''Crotalus scutulatus'' (common names: Mojave rattlesnake,Crothier, B.I. ''et al''. 2003. Scientific and standard English names of amphibians and reptiles of North America north of Mexico: Update. ''Herpetological Review'' 34:196–203 Stebbins, R.C. 2003. ''A Field Guide to Western Reptiles and Amphibians''. Boston: Houghton Mifflin & Co.Campbell JA, Lamar WW. 2004. The Venomous Reptiles of the Western Hemisphere. Comstock Publishing Associates, Ithaca and London. 870 pp. 1500 plates. . Mojave green,) is a highly

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 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 ...

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriat ...

found in the

desert A desert is a barren area of landscape where little precipitation occurs and, consequently, living conditions are hostile for plant and animal life. The lack of vegetation exposes the unprotected surface of the ground to denudation. About on ...

s of 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, N ...

and central

Mexico Mexico (Spanish language, Spanish: México), officially the United Mexican States, is a List of sovereign states, country in the southern portion of North America. It is borders of Mexico, bordered to the north by the United States; to the so ...

. It is perhaps best known for its potent

neurotoxic Neurotoxicity is a form of toxicity in which a biological, chemical, or physical agent produces an adverse effect on the structure or function of the central and/or peripheral nervous system. It occurs when exposure to a substance – specificall ...

- hemotoxic

venom 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 st ...

, which is considered one of the world's most potent

rattlesnake Rattlesnakes are venomous snakes that form the genera ''Crotalus'' and ''Sistrurus'' of the subfamily Crotalinae (the pit vipers). All rattlesnakes are vipers. Rattlesnakes are predators that live in a wide array of habitats, hunting small an ...

venoms. Two

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 specie ...

are recognized, including the

nominate 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 speci ...

described here.

Description

This

grows to an average of less than in length, with a maximum of . The color varies from shades of brown to pale green depending on the surroundings. The green hue found among Mojave rattlesnakes has led to them being known as "Mojave greens" in some areas. Like '' C. atrox'' (the western diamondback rattlesnake), which it closely resembles, ''C. scutulatus'' has a dark diamond pattern along its back. With ''C. scutulatus'', the white bands on the tail tend to be wider than the black, while the band width is usually more equal in ''C. atrox''. Additionally, ''C. scutulatus'' has enlarged scales on top of the head between the supraoculars, and the light postocular stripe passes behind the corner of the mouth. In ''C. atrox'', the crown is covered in small scales, and the light postocular stripe intersects the mouth.Bush, S.P., M.D. Cardwell. 1999. Mojave rattlesnake (''Crotalus scutulatus scutulatus'') identification. ''Wilderness and Environmental Medicine'' 10:6–9. Campbell and Lamar (2004) support the English name "Mohave (Mojave) rattlesnake", but do so with some reluctance because so little of the snake's range lies within the

Mojave Desert The Mojave Desert ( ; mov, Hayikwiir Mat'aar; es, Desierto de Mojave) is a desert in the rain shadow of the Sierra Nevada mountains in the Southwestern United States. It is named for the indigenous Mojave people. It is located primarily ...

. They do not support the spelling "Mojave", because the name "Mohave" derives from the Native American term ''hamakhava''.

Geographic range

This snake is found in the southwestern

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...

in southern

California California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the m ...

, southern

Nevada Nevada ( ; ) is a U.S. state, state in the Western United States, Western region of the United States. It is bordered by Oregon to the northwest, Idaho to the northeast, California to the west, Arizona to the southeast, and Utah to the east. N ...

, northern and eastern

,extreme southwestern

Utah Utah ( , ) is a state in the Mountain West subregion of the Western United States. Utah is a landlocked U.S. state bordered to its east by Colorado, to its northeast by Wyoming, to its north by Idaho, to its south by Arizona, and to its ...

, most of

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 ...

, southern

New Mexico ) , population_demonym = New Mexican ( es, Neomexicano, Neomejicano, Nuevo Mexicano) , seat = Santa Fe, New Mexico, Santa Fe , LargestCity = Albuquerque, New Mexico, Albuquerque , LargestMetro = Albuquerque metropolitan area, Tiguex , Offi ...

, and some of

Texas Texas (, ; Spanish: ''Texas'', ''Tejas'') is a state in the South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2020, it is the second-largest U.S. state by ...

. It also ranges southward through much of

to southern

Puebla Puebla ( en, colony, settlement), officially Free and Sovereign State of Puebla ( es, Estado Libre y Soberano de Puebla), is one of the 32 states which comprise the Federal Entities of Mexico. It is divided into 217 municipalities and its cap ...

. It is found in deserts and other areas with

xeric Deserts and xeric shrublands are a biome defined by the World Wide Fund for Nature. Deserts and xeric (ancient Greek xērós, “dry") shrublands form the largest terrestrial biome, covering 19% of Earth's land surface area. Ecoregions in this h ...

vegetation from near sea level to about 2500 m altitude. No type locality is given. Smith and Taylor (1950) proposed "Wickenburg, Maricopa County, Arizona" (USA), while Schmidt (1953) listed the type locality as "Mojave Desert, California" (USA).

Habitat

Primarily a snake of high

or lower mountain slopes, it is often found near scrub brush such as sage,

mesquite Mesquite is a common name for several plants in the genus '' Prosopis'', which contains over 40 species of small leguminous trees. They are native to dry areas in the Americas. They have extremely long roots to seek water from very far under gr ...

and

creosote Creosote is a category of carbonaceous chemicals formed by the distillation of various tars and pyrolysis of plant-derived material, such as wood or fossil fuel. They are typically used as preservatives or antiseptics. Some creosote types were ...

, but may also reside in lowland areas of sparse vegetation, among

cacti A cactus (, or less commonly, cactus) is a member of the plant family Cactaceae, a family comprising about 127 genera with some 1750 known species of the order Caryophyllales. The word ''cactus'' derives, through Latin, from the Ancient Gree ...

, Joshua tree forests, or grassy plains. It can also range up the Eastern Sierra as far north as Reno and perhaps beyond into southern Eastern Oregon. It tends to avoid densely vegetated and rocky areas, preferring open, arid habitats.

Conservation status

This

is classified as Least Concern (LC) on the

IUCN Red List The International Union for Conservation of Nature (IUCN) Red List of Threatened Species, also known as the IUCN Red List or Red Data Book, founded in 1964, is the world's most comprehensive inventory of the global conservation status of biolo ...

of Threatened Species (v3.1, 2001). Species are listed as such due to their wide distribution, presumed large population, or because they are unlikely to be declining fast enough to qualify for listing in a more threatened category. The population trend was stable when assessed in 2007.

Behavior

''C. scutulatus'' is most active from April to September, and brumates alone or in small groups during the winter. Ambush predators, they eat mostly small

rodent Rodents (from Latin , 'to gnaw') are mammals of the order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are rodents. They are n ...

s and

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 altho ...

s. Females bear live young, from two to 17 (average about eight), from July through September.Klauber LM. 1997. Rattlesnakes: Their Habitats, Life Histories, and Influence on Mankind. Second Edition. First published in 1956, 1972. University of California Press, Berkeley. . They have a reputation for being aggressive towards people and will defend themselves vigorously when disturbed.

Venom

Lethality

The Mojave rattlesnake is the world's most venomous rattlesnake. The most common subspecies of the Mojave rattlesnake has both neurotoxic (nervous system and brain) and hemotoxic (tissue and muscle destruction) venom which is considered to be one of the most debilitating and potentially deadly of all rattlesnakes, and even matching several elapids. However, chances for survival are very good if medical attention is sought as soon as possible after a bite. There have been reported incidents in Red Mountain California of people finding dead snakes, getting pricked by fangs and succumbing to postmortem envenomations.

Prognosis for bite victims

In people bitten by venom A Mojave rattlesnakes (those outside the relatively small Venom B area in south-central Arizona), the onset of serious signs and symptoms can be delayed, sometimes leading to an initial underestimation of the severity of the bite. Significant envenomations (as with all snakebites, the quantity of venom injected is highly variable and unpredictable) can produce vision abnormalities and difficulty swallowing and speaking. In severe cases, skeletal muscle weakness can lead to difficulty breathing and even respiratory failure. Contrary to popular belief, fatalities are uncommon. This is largely due to the wide availability of antivenom, although estimates for mortality in the early 1900s ranged from 5-25% for all snake bites in the United States.

Antivenin

Unlike the rattlesnake antivenin used in the United States over the previous 50 years,

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 of ...

antivenin (approved by the US

Food and Drug Administration The United States Food and Drug Administration (FDA or US FDA) is a federal agency of the Department of Health and Human Services. The FDA is responsible for protecting and promoting public health through the control and supervision of food ...

in October 2001) uses Mojave rattlesnake venom A (in addition to venom from three other species) in its manufacture, making it particularly effective for treatment of venom A Mojave rattlesnake bites. Antibodies in CroFab produced by the other three species' venoms effectively neutralize Mojave rattlesnake venom B.

Unique venom characteristics

All rattlesnake venoms are complex cocktails of enzymes and other proteins that vary greatly in composition and effects, not only between species, but also between geographic populations within the same species. ''C. scutulatus'' is widely regarded as producing one of the most toxic snake venoms in the New World, based on studies in laboratory mice.Glenn, J.L., R.C.Straight. 1982. The rattlesnakes and their venom yield and lethal toxicity. In: Tu, A. (ed) ''Rattlesnake Venoms, Their Actions and Treatment''. New York: Marcel Dekker, Inc. The median lethal dose is 0.23 mg/kg SC. The estimated lethal dose for an adult human is just 10 to 15 mg. Their potent venom is the result of a presynaptic

neurotoxin Neurotoxins are toxins that are destructive to nerve tissue (causing neurotoxicity). Neurotoxins are an extensive class of exogenous chemical neurological insultsSpencer 2000 that can adversely affect function in both developing and mature nerv ...

composed of two distinct

peptide Peptides (, ) are short chains of amino acids linked by peptide bonds. Long chains of amino acids are called proteins. Chains of fewer than twenty amino acids are called oligopeptides, and include dipeptides, tripeptides, and tetrapeptides. ...

subunits.Aird, S.D., ''et al''. 1985. Rattlesnake presynaptic neurotoxins: primary structures and evolutionary origin of the acidic subunit. ''Biochemistry'' 24:7054-58. The basic subunit (a phospholipase A₂) is mildly toxic and apparently rather common in North American rattlesnake venoms.Powell, R.L. 2003. ''Evolutionary Genetics of Mojave Toxin Among Selected Rattlesnake Species (Squamata: Crotalinae)''. Unpublished PhD dissertation. El Paso: University of Texas. The less common acidic subunit is not toxic by itself, but in combination with the basic subunit, produces the potent neurotoxin called "Mojave toxin". Nearly identical neurotoxins have been discovered in five North American rattlesnake species besides ''C. scutulatus''. However, not all populations express both subunits. The venom of many Mojave rattlesnakes from south-central Arizona lacks the acidic subunit and has been designated "venom B", while Mojave rattlesnakes tested from all other areas express both subunits and have been designated "venom A" populations.Glenn, J.L., R.C. Straight. 1978. Mojave rattlesnake ''Crotalus scutulatus scutulatus'' venom: Variation in toxicity with geographical origin. ''Toxicon'' 16:81–84.

Venom differences

Based on median LD₅₀ values in lab mice, venom A from subspecies A Mojave rattlesnakes is more than ten times as toxic as venom B, from type B Mojave green rattlesnakes, which lacks Mojave toxin. Medical treatment as soon as possible after a bite is critical to a positive outcome, dramatically increasing chances for survival. However, venom B causes pronounced

proteolytic Proteolysis is the breakdown of proteins into smaller polypeptides or amino acids. Uncatalysed, the hydrolysis of peptide bonds is extremely slow, taking hundreds of years. Proteolysis is typically catalysed by cellular enzymes called prote ...

and hemorrhagic effects, similar to the bites of other rattlesnake species; these effects are significantly reduced or absent from bites by venom A snakes.Norris RA. 2004. Venom poisoning by North American reptiles. ''In'' Campbell JA, Lamar WW. 2004. The Venomous Reptiles of the Western Hemisphere. Comstock Publishing Associates, Ithaca and London. 870 pp. 1500 plates. . Risk to life and limb is still significant, as with all rattlesnakes, if not treated as soon as possible after a bite.

Subspecies

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 ...

, ''salvini'', is in honor of English

herpetologist Herpetology (from Greek ἑρπετόν ''herpetón'', meaning "reptile" or "creeping animal") is the branch of zoology concerned with the study of amphibians (including frogs, toads, salamanders, newts, and caecilians ( gymnophiona)) and rep ...

Osbert Salvin Osbert Salvin FRS (25 February 1835 – 1 June 1898) was an English naturalist, ornithologist, and herpetologist best known for co-authoring ''Biologia Centrali-Americana'' (1879–1915) with Frederick DuCane Godman. This was a 52 volume ency ...

.Beolens, Bo; Watkins, Michael; Grayson, Michael (2011). ''The Eponym Dictionary of Reptiles''. Baltimore: Johns Hopkins University Press. xiii + 296 pp. . (''Crotalus scutulatus salvini'', p. 232).