Crotalus atroxWestern Diamond-backed Rattlesnake

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.

Habitat

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

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.

Reproduction

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
    AnAge
  • Average age at sexual or reproductive maturity (female)
    Sex: female
    1095 days
    AnAge
  • Average age at sexual or reproductive maturity (male)
    Sex: male
    1095 days
    AnAge

Lifespan/Longevity

Behavior

Western Diamondback Rattlesnakes are aggressive and easily excitable. This species causes more fatalities than any other snake in the United States. They are not apt to attack offensively, but are defensive. Their rattles are used as a warning sign. Their rattles can activate at 40 to 60 cycles a second. The Western Diamondback assumes the threat posture by slightly flattening the body, rolling it together into a spiral, lifting the forebody from the ground into an S-shape, and keeping the tail raised and the rattle rattling.

Ritualized fighting has been observed in C.atrox males. Fighters lift their forebodies up 80 cm. in the air, wrap them around each other, orienting head to head. They keep moving in a surging movement back and forth until one of the males backs off. Common predators of C.atrox include hawks, bald eagles, roadrunners, and wild turkeys.

In the fall, Western Diamondback Rattlesnakes begin migrating to winter hibernacula. In warmer habitats, these hibernacula are fairly makeshift, being found in rock crevices or convenient holes. In colder habitats, such as prairie grasslands, populations are forced to use the holes and tunnels of burrowing mammals, especially the prairie dog. Although prairie dogs may block off the Rattlesnake with an earthen plug, these animals tend to abandon burrows that have been taken over by snakes. During hibernation, populations concentrate as several individuals den together. In warmer habitats, where the hibernation season is shorter and hibernacula more makeshift, fewer individuals congregate. Rattlesnakes are known to be nocturnal hunters, and are less active diurnally

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

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).

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.

Conservation Status

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.

Contributors

Lisa Ingmarsson (author), University of Michigan-Ann Arbor.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

chaparral

Found in coastal areas between 30 and 40 degrees latitude, in areas with a Mediterranean climate. Vegetation is dominated by stands of dense, spiny shrubs with tough (hard or waxy) evergreen leaves. May be maintained by periodic fire. In South America it includes the scrub ecotone between forest and paramo.

desert or dunes

in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.

diurnal
  1. active during the day, 2. lasting for one day.
native range

the area in which the animal is naturally found, the region in which it is endemic.

sedentary

remains in the same area

solitary

lives alone

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5? N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

References

Dittmars, Raymond L., 1936. Reptiles of North America. Doubleday, Doran, & Company, Inc., Garden City, New York. Pp.336, 352-4.

Gloyd, Howard K., 1978. The Rattlesnakes: Genera Sistrurus and Crotalus. Society for the Study of Amphibians and Reptiles, Kansas. Pg.204.

Grzimek's Animal Life Encyclopedia, 1975. Van Nostrand Reinhold Company, New York, New York. Vol#6: Pp.461-6.

Klauber, Laurence M., 1982. Rattlesnakes. University of California Press, Berkeley, California. Pp.133-35, 154-5, 158-9, 233-4, 245-7, 258.