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Overview

Brief Summary

Notes

Holotype: USNM 7761

Type-locality: "Indianola" [Indianola, Calhoun County, Texas, USA] (McDiarmid et al., 1999).

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Distribution

Global Range: (200,000-2,500,000 square km (about 80,000-1,000,000 square miles)) The geographic range extends from southeastern California, possibly southern Nevada, central and southern Arizona, New Mexico, Texas, Oklahoma, and Arkansas south in Mexico to extreme northeastern Baja California, northern Sinaloa, Veracruz, and (at least formerly) disjunctly to Oaxaca (Ernst 1992, Campbell and Lamar 2004). It is unclear whether specimens collected in Kansas represent translocated individuals or part of a natural population (Matlack and Rehmeier 2002). Elevational range extends from near sea level to at least 2,440 meters in San Luis Potosi (Klauber 1972), but most locations are below 1,500 meters (Campbell and Lamar 2004).

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occurs (regularly, as a native taxon) in multiple nations

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National Distribution

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

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Range Description

The species' geographic range extends from southeastern California, possibly southern Nevada, central and southern Arizona, New Mexico, Texas, Oklahoma, and Arkansas in the United States, south in Mexico to extreme northeastern Baja California, northern Sinaloa, Veracruz, and (at least formerly) disjunctly to Oaxaca (Ernst 1992, Campbell and Lamar 2004). It is unclear whether specimens collected in Kansas represent translocated individuals or part of a natural population (Matlack and Rehmeier 2002). The elevational range extends from near sea level up to at least 2,440 m asl in San Luis Potosi (Klauber 1972), but most locations are below 1,500 m asl (Campbell and Lamar 2004).
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Geographic Range

The Western Diamondback Rattlesnake ranges from central and western Texas, through southern New Mexico and Arizona, and into southern California. It also extends well into central Mexico.

Biogeographic Regions: nearctic (Native )

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Southwestern USA and northern Mexico: from central Arkansas and southeastern California (USA) south to northern Sinaloa, Hidalgo, and nothern Veraruz (Mexico). Isolated populations occur in southern Veracruz and southeastern Oaxaca (McDiarmid et al., 1999).

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Continent: Middle-America North-America
Distribution: Canada (Alberta, Saskatchewan, British Columbia), USA (SE California, S Nevada [A Heindl, pers. comm.], Arizona, New Mexico, Texas, Oklahoma, Arkansas), Mexico (Hidalgo, Mexico [HR 35: 190])  tortugensis: Mexico (Isla Tortuga in the Gulf of California); Holotype: CAS 50515
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Physical Description

Morphology

Physical Description

Body length: ~1.5 meters Body weight: up to 6.7 kg. Crotalus atrox has a plump body, short tail, and a broad triangular head. Like all Pit Vipers, it has a pit organ, which is situated in an indentation of the upper jaw, between the nostril and eye. The pit is about 5 mm deep, with an outer and inner chamber separated by a thin membrane. The membrane senses very slight temperature differences between the snake's inner and ambient temperatures. The Western Diamond Rattlesnake also has the self-named rattle on the end of the tail. Each link of the rattle is the remnant of a molted skin; as the snake molts, the last scale loosens but does not fall off. As the snake ages, new rattles are formed with each molt, while old rattles simultaneously fall off. This species has long, tubular fangs, which are characteristic of venomous snakes.

Crotalus atrox can be a yellowish gray, pale blue, or pinkish ground color. The diamond shapes down its length are dark with pale white borders. The tail is white with jet-black rings. The head markings include a pale oblique band from nostril to upper labials, and a similar but narrower band behind the eye.

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Size

Length: 213 cm

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Type Information

Holotype for Crotalus atrox
Catalog Number: USNM 7761
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Amphibians & Reptiles
Sex/Stage: Male;
Preparation: Ethanol
Locality: Indianola, Calhoun, Texas, United States, North America
  • Holotype: Baird, S. F. & Girard, C. 1853. Smithsonian Miscellaneous Collections. 2 (5): 5.
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Paratype for Crotalus atrox
Catalog Number: USNM 7760
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Amphibians & Reptiles
Sex/Stage: Male;
Preparation: Ethanol
Locality: Indianola, Calhoun, Texas, United States, North America
  • Paratype: Baird, S. F. & Girard, C. 1853. Smithsonian Miscellaneous Collections. 2 (5): 5.
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Paratype for Crotalus atrox
Catalog Number: USNM 255
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Amphibians & Reptiles
Sex/Stage: Male;
Preparation: Ethanol
Locality: Indianola, Calhoun, Texas, United States, North America
  • Paratype: Baird, S. F. & Girard, C. 1853. Smithsonian Miscellaneous Collections. 2 (5): 5.
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Paratype for Crotalus atrox
Catalog Number: USNM 4224
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Amphibians & Reptiles
Sex/Stage: ; Juvenile
Preparation: Ethanol
Year Collected: 1851
Locality: San Antonio, Bexar, Texas, United States, North America
  • Paratype: Hallowell, E. 1852. Proc. Acad. Nat. Sci. Philadelphia. 6 (5): 180.
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Ecology

Habitat

Sierra Madre Occidental Pine-oak Forests Habitat

This taxon is found in the Sierra Madre Occidental pine-oak forests ecoregion, which boasts some of the richest biodiversity anywhere in North America, and contains about two thirds of the standing timber in Mexico. Twenty-three different species of pine and about 200 species of oak reside within the Sierra Madre Occidental pine-oak forests ecoregion.

