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Spotted Leaf-nosed Snake (Phyllorhynchus decurtatus)

[/vc_column_text][gap size=”12px” id=”” class=”” style=””][/vc_column][/vc_row][vc_row][vc_column width=”1/2″][vc_single_image image=”2123″ img_size=”large” alignment=”center” style=”vc_box_rounded”][vc_column_text]Photo by Robert Bezy and Kathryn Bolles[/vc_column_text][/vc_column][vc_column width=”1/2″][vc_row_inner][vc_column_inner width=”1/2″][vc_single_image image=”2477″ img_size=”medium” alignment=”center” onclick=”img_link_large”][vc_column_text]Photo by Robert Bezy and Kathryn Bolles[/vc_column_text][gap size=”12px” id=”” class=”” style=””][/vc_column_inner][vc_column_inner width=”1/2″][vc_single_image image=”2478″ img_size=”medium” alignment=”center” style=”vc_box_rounded” onclick=”img_link_large”][vc_column_text]Spotted Leaf-nosed Snake, showing enlarged rostral scale folded over the snout. Photo by Jim Rorabaugh[/vc_column_text][gap size=”12px” id=”” class=”” style=””][/vc_column_inner][/vc_row_inner][vc_row_inner][vc_column_inner width=”1/2″][vc_single_image image=”2479″ img_size=”medium” alignment=”center” style=”vc_box_rounded” onclick=”img_link_large”][vc_column_text]Spotted Leaf-nosed Snake, Avra Valley, AZ © 2007 Manny Rubio / ASDM Sonoran Desert Digital Library[/vc_column_text][gap size=”12px” id=”” class=”” style=””][/vc_column_inner][vc_column_inner width=”1/2″][vc_single_image image=”2480″ img_size=”medium” alignment=”center” style=”vc_box_rounded” onclick=”img_link_large”][vc_column_text]Spotted Leaf-nosed Snake, Imperial Co., CA. Photo by Jim Rorabaugh[/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

The Spotted Leaf-nosed Snake (Phyllorhynchus decurtatus) is a small (< 510 mm total length [TL]) and robust burrowing snake with a distinctive enlarged, triangular rostral scale that is folded over the snout and has its edges raised up. Dorsally, this snake is gray, pinkish, cream, or tan with 17-60 brown, irregular blotches on the body that do not extend to the ventral scales. The tail has 2-5 dorsal blotches. Often there are smaller lateral blotches. A dark brown band crosses the top of the head just anterior to the eyes, then diagonals back across the eyes to the corner of the mouth. The venter is immaculate white or cream. A partial albino specimen was collected from the Borrego Valley, California in 1952 (Brattstrom 1953).

The dorsal scales are smooth to slightly keeled in some males and occur in 19 rows at mid-body. Usually two (range of 1-4) loreals are present on each side. There are 151-196 ventral scales, 20-42 divided subcaudals, and the anal plate is undivided. The pupil is vertically elliptical. Females grow to a smaller size (< 486 mm TL) than males, and their tails are shorter (8-10% of TL vs 14-15% of TL in males) (Miller and Stebbins 1973, Ernst and Ernst 2003). Five subspecies have been named, but none are currently recognized (Crother 2012). Gardner and Mendelson III, J.R. (2004) concluded that the Spotted Leaf-nosed Snake is a “geographically variable species lacking consistent geographic pattern classes.”

The dorsal pattern, combined with the distinctive rostral scale, make this small snake fairly unique in our area. Only the Saddled Leaf-nosed Snake (Phyllorhynchus browni) is similar, but it has 10 to 18 relatively large brown to slate-gray blotches or saddles on the body, and usually no lateral blotches. The morphology of the hemipenis also differs between the two Phyllorhynchus species (Cadle 2011).

In the 100-Mile Circle and southern Arizona, this is a species of the Sonoran Desert – both the Arizona Upland and Lower Colorado subdivisions of that desert. A collection from “ca 15 mi (AZ 286) S Robles Jct” (UAZ 32956) is at or near the ecotone between Sonoran desertscrub and semi-desert grassland. Collections range from 14.4 km E of Tucson west to Yuma, and north along the Florence Highway to Phoenix and westward through Maricopa County and northwest into southern and western Mohave County. It has not been found at Sabino Canyon (Lazaroff et al. 2006), nor at the Rocking K Ranch adjacent to Saguaro National Park East (Murray 1995) or in the Rincon Mountains (Flesch et al. 2010). There are no records in the Circle from Sonora, but presumably it occurs in the deserts east of Sonoyta. Elevational range in the Circle is from about 340 to 760 m. Throughout its range, it occurs from eastern California and southern Nevada south through western Arizona and western Sonora into central Sinaloa. It also occurs throughout much of the arid portions of the Baja California peninsula and on four islands in the Gulf of California (McCleary and McDiarmid 1993, Grismer 2002). Outside of the 100-Mile Circle, the species inhabits Mojave, as well as Sonoran desertscrub, and foothills and coastal thornscrub up to 1158 m elevation (Miller and Stebbins 1973, Ernst and Ernst 2003). Jones (1981) reported it from a mixed broadleaf riparian community in the Hualapai-Aquarius planning area south and southeast of Kingman, Arizona.

