 1996). For T. proximus the head is separated from the body by a distinct neck (Ernst and Ernst 2003). The distinctive head scales that identify this species include 10 infralabials, 1+2 temporals, 3 postoculars, 1 preocular, 1 loreal, and 2 nasals that are partly separated by the nostril (Ernst and Ernst 2003). The number of supralabials, 8 versus 7, on each side of the head can be used to distinguish T. proximus from T. sauritus, respectively (Rossman 1962). When compared to other Thamnophis species, T. proximus has moderately sized eyes averaging a ratio of 0.691 eye diameter:frontal length (Rossman et al. 1996). The anterior part of the face and chin are typically cream or cinnamon colored (Ernst and Ernst 2003). On the top of the head are two large yellow parietal spots fused together across the interparietal suture (Ernst and Ernst 2003; Rossman et al. 1996; Rossman 1962). These spots two large, brightly colored paired parietal spots distinguish T. proximus from T. sauritus, for which dots, if present, are small and dully colored (Rossman 1962). The muzzle is long relative to T. sauritus (75.6% muzzle length: frontal length) with a narrow tip (79.3% internasorostral contact: nasorostral contact) (Rossman et al. 1996).

            For their genus, male T. proximus have relatively short individual (Ernst and Ernst 2003). That is, the hemipenis in this species, when inverted, typically only extends to subcaudal scales seven and eight, whereas the hemipenis in most Thamnophis species extends for 8 to 14 subcaudals (Ernst and Ernst 2003; Rossman et al. 1996). Its sulcus spermaticus, or sperm groove, is straight, terminating at the apex (Ernst and Ernst 2003). On the spermticus, there are several rows of tiny spines on the extreme basal area, the distal half, and the margins of the sulcus (Ernst and Ernst 2003).  The sulcus has a pair of basal hooks on either side, and there are no ornamentations on the apical region (Ernst and Ernst 2003).

            In T. proximus, sexual dimorphism varies from population to population and subspecies to subspecies. On average, males have a relative tail length of 26.0%-33.3%, 142-181 ventral scales, 91-131 subcaudals, and a mean relative height of the first dorsal scale row of 1.6 mm (Ernst and Ernst 2003; Rossman et al. 1996). Females average a relative tail length of 25.2%-33.6%, 141-177 ventral scales, 82-124 subcaudals, and a mean relative height of the first dorsal scale row of 1.7 mm (Ernst and Ernst 2003; Rossman et al. 1996). Female T. proximus have the greatest range in the number of subcaudals compared to all other Thamnophis species (Rossman et al. 1996).

  • Ernst, C.H., and M.E. Ernst. 2003. Snakes of the United States and Canada. Smithsonian Books, Washington, D.C.
  • Rossman, D.A. 1962. Thamnophis proximus (Say), a valid species of garter snake. Copeia 1962: 741-748.
  • Rossman, D.A., N.B. Ford, and R.A. Seigel. 1996. Garter snakes: evolution and ecology. University of Oklahoma Press, Norman, OK.
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Size

Length: 123 cm

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Type Information

Syntype for Thamnophis proximus
Catalog Number: USNM 752
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Amphibians & Reptiles
Preparation: Ethanol
Locality: Prairie Mer Rouge, Morehouse, Louisiana, United States, North America
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Ecology

Habitat

Habitat and Ecology

Habitat and Ecology
This semiaquatic snake occurs in a wide range of habitats, usually in the vicinity of streams, lakes, ponds, sloughs, ditches, swamps, and marshes (Rossman et al. 1996, Werler and Dixon 2000, Ernst and Ernst 2003, Trauth et al. 2004). Sometimes it occurs in terrestrial habitats, but generally close to water. It feeds on earthworms, crayfish, lizards, fishes, frogs, and tadpoles (Rossman et al. 1996). It is a live-bearing species.

Systems
  • Terrestrial
  • Freshwater
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Comments: This semiaquatic snake occurs a wide range of often shrubby habitats in the vicinity of streams, lakes, ponds, sloughs, ditches, swamps, and marshes (Rossman et al. 1996, Werler and Dixon 2000, Ernst and Ernst 2003, Trauth et al. 2004). Often it is in water-edge vegetation. Sometimes it can be found in terrestrial habitats but generally close to water. Hibernation sites may be in upland areas near or some distance from water.

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The Habitat of Thamnophis proximus

The Western Ribbonsnake’s, T. proximus, northern range limit is roughly the line of latitude connecting Ohio to Wyoming; its western limit is western Oklahoma and its southern limit stretching into Mexico (Conant 1998). The southernmost part of its range begins in eastern Mexico and stretches down to Costa Rica, and on the western coast of Mexico they are found in Guerrero and Oaxaca. Within this range T. proximus is found in both aquatic and terrestrial habitats (Ernst 1989).

Habitats of Texan populations of T. proximus include arid, woodland forest, and scrub-brush dominated areas. Despite this wide range of habitats, T. proximus must have a source of water close by. This is largely because its primary food sources are aquatic. Any clean area with a marsh, swamp, rivers, ponds, or ditches will have suitable habitat (Phillips 2012). Thamnophis proximus is also highly dependent on the rainfall patterns within its habitat, since their primary food source is amphibians. When the soil within a habitat grows dry due to lack of rain, the number of amphibians dwindle. This in turn puts pressure on T. proximus population (Clark 1974). However in the northern part of its range, specifically Wisconsin and northern Indiana, T. proximus appears to prefer habitat that is more open and sandy. This could be due to competition for habitat with other Ribbon Snakes, such as the Northern Ribbon Snake (Harding 1997).  

