Thamnophis proximusWestern Ribbon Snake

Geographic Range

Thamnophis proximus, the Western ribbon snake, can be found ranging from the United States specifically Wisconsin and southward, down into Central America, including Belize and Costa Rica. The species is usually found active during early spring into the summer, and is most active during the day or during warm periods. In areas with changeable seasons, the Western Ribbon Snake will hibernate in rocky outcroppings, sometimes with other species. (Clark Jr., 1974; Rossman, 1962; Rossman, et al., 1996; Sunyer, et al., 2013)

This species is found in more brush-heavy habitats, close to water sources. They can also be found basking on rocks or flat vegetation, or in sandy, drier areas that are also close to water. Due to it's slender body, it is believed that this and other garter snake species evolved to adapt to more forest-heavy habitats. (Hampton, 2008; Penn State New Kingston, 2002; Rossman, 1962; Rossman, et al., 1996)


This species can be found in a wide range of habitats, usually around brush-heavy areas with bodies of water like streams, ponds, lakes, etc. It is a semi-aquatic species, and generally does not live far away from a water source (Sunyer et al., 2013). They will dive into water if disturbed, or hide themselves in thick brush or within crevices. Their body coloration helps them hide in these areas. They prefer warmer temperatures, but can be active between 4 and 42 degrees Celsius, with 22-26 their preference. (Rossman, et al., 1996; Sunyer, et al., 2013)

  • Range elevation
    0 to 2438 m
    0.00 to 7998.69 ft
  • Range depth
    0 (low) m
    0.00 (low) ft

Physical Description

The Western Ribbon Snake is often confused with the Eastern Ribbon Snake, which has a very similar look and coloration. A few distinguishing characteristics include the reduction or absence of a broad, brown ventro-lateral stripe found on the Eastern species. The large paired parietal spots, longer muzzle and tail on the Western Ribbon Snake are also a distinguishing features. They have pale undersides, usually a light yellow or green, while their backs will typically be dark brown or black with lighter side stripes. The Western Ribbon Snake have a maximum recorded SVL (snout to vent length) of 1250 mm (around 50 inches). Most remain around 3 feet. Their tail is roughly 30% of their body length.

Juveniles tend to be smaller than adults in body, but with proportionally larger heads. T

Like other garter snakes, this species of snake is non-venomous, and not lethal to humans. (Rossman, 1962; Rossman, et al., 1996; Sunyer, et al., 2013; Wisconsin Department of Natural Resources, 2013)

  • Range length
    210 to 1250 mm
    8.27 to 49.21 in


Thamnophis proximus births live young, which are relatively small compared to adults (around 20 cm). Their tail-to-body ratio, however, is fairly large, and their tails also experience rapid and disproportionate growth. Juveniles are still small compared to adults, but their head size is proportionally larger, giving them an advantage when it comes to catching and consuming larger prey. Adults do not retain this head to body proportion. (Hampton, 2011; Rossman, et al., 1996; Wendelken, 1978; Wisconsin Department of Natural Resources, 2013)


Thamnophis proximus is most reproductively active during the spring, but the exact season in which breeding occurs is unknown. Males will trail females by following their scent in order to copulate. Because their sense of smell is so developed, they can follow for some distance. (Ford, 1981; Rossman, et al., 1996)

Female western ribbon snakes can be gravid as early as April, but births usually occur between June and mid-September. Females incubate the eggs within and then have live births of between 3 and 21 offspring. The offspring's mean length can be 16 to 28cm, with little variation within clutches. Mass size varies greater within clutches, from 1.1 to 3.1 grams. Larger females tend to give birth to larger clutches with greater mass. (Lancaster and Ford, 2003; Rossman, 1962; Rossman, et al., 1996)

  • Breeding interval
    Females breed once per season.
  • Breeding season
    Western ribbon snakes breed in mid to late summer, with most offspring birthed between June and mid-September.
  • Range number of offspring
    4 to 27
  • Average number of offspring
    8.4 to 12.9
  • Range age at sexual or reproductive maturity (female)
    12 to 15 months
  • Average age at sexual or reproductive maturity (female)
    13 months
  • Range age at sexual or reproductive maturity (male)
    7 to 24 months
  • Average age at sexual or reproductive maturity (male)
    12 months
  • Parental Investment
  • female parental care
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female


  • Typical lifespan
    Status: wild
    3 to 6 years
  • Typical lifespan
    Status: captivity
    12 to 20 years