This is usually a species of bajadas and valley bottoms with at least some terrain and sandy to gravelly soils, and sometimes rocks. But it is unlikely to be found in mountains, and is rare or absent in sandy flats, although in some areas it occupies sand dunes (Grismer 2002). At Organ Pipe Cactus National Monument, it is a species of relatively open upland desertscrub and was the eighth most common snake found on Highway 85 (Rosen and Lowe 1996, Rosen et al. 1996). The Spotted Leaf-nosed Snake was the sixth most abundant snake on the Maricopa Road (Hwy 238) and the eighth most abundant snake on the Sun Valley Parkway, Maricopa County (Jones et al. 2011).

Collection records in the Circle run from 7 April to 20 September, but the vast majority of Spotted Leaf-nosed Snakes are found from May into July. One was excavated in Tucson on 28 October. Brattstrom (1953) found a similar pattern in the Borrego Valley of southern California. Of 497 specimens, most were found during April through July, but collections were made every month of the year except December and January. In June, males outnumbered females, presumably because they are actively pursuing mates at that time. To the south, its activity period is extended. For instance, the species is generally active year-round in the Cape Region of Baja California Sur (Grismer 2002).

This is almost exclusively a nocturnal snake. In the Borrego Valley, the greatest numbers were found between 21:00 and 23:30. The phase of the moon did not have an effect on number of snakes collected (Brattstrom 1953). This species is a good burrower, and spends inactive periods buried in sand, under surface debris, or in rodent burrows (Leviton and Banta 1964, Stebbins and Miller 1973, Ernst and Ernst 2003). In winter, Cowles (1941) found Spotted Leaf-nosed Snakes in southern California buried in sand dunes to as deep as 76 cm. The purpose of the enlarged rostral scale is unknown, but it may protect the snout during burrowing activities, or aid in excavating squamate eggs, its principle food (Miller and Stebbins 1973).

In Spotted Leaf-nosed Snakes from the Borrego Valley, the smallest female with eggs was 325 mm SVL and probably three years of age. Eggs were found in snakes mostly in June and July, but also less commonly in April, May, and August. Clutch size was 3-4 (Brattstrom 1953). In the Baja Peninsula, gravid snakes were most often found in June and July, and occasionally in May (Grismer 2002). In specimens from Arizona, the smallest reproductively active males and females were 244 and 248 mm SVL, respectively. Oviductal eggs were found in females collected in July, and only 36% of adult females were reproductively active (Goldberg 1996). Stebbins and McGinnis (2012) report clutch size ranges from two to six. Eggs hatch probably during late August to late September; hatchlings resemble small adults and are about 160-180 mm TL (Trutnau 1986, Grismer 2002, Ernst and Ernst 2003).

Klauber (1935) reported that the Spotted Leaf-nosed Snake eats lizard eggs and the tails of Banded Geckos (Coleonyx variegatus). Captives have also been observed to eat Banded Gecko tails (Miller and Stebbins 1973). Banded Geckos are able to detect integumentary chemicals from Spotted Leaf-nosed Snakes, and in response they typically wave the tail, flee, or engage in defensive attacks (Dial et al. 1989). In the Borrego Valley, Brattstrom (1953) found eggs, probably from Coleonyx, in most stomachs examined, the legs from a small lizard (probably a Zebra-tailed Lizard, Callisaurus draconoides) in one specimen, and an unidentified Hymenopteran (sawflies, wasps, bees and ants) in another. In Spotted Leaf-nosed Snake specimens from southern Nevada, 28 of 109 examined contained food items in the stomach (Clark 1968). All 28 contained eggs. Two size classes of eggs were represented. The author surmised that the smaller eggs were from Banded Geckos and/or Common Side-blotched Lizards (Uta stansburiana), and the larger eggs were from Tiger Whiptails (Aspidoscelis tigris) and/or Zebra-tailed Lizards (Callisaurus draconoides). Rosen et al. (1996) found only lizard eggs in Spotted Leaf-nosed Snakes from the Organ Pipe Cactus National Monument region.  Gardner and Mendelson III, Jr. (2003) found squamate eggs in Spotted Leaf-nosed Snake specimens; two contained Coleonyx tails. Jones and Hegna (2005) found a squamate egg inside a Spotted Leaf-nosed Snake specimen from the Maricopa Road, Maricopa County. The snake was inside the stomach of a road-kill California Kingsnake (Lampropeltis californiae). Goldberg and Bursey (2001) examined Helminths in Spotted Leaf-nosed Snakes.

The Spotted Leaf-nosed Snake is a species of least concern on the IUCN’s 2014 Red List. With a valid Arizona hunting license, four can be collected per year or held in possession, alive or dead, although collection is prohibited in protected areas such as Saguaro National Park and Organ Pipe Cactus National Monument without special authorization. This species is eliminated by urban and agricultural development, such as in the Phoenix and Tucson metropolitan areas and adjacent agriculture. Along Highway 85 from Ajo to the international boundary, the Spotted Leaf-nosed Snake was the most-commonly encountered snake in 1949, but dropped to the eighth most common snake during 1987-1994 (Hensley 1950, Rosen et al. 1996).  Rosen et al. (1996) suggest it may have declined due to increasing vegetation cover during that time period.

