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Western Shovel-nosed Snake (Chionactis annulata)

[/vc_column_text][gap size=”12px” id=”” class=”” style=””][/vc_column][/vc_row][vc_row][vc_column width=”1/2″][vc_single_image image=”174″ img_size=”large” alignment=”center” style=”vc_box_rounded”][vc_column_text]Shovel-nosed Snake, Yuma Desert, AZ. Photo by Jim Rorabaugh[/vc_column_text][/vc_column][vc_column width=”1/2″][vc_row_inner][vc_column_inner width=”1/2″][vc_single_image image=”2526″ img_size=”medium” alignment=”center” onclick=”img_link_large”][vc_column_text]Mojave Shovel-nosed Snake © 1974 Mark A. Dimmitt / ASDM Sonoran Desert Digital Library[/vc_column_text][gap size=”12px” id=”” class=”” style=””][/vc_column_inner][/vc_row_inner][/vc_column][/vc_row][vc_row][vc_column width=”1/6″][/vc_column][vc_column width=”2/3″][vc_column_text]

Description

Editor’s Note:  The following paper was published in mid-2014:

Wood, D.A., R.N. Fisher, and A.G. Vandergast. 2014. Fuzzy boundaries: Color and gene flow patterns among parapatric lineages of the Western Shovel-Nosed Snake and Taxonomic Implication. PLOS ONE, www.plosone.org, May 2014, 9(5):e97494.

Building upon the work of Wood et al. (2008) cited in the paper below, the authors propose that two species be recognized: Chionactis occipitalis and C. annulata. In addition, they recommend retention of two subspecific designations within C. annulata (C. a. annulata and C. a. klauberi).  As defined by Wood et al. (2014), the distributional boundary between C. occipitalis and C. annulata is at the Mojave-Sonoran Desert ecotone.  Thus, only C. annulata occurs within the 100-Mile Circle.  The only area of Arizona where C. occipitalis occurs isnorth of the Bill Williams River in the northwest. The distribution of Chionactis annulata klauberi is more extensive than previously thought.  It extends northwest from the Phoenix area into northwestern La Paz County, as well as in areas previously recognized, and as described in the paper below.  Chionactis annulata annulata occurs elsewhere in southwestern Arizona, northwestern Sonora, and in the Sonoran Desert of California.

On 23 September 2014 the Fish and Wildlife Service published a 12-month finding on the petition to list the Tucson Shovel-nosed Snake as threatened or endangered under the Endangered Species Act.  Listing of the subspecies was found to be not warranted, based in part on the Wood et al. (2014) paper that considerably expanded the range of the subspecies.  As a result, the Tucson Shovel-nosed Snake is no longer a candidate for federal listing.  The finding and other documents regarding the snake can be found at:

http://www.fws.gov/southwest/es/arizona/TucsonShovelNosed.htm

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The Western Shovel-nosed Snake (Chionactis occipitalis) was described by Edward Hallowell as Rhinostoma occipitale in 1854. The type specimen, which is lost, was collected in 1853 by A. L. Heerman, a surgeon and naturalist, during the Pacific Railroad Expedition in the Mojave Desert of California, probably from the vicinity of the Mojave River in western San Bernardino County (Klauber 1951, Mahrdt et al. 2001). Cope (1860) was the first to use the genus name Chionactis for this species, although in subsequent publications it was at times assigned to Contia (Garman 1884) or Sonora (Slevin 1913, Stickel 1941). The Sonoran Shovel-nosed Snake (Chionactis palarostris) was recognized as a species distinct from the Western Shovel-nosed Snake by Klauber (1937). Funk (1967) described C. saxatilis from the vicinity of Fortuna Mine in the Gila Mountains, Yuma County, Arizona, but the description was not widely accepted (Cross 1979, Mahrdt et al. 2001) and that taxon is considered synonymous with C. occipitalis by Crother (2012).  

