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Overview

Brief Summary

Notes

Holotype: USNM 471 (McDiarmid et al., 1999).

Type-locality: "Sierra Verde and Pozo Verde." Pozo Verde is a spring located on the Sonoran side of the USA-Mexico border, near Sasabe. It is on the western slope of the southern end of the Sierra Verde (McDiarmid et al., 1999).

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Common Names

Tiger rattlesnake

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Distribution

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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Global Range: (20,000-2,500,000 square km (about 8000-1,000,000 square miles)) The range extends from central Arizona south through south-central Arizona (Lowe et al. 1986; east to about 47 kilometers east of Douglas: Painter and Milensky, 1993, Herpetol. Rev. 24:155-156; Howland et al., 2002, Herpetol. Rev. 33:149) to southern Sonora, Mexico, including Isla Tiburon in the Gulf of California, at elevations from sea level to about 4,800 feet (1,465 meters) (Stebbins 2003, Campbell and Lamar 2004). Reported occurrences at higher elevations have not been confirmed (Campbell and Lamar 2004).

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Range Description

The species' range extends from central Arizona south through south-central Arizona in the United States (Lowe et al. 1986, Painter and Milensky, 1993, Howland et al. 2002), to southern Sonora, Mexico, including Isla Tiburon in the Gulf of California, at elevations from sea level to about 1,465m asl (4,800 feet) (Stebbins 2003, Campbell and Lamar 2004). Reported occurrences at higher elevations have not been confirmed (Campbell and Lamar 2004).
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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.

Biogeographic Regions: nearctic (Native )

  • 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.
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Continent: Middle-America North-America
Distribution: USA, Mexico (SC Arizona),  Mexico (Sonora)
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Southwestern United States (south-central Arizona) and northwestern Mexico (Sonora); also on Isla Tiburón in the Gulf of California (McDiarmid et al., 1999).

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Physical Description

Morphology

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.

Range mass: 454 (high) g.

Range length: 460 to 910 mm.

Average length: 609 mm.

Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry ; venomous

Sexual Dimorphism: male larger

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

Length: 91 cm

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Type Information

Holotype for Crotalus tigris
Catalog Number: USNM 471
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Amphibians & Reptiles
Preparation: Ethanol
Locality: Sierra Verde Y Pozo Verde, Pima, Arizona, United States, North America
  • Holotype: Kennicott, R. 1859. Reptiles of the Boundary, Vol. 2, pt. 2., United States and Mexican Boundary Survey. U.S. 34th Congress, 1st Session, Executive Document (108). 14, plate 6.
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Paratype for Crotalus tigris
Catalog Number: USNM 472
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Amphibians & Reptiles
Preparation: Ethanol
Locality: Sierra Verde Y Pozo Verde, Pima, Arizona, United States, North America
  • Paratype: Kennicott, R. 1859. Reptiles of the Boundary, Vol. 2, pt. 2., United States and Mexican Boundary Survey. U.S. 34th Congress, 1st Session, Executive Document (108). 14, plate 6.
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Ecology

Habitat

Comments: Habitats include rocky desert canyons, foothills, and bajadas, in vegetation zones ranging from thornscrub, ocotillo-mesquite-creosotebush, saguaro-paloverde, mesquite grassland, and chaparral to tropical deciduous forest (southern Sonora) and the lower edge of oak woodland (Behler and King 1979, Lowe et al. 1986, Ernst and ernst 2003, Stebbins 2003, Campbell and Lamar 2004). In southeastern Arizona, this snake occurs strictly in rocky areas in winter and spring but uses edges of arroyos in summer (Beck 1995). It is a terrestrial species but may climb into low vegetation.

