(Baird & Girard, 1852)
The western whiptail (Aspidoscelis tigris) is a species of lizard in the family Teiidae. The species ranges throughout most of the southwestern United States and northern Mexico. Most of its populations appear stable, and it is not listed as endangered in any of the states comprising its range. It lives in a wide variety of habitats, including deserts and semiarid shrubland, usually in areas with sparse vegetation; it also may be found in woodland, open dry forest, and riparian growth. It lives in burrows. Major differences between this species and the checkered whiptail (Aspidoscelis tesselata) include the lack of enlarged scales anterior to the gular fold and the presence of enlarged postantebrachial scales. It was previously known as Cnemidophorus tigris, until phylogenetic analyses concluded that the genus Cnemidophorus was polyphyletic. Since it does not migrate, a number of forms have developed in different regions, several of which have been given subspecific names – for example the California whiptail, Aspidoscelis tigris munda.
The western whiptail has a long and slender body, small grainy scales on its back, and larger rectangular scales on its belly. The upper side often has light stripes, and the throat can be pinkish or somewhat orange in adults. The maximum snout-to-vent length (SVL) is 102 mm (about 4 inches), and maximum total length (including tail) is 305 mm (about 12 inches). Hatchlings are orange-yellow with dark brown-black spots or stripes.
Geographic range and habitat
The western whiptail is widespread throughout northern Mexico and the western United States. In the US it can be found in the states of Arizona, California, Colorado, Idaho, Nevada, New Mexico, Oregon, and Utah. It is found in hot dry regions, typically with sparse foliage. It can live in woodland, chaparral, riparian areas, or desert. Desert subspecies prefer habitat with vegetation such as sagebrush or shadscale, and rely on burrows to escape the desert heat.
In the northern parts of its range, the western whiptail usually emerges from hibernation in May, and most adults aestivate during the midsummer months, but in the south it is active from April through late August. The seasonal period of activity is therefore considerably shorter in the north. Daily periods of activity are of similar duration from north to south, although the time of emergence tends to be later in northern areas.
Reproduction and sexual characteristics
The western whiptail’s chromosomes show that it is polyploid. It is also a bisexual species, containing both males and females, unlike other species of Aspidoscelis which are all-female. Usually in the northern end of its range, mating occurs in the first half of June, and females begin to lay eggs in late June. The eggs usually begin hatching by mid-August. Females will only lay one clutch (number of eggs laid at a single time) per year. At the southern end of its range, however, females will begin to lay eggs as early as May, and the eggs will usually hatch as early as mid-June. In the southern end of its range, females may also lay two clutches per year instead of just one.
The western whiptail mostly eats insects, spiders, scorpions, lepidopterans (butterflies and moths), crickets, grasshoppers, and beetles. They use their jaws instead of their tongue to capture their prey.
When being attacked by a predator, the western whiptail will drop its tail. The muscles in the tail will continue contracting causing the tail to flop around. This is used to distract the predator from the lizard. However, this is a last ditch effort. It is very stressful for the lizard. It takes a lot of energy to regrow the tail, and the lizard loses a lot of stored food. This is a tactic often used when the lizard is threatened by a domestic or feral cat.
- A. t. aethiops (Cope, 1900)
- A. t. dickersonae (Van Denburgh & Slevin, 1921)
- A. t. disparilis (Dickerson, 1919)
- A. t. multiscutata (Cope, 1892)
- A. t. munda (Camp, 1916)
- A. t. nigroriens (Hendricks & Dixon, 1986)
- A. t. pulchra (K.L. Williams, H.M. Smith & Chrapliwy, 1960)
- A. t. punctata (Walker & Maslin, 1964)
- A. t. punctilinealis (Dickerson, 1919)
- A. t. rubida (Cope, 1892)
- A. t. septentrionalis (Burger, 1950)
- A. t. stejnegeri (Van Denburgh, 1894)
- A. t. tigris (Baird & Girard, 1852)
- A. t. vandenburghi (Dickerson, 1919)
- A. t. variolosa (Cope, 1892)
- A. t. vivida (Walker, 1981)
- Hammerson, G.A.; Frost, D.R.; Santos-Barrera, G. (2007). "Aspidoscelis tigris". IUCN Red List of Threatened Species. Version 2014.3. International Union for Conservation of Nature. Retrieved 16 December 2014.