Four subspecies of the Western Shovel-nosed Snake are currently recognized (Crother 2012), including C. o. occipitalis, the Mohave Shovel-nosed Snake; C. o. annulata, the Colorado Desert Shovel-nosed Snake; C. o. talpina, the Nevada Shovel-nosed Snake; and C. o. klauberi, the Tucson Shovel-nosed Snake (Klauber 1951, Cross 1979). However, Marhdt et al. (2001) and other authors (e.g. Wright and Wright 1957) have noted that these forms intergrade widely throughout the range of the species, and some populations are not diagnosable. Based on analysis of mitochondrial DNA and 14 morphological characters, Wood et al. (2008) found no evidence for four divisions within C. occipitalis. Rather, they identified two clades, one in the northwest and the other in the southeast portion of the species’ range. The former includes specimens typically referred to C. o. talpina, C. o. occipitalis, and C. o. annulata. The southeastern clade includes C. o. klauberi and most of the range of C. o. annulata. The division between the two clades is roughly along the boundary between the Mojave and Sonoran deserts.

Description and Similar SpeciesThe Western Shovel-nosed Snake is small (< 432 mm total length (TL), the tail is 16-21% of TL) and strongly banded dorsally on the body and tail (Fig. 1, 2, & 3). The snout is yellow or cream-colored, sometimes mixed with red-orange or orange. Atop the head

between and posterior to the eyes is a black crescent, the anterior edge of which is concave. Posterior to the black crescent are 17-40 black to brown bands on the body and 5-13 on the tail on a cream or yellow background.  Between these dark bands are often red-orange to brown or black saddles. These saddles do not cross the venter, but at least some of the dark bands do. The color and the degree to which these saddles manifest vary by subspecies. The Mohave Shovel-nosed Snake has little or no evidence of saddles. Saddles are variably expressed in the Colorado Desert Shovel-nosed Snake (Figs. 1 & 2), but usually some orange or red-orange is present between the dark bands, and some specimens are strikingly tricolored. The Tucson Shovel-nosed Snake has red to orange-red saddles that are nearly always infused with dark markings. In the Nevada Shovel-nosed Snake, the primary bands are brown, and the saddles are orange-red, orange-brown, brown, or black (Stickel 1941, Klauber 1951, Mahrdt et al. 2001, Ernst and Ernst 2003).

The snout is relatively long and the jaw is countersunk (Fig. 4). The rostral scale is broad and pointed posteriorly where it meets the suture between the two internasals, which are broadly in contact with each other. One loreal scale is usually present on each side. The smooth dorsal scales are arranged in 15 (rarely 14 or 16) rows at mid-body, and the anal plate and subcaudals are divided (Klauber 1951, Ernst and Ernst 2003).

In our region, the Western Shovel-nosed Snake most closely resembles the Sonoran Shovel-nosed Snake, the Variable Sandsnake (Chilomeniscus stramineus), banded forms of the Western Groundsnake (Sonora semiannulata), and the Sonoran Coralsnake (Micruroides euryxanthus). The Sonoran Shovel-nosed Snake has a relatively wide black band or hood atop the head that is straight or nearly so anteriorly, rather than concave, it usually has fewer than 21 black dorsal bands on the body, 4-5 black dorsal bands on the tail, and has a relatively blunt snout. The Variable Sandsnake is comparatively stout, the rostral scale separates the internasals, and in the banded form that occurs in Arizona, the yellow, orange, or red-orange bands are in contact with the black bands. All bands on the Sonoran Coralsnake encircle the body, the snout is black, and the tail lacks red bands. In banded forms of the Western Groundsnake, the red or orange bands contact the black bands and a dark blotch is present on each scale in the lateral portions of the lighter bands.