Thamnophis proximus can live in areas where there has been human development, such as cattle tanks, the abandoned foundations of concrete buildings, and drainage ditches that provide microhabitats for the snakes. However they do not tend to live in areas where there is constant human disruption. In their Indiana range it was found that human disruption that destroyed wet lowlands greatly decreased the T. proximus population, probably because of a loss of prey (Werler 2000).

 Tinkle (1957) conducted a survey of a habitat choice by T. proximus near New Orleans, Louisiana. The study was conducted over the period of a year (from November of 1953 to December of 1954). The forested area where the research was done contained several different habitat types including: a dry ridge, a swamp, an area with deep ponds, and an area that rapidly fluctuated between shallow pools and dry terrain. Forty snakes were captured in the course of the study. Of these forty, twenty six were on the dry ridge, six were in the swamp, one was swimming in the lake, and the remaining six were in the fluctuating terrain. It was suggested that the ribbon snakes primarily used the ridge for periods of inactivity when not hunting and eating, which are mostly done by the water’s edge. Which would explain why a large quantity of the population was found on the ridges.

Within the same study by Tinkle (1957) it was found that although the snakes are most often seen on the dry ridge, the exact proportions T. proximus in each area changed seasonally as well, as T. proximus is dependent upon external forces for thermal regulation. In the winter months the snakes were primarily found in the dry ridge portion of their habitat, this was when the maple trees that surrounded the area were largely barren and thus sunlight could pass through so the snakes could sun themselves in the cold winter months. However once the canopy begins to fill in in the spring time the snake’s habitat shifts to area with less dense cover so that they can continue to sun themselves. Mating occurs during this time. The juveniles then hatch in the summer. The juveniles and the females tend to cluster in groups, it is not known if these groups are a mother and her offspring or several mothers with their offspring. This could explain, at least for part of the year, why so many T. proximus were found on the dry ridge. During the late summer, when temperatures get extremely high, T. proximus moves back to the ridge with the maples, using the tree cover for shade.

Thamnophis proximus also goes through periods of hibernation during the winter months in the northern part of their range, unlike the previously mentioned Louisiana population that moves throughout the habitat to thermoregulate (Tinkle 1957). The habitat of T. proximus in this part of its range must include an area that can serve as a den. This den can be found in a rocky outcropping or in a rotting log, the material in the den does not seem to be as important as the necessity for it to be above the floor level for the winter rains (Tinkle 1957).  

  • Clark, Donald R. Jr.(1974) The Western Ribbon Snake (Thamnophis proximus): Ecology of a Texas Population. Herpetologists’ League. 30(4), 372-379.
  • Conant, Roger., Collins, Joseph T. (1998)Reptiles and Amphibians: Eastern/Central North America. Peterson Field Guides.
  • Ernst, Carl H.. Barbour, Rodger W. (1989) Snakes of Eastern North America. George Manson University Press.
  • Harding, James H. (1997) Amphibians and Reptiles of the Great Lakes Region. The University of Michigan Press.
  • Phillips, Christopher A. (2012) Thamnophis proximus—Western Ribbonsnake. Illinois Natural History Survey Collections Prairie Research Institute.
  • Tinkle, Donald W. (1957) Ecology, Maturation and Reproduction of Thamnophis Sauritus Proximus. Ecological Society of America. 38(1), 69-77.
  • Werler, John E. & Dixon, James R. (2000). Texas snakes : identification, distribution, and natural history. University of Texas Press.
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Migration

Non-Migrant: No. All populations of this species make significant seasonal migrations.

Locally Migrant: Yes. At least some populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

May migrate between separate winter and summer habitats (Vogt 1981).

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Trophic Strategy

Comments: Eats frogs, toads, tadpoles, salamanders, fishes, insects, earthworms, occasionally carrion (Stebbins 1985, Collins 1982).

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The Trophic Strategies of Thamnophis proximus

Thamnophis proximus, the Western Ribbonsnake, is a carnivore that hunts primarily during the day. It hunts in both terrestrial and aquatic habitats typically in areas where cat tails and aquatic grasses are plentiful, however it can be found in dryer habitats so long as there is a water source in the area (Tinkle 1957).

Thamnophis proximus is a generalist, eating four species of fish, 23 species of anurans, two species of salamanders, one species of lizard, one species of snake, and possibly earthworms in some populations (Hampton 2008). Unlike other Garter and Ribbon snakes, T. proximus does not appear to eat small mammals and invertebrates (Werler 2000).Several species of amphibians have been found in the stomachs of T. proximus (Hampton 2008).  These amphibian species, particularly anurans, seem to be most vulnerable to predation by T. proximus during their breeding seasons, when they are confined in a small area and are largely defenseless while mating (Werler 2000).

Toads secrete poisons during predation events by T. proximus (Werler 2000). Thamnophis proximus appears to be adapted to neutralize these poisons, presumably through enzymes secreted by their adrenal glands, which are slightly enlarged relative to other snakes in their range. However they are not as large as the adrenal glands of the hog-nosed snake, whose includes large toads that tend to be more poisonous than the smaller toads eaten by T. proximus (Werler 2000). 