Pine-oak forests here typically grow on elevations between approximately 1500 and 3300 meters, and occur as isolated habitat islands in northern areas within the Chihuahuan Desert. Soils are typically deep, where the incline allows soil build-up and derived from igneous material, although metamorphic rocks also form part of the soils in the west and northwest portions of the sierra. Steep-sloped mountains have shaped some portions of the Sierra, while others are dominated by their deep valleys, tall canyons and cliffs. These steep-sided cliffs have thinner soils limiting vegetation to chaparral types; characterized by dense clumps of Mexican Manzanita (Arctostaphylos pungens), Quercus potosina and Netleaf Oak (Q. rugosa). There are also zones of natural pasture, with grasses from the genera Arisitida, Panicum, Bromus and Stevis.

The pine-oak forests gradually transform into an oak-grassland vegetative association. Such communities represent an ecological transition between pine-oak forests and desert grasslands..  Here, species such as Chihuahuan Oak (Quercus chihuahuensis), Shin Oak (Q. grisea),  Q. striatula and Emory Oak (Q. emoryi), mark a transition zone between temperate and arid environments, growing in a sparse fashion and with a well-developed herbaceous stratum resembling xeric scrub. Cacti are also part of these transition communities extending well into the woodlands. Some cacti species such as the Little Nipple Cactus (Mammillaria heyderi macdougalii), Greenflower Nipple Cactus (M. viridiflora), Mojave Mound Cactus (Echinocereus triglochidiatus), and Leding's Hedgehog Cactus (E. fendleri var. ledingii) are chiefly centered in these biotic communities. The dominant vegetation in the northernmost part of the ecoregion in the Madrean Sky Islands includes Chihuahua Pine (Pinus leiophylla), Mexican Pinyon (P. cembroides), Arizona Pine (P. arizonica), Silverleaf Oak (Quercus hypoleucoides), Arizona White Oak (Q. arizonica), Emory Oak (Q. emoryi), Netleaf Oak (Q. rugosa), Alligator Juniper (Juniperus deppeana), and Mexican Manzanita (Arctostaphylos pungens).

This ecoregion is an important area for bird richness and bird endemism. Likewise, virtually all of the ecoregion is included in the Sierra Madre Occidental and trans-mexican range Endemic Bird Area. Endemic bird species include the Thick-billed Parrot (Rhynchopsitta pachyrhyncha EN) which is in danger of extinction, with population estimates as low as 500 pairs; the Tufted Jay (Cyanocorax dickeyi NT), Eared Quetzal (Euptilptis neoxenus NT) and the Green-striped Brush Finch (Buarremon virenticeps). Temperate and tropical influences converge in this ecoregion, forming a unique and rich complex of flora and fauna. Many other birds are found in this ecoregion including the Green Parakeet (Aratinga holochlora), Eared Trogon (Euptilotis neoxenus NT), Coppery-tailed Trogon (Trogon elegans), Grey-breasted Jay (Aphelocoma ultramarina), Violet-crowned Hummingbird (Amazilia violiceps), Spotted Owl (Strix occidentalis NT), and Golden Eagle (Aguila chryaetos).  Some species found only in higher montane areas are the Gould's Wild Turkey (Meleagris gallopavo mexicana), Band-tailed Pigeon (Patagioenas fasciata), Mexican Chickadee (Poecile sclateri) and Hepatic Tanager (Piranga flava).

The Sierra Madre Mantled Ground Squirrel (Spermophilus madrensis NT) is an endemic to the Sierra Madre Occidental pine-oak forests, restricted to southwestern Chihuahua, Mexico. The Mexican Gray Wolf (Canis lupus baileyi) and Mexican Grizzly Bear (Ursus horribilis), although considered by most to be extinct from this ecoregion, once roamed these mountains. Mammals also present include White-tailed Deer (Odocoileus virginianus), American Black Bear (Ursus americanus), Buller’s Chipmunk (Tamias bulleri), endemic Zacatecan Deer Mouse (Peromyscus difficilis), rock Squirrel (Spernophilis variegatus), Zacatecas Harvest Mouse (Reithrodontomys zacatecae) and Coati (Nasua nasua), to set forth a subset of mammals present.