Distribution and Habitat Use

The Western Shovel-nosed Snake occurs in the deserts of southeastern California, southern Nevada, and western Arizona in the U.S., and northeastern Baja California and northwestern Sonora in Mexico (Ernst and Ernst 2003). Of the four subspecies, Chionactis o. talpina is the northern-most, occurring in Inyo County, California and adjacent portions of Nevada.  Chionactis o. occipitalis occurs south of talpina in the Mojave Desert of California, adjacent Nevada, and Arizona north of the Bill Williams River. Chionactis o. annulata occurs in the Sonoran Desert of southeastern California, southwestern Arizona, and south into northeastern Baja California probably to Puertocitos and in northwestern Sonora to the vicinity of Puerto Lobos. Chionactis o. klauberi occurs in the Sonoran Desert of central Pima, eastern Maricopa, and western Pinal counties (Mahrdt et al. 2001, Grismer 2002, Ernst and Ernst 2003). The range of the subspecies in Arizona and Sonora is illustrated in Fig. 5. Of Wood et al.’s (2008) two clades, only the southeastern clade occurs in Arizona and Sonora.

At Organ Pipe Cactus National Monument, Rosen and Lowe (1996) found that Chionactis occipitalis was primarily a species of the valley bottoms and lower-most bajadas, whereas C. palarostris was more associated with the middle and upper bajadas. On the Sun Valley Parkway west of Phoenix, and Highway 238 through Mobile to the south of Phoenix, both of which traverse flats and lower bajadas, the Western Shovel-nosed Snake accounted for 3.4 and 7.8%, respectively, of all snakes encountered during nighttime road riding (Jones et al. 2011).

The Western Shovel-nosed Snake’s countersunk jaw, valves that close the nostrils to sand entry, and smooth scales lend themselves well to a life in sandy substrates (Mosauer 1935, Klauber 1951). The snake’s concave ventral surface may be an adaptation to facilitate efficient respiration while burrowing (Pough 1969).  This species is commonly encountered in valleys with abundant windblown sand.  In an area of sandy hummocks in the Coachella Valley, California, Cowles (1941) noted that of 96 reptiles excavated by land grading operations, 41 were Western Shovel-nosed Snakes. Rorabaugh (2002) observed 36 Western Shovel-nosed Snakes during 50.2 hours of walking surveys in sandy flats of the Yuma Desert, and based on an ad hoc mark and recapture effort suggested densities of this snake may approach that of some common desert lizards. Although the Western Shovel-nosed Snake is common on low dunes and vegetated larger dunes, such as the Mohawk Dunes in Yuma County, it is likely scarce or absent in the interior of large, unvegetated dunes, like those found in the Gran Desierto de Altar, Sonora, and the Algodones Dunes in southeastern California. Although most commonly encountered in valleys, this species also occurs on dissected bajadas, and even penetrates into desert mountains along sandy arroyos where soils may be quite gravelly and coarse (pers. observations). A Western Shovel-nosed Snake was found crawling about on a rocky slope about 10 m above a sandy wash near Morongo Valley, California (Miller and Stebbins 1964). Funk (1967) found them in rocky areas with little sand in the Gila Mountains.

Throughout its range, the Western Shovel-nosed Snake is a desert dweller, occurring from below sea level in portions of California to nearly 1500 m (Mahrdt et al. 2001). In the 100-Mile Circle, it occurs primarily in the Colorado Desert Subdivision of Sonoran desertscrub, but also sparingly into the Arizona Upland Subdivision. Elevational range in the Circle is about 325 m near the Gila River south of Phoenix to 700 m in the Waterman Mountains.

Activity and Behavior

Throughout its range, the Western Shovel-nosed Snake has been collected every month of the year; however, in the 100-Mile Circle, it has been found from March to early August, but most are encountered during April into early June. October, November, December, and February records exist for Yuma County and I have observed the distinctive tracks of this species (Fig. 6) near Puerto Peñasco and in the Gran Desierto de Altar, Sonora in mid-February. In Pima, Pinal, and Maricopa counties, the greatest number of collections has occurred in May (Rosen 2003).  During the winter they have been found dormant in burrows or buried in loose sand at depths of 7.7-60 cm (Cowles 1941, Shaw 1953, Wright and Wright 1957).

