:''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 of

venomous Venom or zootoxin is a type of toxin produced by an animal that is actively delivered through a wound by means of a bite, sting, or similar action. The toxin is delivered through a specially evolved ''venom apparatus'', such as fangs or a sti ...

pit viper in the family Viperidae. The subspecies is

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found else ...

to the Southwestern United States and northern

Mexico Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...

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

Etymology

The

subspecific name In zoological nomenclature, a subspecific name is the third part of a trinomen. In zoology there is only one rank below that of species, namely "subspecies". In botanical nomenclature, there are several levels of subspecific names, such as ''var ...

, ''edwardsii'', is in honor of Colonel Dr. Lewis A. Edwards (1824–1877), a U.S. Army surgeon, who collected the type specimen. Baird & 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 Arizona ( ; nv, Hoozdo Hahoodzo ; ood, Alĭ ṣonak ) is a state in the Southwestern United States. It is the 6th largest and the 14th most populous of the 50 states. Its capital and largest city is Phoenix. Arizona is part of the Fou ...

, central and southern

New Mexico ) , population_demonym = New Mexican ( es, Neomexicano, Neomejicano, Nuevo Mexicano) , seat = Santa Fe , LargestCity = Albuquerque , LargestMetro = Tiguex , OfficialLang = None , Languages = English, Spanish ( New Mexican), Navajo, Ke ...

West Texas West Texas is a loosely defined region in the U.S. state of Texas, generally encompassing the arid and semiarid lands west of a line drawn between the cities of Wichita Falls, Abilene, and Del Rio. No consensus exists on the boundary betwee ...

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 North Padre Island is a barrier island along the coast of Texas. It and South Padre Island were formed after the creation of the Port Mansfield Channel split Padre Island in two. From north to south, North Padre Island is located in parts of Nu ...

Matagorda Island Matagorda Island (), ''Spanish for'' "thick brush," is a 38-mile (61 km) long barrier island on the Texas Gulf coast, located approximately south of Port O'Connor, in the southernmost part of Calhoun County. The traditional homeland of ...

, 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, 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, lizards, and

frog A frog is any member of a diverse and largely carnivorous group of short-bodied, tailless amphibians composing the order Anura (ανοὐρά, literally ''without tail'' in Ancient Greek). The oldest fossil "proto-frog" ''Triadobatrachus'' is ...

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 venom that can cause swelling, necrosis, damage to the skin, and severe pain. Medical treatment should be sought immediately for any venomous snake bite. The

antivenin Antivenom, also known as antivenin, venom antiserum, and antivenom immunoglobulin, is a specific treatment for envenomation. It is composed of antibodies and used to treat certain venomous bites and stings. Antivenoms are recommended only if th ...

CroFab, 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.