This species has adapted a special technique of foraging for amphibians, specifically frogs. Thamnophis proximus will move over land and make light thrusts with it's head and upper body, similar to a strike, but with a closed mouth. These thrusts are in sequences of three, each in quick succession and in different directions. A frog will be disturbed by these thrusts, and alert the snake to its location. The snake can then give chase. Thamnophis proximus is fast, and uses this speed for both capturing quick prey like frogs or fish, and for escaping potentially dangerous situations. If disturbed, Thamnophis proximus will disappear into nearby brush or crevices, or even dive into water and swim away if there is a body of water in close proximity. During warm seasons they are active during the day, hunting for food or laying in the sun. In areas with cold seasons, these snakes will hibernate in caves and crevices until a armer period returns. They have been seen emerging while it is still winter, after a few consecutive days of warmth. (Dewey, 2005; Ford, 1981; Hampton, 2011; Rossman, et al., 1996; Wendelken, 1978)

Communication and Perception

This species hunts visually, using its head to startle prey into view and give chase. In general, Thamnophis proximus communicates using its forked tongue, which can collect chemicals from the air that the snake will interpret. This is especially useful when following the trail of a female, looking for a potential mate. They will also use touch as a communication method. Thamnophis proximus can also sense vibrations, which can tell them if a prey species is nearby, or a possible predator. (Dewey, 2005; Ford, 1981; Rossman, et al., 1996; Wendelken, 1978)

Food Habits

The main food for Thamnophis proximus are amphibians, with studies reporting them to be between 80-92% of their diet. Besides amphibians, Thamnophis proximus will consume fish, snails, eggs that they find, crustaceans, and rarely small mammals. Thamnophis proximus varies its diet based on its individual size. Larger than average snakes will catch larger prey, while smaller snakes with smaller mouths and body capacities will eat smaller prey. With this variation in prey size comes a variation in consumption times - after eating larger prey, a snake will have a longer period between meals in order to digest. Juvenile snakes with a relatively smaller body size compared to adults often have a proportionally-larger head in order to increase their gape, and the size of prey available. Adult snakes will eat smaller prey, as the head-to-body proportion does not continue into adulthood, and has not been shown to be advantageous. (Clark Jr., 1974; Hampton, 2008; Hampton, 2011; Rossman, et al., 1996; Wendelken, 1978)

  • Primary Diet
  • carnivore
    • eats terrestrial vertebrates
    • piscivore
    • eats eggs
    • eats non-insect arthropods
    • molluscivore
    • vermivore
    • eats other marine invertebrates
  • Animal Foods
  • amphibians
  • reptiles
  • fish
  • eggs
  • mollusks
  • terrestrial worms
  • aquatic crustaceans


Eaten by various predatory birds and mammals - Weasels, ferrets, large fish, predatory birds (hawks, eagles) and raptors,and other large snakes like rattlesnakes or cottonmouth snakes. When captured by a human or a predator, this snake will thrash its body around to try and escape, usually emitting a foul smell or spraying feces to encourage the foe to release it. The western ribbon snake can also shed its tail, which will continue to move in order to allow the snake to escape. The tail will not regenerate. (Hampton, 2011; Rossman, et al., 1996)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

The western ribbon snake has a diet that consists of mostly amphibians, which controls amphibious populations, but has the potential to decimate those populations in certain areas.

Economic Importance for Humans: Positive

Thamnophis proximus eats pests and helps control prey populations that can be pests, including insects and amphibians. (Hampton, 2011; Lancaster and Ford, 2003; Rossman, et al., 1996; Wendelken, 1978)

  • Positive Impacts
  • controls pest population

Economic Importance for Humans: Negative

No known negative impacts on humans.

Conservation Status

This species is listed as least concern and special status on the IUCN Red List, the US Federal List,, and the State of Michigan list. It is listed as endangered by the Wisconsin DNR.

This species is very much affected by human development and disturbances in their habitat. Water drainage sites drain water sources for them. Roads and highways offer dangerous blockages for their populations. Climate change is also affecting both the western ribbon snake and its prey - amphibians. Drier seasons lead to water shortages, and therefore limit snake habitats and amphibian hibernation sites.

Pesticides, road substrates and road chemicals have a negative affect on snake health, as well as affecting their pheromone emittance. (Wisconsin Department of Natural Resources, 2013)

Other Comments

There are 6 subspecies of Thamnophis proximus: T. p. alpinus (high-elevation), T. p. diabolicus (Colorado and southward through Pecos Valley), T. p. orarius (Coastal Louisiana to Northeastern Tamaulipas), T. p. rubrilineatus (Central Texas plateaus), and T. p. rutiloris (southern Tamaulipas to central Costa Rica). (Rossman, et al., 1996)


Margaret Waters (author), Minnesota State University Mankato, Robert Sorensen (editor), Minnesota State University, Mankato, Tanya Dewey (editor), University of Michigan-Ann Arbor.