Despite eating a wide variety of organisms, T. proximus are dependent on amphibian populations. Amphibians are heavily influenced by water levels in the upper layer of the soil. When moisture levels are low the amphibian population declines, when moisture levels are high the amphibian population surges, a trend which is also seen in T. proximus (Clark 1974). This could indicate that the health of a population of Western Ribbonsnakes is indicated by the prevalence of amphibians in a population.

Thamnophis proximus has only limited competition with other predatory snakes, such as the King Snake, largely because it inhabits both aquatic and terrestrial habitats. (Tinkle 1957). However it seems unlikely that inhabiting two habitats would limit competition from other members of Thamnophis since many of them also hunt near the water (Harding 1997). Thamnophis proximus competes with Nerodia in the water, however some species of Nerodia, such as Nerodia fasciata confluens, are anuran specialists. While T. proximus does eat anurans, it also consumes many other prey items. Therefore the competition between these two groups would be limited (McKnight 2014).

Thamnophis proximus uses two different methods for hunting prey, corresponding to aquatic verses terrestrial predation. When the water level drops in an aquatic environment, T. proximus will swim through the shallow water and hold its mouth open, waiting for the prey that have been concentrated in the very shallow water to come into contact with its jaws. The prey is then snatched up and eaten (Werler 2000).  In a terrestrial environment T. proximus hunts primarily using visual cues. It will probe in a grassy area three times in a semicircular pattern with a striking motion to drive any hidden prey out of the area, the snake then rushes forward to grab the prey before it escapes, the prey is then swallowed whole. If the prey escapes T. proximus it will raise its head up several inches above the ground and search for further movement from the prey. If it finds none then the cycle of striking the grass begins again.  (Werler 2000). Thamnophis proximus does not sue constriction to hunt and is not considered to be venomous. It has been suggested that their saliva is mildly toxic, however more research is needed to confirm (LaDuc).

Thamnophis proximus also uses the tall grasses that make up the terrestrial portion of its habitat as its primary defense against predators. When the snake feels threatened it will dart into the brush to avoid capture (Harding 1997). Thamnophis proximus may also escape into the water, although this has been observed less frequently than terrestrial defense (Paloski 2013). When they are handled or captured they rarely bite, but they do release musk which might cause the predator to release the snake. However it isn’t known how often this method of defense is successful. The chief predators for this species are primarily water fowl, such as herons and cranes; as well as terrestrial birds such as shrikes and hawks. Raccoons, mink, and weasels have also been known to eat T. proximus. Snapping Turtles and other snakes, as well as large frogs and fish will eat juveniles. (Harding 1997). 

  • Clark, Donald R. Jr.(1974) The Western Ribbon Snake (Thamnophis proximus): Ecology of a Texas Population. Herpetologists’ League. 30(4), 372-379.
  • Hampton, Paul M. (2008) Prey Items of the Western Ribbon Snake, Thamnophis proximus. The Southwestern Naturalist. 53(1), 115-118.
  • Harding, James H. (1997) Amphibians and Reptiles of the Great Lakes Region. The University of Michigan Press.
  • LaDuc, Travis. Herps of Texas. Division of Herpetology at the Biodiversity Collections, Department of Integrative Biology at The University of Texas at Austin.
  • McKnight, Donald T. (2014) Notes on the diets of seven sympatric snakes in the genera Agkistrodon, Nerodia, Sistrurus, and Thamnophis. Herpetology Notes. 7, 171-177
  • Paloski, Rori. (2013)Western Ribbonsnake (Thamnophis proximus) Species Guidence. Wisconson Department of Natural Resources.
  • Tinkle, Donald W. (1957) Ecology, Maturation and Reproduction of Thamnophis Sauritus Proximus. Ecological Society of America. 38(1), 69-77.
  • Werler, John E. & Dixon, James R. (2000). Texas snakes : identification, distribution, and natural history. University of Texas Press.
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Population Biology

Number of Occurrences

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: 81 to >300

Comments: This species is represented by a very large number of occurrences (Rossman 1970). Werler and Dixon (2000) mapped hundreds of collection sites in Texas, and Trauth et al. (2004) mapped well over 100 collection sites in Arkansas.

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Global Abundance

100,000 to >1,000,000 individuals

Comments: Total adult population size is unknown but certainly exceeds 100,000. This snake is common in the southern United States.

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            Thamnophis proximus was considered a western subspecies of Thamnophis sauritus until 1962 (Rossman et al. 1996). The few morphological and genetic differences between these species lead scientists to believe that T. proximus has undergone speciation from T. sauritus recently (Gartside et al. 1977; Rossman et al. 1996). The former has since been subdivided into six distinct subspecies (Rossman et al. 1996), primarily based on differences in body color, vertebral stripe color, width, and geographic range (Ernst and Barbour 1989). The geographical distribution that defines these six subspecies ranges from as far south as Costa Rica all the way up to southern Wisconsin and as far west as Colorado and as far east as Louisiana. Its populations range across an elevational range of 0-2438m (Rossman et al. 1996).  Of these six subspecies only two occur east of the Mississippi river (T. proximus proximus and T. proximus orarius) (Ernst and Barbour 1989).

            In a study area just 15 miles north of New Orleans, Tinkle (1957) found that the population densities of Thamnophis proximus (then Thamnophis sauritus proximus) fluctuated through time. Densities spiked during early spring, after hibernation, when the snakes emerged. Density also spiked during summer when gravid females aggregated with young snakes, and during winter when the snakes aggregated in hibernation sites (Tinkle 1957). These spikes in density may not indicate an overall jump in the number of snakes in the area, but rather a change in behavior that made the snakes easier to catch.

