Giant Spotted Whiptail (Aspidoscelis stictogramma)

Giant Spotted Whiptail, Sierra Aconchi, Sonora, MX. Photo by Jim Rorabaugh

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Description

The Giant Spotted Whiptail (Aspidoscelis stictogramma) is our largest (< 140 SVL and 510 mm total length) whiptail, and as with other whiptails it has large plate-like scales on a pointed head, eight longitudinal rows of quadrangular smooth scales on the venter, and an elongated body and tail.  The unbroken tail is usually more than twice as long as the body. The scales on the central rear surface of the forearm (postantebrachial scales) are distinctly enlarged.  When present, the paravertebral light stripes are separated by 5-11 scales.  Scales around the middle of the body number more than 90, and usually more than 98.  This is a bisexual species.

The Giant Spotted Whiptail goes through considerable ontogenetic or developmental changes in coloration and pattern as it ages.  The dorsum of hatchlings and juveniles is brown or dark brown with usually six (sometimes 7) light dorsal stripes with no spotting between the stripes.  The seventh, mid-dorsal stripe, when present, may be diffuse or manifests only as a row of light dots. The tail is orange to orange-red, and that coloration may extend onto the back, limbs, and head.  As the lizards age, sharp-edged light spots develop in the dark fields, the stripes gradually fade and may break up into rows of light spots, orange coloration on the tail fades or disappears but often becomes more prominent on the head and body, and hues of blue, yellow, green or combinations thereof may develop on the body.  The dorsal surface of the limbs of old individuals is usually heavily spotted.  The venter is pale and unmarked (Degenhardt et al. 1996, Rosen et al. 2002, Brennan and Holycross 2006, Rosen 2009).  This species was until recently known as Aspidoscelis burti or Cnemidophorus burti.  Two subspecies were recognized: A. b. stictogramma and A. b. burti.  The latter form is restricted to the coastal region of Sonora in the vicinity of Guaymas and San Carlos.  Based on differences in body size, scutellation, and color patterns, Walker and Cordes (2011) suggested that these represent distinct species.  That suggestion was adopted by Crother (2012).  No subspecies of A. stictogramma are recognized.  Taylor (2006) described a hybrid between A. sonorae and A. stictogramma. 

Based on a combined analysis of mitochondrial DNA, morphology, and allozymes, Reeder et al. (2002) considered the Red-backed Whiptail (Aspidoscelis xanthonota) as a subspecies of the Giant Spotted Whiptail.  However, others consider the two to be distinct species because they are allopatric and morphologically diagnosable (Collins 1991, Dessauer and Cole 1991, and Crother 2012). The Giant Spotted Whiptail is closely related to the Western Mexico Whiptail (A. costata) of Mexico, and the taxonomic divisions within this complex of whiptails needs further study (Reeder et al. 2002).

Exceptionally large, heavily-spotted Giant Spotted Whiptails are easily distinguished from other whiptails in the 100-Mile Circle.  No other whiptail in our area grows larger than 120 mm SVL, and none have more than 90 scales around the mid-body.  That latter character, although diagnostic, is not useful in casual observations of lizards.  Striped juveniles (with or without light spots between the stripes) can be and often are confused with other species.  But the orange to orange-red tail of the hatchling and juvenile distinguishes the Giant Spotted Whiptail from other species in the Circle.  The dorsum of large, old Sonoran Spotted Whiptails (Aspidoscelis sonorae) may rarely become dominated by light spots, but stripes are always retained at least on the neck.  The tail of that species is tan, orange-tan, or brown, sometimes with an olive tint towards the end, but never is it as orange or orange-red as in the Giant Spotted Whiptail.  The Red-backed Whiptail (A. xanthonota) can be confused with the Giant Spotted Whiptail, particularly older individuals.  But its range is to the west of that of the Giant Spotted Whiptail and it does not exceed 114 mm SVL.  The juvenile tail of the Red-backed Whiptail is slate-blue or slate-gray, usually with at least faint blue tinting.  In adults the rusty-orange coloration (sometimes yellow) on the back does not, or only slightly, extends onto the sides of the body, whereas in the Giant Spotted Whiptail, that coloration extends well onto the sides.

Rosen et al. (2002) summarized most records of Giant Spotted Whiptails in Arizona.  Those records extend from the Baboquivari and Quinlan mountains northeast to the Santa Catalina and Rincon mountains, northeast again to the Santa Teresa and Pinaleño mountains, and south and west through the Galiuro/Winchester Mountains, the Whetstones, Santa Rita Mountains, and Pajarito/Tumacacori/Atascosa complex.  The species was also found on the Santa Cruz River near Nogales and at the West Branch in southwestern Tucson, and it was collected in 1970 near San Xavier Mission.  Walker and Cordes (2011) note specimens from the Dragoon Mountains, and the species has also been observed on the western bajada of that range (pers. obs).  Corman (1988) found Giant Spotted Whiptails in small numbers at four locations in the San Pedro Riparian National Conservation Area.  Cogan (2013) reported the species from the Appleton-Whittell Research Ranch near Elgin.  Giant Spotted Whiptails also occur in the Swisshelm and Peloncillo mountains, but have not been found in the Dos Cabezas, Chiricahua, Mule, Huachuca, or Patagonia mountains.  Elevational range in Arizona is 722-1463 m.  In the Sonora portion of the 100-Mile Circle, Giant Spotted Whiptails have only been found near Nogales and in the Sierras Azul and Los Pinitos, but no doubt occur elsewhere in the mountains and bajadas.  The species occurs from southeastern Arizona and extreme southwestern New Mexico (Peloncillo Mountains) south through eastern Sonora to northern Sinaloa.  Its elevational range in Sonora is from about 315 to 1904 m.

