Mohave Rattlesnake

Appearance

This species grows to an average of less than 100 cm in length, with a maximum of 137.3 cm .

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'' , 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.

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. Their potent venom is the result of a presynaptic neurotoxin composed of two distinct peptide subunits. The basic subunit is mildly toxic and apparently rather common in North American rattlesnake venoms. 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.

Naming

Mojave rattlesnake, Mojave green, Mohave rattlesnake, Mojave diamond rattlesnake, Mojave rattler, scutulated rattlesnake. In Mexico, this species is known as ''Chiauhcóatl'' , or ''víbora de cascabel'' . ''C. s. scutulatus'' has also been referred to as the northern Mojave rattlesnake.-->

Campbell and Lamar 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''....snipped...

Status

This species is classified as Least Concern on the IUCN Red List of Threatened Species . 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 rodents and lizards. Females bear live young, from two to 17 , from July through September. 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.

Habitat

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.

Defense

Unlike the rattlesnake antivenom used in the United States over the previous 50 years, CroFab antivenom uses Mojave rattlesnake venom A 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.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. Their potent venom is the result of a presynaptic neurotoxin composed of two distinct peptide subunits. The basic subunit is mildly toxic and apparently rather common in North American rattlesnake venoms. 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.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 Mohave 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 and hemorrhagic effects, similar to the bites of other rattlesnake species; these effects are significantly reduced or absent from bites by venom A snakes. Risk to life and limb is still significant, as with all rattlesnakes, if not treated as soon as possible after a bite.