            Tinkle’s study surveyed the entire community of snake species at his Louisiana study site; he noted over half of the individual snakes (221 of 420) he collected were T. proximus (Tinkle 1957). This contrasted the findings of R.F. Clark’s 1949 study in the uplands of Louisiana, which, while using almost identical methods to Tinkle, found that of the 2083 snakes collected, only 37 (1.8%) were T. proximus. Thus, population densities of T. proximus appear to vary greatly between Louisiana populations. Populations in Missouri were appeared to be stable from 1979 to 1994 (Rossman et al. 1996). However further population studies would be needed from multiple sites to conclude this how general such density variation is in this species.

            In a two year long study of a Brazos County, Texas, population of T. proximus, estimated population density dropped from 61 snakes per hectare in1969 to 16 snakes per hectare in1971 (Clark 1974). However, activity (and perceived density) of the ribbon snakes did fluctuate throughout the year, correlating positively with an increase in water levels in the soil due to rainfalls; there was a negative correlation between population density and the dry season (Clark 1974). This interpretation was supported by the sharp population decline in 1971 following a very dry winter (Clark 1974).

            Size at maturity for T. proximus varies from population to population as well as between the sexes. In Louisiana, Tinkle (1957) reported the smallest gravid female having an SVL (snout vent length) of 485 mm; however in Texas, Clark (1974) reported the smallest gravid female’s SVL at 515 mm (Clark 1974). Additionally, SVL of gravid females from Mexico and Central America have been reported to be smaller than gravid females found in the southern United States (Rossman et al. 1996). Females are thought to reach mature size at about twelve to fifteen month after birth and mate during their second spring (Clark 1974). Clark found that most of the females he studied reached mature size in August-September, at about one year (Clark 1974). Females, on average, are about 500 mm in length when they reach sexual maturity, while males reach maturity at minimum 400 mm (Tinkle 1957; Clark 1974) Males are thought to reach maturity at about two years (Tinkle 1957). Despite T. proximus’s long body length (long body length generally corresponds with large clutch size in snakes; citation), the mean clutch size for the species is low. Females have a clutch size averages of 8.4 to 12.9 (Rossman et al. 1996). The live-bearing females are able to produce two broods in a given year (Ernst and Ernst 2003).

            Despite high relative abundance in some states, T. proximus is categorized as a species of concern in Indiana, threatened species in Kentucky, and endangered species in New Mexico and Wisconsin (Rossman et al. 1996). The major threat facing this species is habitat destruction (Ernst and Ernst 2003). Other threats include the draining and filling of wetlands as well as cultivation of lands (Ernst and Ernst 2003). 

  • Clark, D.R., Jr. 1974. The western ribbon snake (Thamnophis proximus): ecology of a Texas population. Herpetologica 30: 372-379.
  • Clark, R.F. 1949. Snakes of hill parishes of Louisiana. Journal of the Tennessee Academy of Science 24: 244-261.
  • Ernst, C.H., and M.E. Ernst. 2003. Snakes of the United States and Canada. Smithsonian Books, Washington, D.C.
  • Ernst, C.H., and R.W. Barbour. 1989. Snakes of eastern North America. George Mason University Press. Fairfax, V.A.
  • Gartside, D.F., J.S. Rodgers, and H.C. Dessauer. 1997. Speciation with little genic and morphological differentiation in the ribbon snakes Thamnophis proximus and T. sauritus (Colubridae). Copeia 1977: 697-705.
  • Rossman, D.A., N.B. Ford, and R.A. Seigel. 1996. Garter snakes: evolution and ecology. University of Oklahoma Press, Norman, OK.
  • Tinkle, D.W. 1957. Ecology, maturation, and reproduction of Thamnophis sauritus proximus. Ecology 38: 69-77.
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            Thamnophis proximus was considered a western subspecies of Thamnophis sauritus until 1962 (Rossman et al. 1996). The few morphological and genetic differences between these species lead scientists to believe that T. proximus has undergone speciation from T. sauritus recently (Gartside et al. 1977; Rossman et al. 1996). The former has since been subdivided into six distinct subspecies (Rossman et al. 1996), primarily based on differences in body color, vertebral stripe color, width, and geographic range (Ernst and Barbour 1989). The geographical distribution that defines these six subspecies ranges from as far south as Costa Rica all the way up to southern Wisconsin and as far west as Colorado and as far east as Louisiana. Its populations range across an elevational range of 0-2438m (Rossman et al. 1996).  Of these six subspecies only two occur east of the Mississippi river (T. proximus proximus and T. proximus orarius) (Ernst and Barbour 1989).

            In a study area just 15 miles north of New Orleans, Tinkle (1957) found that the population densities of Thamnophis proximus (then Thamnophis sauritus proximus) fluctuated through time. Densities spiked during early spring, after hibernation, when the snakes emerged. Density also spiked during summer when gravid females aggregated with young snakes, and during winter when the snakes aggregated in hibernation sites (Tinkle 1957). These spikes in density may not indicate an overall jump in the number of snakes in the area, but rather a change in behavior that made the snakes easier to catch.