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Habitat and Ecology

Habitat and Ecology
The species' habitats include rocky desert canyons, foothills, and bajadas, in vegetation zones ranging from thornscrub, ocotillo-mesquite-creosote bush, saguaro-paloverde, mesquite grassland, and chaparral to tropical deciduous forest (southern Sonora) and the lower edge of oak woodland (Behler and King 1979, Lowe et al. 1986, Ernst and Ernst 2003, Stebbins 2003, Campbell and Lamar 2004). In southeastern Arizona, this snake occurs strictly in rocky areas in winter and spring but uses edges of arroyos in summer (Beck 1995). It is a terrestrial species but may climb into low vegetation.

Systems
  • Terrestrial
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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.

Range elevation: 1,000 to 5,000 m.

Habitat Regions: terrestrial

Terrestrial Biomes: desert or dune ; savanna or grassland

  • Bartlett, R., A. Tennant. 2000. Snakes of North America Western Region. Houston, Texas: Gulf Publishing Company.
  • Stebbins, R. 2003. A Field Guide to Western Reptiles and Amphibians Third Edition. Boston, New York: Houghton Mifflin Company.
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Migration

Non-Migrant: No. All populations of this species make significant seasonal migrations.

Locally Migrant: No. No 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.

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Trophic Strategy

Comments: Feeds on lizards and small mammals (e.g., kangaroo rats, pocket mice, deer mice, and woodrats) (Stebbins 1985). In southeastern Arizona, survival for a year can be supported by just a few large meals (Beck 1995).

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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.

Animal Foods: mammals; reptiles

Primary Diet: carnivore (Eats terrestrial vertebrates)

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Associations

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.

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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.

Anti-predator Adaptations: cryptic

  • Beaupre, S., D. Duvall. 1998. Integrative biology of rattlesnakes. Bioscience, 48/7: 531-538.
  • Klauber, L. 1997. Rattlesnakes: Their Biology, Life Histories, and Influence on Mankind. Berkeley, CA: University of California Press.
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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: 21 - 300

Comments: On a range-wide scale, Campbell and Lamar (2004) mapped 33 collection sites. Lowe et al. (1986) stated that the species is known from approximately 100 localities throughout the range.

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Global Abundance

10,000 - 1,000,000 individuals

Comments: Adult population size is unknown but presumably exceeds 10,000. This snake is fairly common in some areas, but "some local populations seem small" (Ernst and Ernst 2003).

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General Ecology

In southeastern Arizona, mean home range size was 3.48 ha, and individuals moved an average of 33 m per day during the active season (Beck 1995).

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Life History and Behavior

Behavior

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.

Perception Channels: visual ; infrared/heat ; chemical

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Cyclicity

Comments: Inactive in cold temperatures and extreme heat. May be active both day and night; daytime activity consists mainly of basking on cool days. Often active after warm rains (Stebbins 1985). In southeastern Arizona, active mainly March-October (Beck 1995).

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Life Cycle

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

Lifespan/Longevity

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

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Lifespan, longevity, and ageing

Maximum longevity: 15.3 years (captivity)
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Reproduction

Viviparous.

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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.

Mating System: polygynandrous (promiscuous)

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.

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.

Average birth mass: 9 g.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; ovoviviparous ; sperm-storing

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.

Parental Investment: pre-hatching/birth (Protecting: Female)

  • Goldberg, S. 1999. Reproduction in the Tiger rattlesnake, Crotalus tigris (Serpentes: Viperidae). The Texas Journal of Science, 51/1: 31-36.
  • Lowe, C., C. Schwalbe, T. Johnson. 1989. The Venoumous Reptiles of Arizona. Phoenix, Arizona: Arizona Game and Fish Commission.
  • Rubio, M. 1998. Rattlesnake - Portrait of a Predator. Washington, D.C.: Smithsonian Institution Press.
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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage: Crotalus tigris

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. & Gadsden, H.

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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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.

