Common names: midget faded rattlesnake, yellow rattlesnake, faded rattlesnake.

Crotalus oreganus concolor is a venomous

Venomous snake

"Poisonous snake" redirects here. For true poisonous snakes, see Rhabdophis.Venomous snakes are snakes which have venom glands and specialized teeth for the injection of venom...

 pitviper

Crotalinae

The Crotalinae, commonly known as "pit vipers" or crotaline snakes, are a subfamily of venomous vipers found in Asia and the Americas. They are distinguished by the presence of a heat-sensing pit organ located between the eye and the nostril on either side of the head...

 subspecies

Subspecies

Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...

 found in the western United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

. A small species known for its faded color pattern.

Description

Grows to a maximum length of 750 mm. The smallest gravid female measured was 522 mm.

The color pattern consists of a pinkish, pale brown, yellow-brown, straw-colored, reddish or yellow-brown ground color, overlaid with a series of brown elliptical or rectangular dorsal blotches. However, most specimens are gray or silvery. In juveniles the pattern is distinct, but becomes faded in adults, almost to the point where it is indistinguishable from the ground color.

Geographic range

Found in the United States in the Colorado

Colorado River

The Colorado River , is a river in the Southwestern United States and northwestern Mexico, approximately long, draining a part of the arid regions on the western slope of the Rocky Mountains. The watershed of the Colorado River covers in parts of seven U.S. states and two Mexican states...

 and Green River

Green River (Utah)

The Green River, located in the western United States, is the chief tributary of the Colorado River. The watershed of the river, known as the Green River Basin, covers parts of Wyoming, Utah, and Colorado. The Green River is long, beginning in the Wind River Mountains of Wyoming and flowing...

 basins. This area covers southwestern Wyoming

Wyoming

Wyoming is a state in the mountain region of the Western United States. The western two thirds of the state is covered mostly with the mountain ranges and rangelands in the foothills of the Eastern Rocky Mountains, while the eastern third of the state is high elevation prairie known as the High...

, Utah

Utah

Utah is a state in the Western United States. It was the 45th state to join the Union, on January 4, 1896. Approximately 80% of Utah's 2,763,885 people live along the Wasatch Front, centering on Salt Lake City. This leaves vast expanses of the state nearly uninhabited, making the population the...

 east of long. 111° West (excluding the southeastern corner) and extreme east-central Colorado

Colorado

Colorado is a U.S. state that encompasses much of the Rocky Mountains as well as the northeastern portion of the Colorado Plateau and the western edge of the Great Plains...

. The type locality given is "King's Ranch, Garfield Co., at the base of the Henry Mts [Utah]."

Venom

This subspecies possesses the most toxic venom of the C. oreganus

Crotalus oreganus

Crotalus oreganus is a venomous pitviper species found in North America in the western United States, parts of British Columbia and northwestern Mexico. Seven subspecies are currently recognized, including the nominate subspecies described here....

 / C. viridis

Crotalus viridis

Crotalus viridis is a venomous pitviper species native to the western United States, southwestern Canada, and northern Mexico. Currently, nine subspecies are recognized, including the nominate subspecies described here.-Description:...

 group, although there is apparently considerable variability among local populations (Glenn and Straight, 1977, 1978). It is even one of the most potent venoms found in North America (Glenn and Straight, 1977), and according to LD50 studies the venom is many times more potent than that of an Asiatic Cobra. It is characterized by the presence of a presynaptic neurotoxin

Neurotoxin

A neurotoxin is a toxin that acts specifically on nerve cells , usually by interacting with membrane proteins such as ion channels. Some sources are more general, and define the effect of neurotoxins as occurring at nerve tissue...

, referred to as concolor toxin, the amount of which varies in individual snakes (Glenn and Straight, 1977, 1990; Wetstein et al., 1985).

External links

• Image of C. o. concolor at UtahHerps.info. Accessed 18 June 2008.