            Tinkle’s study surveyed the entire community of snake species at his Louisiana study site; he noted over half of the individual snakes (221 of 420) he collected were T. proximus (Tinkle 1957). This contrasted the findings of R.F. Clark’s 1949 study in the uplands of Louisiana, which, while using almost identical methods to Tinkle, found that of the 2083 snakes collected, only 37 (1.8%) were T. proximus. Thus, population densities of T. proximus appear to vary greatly between Louisiana populations. Populations in Missouri were appeared to be stable from 1979 to 1994 (Rossman et al. 1996). However further population studies would be needed from multiple sites to conclude this how general such density variation is in this species.

            In a two year long study of a Brazos County, Texas, population of T. proximus, estimated population density dropped from 61 snakes per hectare in1969 to 16 snakes per hectare in1971 (Clark 1974). However, activity (and perceived density) of the ribbon snakes did fluctuate throughout the year, correlating positively with an increase in water levels in the soil due to rainfalls; there was a negative correlation between population density and the dry season (Clark 1974). This interpretation was supported by the sharp population decline in 1971 following a very dry winter (Clark 1974).

            Size at maturity for T. proximus varies from population to population as well as between the sexes. In Louisiana, Tinkle (1957) reported the smallest gravid female having an SVL (snout vent length) of 485 mm; however in Texas, Clark (1974) reported the smallest gravid female’s SVL at 515 mm (Clark 1974). Additionally, SVL of gravid females from Mexico and Central America have been reported to be smaller than gravid females found in the southern United States (Rossman et al. 1996). Females are thought to reach mature size at about twelve to fifteen month after birth and mate during their second spring (Clark 1974). Clark found that most of the females he studied reached mature size in August-September, at about one year (Clark 1974). Females, on average, are about 500 mm in length when they reach sexual maturity, while males reach maturity at minimum 400 mm (Tinkle 1957; Clark 1974) Males are thought to reach maturity at about two years (Tinkle 1957). Despite T. proximus’s long body length (long body length generally corresponds with large clutch size in snakes; citation), the mean clutch size for the species is low. Females have a clutch size averages of 8.4 to 12.9 (Rossman et al. 1996). The live-bearing females are able to produce two broods in a given year (Ernst and Ernst 2003).

            Despite high relative abundance in some states, T. proximus is categorized as a species of concern in Indiana, threatened species in Kentucky, and endangered species in New Mexico and Wisconsin (Rossman et al. 1996). The major threat facing this species is habitat destruction (Ernst and Ernst 2003). Other threats include the draining and filling of wetlands as well as cultivation of lands (Ernst and Ernst 2003). 

  • Clark, D.R., Jr. 1974. The western ribbon snake (Thamnophis proximus): ecology of a Texas population. Herpetologica 30: 372-379.
  • Clark, R.F. 1949. Snakes of hill parishes of Louisiana. Journal of the Tennessee Academy of Science 24: 244-261.
  • Ernst, C.H., and M.E. Ernst. 2003. Snakes of the United States and Canada. Smithsonian Books, Washington, D.C.
  • Ernst, C.H., and R.W. Barbour. 1989. Snakes of eastern North America. George Mason University Press. Fairfax, V.A.
  • Gartside, D.F., J.S. Rodgers, and H.C. Dessauer. 1997. Speciation with little genic and morphological differentiation in the ribbon snakes Thamnophis proximus and T. sauritus (Colubridae). Copeia 1977: 697-705.
  • Rossman, D.A., N.B. Ford, and R.A. Seigel. 1996. Garter snakes: evolution and ecology. University of Oklahoma Press, Norman, OK.
  • Tinkle, D.W. 1957. Ecology, maturation, and reproduction of Thamnophis sauritus proximus. Ecology 38: 69-77.
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Life History and Behavior

Behavior

     Thamnophis proximus (Western Ribbon Snake) is diurnal, or predominantly active during the day (Ernst and Barbour, 1989). When the temperatures are hot during the mid-summer they tend to become crepuscular, or active at dawn and dusk (Ernst andBarbour, 1989). They can also hunt during the night if it is warm enough (Ernst and Barbour, 1989; Ernst and Ernst, 2003). The species is an active hunter that uses eyesight to find amphibians, its primary prey. The species T. proximus is often found hunting in brush and grass near water sources. At times it can be seen swimming open mouthed catching prey as it contacts it (Western Ribbon Snake Photos and Facts). Individuals become more active during periods of high rainfall, especially when it is currently raining. Such periods of activity may correspond to their amphibian prey becoming more active during wet periods (Clark, 1974; Tinkle, 1957).

     T. proximus uses both terrestrial and aquatic habitats. This catholic lifestyle and is often different than their competitors and therefore reduces competition for prey (Tinkle 1957). When hunting prey T. proximus probes areas where prey could hide, like thick grasses. This probing consist of pushing the head quickly into three different areas of a spot where prey has been sighted (Ernst and Barnour, 1989). When the disturbed prey leaves the safety of the grass T. proximus will crawl after it (Ernst and Barbour, 1989). Once the prey is captured it is swallowed whole and the stomach muscles crush the specimen to aid digestion (snakeestate.net).

     Predators of T. proximus are wading birds (Ernst and Ernst, 2003). If T. proximus is disturbed by a predator it will dash away into hiding. A hiding mechanism that is often used is diving into a body of water if it is close enough and swimming to the bottom to hide there. This is beneficial since their predators are shorebirds. It can also at times emit a pungent liquid, or musk, that may keep predators away (Harding, 1997.).