Suggested Reading:

Brattstrom, B.H. 1953. Notes on a population of leaf-nosed snakes Phyllorhynchus decurtatus perkinsi. Herpetologica 9(2): 57-64.

Brennan, T.C., and A.T. Holycross. 2006. Amphibians and Reptiles in Arizona. Arizona Game and Fish Department, Phoenix, AZ.

Cadle, J.E. 2011. Hemipenial morphology in the North American snake genus Phyllorhynchus (Serpentes: Colubridae), with a review of and comparisons with natricid hemipenes. Zootaxa 3092:1–25.

Crother, B.I. 2012. Scientific and standard English names of amphibians and reptiles of North America north of Mexico, with comments regarding confidence in our understanding, seventh edition. Society for the Study of Amphibians and Reptiles, Herpetological Circular (39):1-92.

Dial. B.E., P.J. Weldon, and B. Curtis. 1989. Chemosensory identification of snake predators (Phyllorhynchus decurtatus) by Banded Geckos (Coleonyx variegatus). Journal of Herpetology 23(3):224-229.

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

Flesch, A.D., D.E. Swann, D.S. Turner, and B.F. Powell. 2010. Herpetofauna of the Rincon Mountain, Arizona. The Southwestern Naturalist 55(2):240–253.

Gardner, S.A. & Mendelson III, J.R. 2003. Diet of the Leaf-nosed Snakes, Phyllorynchus (Squamata: Colubridae): squamate egg specialists. The Southwestern Naturalist 48(4):550-556.

Gardner, S.A. & Mendelson III, J.R. 2004. Taxonomy and geographic variation in the leaf-nosed Snake Phyllorhynchus decurtatus (Squamata: Colubridae). Journal of Herpetology 38(2): 187-196.

Goldberg, S.R. 1996. Reproduction in the Saddled Leaf-nosed Snake, Phylloryhnchus browni, and the Spotted Leaf-nosed Snake, Phyllorynchus decurtatus, from Arizona. Journal of Herpetology 30(2):280-282.

Goldberg, S.R., and C.R. Bursey. 2001. Helminths of six species of Colubrid snakes from Southern California. Bulletin of the Southern California Academy of Sciences 100(2): 109-116.

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.

Hensley, M.M. 1950. Results of a herpetological reconnaissance in extreme southern Arizona and adjacent Sonora with a description of a new subspecies of sonoran whipsnake, Masticophis bilineatus. Transactions of the Kansas Academy of Science 53(2):270-288.

Jones, T.R., R.D. Babb, F.R. Hensley, C. LiWanPo, and B.K. Sullivan. 2011. Sonoran Desert snake communities at two sites: Concordance and effects of increased road traffic. Herpetological Conservation and Biology 6:61-71.

Jones, T.R., and R.H. Hegna. 2005. Phylloryhnchus decurtatus (Spotted Leaf-nosed Snake). Predator-prey interactions. Herpetological Review 36(1):70.

Klauber, L.M. 1935. Phyllorhynchus, the leaf-nosed snake. Bulletin of the Zoological Society of San Diego12:1-27.

Lazaroff, D.W., P.C. Rosen, and C.H. Lowe. 2006. Amphibians, Reptiles, and Their Habitats at Sabino Canyon. University of Arizona Press, Tucson.

Leviton, A.E., and B.H. Banta. 1964. Midwinter reconnaissance of the herpetofauna of the Cape Region of Baja California, Mexico. Proceedings of the California Academy of Science, 4^th series, 30:127-156.

McCleary R J R; McDiarmid R W 1993. Phyllorhynchus decurtatus (Cope), spotted leaf-nosed snake. Catalogue of American Amphibians and Reptiles 580: 1-7.

Murray, R.C. 1995. Reptile and amphibian inventory. Pages 50-79 in L.K. Harris and C.R. Schwalbe (eds), Wildlife inventory of the Rincon Valley. Arizona Game and Fish Department, Heritage Project U93007. Final report. Cooperative Park Studies Unit, University of Arizona, Tucson.

Rosen, P.C., P.A. Holm, and C.H. Lowe. 1996. Ecology and status of shovelnose snakes (Chionactus) and leafnose snakes (Phyllorhynchus) at and near Organ Pipe Cactus National Monument. Final Report, Arizona Game and Fish Department, Phoenix.

Stebbins, R.C., and S.M. McGinnis. 2012. Field Guide to Amphibians and Reptiles of California. California Natural History Guides, University of California Press, Berkeley.

Trutnau, L. 1986. Nonvenomous snakes: A comprehensive guide to care and breeding of over 100 species. Stuttgart, Germany, Eugen Ulmer.

Turner, F.B., and R.H. Wauer. 1963. A survey of the herpetofauna of the Death Valley area. Great Basin Naturalist 23:119-128.

Author: Jim Rorabaugh

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