US Federal List: no special status

CITES: no special status

State of Michigan List: no special status

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, number of subpopulations, and population size probably are relatively stable or declining at a rate of 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
On a range-wide scale, Campbell and Lamar (2004) mapped 33 collection sites. Lowe et al. (1986) stated that the species is known from approximately 100 localities throughout the range. The adult population size is unknown but presumably exceeds 10,000. This snake is fairly common in some areas, but "some local populations seem small" (Ernst and Ernst 2003). Its extent of occurrence, area of occupancy, number of subpopulations, and population size are probably relatively stable or declining at a rate of less than 10% over 10 years or three generations.

Population Trend
Stable
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Threats

Degree of Threat: Medium

Comments: Southern populations on the flatter areas of the coastal plain of Sonora are probably losing habitat due to the intensification of agriculture. Overall, however, this species is not seriously threatened.

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Major Threats
Southern populations on the flatter areas of the coastal plain of Sonora are probably losing habitat due to the intensification of agriculture. However, overall, this species is not seriously threatened.
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Management

Global Protection: Several (4-12) occurrences appropriately protected and managed

Comments: Some occurrences are in protected areas.

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Conservation Actions

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

Benefits

Economic Uses

Comments: Venomous.

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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.

Negative Impacts: injures humans (bites or stings, venomous )

  • 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.
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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.

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

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Wikipedia

Crotalus tigris

Common names: tiger rattlesnake, tiger rattler.[2]

Crotalus tigris is a highly venomous pit viper species found in the southwestern United States and northwestern Mexico. No subspecies are currently recognized.[3] The specific name, tigris, Latin for "tiger", refers to the many narrow dorsal crossbands, which create a pattern of vertical stripes when viewed from the side.[4]

Physical Description[edit]

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. The color pattern consists of a gray, lavender, blue-gray, pink, or buff ground color that usually turns to pink, pale orange or cream on the sides. 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 consisting mainly of heavy punctations. These crossbands have vague borders and are wider dorsally than laterally. Also mid-dorsally, the crossbands become wider than the spaces that separate them. Posteriorly, the crossbands become darker and more clearly defined. They have 6 to 10 posterior rings. The markings on the head are mostly vague and irregular, although towards the rear of the head, a few dark markings may be arranged as paired occipital blotches and upper temporal streaks. The most distinguishable mark on the head is a dark cheek strip. Dorsal scales are keeled and in 21 to 27 rows. A relatively small species, individuals can weigh as much as 454 g (16.0 oz) and can range in length from 460 mm (18 in) to 910 mm (36 in), with an average length of 609 mm (24.0 in). The largest specimen on record measured 88.5 cm (34.8 in) (Klauber, 1956), until H.M. Smith and Brodie (1982) reported a maximum length of 91.2 cm (35.9 in).[5] 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.[4][6][7]

Range MassRange LengthAverage LengthOther Physical FeaturesSexual Dimorphism
454 g (16.0 oz)460 mm (46 cm; 18 in) – 910 mm (91 cm; 36 in)609 mm (60.9 cm; 24.0 in)ectothermic; heterothermic; bilateral symmetry; venomousMales larger than females

Distribution and Geographic range[edit]

The species' range extends from central Arizona south through south-central Arizona in the United States,[8][9][10] to southern Sonora, Mexico, including Isla Tiburón in the Gulf of California and was recently discovered in the southern Peloncillo Mountains of Arizona. The type locality is described as "Sierra Verde and Pozo Verde". The latter is a spring located on the Sonora side of the US-Mexico border, near Sasabe. According to Stejneger (1893), this spring is on the western slope of the southern Sierra Verde, which is also known as the Sierra del Pozo Verde.[1] In these areas, the Tiger rattlesnake is observed at elevations from sea level to about 1,465 metres (4,806 ft)[11][12] Reported occurrences at higher elevations have not been confirmed.[12]

Habitat and Ecology[edit]

The Tiger rattlesnakes habitats include rocky desert canyons, foothills, and bajadas, in vegetation zones ranging from thornscrub, ocotillo-mesquite-creosote bush, saguaro-paloverde, mesquite grassland, and chaparral to tropical deciduous forest (southern Sonora) and the lower edge of oak woodland.[4][8][11] In southeastern Arizona, this snake occurs strictly in rocky areas in winter and spring but uses edges of arroyos in summer.[13] It is a terrestrial species but may climb into low vegetation.