     In some northern populations T. proximus hibernates in any area suitable for a den (or hibernacula). It will enter dens with other snakes of both the same and different species (Tinkles, 1957). Dens may exist in rock or gravel banks, but other hibernacula include mammal burrows, drainage ditches, rotten logs or trees, and springs (Ernst and Ernst, 2003). These are preferred areas because these areas are safe and regulate temperature, or their temperature does not fluctuate as easily being water or underground. Individuals in southern populations of T. proximus will be active whenever the temperatures are appropriately warm, so some years they do not hibernate at all (Tinkle 1957). When the weather is cooler during the winter, the species will stay in open sunny areas.

     T. proximus has a fairly large home range and they are prone to wander it instead of staying in one place (Tinkle, 1957). Immature females move less than mature females and males. Males on average move 2.5 m/day and females average 1.1 m/day. Between re-captures males moved up to 209 m from where they were first captured and females moved up to 97 m from where they were first captured (Clark, 1974).

  • Clark, D. R. Jr. 1974. The western ribbon snake (Thamnophis proximus): Ecology of a Texas population. Herpetologica 30: 372-379.
  • Ernst, C. H. and E. M. Ernst. 2003. Snakes of the United States and Canada. Smithsonian Institution Press. Washington, D.C.
  • Ernst, C.H., and R.W. Barbour. 1989. Snakes of eastern North America. George Mason University Press. Fairfax, V.A.
  • Ford N. B and R. A. Seigel. 2015. The influence of female body size and shape on the trade-off between offspring number and offspring size in two viviparous snakes. Journal of Zoology 295:154-158
  • Harding, J.H. (1997) Amphibians and Reptiles of the Great Lakes Region. University of Michigan Press, Michigan.
  • Tinkle D. W. 1957. Ecology, Maturation and Reproduction of Thamnophis Sauritus Proximus. Ecology 38:69–77.
  • Western Ribbon Snake. (n.d.). Retrieved April 28, 2015, from http://www.snakeestate.com/ribbon-snakes/western-ribbon-snake.html
  • Western ribbon snake photos and facts. (n.d.). Retrieved April 28, 2015, from http://www.arkive.org/western-ribbon-snake/thamnophis-proximus/
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     Thamnophis proximus (Western Ribbon Snake) is diurnal, or predominantly active during the day (Ernst and Barbour, 1989). When the temperatures are hot during the mid-summer they tend to become crepuscular, or active at dawn and dusk (Ernst andBarbour, 1989). They can also hunt during the night if it is warm enough (Ernst and Barbour, 1989; Ernst and Ernst, 2003). The species is an active hunter that uses eyesight to find amphibians, its primary prey. The species T. proximus is often found hunting in brush and grass near water sources. At times it can be seen swimming open mouthed catching prey as it contacts it (Western Ribbon Snake Photos and Facts). Individuals become more active during periods of high rainfall, especially when it is currently raining. Such periods of activity may correspond to their amphibian prey becoming more active during wet periods (Clark, 1974; Tinkle, 1957).

     T. proximus uses both terrestrial and aquatic habitats. This catholic lifestyle and is often different than their competitors and therefore reduces competition for prey (Tinkle 1957). When hunting prey T. proximus probes areas where prey could hide, like thick grasses. This probing consist of pushing the head quickly into three different areas of a spot where prey has been sighted (Ernst and Barnour, 1989). When the disturbed prey leaves the safety of the grass T. proximus will crawl after it (Ernst and Barbour, 1989). Once the prey is captured it is swallowed whole and the stomach muscles crush the specimen to aid digestion (snakeestate.net).

     Predators of T. proximus are wading birds (Ernst and Ernst, 2003). If T. proximus is disturbed by a predator it will dash away into hiding. A hiding mechanism that is often used is diving into a body of water if it is close enough and swimming to the bottom to hide there. This is beneficial since their predators are shorebirds. It can also at times emit a pungent liquid, or musk, that may keep predators away (Harding, 1997.).

     In some northern populations T. proximus hibernates in any area suitable for a den (or hibernacula). It will enter dens with other snakes of both the same and different species (Tinkles, 1957). Dens may exist in rock or gravel banks, but other hibernacula include mammal burrows, drainage ditches, rotten logs or trees, and springs (Ernst and Ernst, 2003). These are preferred areas because these areas are safe and regulate temperature, or their temperature does not fluctuate as easily being water or underground. Individuals in southern populations of T. proximus will be active whenever the temperatures are appropriately warm, so some years they do not hibernate at all (Tinkle 1957). When the weather is cooler during the winter, the species will stay in open sunny areas.

     T. proximus has a fairly large home range and they are prone to wander it instead of staying in one place (Tinkle, 1957). Immature females move less than mature females and males. Males on average move 2.5 m/day and females average 1.1 m/day. Between re-captures males moved up to 209 m from where they were first captured and females moved up to 97 m from where they were first captured (Clark, 1974).