Atlantic Ocean

the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.

World Map


living in the southern part of the New World. In other words, Central and South America.

World Map

Pacific Ocean

body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.

World Map


uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.


a wetland area rich in accumulated plant material and with acidic soils surrounding a body of open water. Bogs have a flora dominated by sedges, heaths, and sphagnum.

brackish water

areas with salty water, usually in coastal marshes and estuaries.


an animal that mainly eats meat


uses smells or other chemicals to communicate


the nearshore aquatic habitats near a coast, or shoreline.


having a worldwide distribution. Found on all continents (except maybe Antarctica) and in all biogeographic provinces; or in all the major oceans (Atlantic, Indian, and Pacific.


having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

  1. active during the day, 2. lasting for one day.

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature


an area where a freshwater river meets the ocean and tidal influences result in fluctuations in salinity.

female parental care

parental care is carried out by females


forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.


mainly lives in water that is not salty.


having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.


the state that some animals enter during winter in which normal physiological processes are significantly reduced, thus lowering the animal's energy requirements. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals.


offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).


marshes are wetland areas often dominated by grasses and reeds.


eats mollusks, members of Phylum Mollusca


having the capacity to move from one place to another.


specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.


reproduction in which eggs develop within the maternal body without additional nourishment from the parent and hatch within the parent or immediately after laying.


an animal that mainly eats fish


the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.


rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

scent marks

communicates by producing scents from special gland(s) and placing them on a surface whether others can smell or taste them

seasonal breeding

breeding is confined to a particular season


reproduction that includes combining the genetic contribution of two individuals, a male and a female


a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.


uses touch to communicate


that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).


Living on the ground.


the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.


movements of a hard surface that are produced by animals as signals to others


uses sight to communicate


reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.


2011. "Western ribbon snake fact file" (On-line). Widescreen Archive. Accessed February 14, 2017 at

Clark Jr., C. 1974. The Western Ribbon Snake (Thamnophis proximus): Ecology of a Texas Population. Herpetologica, 30 No. 4: 372-379.

Dewey, T. 2005. "Thamnophis sauritus - Eastern Ribbonsnake" (On-line). Animal Diversity Web. Accessed April 05, 2017 at

Ford, N. 1981. Seasonality of Pheromone Trailing Behavior in Two Species of Garter Snake, Thamnophis (Colubridae). The Southwestern Naturalist, 26/4: 385-388.

Hampton, P. 2011. Feeding performance in the Western Ribbon Snake (Thamnophis proximus): ontogeny and the effects of prey type and size. Canadian Journal of Zoology, 89: 945.

Hampton, P. 2008. Prey Items of the Western Ribbon Snake, Thamnophis proximus. The Southwestern Naturalist, 53: 115-118.

Lancaster, D., N. Ford. 2003. Reproduction in western ribbon snakes, Thamnophis proximus (Serpentes: Colubridae), from an east Texas bottomland. The Texas Journal of Science, 55: 25.

Penn State New Kingston, 2002. "The Virtual Nature Trail at Penn State New Kingston" (On-line). The Virtual Nature Trail at Penn State New Kingston. Accessed April 19, 2017 at

Rossman, D., N. Ford, R. Seigel. 1996. The Garter Snakes: Evolution and Ecology. University of Oklahoma Press, Norman.: University of Oklahoma Press.

Rossman, D. 1962. Thamnophis proximus (Say), a Valid Species of Garter Snake. Copeia, 1962 No. 4: 741-748.

Sunyer, J., G. Chaves, W. Lamar, L. Porras, A. Solórzano, G. Hammerson. 2013. "Thamnophis proximus" (On-line). The IUCN Red List of Threatened SpeciesThe IUCN Red List of Threatened Species. Accessed February 14, 2017 at

Wendelken, P. 1978. On Prey-Specific Hunting Behavior in the Western Ribbon Snake, Thamnophis Proximus (Reptilia, Serpentes, Colubridae). Journal of Herpetology, 12/4: 577-578. Accessed April 05, 2017 at

Wisconsin Department of Natural Resources, 2013. "Western Ribbonsnake Species Guidance" (On-line). Wisconsin Department of Natural Resources. Accessed April 19, 2017 at