This is primarily a nocturnal snake. Klauber (1951) found they are most commonly encountered on roads from 1900 to 2200 h and when temperatures are from 21-32⁰ C. However, they are occasionally found on the surface in the morning and late afternoon (Klauber 1951, Brattstrom 1952, Warren 1953, Miller and Stebbins 1964). The 36 Western Shovel-nosed Snakes observed by Rorabaugh (2002) were all during daylight hours, from 0635 to 1215 and 1500 to 1930 h. Surface temperatures in the sun ranged from 24-46⁰ C. Cowles and Bogert (1944) listed the minimum and maximum voluntary temperatures for this species as 20 and 31⁰ C, respectively.

These snakes are most commonly found on roads at night, but as mentioned, they can be encountered on the surface while walking through their habitat. During walking surveys on the eastern edge of the Algodones Dunes, Imperial County, California, I have observed up to seven of these snakes during a three hour period after sunset. Twelve were found at night during two hours while walking with a Coleman lantern in the Coachella Valley (Warren 1953). Following their distinctive serpentine tracks (Fig. 5) across loose sand sometimes results in a capture (Warren 1953, pers. observations). They also are readily captured in pitfall traps (pers. observations), and are occasionally found under boards or other surface debris during the day (Cunningham 1966).  Funk (1967) found Western Shovel-nosed Snakes in the Gila Mountains by turning rocks.

Through undulatory movements, this species can quickly “swim” into loose sand, almost as easily and rapidly as it moves about on the surface (Klauber 1951). It spends most of the daylight hours underground in rodent or scorpion burrows, under surface debris, or simply buried in loose sand (Klauber 1951, Miller and Stebbins 1964). The end of the tail of buried snakes may be exposed on the surface (Warren 1953, Norris and Kavanau 1966). Surface active snakes can move quite rapidly, and as with other tricolored banded snakes, the banding pattern appears to blur during rapid movement. If confronted by a human or predator, this snake typically flees from the threat at high speed. However, if cornered, it may coil and strike repeatedly, usually with the mouth closed. Warren (1953) found that some Western Shovel-nosed Snakes pursued in the field climbed short distances up into creosote bushes (Larrea tridentata). Captured Western Shovel-nosed Snakes will usually smear their captors with musk and feces (Ernst and Ernst 2003). During a photo shoot that required repeated repositioning of the snake, Mitchell (1978) observed a captive that rolled into a tight ball with its head hidden amidst its coils.

Klauber (1951) reported that Western Shovel-nosed Snakes were preyed upon by a domestic cat and a Coachwhip (Coluber flagellum). Mahrdt and Banta (1996) found two Western Shovel-nosed Snakes impaled on an ocotillo (Fouquieria splendens), apparently by a Loggerhead Shrike, in the Yuha Desert of Imperial County, California. In 1978, I also observed a Western Shovel-nosed Snake impaled, almost certainly by a Loggerhead Shrike, on a desert willow (Chilopsis linearis) in Bow Willow Canyon, eastern San Diego County, California. C.H. Lowe found remnants of a Western Shovel-nosed Snake in a Great Horned Owl pellet at the Mohawk Dunes (Mahrdt et al. 2001).

The smallest mature male reported was 194 mm SVL (Goldberg 1997). Ernst and Ernst (2003) surmised that most individuals mature at 250-260 mm TL. Mating behavior has been observed in the wild in late May (Klauber 1951). Clutches of usually 2-4 eggs (6 was noted by Funk (1967), and Cowles (1941) noted 6 and 9 ova in two females) are laid primarily from May into July (Mattison 1989, Golberg 1997, Goldberg and Rosen 1999); however, Funk (1967) reported three captive females from the Gila Mountains that laid eggs in late March. Those eggs hatched 94-99 days later.  Hatching probably occurs from June into September. Hatchlings resemble adults but are 112-124 mm TL (Klauber 1951, Wright and Wright 1957, Funk 1967). On 10 May, Goode and Schuett (1994) observed combat between two adult, captive males captured the previous month at the Mohawk Dunes. The snakes intertwined and writhed under the sand for less than a minute.  In a subsequent encounter, short bouts (less than 30 seconds) of biting and entwining occurred. One male was also observed to vibrate its tail when the other approached.

