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The rosy boa (Lichanura trivirgata) is a species of snake of the family Boidae. The rosy boa is one of only two members of that family native to the United States, the other being the rubber boa (Charina bottae). The rosy boa is native to the American Southwest, and adjacent Baja California and Sonora, Mexico.
These small, attractive snakes normally attain a length of 17–34 in (43–86 cm), although some Coastal specimens from California reach 36–44 in (91–112 cm). A large adult has a body width about the diameter of a golf ball. Coloration in rosy boas is highly variable, and usually locale-specific. The common name is derived from the rosy or salmon coloration that is common on the belly of rosy boas originating from coastal southern California and Baja Mexico. Most rosy boas do not have this ventral coloration but instead have a series of dark to orange spots on a light-colored background.
Almost all rosy boas have at least some trace of three longitudinal stripes, one down the center of the back, and two on the lower sides. The appearance of these stripes varies widely, from extremely straight and having high contrast with the interspaces, to extremely broken with almost no contrast with the interspaces. Stripe colors can be orange, maroon, rust, brown, or black. Interspace colors can be shades of light to dark gray, yellow, or tan.
The rosy boa is found in the southwestern United States in the states of California and Arizona, and northwestern Mexico in the states of Baja California and Sonora. In California, the rosy boa ranges throughout the Colorado and Mojave deserts and also occupies the coastal areas of Los Angeles, Orange, Riverside, and San Diego counties. In Arizona, the rosy boa occupies the Mojave Desert and the western areas of the Sonoran Desert. It is absent from the eastern and northern halves of the state. In Sonora, the rosy boa ranges from the border with the United States south throughout the Sonoran Desert to at least as far south as Ortiz. In Baja California, the rosy boa is almost ubiquitous ranging throughout the entire peninsula except in areas of extremely dry or rockless desert.
Rosy boas spend most of their lives concealed beneath rocks and in crevices to escape the elements and natural predators. Granite outcroppings are the most common geologic association inhabited by the rosy boa. Less often they are found in association with volcanic or other rock types. Only in rare places do rosy boas inhabit rockless environments. In areas with few rocks rosy boas will use rodent burrows for concealment.
Rosy boas' activity season follows local weather patterns; however, they are generally dormant during the winter, and active during the spring, summer and fall. Like all snakes, they are dependent on external temperatures to promote such normal bodily functions as digestion and gestation. Throughout most of their range the winter is too cold for these functions and the rosy boas go into a dormant state called brumation. The spring is breeding season for Rosy Boas, resulting in their highest rate of activity. Most Rosy Boas are encountered in spring as they leave the security of their rock piles and crevices to seek mates. Another reason rosy boas may be active on the surface of the ground is to find prey or new territory.
The surface activity of rosy boas can take place during any hour of the day, but during hot weather they are primarily nocturnal. In the spring, they are often abroad in the afternoon and early evening. In the late spring and summer, this activity period switches from dusk to late into the night. Because most populations of rosy boas live in exceedingly dry habitats, their activity is often highly moisture dependent. During dry periods they remain deep underground to assist in remaining hydrated. Recent rainfall often results in a flurry of surface activity.
These snakes forage mainly for small mammals but have occasionally been known to take other prey items such as birds and lizards. Pack rats, baby rabbits, deer mice, and kangaroo rats make up a large portion of their diet. Rosy boas are one of the slowest-moving species of snake in the world. They are unable to pursue prey and must either wait in ambush or stalk their meals. When a meal is within reach, usually a few inches, a rosy boa will strike with surprising speed and accuracy. Prey is secured with tiny rows of needle-sharp teeth, then suffocated through constriction.
Rosy boas are extremely docile when encountered by humans. When disturbed they usually roll into a compact ball with the head in the center. The species is not prone to bite in defense, and when human bites have occurred they have usually been the result of a feeding response with a captive animal. All rosy boa bites are nonvenomous. Their extreme docility and their attractive coloration have made rosy boas very popular with herpetoculturists.
Rosy boas bear live young, about six in a brood, with newborns about 30 cm (12 in.) in length.