Reptiles are also numerous in this ecoregion. Fox´s Mountain Meadow Snake (Adelophis foxi) is an endemic taxon to the ecoregion, only observed at the type locality at four kilometers east of  Mil Diez, about  3.2 kilometers west of El Salto, in southwestern Durango, Mexico. There are at least six species of rattlesnakes including the Mexican Dusky Rattlesnake (Crotalis triseriatus), Mojave Rattlesnake (C. scutulatus), Rock Rattlesnake (C. lepidus), Western Diamondback Rattlesnake (C. atrox), Twin-spotted Rattlesnake (C. pricei), and Ridgenose Rattlesnakes (C. willardi).  Clark's Spiny Lizard (Sceloporus clarkii) and Yarrow's Spiny Lizard (S. jarrovii), Bunchgrass Lizard (S. scalaris), and Striped Plateau Lizard (S. virgatus) are several of the lizards found in the Sierra Madre Occidental pine-oak forests.

Along springs and streams the Western Barking Frog (Craugastor augusti) and the Tarahumara Frog (Rana tamahumarae) are two anuran taxa occurring in the ecoregion. Other anuran taxa found here include: Bigfoot Leopard Frog (Lithobates megapoda), Northwest Mexico Leopard Frog (Lithobates magnaocularis) and the Blunt-toed Chirping Frog (Eleutherodactylus modestus VU). The Sacramento Mountains Salamander (Aneides hardii) is an endemic salamander found in the Sierra Madre Occidental pine-oak forests, restricted to the Sacramento Mountains, Capitan Mountains, and Sierra Blanca in Lincoln and Otero Counties within southern New Mexico, USA.

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Comments: Habitat encompasses arid and semiarid regions, from plains to mountains and from sandy flats to rocky uplands, including desert, grassland, shrubland, woodland, open pine forest, river bottoms, and coastal islands (Degenhardt et al. 1996, Tennant 1998, Werler and Dixon 2000, Stebbins 2003, Campbell and Lamar 2004). In southeastern Arizona, this snake is more numerous in desert scrub than in semidesert grassland (Mendelson and Jennings 1992). It hibernates in rock crevices or cavities or sometimes in animal burrows or under other cover (Ernst 1992). Hibernation sometimes occurs communally in brushy upland ridges. A population in southeastern Arizona used mainly creosotebush flats but switched to rocky slopes during winter (Beck 1995). This primarily terrestrial snake sometimes climbs into vegetation or enters water.

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Habitat and Ecology

Habitat and Ecology
The species' habitat encompasses arid and semi-arid regions, from plains to mountains and from sandy flats to rocky uplands, including desert, grassland, shrubland, woodland, open pine forest, river bottoms, and coastal islands (Degenhardt et al. 1996, Tennant 1998, Werler and Dixon 2000, Stebbins 2003, Campbell and Lamar 2004). In southeastern Arizona, this snake is more numerous in desert scrub than in semi-desert grassland (Mendelson and Jennings 1992). It hibernates in rock crevices or cavities or sometimes in animal burrows or under other cover (Ernst 1992). Hibernation sometimes occurs communally in brushy upland ridges. A population in southeastern Arizona used mainly creosote bush flats but switched to rocky slopes during winter (Beck 1995). This primarily terrestrial snake sometimes climbs into vegetation or enters water.

Systems
  • Terrestrial
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Western Diamondback Rattlesnakes inhabit dry, rocky, shrub-covered terrain where they can conceal themselves inside crevices in the rocks or in mouse holes.

Terrestrial Biomes: desert or dune ; savanna or grassland ; chaparral

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Migration

Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.

Locally Migrant: Yes. At least some populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

Migrates up to 3.5 km between winter den and summer range (Landreth 1973).

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Trophic Strategy

Comments: Eats mainly mammals (rabbits, squirrels, mice, rats), also lizards and birds (Stebbins 1985); apparently sometimes eats carrion. Forages actively or ambushes prey. In southeastern Arizona, survival for a year can be supported by just a few large meals (Beck 1995).

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Food Habits

Crotalus atrox preys on small mammals and birds, and sometimes other reptiles and amphibians, and even fish and invertebrates. In a matter of seconds, individuals of this species can leave a fatal bite by injecting venom into its prey. The teeth often remain inside the prey, but are replaced 2 to 4 times annually by reserve teeth. Muscles surrounding the venom glands control the amount of venom released, as well as the flow of venom to the fangs. Rattlesnakes swallow their prey whole, then digest as the food passes though the body. Rattlesnakes in the wild eat every 2 to 3 weeks on average. Annual water intake in rattlesnakes roughly equals body weight. In drier climates, where water availability is lower, moisture is assimilated from prey. More water is absorbed during shedding due to desiccation and evaporation.