Diet

This small snake is almost certainly an active forager, seeking prey on the surface and perhaps below ground, as well. Scorpions, centipedes, an egg from a Common Side-blotched Lizard (Uta stansburiana), spiders, moth or butterfly pupa, beetles and their larvae, various insect parts, and unidentified pupa have been found in the stomachs of Western Shovel-nosed Snakes (Klauber 1951, Rosen et al. 1996, see review in Ernst and Ernst 2003). I observed a Western Shovel-nosed Snake eating a small scorpion (probably Paruroctonus or Smeringurus) at night in an area of windblown sand in the Mohawk Dunes. Captives have consumed moths, crickets, grasshoppers, silverfish, earwigs, cockroaches, termites, spiders – including black widows, mealworm larvae and pupa, waxworm larvae, various other insects, scorpions, centipedes, solpugids, a hatchling Common Side-blotched Lizard, and the tail from a hatchling Tiger Whiptail (Aspidoscelis tigris) (Klauber 1951, Stebbins 1954, Cunningham 1959, Norris and Kavanau 1966, Funk 1967, Glass 1972, Mattison 1989, Rosen et al. 1996). These snakes are adept at capturing and eating scorpions. They are sometimes stung in the process, but do not show any apparent ill effects (Norris and Kavanau 1966, Glass 1972). Western Shovel-nosed Snakes will often hold larger prey down with a loop of the body, although captive snakes did not employ this strategy with scorpions (Glass 1972). Three moderately enlarged, grooved teeth are present on each side in the rear of the upper jaw (Wright and Wright 1957) that may be used to deliver salivary toxins to prey.

Conservation

Most of the urban and agricultural development in the desert Southwest occurs in valleys, and as the Western Shovel-nosed Snake is primarily a denizen of valleys, it is not surprising that habitat loss has occurred in many areas, particularly in the Coachella, Imperial, and Borrego valleys of California; the Mexicali and Río Colorado valleys in Mexico; the Yuma Valley and Mesa; the Gila River Valley; and in the Phoenix metropolitan area and Interstate 10 Tucson-Phoenix corridor in Arizona. Nonetheless, over the entire range of the species, habitat loss is relatively small and localized. The Western Shovel-nosed Snake is listed as a species of least concern on the IUCN’s 2013 Red List. With a valid Arizona hunting license, four may be collected per year or held in possession alive or dead, except that take of these snakes is prohibited without special authorization in protected areas, such as National Wildlife Refuges and National Park Service lands.

On 15 December 2004, the Center for Biological Diversity (2004) petitioned the U.S. Fish and Wildlife Service (USFWS) to list the Tucson Shovel-nosed Snake as endangered with critical habitat under the Endangered Species Act. In a Federal Register notice dated 31 March 2010, USFWS found that the Tucson Shovel-nosed Snake (excluding intergrade populations) warranted listing but was precluded by higher priority listing actions (USFWS 2010). Nonetheless, the warranted finding adds the Tucson Shovel-nosed Snake to the list of candidate species and commits USFWS to publishing a rule proposing the subspecies as threatened or endangered, possibly with critical habitat, barring new information that such a rule is unnecessary. The primary basis for the warranted finding is that as of 2001, over one-third of the area within the range of the Tucson Shovel-nosed Snake had been converted to urban or agricultural development, and that anticipated future development and habitat degradation is likely to increase that percentage substantially unless protective measures are taken (USFWS 2010). The last Tucson Shovel-nosed Snake seen in Pima County was in the Avra Valley in 1979 (Rosen 2003). Recent surveys indicate populations persist in areas dominated by creosote flats along State Route 79 between Florence and Highway 60, along the Maricopa Road between Maricopa and Gila Bend, east of the San Tan Mountains, along State Route 349 between Maricopa and Casa Grande, south of Interstate 8 near the northern boundary of the Tohono O’odham Nation, in the vicinity of the Santa Cruz Flats near Eloy and Picacho, and potentially in the Rainbow Valley and portions of Vekol Wash (Rosen 2003, 2007; Mixen and Lowery 2008; USFWS 2010).