- Smith, Hobart M.; Brodie, Edmund D., Jr. (1982). Reptiles of North America: A Guide to Field Identification. New York: Golden Press. 240 pp. ISBN 0-307-13666-3. (Cnemidophorus tigris, pp. 96-97).
- Hammerson, G.A. (1982). Amphibians and Reptiles in Colorado. Denver: Colorado Division of Wildlife. vii + 131 pp.
- Cole, Charles J.; Painter, Charles W.; Dessauer, Herbert C.; Taylor, Harry L. (2007). "Hybridization Between the Endangered Unisexual Gray-Checkered Whiptail Lizard (Aspidoscelis dixoni) and the Bisexual Western Whiptail Lizard (Aspidoscelis tigris) in Southwestern New Mexico". American Museum Novitates 3555.1: 1-31. Web.
- "California Whiptail - Aspidoscelis tigris munda ". www.californiaherps.com. Retrieved 2016-05-02.
- Pianka, Eric R. (1970). "Comparative autecology of the lizard Cnemidophorus tigris in different parts of its geographic range". Ecology. 51 (4): 703–720. JSTOR 1934053. doi:10.2307/1934053.
- Burkholder, Gary L. (1973). "Habitat and Reproduction of the desert whiptail lizard, Cnemidophorus tigris Baird and Girard in southwestern Idaho at the northern part of its range". Herpetologica. 29 (1): 76–83. JSTOR 3891208.
- McCoy, C.J. (1965). Life history and ecology of Cnemidophorus tigris septentrionalis. Ph.D. thesis, University of Colorado, Boulder.
- Vitt, Laurie J. (1977). "Ecology and Reproduction of Lower Colorado River Lizards: II. Cnemidophorus tigris (Teiidae), with Comparisons". Herpetologica 33.2: 223-234. JSTOR. Web. 10 Nov. 2014.
- Goldberg, Stephen R.; Lowe, Charles H. (1966). "The Reproductive Cycle of the Western Whiptail Lizard (Cnemidophorus tigris) in Southern Arizona". Journal of Morphology 118.4: 543-548. Web.
- Anderson, Roger A. (1988). "Energetics of the Lizard Cnemidophorus tigris and Life History Consequences of Food-Acquisition Mode". Ecological Monographs 58.2: 79-110. JSTOR. Web. 10 Nov. 2014.
- "Aspidoscelis tigris ". The Reptile Database. www.reptile-database.org.
- Beolens, Bo; Watkins, Michael; Grayson, Michael (2011). The Eponym Dictionary of Reptiles. Baltimore: Johns Hopkins University Press. xiii + 296 pp. ISBN 978-1-4214-0135-5. (Aspidoscelis tigris dickersonae, p. 72; A. t. stejnegeri, p. 252; "Van Denburgh", p. 271).
- www.natureserve.org — An excellent, well-documented site for information on this and other American species.
- Baird, Spencer F.; Girard, Charles (1852). "Characteristics of some New Reptiles in the Museum of the Smithsonian Institution". Proc. Acad. Nat. Sci. Philadelphia 6: 68-70. (Cnemidophorus tigris, new species, p. 69).
- Behler, John L.; King, F. Wayne (1979). The Audubon Society Field Guide to North American Reptiles and Amphibians. New York: Alfred A. Knopf. 743 pp. ISBN 0-394-50824-6. (Cnemidophorus tigris, pp. 563–564 + Plate 420).
- Conant, Roger (1975). A Field Guide to Reptiles and Amphibians of Eastern and Central North America, Second Edition. Boston: Houghton Mifflin Company. xviii + 429 pp. + Plates 1-48. ISBN 0-395-19979-4 (hardcover), ISBN 0-395-19977-8 (paperback). (Cnemidophorus tigris, pp. 119–120 + Plate 18 + Map 85).
- Stebbins, Robert C. (2003). A Field Guide to Western Reptiles and Amphibians, Third Edition. The Peterson Field Guide Series ®. Boston and New York: Houghton Mifflin Company. xiii + 533 pp. ISBN 978-0-395-98272-3. (Cnemidophorus tigris, pp. 326–328 + Plate 37 + Map 115).
- Zim, Herbert S.; Smith, Hobart M. (1956). Reptiles and Amphibians: A Guide to Familiar American Species: A Golden Nature Guide. New York: Simon and Schuster. 160 pp. (Cnemidophorus tigris, pp. 65, 155).