Reproduction

Behavior

Habitat

Biomes: desert, scrubland

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Associations

Known prey organisms

Crotalus atrox preys on:
Chaetodipus nelsoni

This list may not be complete but is based on published studies.
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Population Biology

Number of Occurrences

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: 81 to >300

Comments: This species is represented by a large number of occurrences. Campbell and Lamar (2004) mapped hundreds of collection sites.

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Global Abundance

100,000 to >1,000,000 individuals

Comments: Adult population size is unknown but certainly exceeds 100,000. This is a common snake in much of its range.

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General Ecology

May congregate at winter dens; at least formerly, dens served up to 100-200 individuals.

Movements tend to be greatest in spring, less in summer and fall (e.g., around 45-60 m per day), and least in winter (Landreth 1973). In southeastern Arizona, mean home range size was 5.42 ha and individuals moved an average of 51 m per day during the active season (Beck 1995).

In Oklahoma, slightly more than half of the snakes collected in rattlesnake roundups in April were second-year young and young adults thought to be 3-4 years old; annual adult mortality was estimated at 20% (Fitch and Pisani 1993).

Young are vulnerable to various carnivorous animals; humans are the only significant predators on adults.

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Life History and Behavior

Cyclicity

Comments: Mostly crepuscular and nocturnal in summer, but active diurnally as well, especially in cooler months. In north, active mainly from April to late September or early October but may appear on surface during mild winter weather, especially in south (Tennant 1984). Active mainly March-October in southeastern Arizona (Beck 1995). In Chihuahua, active mainly July-September, with a peak in August (Reynolds, cited by Ernst 1992).

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Life Expectancy

Lifespan/Longevity

Average lifespan

Sex: female

Status: captivity:
25.8 years.

Average lifespan

Status: captivity:
22.0 years.

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Lifespan, longevity, and ageing

Maximum longevity: 27 years (captivity)
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Reproduction

In Oklahoma, births occur evidently in August and early September, sexual maturity is attained apparently in third year, breeding apparently is annual, fecundity (4-24 yolked follicles, mean 13) increases with female size, and the largest and oldest snakes probably are 10-15 years old (based on snakes examined at several rattlesnake roundups in Oklahoma, Fitch and Pisani 1993).

In south-central Arizona, mating occurred in spring and fall; females underwent vitellogenesis exclusively in spring, ovulated in early summer, and gave birth in August; over four years, no females gave birth more than once, indicating that reproduction is less than annual; litter sizes ranged from 2-7 (mean = 4.5) (Taylor and DeNardo 2005).

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Crotalus atrox reaches sexual maturity at 3 years. Mating occurs in the spring following emergence from hibernation. Females are passive during courtship, while the male crawls in jerks on top of the female, all the while flicking his tongue. Vigorously jerking the hind portion of his body, he presses his tail beneath that of his partner, who in turn lifts her tail. Their cloacas make contact, and the male then inserts his hemipenis, which is deeply forked. Copulation lasts for hours, with several interspersed resting periods.

The gestation period lasts for 167 days. The birthing process may last for 3 to 5 hours and produce 10 to 20 young. This species is ovoviviparous; the young pierce their thin egg membranes immediately before birth and are born live. The young only stay with the mother for a couple of hours, for a day at the most. Then they scatter in search for food and potential winter refuge. The young population declines drastically after the first winter due to lack of food, freezing temperatures, and vulnerability to predators.

Average number of offspring: 14.

Average age at sexual or reproductive maturity (male)

Sex: male:
1095 days.

Average age at sexual or reproductive maturity (female)

Sex: female:
1095 days.

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Evolution and Systematics

Functional Adaptations

Functional adaptation

Fangs fold for storage: western diamondback rattlesnake
 

The curving fangs of a western diamondback rattlesnake are stored when not in use by folding against the roof of the mouth via hinges.

   
  "A western diamondback rattlesnake strikes at an intruder. The snake's jaws are specially hinged to allow it to open them extremely wide. This is necessary because the fangs curve inwards and need to be plunged vertically into the prey. When not in use they are folded back against the roof of the mouth (see diagram). The snake's windpipe is protruding at the bottom of its mouth -- this is so that the snake can still breathe after it has a mouthful of prey." (Foy and Oxford Scientific Films 1982:149)
  Learn more about this functional adaptation.
  • Foy, Sally; Oxford Scientific Films. 1982. The Grand Design: Form and Colour in Animals. Lingfield, Surrey, U.K.: BLA Publishing Limited for J.M.Dent & Sons Ltd, Aldine House, London. 238 p.
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Functional adaptation

Breathing occurs even with full mouth: diamondback rattlesnake
 

The windpipe of a western diamondback rattlesnake allows breathing with a mouthful of prey because it protrudes from the bottom of the snake's mouth.

