Western ribbon snake (Thamnophis proximus)

The western ribbon snake (Thamnophis proximus) is a long, slender garter snake with a stripy body and a very long tail, which makes up nearly a third of its total length ^{(2) (3) (4) (5)}. The background colour of the western ribbon snake varies from dark brown to olive-grey, olive-brown or black, and there are three light stripes running along the body. The central stripe, running down the spine, ranges from greyish-tan to gold, reddish or orange, while the two stripes along the sides are usually pale yellowish. The belly of the western ribbon snake is an immaculate white, cream, pale yellow or pale greenish ^{(2) (3) (4) (5) (6)}.

The head of the western ribbon snake is distinctly wider than the neck, and the eyes are moderately large, with round pupils ^{(3) (5)}. On top, the head is dark brown or black and is marked with a pair of small, bright yellow spots, which are sometimes joined together ^{(2) (4) (5) (6)}. There is also a pale vertical bar in front of each eye ⁽⁴⁾. The lip scales of the western ribbon snake are usually white, cream, pale greenish or yellowish-orange, without any dark markings ^{(2) (3) (4) (5) (6)}.

Male and female western ribbon snakes are similar in appearance ⁽³⁾, but the male is generally smaller and more slender than the female, and has a slightly longer tail ⁽⁵⁾. Newborns are patterned like the adults ⁽⁵⁾.

Although originally described as a distinct species, the western ribbon snake was for many years treated as a subspecies of the eastern ribbon snake (Thamnophis sauritus) ^{(2) (3) (7)}. It is distinguished from the eastern ribbon snake by its larger, more conspicuous pale spots on the head, as well as a by its longer snout, shorter tail, and greater number of scales on the upper lip ^{(5) (7)}. Compared to other garter snakes (Thamnophis species), the western ribbon snake is less stocky and has a much longer tail. It is also distinguished by the lack of dark markings on the lips and belly ^{(4) (5) (6)}.

The western ribbon snake shows considerable variation in its background colour and in the width and colour of its stripes. Six subspecies are recognised: the western ribbon snake (Thamnophis proximus proximus), arid land ribbon snake (Thamnophis proximus diabolicus), Gulf Coast ribbon snake (Thamnophis proximus orarius), Mexican ribbon snake (Thamnophis proximus rutiloris), redstripe ribbon snake (Thamnophis proximus rubrilineatus) and Chiapas Highland ribbon snake (Thamnophis proximus alpinus) ^{(1) (2) (3)}.

Also known as

arid land ribbon snake, Chiapas highland ribbon snake, Gulf Coast ribbon snake, Mexican ribbon snake, redstripe ribbon snake, red-striped ribbon snake.

Synonyms

Coluber proximus, Eutaenia proxima, Eutaenia rutiloris, Eutainia faireyi, Thamnophis proxima, Thamnophis saurita proxima, Thamnophis sauritus proxima, Thamnophis sauritus proximus.

Size

Snout-vent length: up to 90 cm ⁽²⁾

Total length: up to 125 cm ⁽³⁾

The diet of the western ribbon snake consists mainly of amphibians, including frogs, toads and salamanders, as well as their larvae ^{(2) (3) (5) (6) (8) (9)}. It also takes small fish ^{(2) (3) (5) (6) (8)}, and has been recorded eating skinks and crayfish ^{(2) (8)}. The western ribbon snake is an active predator that hunts largely by sight. It may search for food by probing in vegetation, chasing prey that is flushed out, and has also been seen swimming with its mouth open, snatching up prey as it comes into contact with it ^{(2) (5) (6)}. If threatened, the western ribbon snake may dash or swim into vegetation ^{(5) (6)}, and if caught it can emit a pungent liquid to deter predators ⁽⁶⁾.

The western ribbon snake is usually active during the day ^{(2) (3)}, but may also be active at night when daytime temperatures become too hot ⁽⁶⁾. In some areas, the western ribbon snake hibernates during the winter months, sheltering in a rocky bank, rocky outcrop, rodent burrow, rotten log or other suitable site, which it often shares with other hibernating snakes ^{(2) (5) (10)}. This species is usually active between about April and October in northern areas, but in more southern locations it may be active throughout the year when conditions are favourable ^{(2) (5) (6) (10)}. Rainfall often stimulates activity in the western ribbon snake, probably due to an associated increase in the activity of its amphibian prey ^{(2) (6) (10)}.

Mating takes place in spring, soon after the western ribbon snake emerges from hibernation. The female usually gives birth between July and September ^{(2) (5) (6) (9)}, with females from southern populations usually giving birth slightly earlier than those from northern ones ⁽¹⁰⁾. The western ribbon snake gives birth to between 4 and 27 live young ^{(5) (6)}, with the average litter size being about 8 to 13 ^{(2) (5) (6) (10)}. The newborn snakes measure around 16 to 29 centimetres in length ^{(3) (5) (6)}.

