:''Common names: desert massasauga, Conant R (1975). ''A Field Guide to Reptiles and Amphibians of Eastern and Central North America, Second Edition''. (First Edition published in 1958). Boston: Houghton Mifflin Company. xviii + 429 pp + 48 plates. (hardcover), (paperback). Edward's massasauga, Wright AH, Wright AA (1957). ''Handbook of Snakes of the United States and Canada''. Ithaca and London: Comstock Publishing Associates, a Division of Cornell University Press. (7th printing, 1985). 1,105 pp. . Edward's rattlesnake. Ditmars RL (1933). ''Reptiles of the World''. Revised Edition. New York: The MacMillan Company. 329 pp. 89 plates.'' ''Sistrurus catenatus edwardsii'' is a

subspecies In biological classification, subspecies is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (morphology), but that can successfully interbreed. Not all species ...

of venomous

pit viper The Crotalinae, commonly known as pit vipers,Mehrtens JM (1987). ''Living Snakes of the World in Color''. New York: Sterling Publishers. 480 pp. . crotaline snakes (from grc, κρόταλον ''krotalon'' castanet), or pit adders, are a subfa ...

in the family Viperidae. The subspecies is endemic to the

Southwestern United States The Southwestern United States, also known as the American Southwest or simply the Southwest, is a geographic and cultural region of the United States that generally includes Arizona, New Mexico, and adjacent portions of California, Colorado, Ne ...

and northern Mexico. In places, its range overlaps that of '' S. c. tergeminus'', and intergrading of the two subspecies is known.

Etymology

The subspecific name, ''edwardsii'', is in honor of Colonel Dr. Lewis A. Edwards (1824–1877), a U.S. Army surgeon, who collected the type specimen.

Baird Baird may refer to: Places United States * Baird, Mississippi, an unincorporated community * Baird, Missouri, an unincorporated community * Baird, Texas, a city * Baird, Washington, a community * Baird Mountains, Alaska * Baird Inlet, Alaska ...

& Girard (1853).

Description

''S. c. edwardsii'' is more slender and smaller than ''S. c. tergeminus'', reaching a maximum total length (including tail) of . Its color pattern consists of a light gray or white base color, with dark gray or gray-brown blotches. It has a distinctive, dark stripe that runs along the side of the head, which passes over the eye. The rattle is significantly higher pitched than those of larger species of rattlesnakes, sometimes giving it the nickname "buzztail". Compared to ''S. c. tergeminus'', it is paler in color, and its belly is nearly white. Midbody, it has 23 rows of dorsal scales instead of 25, and fewer ventral scales and dorsal blotches.

Geographic range

''S. c. edwardsii'' is found in extreme southeastern Arizona, central and southern New Mexico, West Texas about as far north and east as the Colorado River, in the Rio Grande Valley, in many of the Gulf Coast counties about as far north as Brazoria, and on several barrier islands including North Padre Island, Matagorda Island, and San José Island. In addition, isolated populations have been reported in northeastern Mexico. Klauber LM (1997). ''Rattlesnakes: Their Habitats, Life Histories, and Influence on Mankind''. Second Edition. First published in 1956, 1972. Berkeley: University of California Press. .Campbell JA, Lamar WW (2004). ''The Venomous Reptiles of the Western Hemisphere''. Ithaca and London: Comstock Publishing Associates. 870 pp. 1,500 plates. . The type locality is listed as "Tamaulipas ... S. Bank of Rio Grande ... Sonora".

Habitat

''S. c. edwardsii'' is primarily found in rocky, semiarid, and arid areas. According to Conant (1975), it is mostly found in desert grasslands.

Behavior

This subspecies is primarily

nocturnal Nocturnality is an animal behavior characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnal meaning the opposite. Nocturnal creatures generally have highly developed sens ...

, especially during the summer, when the weather is too hot for it to be active, but it can sometimes be found basking.

Feeding

The diet of ''S. c. edwardsii'' consists primarily of rodents,

lizard Lizards are a widespread group of squamate reptiles, with over 7,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The group is paraphyletic since it excludes the snakes and Amphisbaenia alt ...

s, and frogs.

Venom

Drop for drop, massasauga venom is more potent than that of many larger species of rattlesnakes, but due to the lower yield (the amount it is capable of delivering in a single bite), its potential for harm is greatly reduced. It is not considered to be deadly, but the venom is a powerful

cytotoxic Cytotoxicity is the quality of being toxic to cells. Examples of toxic agents are an immune cell or some types of venom, e.g. from the puff adder (''Bitis arietans'') or brown recluse spider (''Loxosceles reclusa''). Cell physiology Treating cells ...

venom that can cause swelling,

necrosis Necrosis () is a form of cell injury which results in the premature death of cells in living tissue by autolysis. Necrosis is caused by factors external to the cell or tissue, such as infection, or trauma which result in the unregulated dige ...

, damage to the skin, and severe pain. Medical treatment should be sought immediately for any venomous snake bite. The antivenin

CroFab Crotalidae polyvalent immune fab, sold under the brandname CroFab, is a snake antivenin, indicated for minimal or moderate North American Crotalid ( Rattlesnake, Copperhead and Cottonmouth/Water moccasin) snake envenomation. CroFab is composed o ...

, while not type-specific, can be used to treat severe envenomations from massasaugas.

Conservation status

The desert massasauga is listed as a species of concern in Colorado, due to its limited range in the state, and it is protected by Arizona state law. It is listed as a sensitive species by the United States Forest Service.