Tiger rattlesnakes have also often been observed in the foothills, rocky canyons, and ravines of deserts or mesquite grasslands from 1,000 feet (300 m) to 5,000 feet (1,500 m) in elevation, throughout their geographic range. Tiger rattlesnakes also inhabit escarpments, outcroppings and cliff-faces in thorny scrub desert habitat.[6][11][14] In southeastern Arizona, mean home range size was 3.48 hectares (0.0134 sq mi; 0.0348 km2), and individuals moved an average of 33 metres (108 ft) per day during the active season.[13]

Little information is available concerning the average home range size of tiger rattlesnakes. One study reported an observed home range of approximately 3.5 km2 (1.4 sq mi).[13]

Behavior and Habits[edit]

Tiger rattlesnakes are terrestrial (ground-dwelling) snakes and are nocturnal during the hot summer months (June–August), but become diurnal and crepuscular in during the fall season. It hibernates during the cold months of late fall and winter in rock crevices or animal burrows. In spite of being a ground-dwelling inhabitant of the desert, its activity is not restricted to the ground. It swims readily and also has been found in bushes 60 cm (24 in) above the floor.[15] There is little information available concerning communication and perception among tiger rattlesnakes. However, like other pit-vipers, tiger rattlesnakes have heat sensing pits (located on each side of the face between the eye and nostril) to detect warm-blooded predators and prey.[16]

This snake is inactive in cold temperatures (December/January) and extreme heat (July/August). It may be active both day and night; daytime activity consists mainly of basking on cool days. These snakes are often observed being active after warm rains.[11] In southeastern Arizona, they are active mainly from March to October.[13]

Diet and Food Habits[edit]

Tiger rattlesnakes generally feed on mammals such as rodents, but they have also been known to prey on lizards. The tiger rattlesnake ambushes much of its prey but also actively forages small rodents and lizards, juveniles relying heavily on lizards and adults depending more on rodents. In addition, these small rattlesnakes have been known to eat fairly large prey, including kangaroo rats, deer mice, packrats, and even spiny lizard.[17] This species' venom is considered the most toxic of all 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.[11][14][16]

Predators[edit]

There is little to no information available regarding predators specific to tiger rattlesnakes. However, 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. Tiger rattlesnakes are known to have an irascible temperament and are easily excitable and can be quite aggressive.[18]

Reproduction[edit]

Tiger rattlesnakes are 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 this species. 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.[19]

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 (21.3 in; 54.1 cm) snout-vent length (SVL), while the smallest mature male measured 512 mm (20.2 in; 51.2 cm) SVL.[8][19][20]

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.[20]

Breeding intervalBreeding seasonRange number of offspringAverage number of offspring
Tiger rattlesnake females mate biennially, and males mate annuallyLate May to mid August, during the summer monsoon season1 to 64 to 6

Development[edit]

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.[20]

Conservation status[edit]

This species is classified as Least Concern on the IUCN Red List of Threatened Species (v3.1, 2001).[21] 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.[22]

Population[edit]

The population trend of the tiger rattlesnake is considered to be stable. On a range-wide scale, Campbell and Lamar (2004) mapped 33 collection sites. Lowe et al. (1986) stated that the species is known from approximately 100 localities throughout the range. The adult population size is unknown but presumably exceeds 10,000. This snake is fairly common in some areas, but "some local populations seem small" (Ernst and Ernst 2003). Its extent of occurrence, area of occupancy, number of subpopulations, and population size are probably relatively stable or declining at a rate of less than 10% over 10 years or three generations.[21]

Threats[edit]