The male western ribbon snake reaches maturity from around 7 to 9 months, at a length of at least 41 centimetres ^{(2) (9) (10)}. Females mature later, and may not start breeding until their second or third year ^{(2) (5) (6) (9) (10)}. The size at which the female western ribbon snake reaches maturity varies between populations, ranging from about 35 to 51 centimetres ^{(2) (3) (9) (10)}.

The western ribbon snake occurs from Ohio, Indiana, Illinois and southern Wisconsin in the central United States, west through the Great Plains to Kansas, Nebraska and Oklahoma, and south into Central America, as far as Costa Rica ^{(1) (2) (3) (5)}.

The subspecies T. p. proximus occurs in the United States ^{(2) (5)}, while T. p. diabolicus and T. p. orarius range from the U.S. to Mexico. T. p. rubrilineatus is confined to the Edwards Plateau of central Texas, while T. p. rutiloris occurs from Mexico to Costa Rica, and T. p. alpinus is restricted to high elevations in central Chiapas, Mexico ⁽²⁾.

A semiaquatic species, the western ribbon snake is most commonly associated with brushy or grassy areas close to water. It may be found close to swamps, marshes, ponds, rivers, streams, lakes, or damp meadows, and has even been found around cattle tanks and ditches ^{(2) (3) (4) (5) (6)}. This species also sometimes occurs at the edges of wet woodlands ^{(4) (6)}.

The western ribbon snake has been recorded from a range of elevations, from sea level to around 2,400 metres ^{(2) (3)}.

The western ribbon snake has yet to be classified by the IUCN.

The main threats to the western ribbon snake are likely to come from the drainage and filling of its wetland habitats ^{(2) (5)}. It may also be affected by the degradation of its habitat due to pollution and recreational activities, as well as by habitat loss due to agricultural development ⁽⁵⁾. In some areas, activities such as land cultivation and the loss of wetlands have resulted in the rapid disappearance of this species ⁽⁴⁾.

Although reported to have a rather nervous nature in captivity, the western ribbon snake is often kept as a pet, and is one of the most common snakes to be sold in pet stores in the United States ⁽²⁾. However, the impacts of this on the wild population are unknown.

There are no known specific conservation measures currently in place for the western ribbon snake, and the conservation status of this species has yet to be assessed by the IUCN ⁽¹¹⁾.

Find out more about the western ribbon snake:

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

More information on reptile conservation:

• International Reptile Conservation Foundation:
  http://www.ircf.org/

This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:
arkive@wildscreen.org.uk

Hibernation

A winter survival strategy in which the animal passes the winter in a resting state. This period of inactivity is characterised by specific biological and biochemical changes including lowered blood pressure and respiration rate. In reptiles, this is also known as brumation.

Larvae

Stage in an animal’s lifecycle after it hatches from the egg. Larvae are typically very different in appearance to adults; they are able to feed and move around but usually are unable to reproduce.

Subspecies

A population usually restricted to a geographical area that differs from other populations of the same species, but not to the extent of being classified as a separate species.

1. The Reptile Database (June, 2011)
   http://reptile-database.reptarium.cz/search.php
2. Rossman, D.A., Ford, N.B. and Seigel, R.A. (1996) The Garter Snakes: Evolution and Ecology. University of Oklahoma Press, Norman.
3. Savage, J.M. (2002) The Amphibians and Reptiles of Costa Rica: A Herpetofauna between Two Continents, between Two Seas. University of Chicago Press, Chicago.
4. Dixon, J.R. and Werler, J.E. (2005) TexasSnakes: A Field Guide. University of Texas Press, Austin, Texas.
5. Harding, J.H. (1997) Amphibians and Reptiles of the Great Lakes Region. University of Michigan Press, Michigan.
6. Werler, J.E. and Dixon, J.R. (2000) TexasSnakes: Identification, Distribution, and Natural History. University of Texas Press, Austin, Texas.
7. Rossman, D.A. (1962) Thamnophis proximus (Say), a valid species of garter snake. Copeia, 1962(4): 741-748.
8. Ford, N.B. and Hampton, P.M. (2009) Ontogenetic and sexual differences in diet in an actively foraging snake, Thamnophis proximus. Canadian Journal of Zoology, 87(3): 254-261.
9. Clark Jr, D.R. (1974) The western ribbon snake (Thamnophis proximus): ecology of a Texas population. Herpetologica, 30(4): 372-379.
10. Tinkle, D.W. (1957) Maturation and reproduction of Thamnophis sauritus proximus. Ecology, 38(1): 69-77.
11. IUCN Red List (June, 2011)
    http://www.iucnredlist.org/