   
  "A western diamondback rattlesnake strikes at an intruder. The snake's jaws are specially hinged to allow it to open them extremely wide. This is necessary because the fangs curve inwards and need to be plunged vertically into the prey. When not in use they are folded back against the roof of the mouth (see diagram). The snake's windpipe is protruding at the bottom of its mouth -- this is so that the snake can still breathe after it has a mouthful of prey." (Foy and Oxford Scientific Films 1982:149)
  Learn more about this functional adaptation.
  • Foy, Sally; Oxford Scientific Films. 1982. The Grand Design: Form and Colour in Animals. Lingfield, Surrey, U.K.: BLA Publishing Limited for J.M.Dent & Sons Ltd, Aldine House, London. 238 p.
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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage: Crotalus atrox

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 5
Species With Barcodes: 1
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Conservation

Conservation Status

National NatureServe Conservation Status

United States

Rounded National Status Rank: N5 - Secure

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NatureServe Conservation Status

Rounded Global Status Rank: G5 - Secure

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IUCN Red List Assessment


Red List Category
LC
Least Concern

Red List Criteria

Version
3.1

Year Assessed
2007

Assessor/s
Frost, D.R., Hammerson, G.A. & Santos-Barrera, G.

Reviewer/s
Cox, N., Chanson, J.S. & Stuart, S.N. (Global Reptile Assessment Coordinating Team)

Contributor/s

Justification
Listed as Least Concern in view of its wide distribution, presumed large population, and because it is unlikely to be declining fast enough to qualify for listing in a more threatened category.
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Largely due to the risk and danger of snake bites, rattlesnakes have come to instill paranoia and fear in humans. As a result, there are numerous forms of rattler control, such as bounties, poisons, traps, and the destruction of food supplies and refuges. However, Crotalus atrox is a highly successful and fertile species, and therefore are not currently threatened by any forms of mass destruction or species control.

IUCN Red List of Threatened Species: least concern

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Global Short Term Trend: Relatively stable (=10% change)

Comments: Extent of occurrence, area of occupancy, and number of subpopulations probably are relatively stable; population size probably is declining at less than 10 percent over 10 years or three generations.

Global Long Term Trend: Increase of 10-25% to decline of 30%

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Population

Population
This species is represented by a large number of occurrences. Campbell and Lamar (2004) mapped hundreds of collection sites. The adult population size is unknown but certainly exceeds 100,000. This is a common snake in much of its range. Its extent of occurrence, area of occupancy, and number of subpopulations are probably relatively stable; population size is probably declining at less than 10% over 10 years or three generations.

Population Trend
Stable
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Threats

Degree of Threat: Medium

Comments: No major threats are known. Some populations have been decimated by habitat destruction, automobile traffic, and/or direct killing by humans, especially in conjunction with "rattlesnake roundups."

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Major Threats
No major threats have been identified. Some populations have been decimated by habitat destruction, automobile traffic, and/or direct killing by humans, especially in conjunction with "rattlesnake roundups."
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Management

Conservation Actions

Conservation Actions
Several occurrences of this species are in protected areas.
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Relevance to Humans and Ecosystems

Benefits

Economic Uses

Comments: Venomous; adults are dangerous to humans (probably has caused more human deaths in U.S. than any other snake); antivenin treatment is advisable; see Ernst (1992).

See Weir (1992) for detailed information on the Sweetwater (Texas) rattlesnake round-up, including recommendations for modifications that would be ecologically favorable while at the same time maintaining the social and ecomonic benefits of the event.

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Economic Importance for Humans: Negative

The Western Diamondback Rattlesnake is notorious for its fatal bite, and has instilled a certain fear and paranoia in humans.

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Economic Importance for Humans: Positive

Crotalus atrox is good at controlling rodent problems. It also keeps well in captivity; this makes it a good educational resource in zoos and snake shows. Rattlesnakes are key in Native American culture, in which their flesh, oil, and venom have been used as a food source and as a basis for medicinal preparations for a long time. Rattlesnake skins are regularly used for skin products such as shoes and belts. Rattlesnakes are also prominent on the live-snake market, where they sell for $2 to $3 per foot (Klauber 158).

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Wikipedia

Crotalus atrox

Common names: western diamondback rattlesnake,[2] Texas diamond-back,[3] more.

Crotalus atrox, the western diamondback rattlesnake, is a venomous rattlesnake species found in the United States and Mexico. It is likely responsible for the majority of snakebite fatalities in northern Mexico and the second-greatest number in the USA after C. adamanteus.[4] No subspecies is currently recognized.[2]

Description[edit]

Adults commonly grow to 120 cm (4 ft) in length. Specimens over 150 cm (5 ft) are infrequently encountered, while those over 180 cm (6 ft) are very rare. The maximum reported length considered to be reliable is 213 cm (7 ft).[5] Males become much larger than females, although this difference in size does not occur until after they have reached sexual maturity.[6] Rattlesnakes of this species considered medium-sized weighed 1.8 to 2.7 kg (4 to 6 lb), while very large specimens can reportedly weigh up to 6.7 kg (15 lb).[7][8]