Southern populations on the flatter areas of the coastal plain of Sonora are probably losing habitat due to the intensification of agriculture. Overall, however, this species is not seriously threatened.[21]

Relevance to Humans and Ecosystems[edit]

Negative[edit]

Although tiger rattlesnakes are reluctant to strike, they are highly venomous, cantankerous and as a result 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, their venom is the most toxic of any snake in the Western Hemisphere. The combination of neuro- and mytoxins in their venom makes them extremely dangerous to humans.[23]

Positive[edit]

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. 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.[20]

Venom[edit]

Although it has a comparatively low venom yield,[24] its toxicity is considered to be the highest of all rattlesnake venoms, and the highest of all snakes in the Western Hemisphere. It has a high neurotoxic fraction that is antigenically related to Mojave toxin (see Crotalus scutulatus, venom A), and includes another component immunologically identical to crotamine, which is a myotoxin also found in tropical rattlesnakes (see Crotalus durissus). A low but significant protease activity is in the venom, although there does not seem to be any hemolytic activity.[25]

Brown (1973) lists an average venom yield of 11 mg (dried venom) and an LD50 value of 0.6 mg/kg IP for toxicity.[26] Other studies give LD50 values of 0.07 mg/kg IP, 0.056 mg/kg IV, and 0.21 mg/kg SC.[17] Minton and Weinstein (1984) list an average venom yield of 6.4 mg (based on two specimens). Weinstein and Smith (1990) list a venom yield of 10 mg.[27]

There is very little information available for bite symptoms. Human bites by the tiger rattlesnake are infrequent, and literature available on bites by this snake is scarce. The several recorded human envenomations by tiger rattlesnakes produced little local pain, swelling, or other reaction following the bite, and despite the toxicity of its venom no significant systemic symptoms. The comparatively low venom yield (6.4–11 mg dried venom) and short 4.0 mm (0.40 cm) to 4.6 mm (0.46 cm) fangs of the tiger rattlesnake possibly prevent severe envenoming in adult humans. However, the clinical picture could be much more serious if the person bitten was a child or a slight build individual. The early therapeutic use of antivenom is important if significant envenomation is suspected. Despite the low venom yield, a bite by this rattlesnake should be considered a life-threatening medical emergency. Untreated mortality rate is unknown but this snake has a very high venom toxicity and its bites are capable of producing major envenomation.[25][27]