This is a strictly diurnal species.  It is wary and difficult to approach or observe; however, it can be seen moving around on the ground, probing in leaf litter and digging under objects for prey.  Records in the 100-Mile Circle range from early February to mid October, but most are found April-September.  Goldberg (1987) found that Giant Spotted Whiptails in Pima County emerged from hibernation in April and early May. The adults are rarely seen after early September.  Despite their size, these lizards are often infrequently observed and easy to overlook.

In the 100-Mile Circle, this is a species of Sonoran and Chihuahuan desertscrub, semi-desert grassland, inland chaparral and oaks, and oak savanna and woodland.  It likely occurs in foothills thornscrub in the southern portion of the Circle, and may occur in lower pine-oak woodland.  Within these communities, it is often, but not always found in thickets along arroyos, and sometimes in riparian corridors.  It is not a valley bottom species, except rarely along riparian corridors (such as the West Branch of the Santa Cruz River), but rather is usually found in montane canyons, slopes, and adjacent bajadas.

Mating likely occurs in April and May, and clutches of 3-10 eggs are laid probably in June and July.  Two clutches may possibly be produced in favorable years (Degenhardt et al. 1996).  Adults are >89 SVL (males) and >90 mm SVL (females, Goldberg 1987).  Hatchings begin to appear in early August and measure about 33 mm SVL (Degenhardt et al. 1996).

Prey of the Giant Spotted Whiptail consists of a variety of invertebrates and possibly small lizards.  At two sites in northeastern Sonora, the most important dietary items were termites and ants. Other important items included caterpillars and beetles and their larvae. Plant material was found in one stomach (Paulissen and Walker 1996).  In captivity, Giant Spotted Whiptails fed upon mealworms and crickets (Rosen et al. 2002).

The Giant Spotted Whiptail is listed (as Aspidoscelis burti) as a species of least concern on the IUCN’s 2014 Red List.  With a valid Arizona hunting license, 20 can be captured per day or held in possession, alive or dead.  This species was once on the Category 2 Candidate List for federal listing under the Endangered Species Act, but is not currently a candidate species.  Rosen et al. (2002) concluded that populations in montane canyons were faring well, but that the few valley bottom populations were not.  As this species is often found in thickets, including riparian bottomlands, it is susceptible to fire, livestock grazing, groundwater pumping, and other processes and human impacts that reduce vegetation density in those thickets.

Suggested Reading:

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

Cogan, R.C. 2013. Herpetofauna of the Appleton-Whittell Research Ranch. Pages 466-467 in G.J. Gottfried, P.F. Ffolliott, B.S. Gebow, L.G. Eskew, L.C. Collins (compilers), Proceedings: Merging science and management in a rapidly changing world: Biodiversity and management of the Madrean Archipelago III and 7th Conference on Research and Resource Management in the Southwestern Deserts. May 1-5 2012. Tucson, AZ. RMRS-P-67. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station.

Collins, J.T. 1991. Viewpoint: a new taxonomic arrangement for some North American amphibians and reptiles. Herpetological Review 22:42-43.

Corman, T.E. 1988. Abundance, distribution, and habitat management of the reptiles and amphibians of the San Pedro Riparian National Conservation Area. Bureau of Land Management, San Pedro Project Office, Fairbank, AZ.

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.

Degenhardt, W.G., C.W. Painter, and A.H. Price. 1996.  Amphibians and Reptiles of New Mexico. University of New Mexico Press, Albuquerque.

Dessauer, H.C., and C.J. Cole. 1989. Diversity between and within nominal forms of unisexual teiid lizards. Pages 49-71 in R.M. Dawley and J.P. Bogart (editors), Evolution and Ecology of Unisexual Vertebrates. Bulletin of the New York State Museum (466).

Goldberg, S.R. 1987. Reproductive cycle of the giant spotted whiptail, Cnemidophorus burti stictogrammus, in Arizona. Southwestern Naturalist 32(4):510-511.

Paulissen, M.A., and J.M. Walker. 1996. Cnemidophorus burti stictogrammus (Giant spotted whiptail). Diet. Herpetological Review 27(4):200-201.

Reeder, T.W., C.J. Cole, and H.C. Dessauer. 2002. Phylogenetic relationships of whiptail lizards of the genus Cnemidophorus (Squamata: Teiidae): a test of monophyly, reevaluation of karyotypic evolution, and review of hybrid origins. American Museum Novitates 3365:1-61.

Rorabaugh, J.C., and J.A. Lemos Espinal. 2016. A Field Guide to the Amphibians and Reptiles of Sonora, Mexico. ECO Herpetological Publishing and Distribution, Rodeo, New Mexico, USA.

Rosen, P.C. 2009. Canyon Spotted Whiptail, Aspidoscelis burti (Taylor, 1938). Pages 330-333 in Jones, L.L.C., and R.E. Lovich (eds.), Lizards of the American Southwest: A Photographic Field Guide.  Rio Nuevo Publishers, Tucson, AZ.

Rosen, P.C., R.B. Duncan, P.A. Holm, T.B. Persons, S.S. Sartorius, and C.R. Schwalbe. 2002. Status and ecology of the Giant Spotted Whiptail (Cnemidophorus burti stictogrammus) in Arizona. Final report for the Arizona Game and Fish Department, Heritage Grant (IIPAM program) I99018.

Taylor, H.L.  2006. A male hybrid from Aspidoscelis sonorae (parthenogenetic) and A. burti stictogramma (bisexual): Squamata, Teiidae. