Crotalus scutulatus

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Crotalus scutulatus
Crotalus scutulatus 02.JPG
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Squamata
Suborder: Serpentes
Family: Viperidae
Genus: Crotalus
C. scutulatus
Binomial name
Crotalus scutulatus
(Kennicott, 1861)
  • Caudisona scutulata Kennicott, 1861
  • C[rotalus]. scutulatus - Cope In Yarrow in Wheeler, 1875
  • Crotalus adamanteus scutulatus - Cope, 1875
  • Crotalus scutulatus - Boulenger, 1896
  • Crotalus confluentus kellyi Amaral, 1929
  • Crotalus scutulatus scutulatus - Gloyd, 1940 [1]

Crotalus scutulatus (common names: Mojave rattlesnake, [2] [3] [4] Mojave green, [3] ) is a highly venomous pit viper species found in the deserts of the southwestern United States and central Mexico. It is perhaps best known for its potent neurotoxic-hemotoxic venom, which is considered the world's most potent rattlesnake venom. Two subspecies are recognized, including the nominate subspecies described here. [5]

Mojave Desert desert in southwestern United States

The Mojave Desert is an arid rain-shadow desert and the driest desert in North America. It is in the southwestern United States, primarily within southeastern California and southern Nevada, and it occupies 47,877 sq mi (124,000 km2). Very small areas also extend into Utah and Arizona. Its boundaries are generally noted by the presence of Joshua trees, which are native only to the Mojave Desert and are considered an indicator species, and it is believed to support an additional 1,750 to 2,000 species of plants. The central part of the desert is sparsely populated, while its peripheries support large communities such as Las Vegas, Barstow, Lancaster, Palmdale, Victorville, and St. George.

Venomous snakes are species of the suborder Serpentes that are capable of producing venom, which they use for killing prey, for defense, and to assist with digestion of their prey. The venom is typically delivered by injection using hollow or grooved fangs, although some venomous snakes lack well-developed fangs. Common venomous snakes include the families Elapidae, Viperidae, Atractaspididae, and some of the Colubridae. The toxicity of venom is mainly indicated by murine LD50, while multiple factors are considered to judge the potential danger to humans. Other important factors for risk assessment include the likelihood that a snake will bite, the quantity of venom delivered with the bite, the efficiency of the delivery mechanism, and the location of a bite on the body of the victim. Snake venom may have both neurotoxic and hemotoxic properties.

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 appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. Other ways of defining species include their karyotype, DNA sequence, morphology, behaviour or ecological niche. In addition, paleontologists use the concept of the chronospecies since fossil reproduction cannot be examined. While these definitions may seem adequate, when looked at more closely they represent problematic species concepts. For example, the boundaries between closely related species become unclear with hybridisation, in a species complex of hundreds of similar microspecies, and in a ring species. Also, among organisms that reproduce only asexually, the concept of a reproductive species breaks down, and each clone is potentially a microspecies.



C. scutulatus Crotalus scutulatus 03.jpg
C. scutulatus

This species grows to an average of less than 100 cm (3.3 ft) in length, with a maximum of 137.3 cm (4.50 ft). [4]

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. [3] [6]

Campbell and Lamar (2004) [4] support the English name "Mohave rattlesnake", but do so with some reluctance because so little of the snake's range lies within the Mojave Desert. They do not support the spelling "Mojave", because the name "Mohave" derives from the Native American term hamakhava. [4]

Geographic range

C. scutulatus range map C scutulatus range.jpg
C. scutulatus range map

This snake is found in the southwestern United States in southern California, southern Nevada, extreme southwestern Utah, most of Arizona, southern New Mexico, and some of Texas. It also ranges southward through much of Mexico to southern Puebla. It is found in deserts and other areas with xeric 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). [1]

United States federal republic in North America

The United States of America (USA), commonly known as the United States or America, is a country composed of 50 states, a federal district, five major self-governing territories, and various possessions. At 3.8 million square miles, the United States is the world's third or fourth largest country by total area and is slightly smaller than the entire continent of Europe's 3.9 million square miles. With a population of over 327 million people, the U.S. is the third most populous country. The capital is Washington, D.C., and the largest city by population is New York City. Forty-eight states and the capital's federal district are contiguous in North America between Canada and Mexico. The State of Alaska is in the northwest corner of North America, bordered by Canada to the east and across the Bering Strait from Russia to the west. The State of Hawaii is an archipelago in the mid-Pacific Ocean. The U.S. territories are scattered about the Pacific Ocean and the Caribbean Sea, stretching across nine official time zones. The extremely diverse geography, climate, and wildlife of the United States make it one of the world's 17 megadiverse countries.

California State of the United States of America

California is a state in the Pacific Region of the United States. With 39.6 million residents, California is the most populous U.S. state and the third-largest by area. The state capital is Sacramento. The Greater Los Angeles Area and the San Francisco Bay Area are the nation's second and fifth most populous urban regions, with 18.7 million and 9.7 million residents respectively. Los Angeles is California's most populous city, and the country's second most populous, after New York City. California also has the nation's most populous county, Los Angeles County, and its largest county by area, San Bernardino County. The City and County of San Francisco is both the country's second-most densely populated major city after New York City and the fifth-most densely populated county, behind only four of the five New York City boroughs.

Nevada State of the United States of America

Nevada is a state in the Western 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. Nevada is the 7th most extensive, the 32nd most populous, but the 9th least densely populated of the U.S. states. Nearly three-quarters of Nevada's people live in Clark County, which contains the Las Vegas–Paradise metropolitan area where three of the state's four largest incorporated cities are located. Nevada's capital, however, is Carson City.


Primarily a snake of high desert or lower mountain slopes, it is often found near scrub brush such as mesquite and creosote, but may also reside in lowland areas of sparse vegetation, among cacti, Joshua tree forests, or grassy plains. It tends to avoid densely vegetated and rocky areas, preferring open, arid habitats. [4]

Desert Area of land where little precipitation occurs

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 the processes of denudation. About one-third of the land surface of the world is arid or semi-arid. This includes much of the polar regions where little precipitation occurs and which are sometimes called polar deserts or "cold deserts". Deserts can be classified by the amount of precipitation that falls, by the temperature that prevails, by the causes of desertification or by their geographical location.


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 the southwestern United States and Mexico. The mesquite originates in the Tamaulipan mezquital ecoregion, in the deserts and xeric shrublands biome, located in the southern United States and northeastern Mexico. The region covers an area of 141,500 km2, encompassing a portion of the Gulf Coastal Plain in southern Texas, northern Tamaulipas, northeastern Coahuila, and part of Nuevo León. As a legume, mesquite is one of the few sources of fixed nitrogen in the desert habitat.

<i>Yucca brevifolia</i> species of plant

Yucca brevifolia is a plant species belonging to the genus Yucca. It is tree-like in habit, which is reflected in its common names: Joshua tree, yucca palm, tree yucca, and palm tree yucca.

Conservation status

This species is classified as Least Concern (LC) on the IUCN Red List of Threatened Species (v3.1, 2001). [7] 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. [8]


A C. scutulatus attacking a kangaroo rat

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 rodents and lizards. Females bear live young, from two to 17 (average about eight), from July through September. [3] [9] Although they have a reputation for being aggressive towards people, such behavior is not described in the scientific literature. Like other rattlesnakes, however, they will defend themselves vigorously when disturbed.[ citation needed ]



The Mojave rattlesnake is one of the world's most venomous snakes. The most common subspecies of Mojave rattlesnake (type A) has a neurotoxic venom that is considered to be the most debilitating and potentially deadly of all rattlesnakes, and even matching several elapids. [10] However, chances for survival are very good if medical attention is sought as soon as possible after a bite. [11]

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. [12] Contrary to popular belief, fatalities are uncommon. [13] [14] 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. [15]


Unlike the rattlesnake antivenom used in the United States over the previous 50 years, CroFab antivenom (approved by the US Food and Drug Administration in October 2001) uses Mojave rattlesnake venom A (in addition to venom from three other species) in its manufacture, [16] 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 LD50 studies in laboratory mice. [17] Their potent venom is the result of a presynaptic neurotoxin composed of two distinct peptide subunits. [18] The basic subunit (a phospholipase A2) is mildly toxic and apparently rather common in North American rattlesnake venoms. [19] 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. [19] 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. [20]

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. [21] Medical treatment as soon as possible after a bite is critical to a positive outcome, dramatically increasing chances for survival. [22]

However, venom B causes pronounced proteolytic and hemorrhagic effects, similar to the bites of other rattlesnake species; these effects are significantly reduced or absent from bites by venom A snakes. [12] Risk to life and limb is still significant, as with all rattlesnakes, if not treated as soon as possible after a bite.


Subspecies [5] Taxon author [5] Common name [9] Geographic range [4]
C. scutulatus salvini Günther, 1895Huamantlan rattlesnake Mexico, from Hidalgo through Tlaxcala and Puebla to southwestern Veracruz
C. scutulatus scutulatus(Kennicott, 1861)Mojave rattlesnakeThe United States from California eastward to west Texas and southward to Querétaro in Mexico

The subspecific name, salvini, is in honor of English herpetologist Osbert Salvin. [23]

See also

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