The color pattern generally consists of a dusty-looking gray-brown ground color, but it may also be pinkish-brown, brick red, yellowish, pinkish, or chalky white. This ground color is overlaid dorsally with a series of 24-25 dorsal body blotches that are dark gray-brown to brown in color. The first of these may be a pair of short stripes that extend backwards to eventually merge. Some of the first few blotches may be somewhat rectangular, but then become more hexagonal and eventually take on a distinctive diamond shape. The tail has two to eight (usually four to six) black bands separated by ash white or pale gray interspaces; this led to the nickname of "coon tail", though other species (e.g., Mojave rattlesnake) have similarly banded tails. Its postocular stripe is smoky gray or dark gray-brown and extends diagonally from the lower edge of the eye across the side of the head. This stripe is usually bordered below by a white stripe running from the upper preocular scale down to the supralabial scales just below and behind the eye.[6] Its off-white belly is usually unmarked, its anal scale is undivided, and its dorsal scales are extremely keeled, often in rows of 25 to 27 near the midbody.[citation needed]

The wide range of this species overlaps, or is close to, that of many others. It may be confused with them, but differences exist. The Mohave rattlesnake, C. scutulatus, also has tail rings, but the black rings are narrow relative to the pale ones. The timber rattlesnake, C. horridus, has no tail rings. In the western rattlesnake, C. oreganus, the pale tail rings are the same color as the ground. The tail of the black-tailed rattlesnake, C. molossus, is a uniform black, or has indistinct tail rings. The Mexican west coast rattlesnake, C. basiliscus, also has a mostly dark tail with obscure or absent rings. The tiger rattlesnake, C. tigris, has a relatively small head and large rattle along with a dorsal pattern consisting more of crossbands. The Middle American rattlesnake, C. simus, has a generally uniform gray tail without any rings, as well as a pair of distinctive paravertebral stripes running down the neck. Members of the genus Sistrurus lack tail rings and have enlarged head plates.[6]

Common names[edit]

Common names for this species include: western diamondback rattlesnake, western diamond-backed rattlesnake,[2] adobe snake, Arizona diamond rattlesnake, coon tail, desert diamond-back, desert diamond rattlesnake, fierce rattlesnake, spitting rattlesnake, Texan rattlesnake, and Texas diamond-back.

Geographic range[edit]

It is found in the United States from central Arkansas to southeastern and Central California, south into Mexico as far as northern Sinaloa, Hidalgo and northern Veracruz. Disjunct populations exist in southern Veracruz and southeastern Oaxaca. The type locality given is "Indianola" (Indianola, Calhoun County, Texas, USA).[1]

In the United States, it occurs in central and western Arkansas, Oklahoma excluding the northeast, north-central region and the panhandle, Texas excluding the northern panhandle and the east, southern and central New Mexico and Arizona, extreme southern Nevada, southwestern Idaho, and in southeastern California on either side of the Chocolate Mountains. Records from extreme southern Kansas (Cowley and Sumner Counties) may be based on a natural occurrence of the species, while multiple records from near Kanopolis Reservoir in Ellsworth County seem to indicate a viable (although isolated) population.[6]

In Mexico, it occurs in Nuevo León, Coahuila, Chihuahua, Sonora, extreme northeastern Baja California, northern Sinaloa, northeastern Durango, Zacatecas, most of San Luis Potosí, northern Veracruz, Hidalgo, and Querétaro. Specimens have been collected in the mountains northwest of Tehuantepec, Oaxaca, on numerous occasions, but have not been reported there since the 1940s.[6]

This species has also been reported on a number of islands in the Gulf of California, including San Pedro Mártir, Santa María (Sinaloa), Tíburon and the Turner Islands.[6]

Habitat[edit]

Its habitats range from flat coastal plains to steep rocky canyons and hillsides; it is associated with many different vegetation types, including desert, sandy creosote areas, mesquite grassland, desert scrub, and pine-oak forests. Towards the southern edge of its range, this species may be found in thorn forest and tropical deciduous forest.[6]

Behavior[edit]

C. atrox, patternless specimen

C. atrox are solitary except during the mating season. Usually inactive between late October and early March, occasionally these ectotherms may be seen basking in the sun on warm winter days. In the winter, they hibernate or brumate in caves or burrows, sometimes with many other species of snakes. Life expectancy is more than 20 years.[citation needed]

They are poor climbers. Natural predators include raptors such as hawks, eagles, roadrunners, and other snakes. When threatened, they usually coil and rattle to warn aggressors.

