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Crotalus tigrisTiger Rattlesnake

By Victoria Wesolowski

Geographic Range

Crotalus tigris (Tiger rattlesnake) is found from south central Arizona to Sonora, Mexico. This species of rattlesnake is easily found in the foothills of the Arizona Upland desert scrub but is also resident to the Interior Chaparral and Madrean Evergreen Woodland. Crotalus tigris has also been observed on Isla Tiburon in the gulf of California and was recently discovered in the southern Peloncillo Mountains of Arizona. (Brennan and Holycross, 2006; Ernst, 1992)

Habitat

Crotalus tigris has been observed in the foothills, rocky canyons, and ravines of deserts or mesquite grasslands from 1000 to 5000 m in elevation, throughout their geographic range. Plants native to this habitat type include cactus, mesquite, creosote bush, ocotillo, saguaro, and palo verde. Crotalus tigris also inhabit escarpments, outcroppings and cliff-faces in thorny scrub desert habitat. (Bartlett and Tennant, 2000; Ernst, 1992; Stebbins, 2003)

  • Range elevation
    1,000 to 5,000 m
    to ft

Physical Description

Tiger rattlesnakes are easily identified by their small, spade shaped head, which is about 1/25 of their total body length. They have the smallest head of any rattlesnake and a large rattle. They can be gray, lavender, pink, yellowish brown, or orange. Tiger rattlesnakes are the only rattlesnake with crossbands on the anterior portion of the body, with a series of 35 to 52 gray, olive, or brown bands across the dorsum. They have 6 to 10 posterior rings, and the only distinguishable mark on the head is a dark cheek strip. Dorsal scales are keeled and in 21 to 27 rows. Individuals can weigh as much as 454 grams and can range in length from 460 to 910 mm, with an average length of 609 mm. Females have 164 to 177 ventral scales, and males have 158 to 172 ventral scales. Females have 16 to 21 caudal scales, and males have 23 to 27 caudal scales and are typically larger than females. They have relatively small eyes with an elliptical pupil. Tiger rattlesnakes are often confused with speckled rattlesnakes, western rattlesnakes, black-tailed rattlesnakes, western diamondback ratttlesnakes, and Mojave rattlesnakes. (Ernst, 1992; Fowlie, 1965)

  • Sexual Dimorphism
  • male larger
  • Range mass
    454 (high) g
    16.00 (high) oz
  • Range length
    460 to 910 mm
    18.11 to 35.83 in
  • Average length
    609 mm
    23.98 in

Development

Tiger rattlesnake embryos are retained inside the female in a transparent, membranous sac, where some materials and gasses are exchanged between embryo and mother. Embryos receive fluids and sustenance from the yolk mass. Once born, neonates break through the embryonic sac and travel a short distance to a safe nook with its siblings. Young tiger rattlesnakes are not born with a rattle. Neonates have a skin cap at the tip of the tail and after every molt, a new rattle segment is added. Like all rattlesnakes, tiger rattlesnakes are ovoviviparous and thus, are well developed at birth. (Rubio, 1998)

Reproduction

Crotalus tigris is polygynandrous, and either the male, female, or both have more than one mate within a single breeding season. Little else is known of the reproductive behavior of C. tigris. The reproductive behavior of this species is thought to be similar to the that of Crotalus atrox and Crotalus scutulatus. Copulation in viperids can take minutes, hours, or days and can occur multiple times within a couple of days. (Goldberg, 1999)

Tiger rattlesnake females follow a biennial reproductive cycle. Males follow a seasonal reproductive cycle, where sperm is stored in the vasa deferentia during winter. Breeding occurs from late May to mid August, during the summer monsoon season. Like the majority of rattlesnakes, tiger rattlesnakes are ovoviviparous. Mean clutch size for is 4 to 6 young. The smallest known sexually reproducing female measured 541 mm snout-vent length (SVL), while the smallest mature male measured 512 mm SVL. (Goldberg, 1999; Lowe, et al., 1989; Rubio, 1998)

  • Breeding interval
    Tiger rattlesnake females mate biennially, and males mate annually.
  • Breeding season
    Late May to mid August, during the summer monsoon season
  • Range number of offspring
    1 to 6
  • Average number of offspring
    4 to 6

Generally, rattlesnakes invest little in offspring following birth. However, like other viperids, female tiger rattlesnakes invest in provisioning resources for developing embryos. She eats early in the pregnancy and then find a safe place to hide while providing the optimal thermal environment for development. (Rubio, 1998)

  • Parental Investment
  • pre-hatching/birth
    • protecting
      • female

Lifespan/Longevity

There is no information regarding the average lifespan of tiger rattlesnakes.

Behavior

Tiger rattlesnakes are primarily nocturnal, even during cold temperatures. However, they are occasionally found basking during the day and after warm rains. Although they appear to be reluctant to strike when threatened, if agitated enough they will attack. Prior to attacking, however, they rapidly shake their rattle as a sign of irritation. Their venom is considered the most toxic of all neotropical rattlesnakes and contains a myotoxin known to cause muscle necrosis and a neurotoxin similar to Mojave toxin. (Bartlett and Tennant, 2000; Stebbins, 2003)

  • Average territory size
    3.5 km^2

Home Range

Little information is available concerning the average home range size of tiger rattlesnakes. One study reported an observed home range of approximately 3.5 km^2. (Beck, 1995)

Communication and Perception

There is little information available concerning communication and perception in tiger rattlesnakes. However, like other vipers, tiger rattlesnakes have heat sensing pits to detect prey and predators. (Brennan, 2008)