USFWS’s 2010 finding downplays Wood et al.’s (2008) work by saying that the “study’s inference was based on a single genetic marker of mitochondrial DNA and did not include examination of nuclear markers, which would more fully elucidate our understanding of the taxonomic standing of this subspecies.” In the latest version of the Society for the Study of Amphibians and Reptiles (SSAR) list of amphibians and reptiles of North America (Crother 2012), the four subspecies of Chionactis, including the Tucson Shovel-nosed Snake, are still recognized. However, if the conclusions of Wood et al. (2008) are subsequently accepted, and the Tucson Shovel-nosed Snake is no longer recognized as a valid taxon, USFWS may be hard pressed to identify a listable entity within Chionactis that meets the definition of a threatened or endangered “species” under sections 3 and 4 of the Endangered Species Act, even though the 2010 finding and the 2004 petition make a strong case that Western Shovel-nosed Snakes in the Tucson to Phoenix area are substantially threatened with habitat loss and degradation.

Literature Cited

Brattstrom, B.H. 1952. Diurnal activities of a nocturnl animal. Herpetologica 8:61-63.

Center for Biological Diversity. 2004. Petition to list the Tucson Shovel-nosed Snake (Chionactis occipitalis klauberi) as an endangered species. Center for Biological Diversity, Portland, OR.

Cope, E.D. 1860. Catalogue of the Colubridae in the museum of the Academy of Natural Sciences of Philadelphia, with notes and descriptions of new species. Part 2. Proceedings of the Academy of Natural Sciences, Philadelphia 12:241-266.

Cowles, R.B. 1941. Observations on the winter activities of desert reptiles. Ecology 22:125-140

Cowles, R.B., and C.M. Bogert. 1944. A preliminary study of the thermal requirements of desert reptiles. Bulletin of the American Museum of Natural History 83:265-296.

Cross, J.K. 1979. Multivariate and univariate character geography in Chionactis (Reptilia; Serpentes). Ph.D dissertation, University of Arizona, Tucson.

Crother, B. I. (ed.) 2012. Standard common and current scientific names for North American amphibians, turtles, reptiles, and crocodilians, seventh edition. SSAR Herpetological Circular 39:1-92.

Cunningham, J.D. 1959. Reproduction and food of some California snakes. Herpetologica 15:17-19.

Cunningham, J.D. 1966. Additional observations on the body temperatures of reptiles. Herpetologica 22:184-189.

Ernst, C.H., and E.M. Ernst. 2003. Snakes of the United States and Canada. Smithsonian Books, Washington, D.C.

Funk, R.S. 1967. A new Colubrid snake of the genus Chionactis from Arizona. The Southwestern Naturalist 12(2):180-188.

Garman, S.W. 1884 (dated 1883). The reptiles and batrachians of North America, Part 1: Ophidia-Serpents. Memoires of the Museum of Comparative Zoology 8(3): 1-185

Glass, J.K. 1972. Feeding behavior of the Western Shovel-nosed Snake, Chionactis occipitalis klauberi, with special reference to scorpions. The Southwestern Naturalist 16:445-447.

Goode, M.J., and G.W. Schuett. 1994. Male combat in the western shovelnose snake (Chionactis occipitalis). Herpetological Natural History 2(1):115-117.

Golberg, S.R. 1997. Reproduction in the western shovel-nosed snake, Chionactis occipitalis (Colubridae), from California. Great Basin Naturalist 57:85-87.

Goldberg, S.R., and P.C. Rosen. 1999. Reproduction in the Sonoran shovelnosed snake (Chionactis palarostris) and the western shovelnosed snake (Chionactis occipitalis) (Serpentes: Colubridae). Texas Journal of Science 51:153-158.

Grismer, L. 2002. Amphibians and Reptiles of Baja California Including its Pacific Islands and the Islands in the Sea of Cortes. University of California Press, Berkeley.

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Mattison, C. 1989. Notes on shovel-nosed snakes and sand snakes, Chionactis and Chilomeniscus. British Herpetological Society Bulletin 28:25-30.