Prey[edit]

A comprehensive study by Beavers (1976) on the prey of C. atrox in Texas showed, by weight, 94.8% of their prey consisted of small mammals.[6] According to Pisani and Stephenson (1991), who conducted a study of the stomach contents of C. atrox in the fall and spring of Oklahoma, mammalian prey included prairie dogs (Cynomys ludovicianus), kangaroo rats (Dipodomys ordii), pocket gophers (Geomys bursarius and Cratogeomys castanops), voles (Microtus ochrogaster), woodrats (Neotoma floridana), pocket mice (Perognathus hispidus and P. flavescens), white-footed mice (Peromyscus leucopus and P. maniculatus), Old World rats and mice (Rattus norvegicus and Mus ssp.), harvest mice (Reithrodontomys megalotis), fox squirrels (Sciurus niger), cotton rats (Sigmodon hispidus), ground squirrels (Spermophilus spilosoma), rabbits (Sylvilagus floridanus), jackrabbits (Lepus californicus), and an unidentified mole species.[6] Klauber (1972) mentioned large specimens are capable of swallowing adult cottontail rabbits and even adult jackrabbits, although he figured the latter required confirmation.[9]

Birds, lizards, and mice are also preyed upon, with lizards mostly being eaten by young snakes. Avian prey include mockingbirds (Mimidae), quail, a nearly full-grown Gambel's quail, a burrowing owl (Athene cunicularia),[9] a fledgling horned lark (Eremophila alpestris) a black-throated sparrow (Amphispiza bilineata), and an eastern meadowlark (Sturnella magna).[6] Lizard prey include a whiptail lizard (Cnemidophorus), spiny lizards (Sceloporus), a Texas banded gecko (Coleonyx brevis),[9] and a side-blotched lizard (Uta palmeri). One case reported by Vorhies (1948) involved a juvenile specimen that had attempted to eat a horned lizard (Phrynosoma solare), but died after the lizard's horns had punctured its esophagus, leaving the lizard stuck there.[6]

Hermann (1950) reported C. atrox also feeds on lubber grasshoppers (Brachystola magna). Klauber (1972) once found a single specimen in which the stomach contents included grasshoppers, beetles, and ants. However, mammal hairs and an iguanid lizard were also found in the same stomach, which made it more likely that the insects had first been eaten by the mammal or the lizard before they had been eaten by the snake.[9]

They hunt (or ambush prey) at night or in the early morning.

These snakes can go for up to two years without food in the wild. A 5½-month starvation study showed the snakes reduced energy expenditures by an average of 80% over the length of the study. The snakes also feed from within on energy-rich lipid stores. The most interesting finding was the snakes grew during the study, indicating while the snake's mass was shrinking, it was putting its resources into skeletal muscles and bone.[10]

A key participant in the food chain, it is an important predator of many small rodents, rabbits, and birds. In turn, it is preyed upon by a variety of larger mammals and birds, such as coyotes, foxes, and hawks. Crotalus atrox can be active at any time of the day or night when conditions are favorable. It is primarily diurnal and crepuscular in spring and fall and becomes primarily nocturnal and crepuscular during the hot summer months. [11]

Venom[edit]

Like most other American pit vipers, the venom contains proteolytic enzymes. Proteolytic venoms are concentrated secretions that destroy tissues as a result of catabolism of structural and other proteins. The venom of C. atrox is primarily hemotoxic, affecting mainly the blood vessels, blood cells and the heart. The venom contains hemorrhagic components called zinc metalloproteinases.[12][13] The venom also contains cytotoxins and myotoxins.[14] In addition to hemorrhage, venom metalloproteinases induce myonecrosis (skeletal muscle damage), which seems to be secondary to the ischemia that ensues in muscle tissue as a consequence of bleeding and reduced perfusion. Microvascular disruption by metalloproteinases also impairs skeletal muscle regeneration, being therefore responsible for fibrosis and permanent tissue loss after bites from this species.[15] General local effects include pain, bleeding, severe swelling, bruising, blistering, and necrosis; systemic effects are variable and not specific, but may include headache, nausea, vomiting, abdominal pain, diarrhea, dizziness, and convulsions. Hemorrhagins causing bleeding is a major clinical effect.[16]

This species has LD50 values of 2.72 mg/kg intravenous, 20 mg/kg intramuscular and 18.5 mg/kg subcutaneous, which is far less toxic than many other rattlesnakes.[17][18] The average venom yield per bite is usually between 250 and 350 mg, with a maximum of 700–800 mg.[4][19] Severe envenomation is rare, but possible, and can be lethal. Mortality rate of untreated bites is between 10 and 20%.[16]

Reproduction[edit]

A male crotalus atrox with a pair of intromittent organs called hemipenes, used for reproduction

Rattlesnakes, including C. atrox, are viviparous. Gestation lasts six or seven months, and broods average about a dozen young. However, the young only stay with the mother for a few hours before they set off on their own to hunt and find cover, thus the mortality rate is very high. Mating occurs in the fall, and the females give birth to as many as 25 young, which may be as long as 30 cm (12 in). The young are fully capable of delivering a venomous bite from the moment they are born.