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).
  2. ^ Wright AH, Wright AA. 1957. Handbook of Snakes. Comstock Publishing Associates. (7th printing, 1985). 1105 pp. ISBN 0-8014-0463-0.
  3. ^ "Crotalus tigris". Integrated Taxonomic Information System. Retrieved 16 May 2007. 
  4. ^ a b c 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.
  5. ^ Smith, H.M. and Edmund D. Brodie, Jr. 1982. Reptiles of North America: A Guide to Field Identification. Golden Press. New York. 240 pp. ("TIGER RATTLESNAKE (Crotalus tigris)", pp. 204–205.)
  6. ^ a b Ernst, Carl H. (1992). Venomous Reptiles of North America. USA: Smithsonian Inst Pr. ISBN 1-56098-114-8. 
  7. ^ Fowlie, JA (1965). The Snakes of Arizona. USA: Azul Quinta Press. 
  8. ^ a b c Lowe, CH (1986). The Venomous Reptiles of Arizona. USA: Arizona Game and Fish Department. ISBN 0-917563-03-4. 
  9. ^ Painter, CW; Milensky, CM (1993). "Crotalus tigris (tiger rattlesnake)". Herpetological Review 24 (4): 155–156. 
  10. ^ Howland, JM; Enderson, E.F., Bezy, R.L., Sigafus, B.H. and Titcomb, A (2002). "Crotalus tigris (Tiger Rattlesnake). Geographic Distribution". Herpetological Review 33 (2): 149. 
  11. ^ a b c d e Stebbins, Robert C. (2003). A Field Guide to Western Reptiles and Amphibians. USA: Houghton Mifflin Harcourt; 3 edition. ISBN 0-395-98272-3. 
  12. ^ a b Campbell, Lamar, Jonathan, William (2004). The Venomous Reptiles of the Western Hemisphere. Comstock Publishing Associates; Two-volume set edition. ISBN 0-8014-4141-2. 
  13. ^ a b c d Beck, DD (June 1995). "Ecology and energetics of three sympatric rattlesnakes in the Sonoran Desert". Journal of Herpetology 29 (2): 211–223. doi:10.2307/1564558. 
  14. ^ a b Bartlett, Tennant, R.D., Alan (1999). Snakes of North America: Western Region. USA: Taylor Trade Publishing. ISBN 0-87719-312-6. 
  15. ^ Briscoe, PhD, MS (April 1957). "Rattlesnakes, Their Habits, Life Histories, And Influence On Mankind". Journal of the Medical Library Association 45 (2): 274–275. PMC 200126. Retrieved 20 October 2013. 
  16. ^ a b Brennan, T. C. "The Reptiles and Amphibians of Arizona. An Online Field Guide". Retrieved 20 October 2013. 
  17. ^ a b CALVETE, Juan J.; Alicia PÉREZ; Bruno LOMONTE; Elda E. SÁNCHEZ; Libia SANZ (3 February 2012). "Snake Venomics of Crotalus tigris: The Minimalist Toxin Arsenal of the Deadliest Neartic Rattlesnake Venom". Journal of Proteome Research 11 (2): 1382–1390. doi:10.1021/pr201021d. PMC 3272105. PMID 22181673. Retrieved 19 October 2013. 
  18. ^ Beaupre, Steven J.; Duvall, David J. (July 1998). "Integrative Biology of Rattlesnakes". BioScience 48 (7): 531–538. doi:10.2307/1313315. Retrieved 20 October 2013. 
  19. ^ a b Goldberg, S. (1999). ".Reproduction in the Tiger rattlesnake, Crotalus tigris (Serpentes: Viperidae)". The Texas Journal of Science 51 (1): 31–36. 
  20. ^ a b c d Rubio, Manny (1998). Rattlesnake – Portrait of a Predator. Smithsonian Institution Press; 1St Edition edition. ISBN 1-56098-808-8. 
  21. ^ a b c Crotalus tigris at the IUCN Red List. Accessed 13 September 2007.
  22. ^ 2001 Categories & Criteria (version 3.1) at the IUCN Red List. Accessed 13 September 2007.
  23. ^ Powell, RL; Lieb, CS; Rael, ED (March 2004). "Identification of a Neurotoxic Venom Component in the Tiger Rattlesnake, Crotalus tigris". Journal of Herpetology 38 (1): 149–152. doi:10.1670/76-03N. Retrieved 20 October 2013. 
  24. ^ Weinstein and Smith (1990)
  25. ^ 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.
  26. ^ 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.
  27. ^ a b "University of Adelaide Clinical Toxinology Resources". 

Further reading[edit]

  • Kennicott, R. In Baird, S.F. 1859. Reptiles of the Boundary, with Notes by the Naturalists of the Survey. In Report of the United States and Mexican Boundary Survey, Under the Order of Lieut. Col. W.H. Emory, Major First Cavalry, and United States Commissioner, vol. 2, no. 2. Department of the Interior. Washington, District of Columbia. 35 pp.
  • Klauber, L.M. 1956. Rattlesnakes: Their Habits, Life Histories and Influence on Mankind. 2 volumes. University of California Press. Berkeley, California. 1,533 pp.
  • Stejneger, L.H. 1893. Annotated List of the Reptiles and Batrachians Collected by the Death Valley Expedition in 1891, with Descriptions of New Species. North American Fauna, No. 7, Part II, pp. 159–228.
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