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Mitchell, J.C. 1978. Balling behavior in Chionactis occipitalis (Reptilia, Serpentes, Colubridae). Journal of Herpetology 12:435-436.

Mixen, R., and S. Lowery. 2008. Tucson Shovel-nosed Snake surveys on the Florence Military Reservation. http://www.azgfd.gov/w_c/research_TSNS.shtml.

Mosauer, W. 1935. The reptiles of a sand dune area and its surroundings in the Colorado Desert, California: A study in habitat preferences. Ecology 16:13-27.

Norris, K.S., and K.L. Kavanau. 1966. The burrowing of the Western Shovel-nosed Snake, Chionactis occipitalis Hallowell, and the undersand environment. Copeia 1966:650-664.

Pough, F.H. 1969. The morphology of undersand respiration in reptiles. Herpetologica 25:216-233.

Rorabaugh, J.C. 2002. Diurnal activity and a minimum population density estimate of the Colorado Desert shovel-nosed snake, Chionactis occipitalis annulata. Sonoran Herpetologist 15(4):42-43.

Rosen, P.C. 2003. Avra Valley snakes: Marana survey report for Tucson Shovel-nosed Snake (Chionactis occipitalis klauberi). Prepared for the Town of Marana, University of Arizona.

Rosen, P.C. 2007. 2007 survey results for the Tucson Shovel-nosed Snake (Chionactis occipitalis klauberi), with evidence for ecological change in south-central Arizona. University of Arizona.

Rosen, P.C., P.A. Holm, and C.H. Lowe. 1996. Ecology and status of shovelnose snakes (Chionactis) and leafnose snakes (Phylloryhnchus) at and near Organ Pipe Cactus National Monument, Arizona. Heritage Program, Arizona Game and Fish Department, Phoenix.

Rosen, P.C., and C.H. Lowe. 1996. Ecology of the amphibians and reptiles at Organ Pipe Cactus National Monument, Arizona. USDI, National Biological Service, Cooperative Park Studies Unit, University of Arizona and the National Park Service, Organ Pipe Cactus National Monument. Technical Report No. 53.

Shaw, C.E. 1953. A hibernating Chionactis occipitalis annulata. Herpetologica 9:72

Slevin, J.R. 1913. A handbook of reptiles and amphibians of the Pacific states including certain eastern species. California Academy of Sciences Special Publication, 1-73.

Stebbins, R.C. 1954. Amphibians and Reptiles of Western North America. McGraw-Hill Book Co., New York.

Stickel, W.H. 1941. The subspecies of the spade-nosed snake, Sonora occipitalis. Bulletin of the Chicago Academy of Science 6:135-140.

USFWS. 2010. Endangered and threatened wildlife and plants; 12-Month finding on a petition to list the Tucson Shovel-nosed Snake (Chionactis occipitalis klauberi) as threatened or endangered with critical habitat. Federal Register 75(61):16050-16065.

Warren, J.W. 1953. Notes on the behavior of Chionactis occipitalis. Herpetologica 9:121-124.

Wood, D.A., J.M. Meik, A.T. Holycross, R.N. Fisher, and A.G. Vandergast. 2008. Molecular and phenotypic diversity in Chionactis occipitalis (Western Shovel-nosed Snake), with emphasis on the status of C. o. klauberi (Tucson Shovel-nosed Snake). Conservation Genetics 9:1489–1515.

Wright, A.H., and A.A. Wright. 1957. Handbook of Snakes of the United States and Canada. Volume 1. Comstock Publishing Associates, Ithaca, NY.

Author: Jim Rorabaugh. Originally published in the Sonoran Herpetologist June 2014:38-44.

For additional information on this species, please see the following volumes and pages in the Sonoran Herpetologist: 2002 Apr:42-43; 2010 May:74.[/vc_column_text][/vc_column][vc_column width=”1/6″][/vc_column][/vc_row][vc_row][vc_column][gap size=”30px” id=”” class=”” style=””][/vc_column][/vc_row]