Conservation status[edit]

This species is classified as Least Concern on the IUCN Red List (v3.1, 2001).[20] 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.[21]

They are also heavily collected from the wild, frequently being drawn out of their hiding places with gasoline, and used in Rattlesnake Round-Ups, where they are killed for food, skins, and entertainment.

Gallery[edit]

See also[edit]

References[edit]

  1. ^ a b McDiarmid RW, Campbell JA, Touré T. 1999. Snake Species of the World: A Taxonomic and Geographic Reference, vol. 1. Herpetologists' League. 511 pp. ISBN 1-893777-00-6 (series). ISBN 1-893777-01-4 (volume).[page needed]
  2. ^ a b c "Crotalus atrox". Integrated Taxonomic Information System. Retrieved 28 November 2006. 
  3. ^ Wright AH, Wright AA. 1957. Handbook of Snakes. Comstock Publishing Associates. (7th printing, 1985). 1105 pp. ISBN 0-8014-0463-0.[page needed]
  4. ^ a b Norris R. 2004. Venom Poisoning in 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. ISBN 0-8014-4141-2.[page needed]
  5. ^ Klauber, 1972
  6. ^ a b c d e f g h i j k Campbell JA, Lamar WW. 2004. The Venomous Reptiles of the Western Hemisphere. Comstock Publishing Associates, Ithaca and London. 870 pp. 1500 plates. ISBN 0-8014-4141-2.[page needed]
  7. ^ Stolpe, Michael R; Norris, Robert L; Chisholm, Carey D; Hartshorne, Michael F; Okerberg, Carl; Ehler, William J; Posch, John (1989). "Preliminary observations on the effects of hyperbaric oxygen therapy on western diamondback rattlesnake (Crotalus atrox) venom poisoning in the rabbit model". Annals of Emergency Medicine 18 (8): 871–4. doi:10.1016/S0196-0644(89)80216-1. PMID 2757285. 
  8. ^ http://eol.org/pages/795269/details[full citation needed]
  9. ^ a b c d Klauber LM. 1997. Rattlesnakes: Their Habitats, Life Histories, and Influence on Mankind. Second Edition. First published in 1956, 1972. University of California Press, Berkeley. ISBN 0-520-21056-5.[page needed]
  10. ^ McCue, Marshall D. (2006). "Characterizing the starvation syndrome in the western diamond-back rattlesnake, a species well-suited to tolerate long-term fasting". The FASEB Journal 20 (5): A827. Lay summaryScienceDaily (April. 6, 2006). 
  11. ^ http://www.reptilesofaz.org/Snakes-Subpages/h-c-atrox.html
  12. ^ Bjarnason, Jon Bragi; Fox, Jay William (1988). "Hemorrhagic Toxins from Snake Venoms". Toxin Reviews 7 (2): 121–209. doi:10.3109/15569548809059729. 
  13. ^ Bjarnason, Jon B.; Tu, Anthony T. (1978). "Hemorrhagic toxins from western diamondback rattlesnake (Crotalus atrox) venom: Isolation and characterization of five toxins and the role of zinc in hemorrhagic toxin e". Biochemistry 17 (16): 3395–404. doi:10.1021/bi00609a033. PMID 210790. 
  14. ^ Calvete, Juan J.; Fasoli, Elisa; Sanz, Libia; Boschetti, Egisto; Righetti, Pier Giorgio (2009). "Exploring the Venom Proteome of the Western Diamondback Rattlesnake, Crotalus atrox, via Snake Venomics and Combinatorial Peptide Ligand Library Approaches". Journal of Proteome Research 8 (6): 3055–67. doi:10.1021/pr900249q. PMID 19371136. 
  15. ^ Gutiérrez, J; Rucavado, A (2000). "Snake venom metalloproteinases:Their role in the pathogenesis of local tissue damage". Biochimie 82 (9–10): 841–50. doi:10.1016/S0300-9084(00)01163-9. PMID 11086214. 
  16. ^ a b Clinical Toxinology Resource (Crotalus atrox)
  17. ^ Sean Thomas LD50
  18. ^ LD50 Menu (Dr. Bryan Grieg Fry)
  19. ^ Brown JH. 1973. Toxicology and Pharmacology of Venoms from Poisonous Snakes. Springfield, Illinois: Charles C. Thomas. 184 pp. LCCCN 73-229. ISBN 0-398-02808-7.[page needed]
  20. ^ Crotalus atrox at the IUCN Red List. Accessed 13 September 2007.
  21. ^ 2001 Categories & Criteria (version 3.1) at the IUCN Red List. Accessed 13 September 2007.

Further reading[edit]

  • Baird, S.F. & C. Girard. 1853. Catalogue of North American Reptiles in the Museum of the Smithsonian Institution. Part I. – Serpents. Smithsonian Institution. Washington, District of Columbia. xvi + 172 pp. (Crotalus atrox, pp. 5–6.)
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