Food Habits

Tiger rattlesnakes generally feed on lizards and small mammals such as pocket mice, kangaroo rats, deer mice, and woodrats. Their venom is considered the most toxic of all neotropical rattlesnakes and contains a myotoxin known to cause muscle necrosis and a neurotoxin similar to Mojave toxin. Like all venomous snakes, tiger rattlesnakes inject venom into prey through long, hollow, retractable fangs. If envenomated prey crawl into a small crevice, this species is especially suited for extracting them due to its unusually small head. (Bartlett and Tennant, 2000; Brennan, 2008; Stebbins, 2003)

  • Primary Diet
  • carnivore
    • eats terrestrial vertebrates
  • Animal Foods
  • mammals
  • reptiles

Predation

There is no information available regarding predators specific to tiger rattlesnakes. Likely predators include hawks, eagles, coyotes, and other snakes. Their cryptic coloration helps camouflage them from potential predators and helps reduce risk of predation. If disturbed, they rapidly shake their rattle and may strike in defense. (Beaupre and Duvall, 1998; Klauber, 1997; Rubio, 1998)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Tiger rattlesnakes feed on a number of small vertebrate species and likely help regulate their abundance and distribution. There is no information regarding parasites specific to this species. (Rubio, 1998; Rubio, 1998)

Economic Importance for Humans: Positive

In general, rattlesnake skin and tail rattles are often considered valuable and are often sold as souvenirs throughout the American Southwest. Rattlesnake venom is often used in biomedical research investigating neurological diseases. Finally, tiger rattlesnakes prey upon a number of rodent species considered pests by humans throughout their geographic range. (Rubio, 1998)

  • Positive Impacts
  • body parts are source of valuable material
  • source of medicine or drug
  • research and education
  • controls pest population

Economic Importance for Humans: Negative

Although tiger rattlesnakes are reluctant to strike, they are venomous and pose a potential threat to humans. Their venom contains a neurotoxin called Mojave toxin and a myotoxin known to cause muscle necrosis. Although venom production is low compared to other rattlesnakes, the combination of neuro- and mytoxins in their venom makes them one of the most toxic rattlesnakes known. (Powell, et al., 2004)

  • Negative Impacts
  • injures humans

Conservation Status

Tiger rattlesnakes are classified as a species of least concern on the IUCN's Red List of Threatened Species. Habitat loss due to agricultural expansion is a potential threat, however, this species is not seriously threatened at present.

Contributors

Victoria Wesolowski (author), Indiana University-Purdue University Fort Wayne, Mark Jordan (editor), Indiana University-Purdue University Fort Wayne, John Berini (editor), Animal Diversity Web Staff.

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

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

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.
drug

a substance used for the diagnosis, cure, mitigation, treatment, or prevention of disease

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

hibernation

the state that some animals enter during winter in which normal physiological processes are significantly reduced, thus lowering the animal's energy requirements. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals.

infrared/heat

(as keyword in perception channel section) This animal has a special ability to detect heat from other organisms in its environment.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

native range

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

nocturnal

active during the night

ovoviviparous

reproduction in which eggs develop within the maternal body without additional nourishment from the parent and hatch within the parent or immediately after laying.

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

sperm-storing

mature spermatozoa are stored by females following copulation. Male sperm storage also occurs, as sperm are retained in the male epididymes (in mammals) for a period that can, in some cases, extend over several weeks or more, but here we use the term to refer only to sperm storage by females.

terrestrial

Living on the ground.

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

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.

venomous

an animal which has an organ capable of injecting a poisonous substance into a wound (for example, scorpions, jellyfish, and rattlesnakes).

visual

uses sight to communicate

References

Bartlett, R., A. Tennant. 2000. Snakes of North America Western Region. Houston, Texas: Gulf Publishing Company.

Beaupre, S., D. Duvall. 1998. Integrative biology of rattlesnakes. Bioscience, 48/7: 531-538.

Beck, D. 1995. Ecology and energetics of three sympatric rattlesnake species in the Sonoran Desert. Journal of Herpetology, 29: 211-223. Accessed May 14, 2011 at http://www.cwu.edu/~biology/faculty/currentFaculty/beck/pdfpublicationfiles/beck1995.pdf.

Brennan, T. 2008. "Online Field Guide to The Reptiles and Amphibians of Arizona" (On-line). Tiger Rattlesnake (Crotalus tigris)- Reptiles of Arizona. Accessed February 23, 2011 at http://www.reptilesofaz.org/Snakes-Subpages/h-c-tigris.html.

Brennan, T., A. Holycross. 2006. A Field Guide to Amphibians and Reptiles in Arizona. Phoenix, Arizona: Arizona Game and Fish Department.

Ernst, C. 1992. Venomous Reptiles of North America. Washington: Smithsonian Institution Press.

Fowlie, J. 1965. The Snakes of Arizona. Fallbrook, California: Azul Quinta Press.

Goldberg, S. 1999. Reproduction in the Tiger rattlesnake, Crotalus tigris (Serpentes: Viperidae). The Texas Journal of Science, 51/1: 31-36.

Klauber, L. 1997. Rattlesnakes: Their Biology, Life Histories, and Influence on Mankind. Berkeley, CA: University of California Press.

Lowe, C., C. Schwalbe, T. Johnson. 1989. The Venoumous Reptiles of Arizona. Phoenix, Arizona: Arizona Game and Fish Commission.

Powell, R., C. Lieb, E. Rael. 2004. Identification of a neurotoxic venom component in the Tiger rattlesnake, Crotalus tigris. Journal of Herpetology, 38/1: 149-152.

Rubio, M. 1998. Rattlesnake - Portrait of a Predator. Washington, D.C.: Smithsonian Institution Press.

Stebbins, R. 2003. A Field Guide to Western Reptiles and Amphibians Third Edition. Boston, New York: Houghton Mifflin Company.

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