  • Clark, D. R. Jr. 1974. The western ribbon snake (Thamnophis proximus): Ecology of a Texas population. Herpetologica 30: 372-379.
  • Ernst, C. H. and E. M. Ernst. 2003. Snakes of the United States and Canada. Smithsonian Institution Press. Washington, D.C.
  • Ernst, C.H., and R.W. Barbour. 1989. Snakes of eastern North America. George Mason University Press. Fairfax, V.A.
  • Ford N. B and R. A. Seigel. 2015. The influence of female body size and shape on the trade-off between offspring number and offspring size in two viviparous snakes. Journal of Zoology 295:154-158
  • Harding, J.H. (1997) Amphibians and Reptiles of the Great Lakes Region. University of Michigan Press, Michigan.
  • Tinkle D. W. 1957. Ecology, Maturation and Reproduction of Thamnophis Sauritus Proximus. Ecology 38:69–77.
  • Western Ribbon Snake. (n.d.). Retrieved April 28, 2015, from http://www.snakeestate.com/ribbon-snakes/western-ribbon-snake.html
  • Western ribbon snake photos and facts. (n.d.). Retrieved April 28, 2015, from http://www.arkive.org/western-ribbon-snake/thamnophis-proximus/
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     Thamnophis proximus (Western Ribbon Snake) is diurnal, or predominantly active during the day (Ernst and Barbour, 1989). When the temperatures are hot during the mid-summer they tend to become crepuscular, or active at dawn and dusk (Ernst andBarbour, 1989). They can also hunt during the night if it is warm enough (Ernst and Barbour, 1989; Ernst and Ernst, 2003). The species is an active hunter that uses eyesight to find amphibians, its primary prey. The species T. proximus is often found hunting in brush and grass near water sources. At times it can be seen swimming open mouthed catching prey as it contacts it (Western Ribbon Snake Photos and Facts). Individuals become more active during periods of high rainfall, especially when it is currently raining. Such periods of activity may correspond to their amphibian prey becoming more active during wet periods (Clark, 1974; Tinkle, 1957).

     T. proximus uses both terrestrial and aquatic habitats. This catholic lifestyle and is often different than their competitors and therefore reduces competition for prey (Tinkle 1957). When hunting prey T. proximus probes areas where prey could hide, like thick grasses. This probing consist of pushing the head quickly into three different areas of a spot where prey has been sighted (Ernst and Barnour, 1989). When the disturbed prey leaves the safety of the grass T. proximus will crawl after it (Ernst and Barbour, 1989). Once the prey is captured it is swallowed whole and the stomach muscles crush the specimen to aid digestion (snakeestate.net).

     Predators of T. proximus are wading birds (Ernst and Ernst, 2003). If T. proximus is disturbed by a predator it will dash away into hiding. A hiding mechanism that is often used is diving into a body of water if it is close enough and swimming to the bottom to hide there. This is beneficial since their predators are shorebirds. It can also at times emit a pungent liquid, or musk, that may keep predators away (Harding, 1997.).

     In some northern populations T. proximus hibernates in any area suitable for a den (or hibernacula). It will enter dens with other snakes of both the same and different species (Tinkles, 1957). Dens may exist in rock or gravel banks, but other hibernacula include mammal burrows, drainage ditches, rotten logs or trees, and springs (Ernst and Ernst, 2003). These are preferred areas because these areas are safe and regulate temperature, or their temperature does not fluctuate as easily being water or underground. Individuals in southern populations of T. proximus will be active whenever the temperatures are appropriately warm, so some years they do not hibernate at all (Tinkle 1957). When the weather is cooler during the winter, the species will stay in open sunny areas.

     T. proximus has a fairly large home range and they are prone to wander it instead of staying in one place (Tinkle, 1957). Immature females move less than mature females and males. Males on average move 2.5 m/day and females average 1.1 m/day. Between re-captures males moved up to 209 m from where they were first captured and females moved up to 97 m from where they were first captured (Clark, 1974).

  • Clark, D. R. Jr. 1974. The western ribbon snake (Thamnophis proximus): Ecology of a Texas population. Herpetologica 30: 372-379.
  • Ernst, C. H. and E. M. Ernst. 2003. Snakes of the United States and Canada. Smithsonian Institution Press. Washington, D.C.
  • Ernst, C.H., and R.W. Barbour. 1989. Snakes of eastern North America. George Mason University Press. Fairfax, V.A.
  • Ford N. B and R. A. Seigel. 2015. The influence of female body size and shape on the trade-off between offspring number and offspring size in two viviparous snakes. Journal of Zoology 295:154-158
  • Harding, J.H. (1997) Amphibians and Reptiles of the Great Lakes Region. University of Michigan Press, Michigan.
  • Tinkle D. W. 1957. Ecology, Maturation and Reproduction of Thamnophis Sauritus Proximus. Ecology 38:69–77.
  • Western Ribbon Snake. (n.d.). Retrieved April 28, 2015, from http://www.snakeestate.com/ribbon-snakes/western-ribbon-snake.html
  • Western ribbon snake photos and facts. (n.d.). Retrieved April 28, 2015, from http://www.arkive.org/western-ribbon-snake/thamnophis-proximus/
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Cyclicity

Comments: Active day or night; nocturnal in hot weather (Collins 1982). Active from March to October in north (Collins 1982).

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Reproduction

Gives birth to litter of 4-27 young, mainly July-September. Sexually mature in 2nd or 3rd year (Fitch 1970).

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     Thamnophis proximus females and males mature around 2 years old (Tinkle 1957). Although in some populations in Texas the majority of males are capable of mating in their first spring (Clark, 1974). Mature females measure approximately 500mm (+/- 15mm) snout-vent length and mature males measure approximately 409mm (+/- 9mm) snout-vent length (Clark, 1974). Mating starts earlier in the spring in the south and later in the spring in the north.

     In many Thamnophis species copulation occurs once with males competing for the female. After mating, the gestation period is approximately 3 months long (Tinkle, 1957). Young are born in late summer, the timing depending on latitude and when populations emerged from hibernation (Tinkle, 1957). Males pursue females that produce epidermal lipids. These lipids signal an attraction and the males find shelters that females have settled in or are settled in (Ernst and Ernst, 2003). The actual courtship process has not been noted for this species.