The epithet trivirgata refers to the distinct three stripes that are characteristic of the species. The rosy boa is considered to be the only species within the genus Lichanura, but one researcher has placed it in the genus Charina with the rubber boa. Newer phylogenetic research supports the original arrangement but herpetologists are still not unified on rosy boa taxonomy. The subspecific designations are just as uncertain with many sources not accepting "arizonae" or "saslowi"
- Arizona rosy boa, Lichanura trivirgata arizonae Spiteri, 1991
- Desert rosy boa, Lichanura trivirgata gracia Klauber, 1931 – Ground color laced with well-defined pink, orange or tan longitudinal stripes.
- Coastal rosy boa, Lichanura trivirgata roseofusca Cope, 1868 – Ground color laced with blotchy reddish-brown longitudinal stripes.
- Baja rosy boa, Lichanura trivirgata saslowi Spiteri, 1987
- Mexican rosy boa, Lichanura trivirgata trivirgata Cope, 1861 – Ground color laced with pale, creamy broad longitudinal stripes.
Their generally docile temperament and small size make rosy boas an ideal choice for pet snakes due to their easy care and small enclosure size of 20 US gal (76 l). They are frequently captive bred, and readily feed on commercially available mice. Many color variations are available, including albinos as well as the different subspecies. With other species, such as corn snakes, milk snakes, and ball pythons, dominating the majority of the market, the popularity of rosy boas hasn't been as high as other species.
- Hammerson GA, Frost DR, Gadsden H (2007). "Lichanura trivirgata". IUCN Red List of Threatened Species. Version 2014.3. International Union for Conservation of Nature. Retrieved 5 March 2015.
- Stejneger L, Barbour T (1917). A Check List of North American Amphibians and Reptiles. Cambridge, Massachusetts: Harvard University Press. 125 pp. (Lichanura, p. 73).
- Schmidt KP, Davis DD (1941). Field Book of Snakes of the United States and Canada. New York: G.P. Putnam's Sons. 365 pp. (Lichanura roseofusca, pp. 96–98 & Plate 8).
- Behler JL, King FW (1979). The Audubon Society Field Guide to North American Reptiles and Amphibians. New York: Alfred A. Knopf. 743 pp. ISBN 9780394508245. (Lichanura trivirgata, pp. 587–588 + Plates 508, 525).
- Boulenger GA (1893). Catalogue of the Snakes in the British Museum (Natural History). Volume I., Containing the Families ... Boidæ ... London: Trustees of the British Museum (Natural History). (Taylor and Francis, printers). xiii + 448 pp. + Plates I-XXVIII. (Lichanura trivirgata, p. 129).
- Goin CJ, Goin OB, Zug GR (1978). Introduction to Herpetology, Third Edition. San Francisco: W.H. Freeman. xi + 378 pp. ISBN 0-7167-0020-4. (Lichanura roseofusca, pp. 50, 318-319).
- Smith HM, Brodie ED Jr (1982). Reptiles of North America: A Guide to Field Identification. New York: Golden Press. 240 pp. ISBN 0-307-13666-3. (Lichanura trivirgata, pp. 138–139).
- Stebbins RC (2003). A Field Guide to Western Reptiles and Amphibians, Third Edition. The Peterson Field Guide Series ®. Boston and New York: Houghton Mifflin. xiii + 533 pp. ISBN 978-0-395-98272-3. (Charina trivirgata, pp. 343–344 + Plate 42 + Map 131).
- Wright AH, Wright AA (1957). Handbook of Snakes of the United States and Canada. Ithaca and London: Comstock Publishing Assosciates. 1,035 pp. (2 volumes). (Lichanura roseofusca, pp. 60–66, figures 17-18, map 9).
- Zim HS, Smith HM (1956). Reptiles and Amphibians: A Guide to Familiar American Species. Golden Nature Guides. New York: Simon and Schuster. 160 pp. (Lichanura roseofusca, pp. 73, 156).
- "Charina trivirgata ". Integrated Taxonomic Information System. Retrieved 25 May 2006.
- Species Lichanura trivirgata at The Reptile Database