     The genus Thamnophis has viviparous reproductive strategy. Young are born live and stay with the mother for only a few days. Birth occurs in a hidden area similar to hibernation areas. The young then disperse on their own to find food and shelter. New born offspring of both sexes are about the same size: 210mm total body length and 160mm snout-vent length. Clutch size is variable being anywhere from 4-36 individuals. Average clutch size is ten in a Louisiana population that was studied (Ernst and Barbour, 1989). A Texas population had an average clutch size of eight (Ernst and Barbour, 1989).

     When females are sexually mature and ready to conceive, their egg follicles grow in length from <5mm to approximately 8mm. Before sexual maturity, juvenile females have egg follicles under 3mm in length (Tinkle 1957). The right follicle is larger and produces the majority of the eggs (Ernst and Ernst, 2003).  Males T. proximus have two hemipenes, which is shorter than average in Thamnophis proximus, relative to other Thamnophis species: when inverted the hemipene only extends to subcaudal scales seven and eight (Ernst and Ernst, 2003). The sulcus spermaticus is straight and ends at the apex (Ernst and Ernst, 2003).

     Ford and Seigel (2014) showed a trade-off that existed between brood size and offspring size in T. proximus. Brood size and offspring size are negatively correlated, but this correlation was strongest in smaller females. Large females are able to have many, large offspring. Since T. proximus is a slimmer snake than other Thamnophis species that could be affecting the number of individuals or size of individuals born in a brood (Ford and Seigel, 2014). 

  • Clark, D. R. Jr. 1974. The western ribbon snake (Thamnophis proximus): Ecology of a Texas population. Herpetologica 30: 372-379.
  • Ernst, C. H. and E. M. Ernst. 2003. Snakes of the United States and Canada. Smithsonian Institution Press. Washington, D.C.
  • Ernst, C.H., and R.W. Barbour. 1989. Snakes of eastern North America. George Mason University Press. Fairfax, V.A.
  • Ford N. B and R. A. Seigel. 2015. The influence of female body size and shape on the trade-off between offspring number and offspring size in two viviparous snakes. Journal of Zoology 295:154-158
  • Harding, J.H. (1997) Amphibians and Reptiles of the Great Lakes Region. University of Michigan Press, Michigan.
  • Tinkle D. W. 1957. Ecology, Maturation and Reproduction of Thamnophis Sauritus Proximus. Ecology 38:69–77.
  • Western Ribbon Snake. (n.d.). Retrieved April 28, 2015, from http://www.snakeestate.com/ribbon-snakes/western-ribbon-snake.html
  • Western ribbon snake photos and facts. (n.d.). Retrieved April 28, 2015, from http://www.arkive.org/western-ribbon-snake/thamnophis-proximus/
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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage: Thamnophis proximus

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 7
Species With Barcodes: 1
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Conservation

Conservation Status

IUCN Red List Assessment


Red List Category
LC
Least Concern

Red List Criteria

Version
3.1

Year Assessed
2013

Assessor/s
Chaves, G., Lamar, W., Porras, L.W., Solórzano, A., Sunyer, J. & Hammerson, G.A.

Reviewer/s
Bowles, P.

Contributor/s

Justification
Listed as Least Concern because it has a wide distribution, large population, and is unlikely to be declining fast enough to qualify for listing in a more threatened category.
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National NatureServe Conservation Status

United States

Rounded National Status Rank: N5 - Secure

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NatureServe Conservation Status

Rounded Global Status Rank: G5 - Secure

Intrinsic Vulnerability: Moderately vulnerable

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Population

Population
This is a locally common species.

Population Trend
Stable
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Global Short Term Trend: Relatively stable (=10% change)

Comments: Currently, the extent of occurrence, area of occupancy, number of subpopulations, and population size probably are relatively stable or declining at a rate of less than 10 percent over 10 years or three generations.

Global Long Term Trend: Increase of 10-25% to decline of 30%

Comments: Area of occupancy, number of subpopulations, and population size have declined modestly, especially at the margins of the range. For example, this species declined at the northern fringe of the range in northwestern Indiana between the 1930s and 1990s (Brodman et al. 2002).

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Threats

Major Threats
No major threats are known. Locally, wetland loss and degradation have extirpated or reduced some populations.
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Degree of Threat: Medium

Comments: No major threats are known. Locally, wetland loss and degradation have extirpated or reduced some populations.

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Management

Conservation Actions

Conservation Actions
Currently, this species is of relatively low conservation concern and does not require significant additional protection or major management, monitoring, or research action. It is present in several protected areas.
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Global Protection: Very many (>40) occurrences appropriately protected and managed

Comments: Many occurrences are in protected areas.

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Wikipedia

Western ribbon snake

The western ribbon snake (Thamnophis proximus) is a species of garter snake, with several subspecies.

Taxonomy[edit]

  • Western ribbon snake, T. proximus
    • Chiapas Highland ribbon snake, T. p. alpinus (Rossman, 1963)
    • Arid land ribbon snake, T. p. diabolicus (Rossman, 1963)
    • Gulf Coast ribbon snake, T. p. orarius (Rossman, 1963)
    • Western ribbon snake, T. p. proximus (Say, 1823)
    • Redstripe ribbon snake, T. p. rubrilineatus (Rossman, 1963)
    • Mexican ribbon snake, T. p. rutiloris (Cope, 1885)
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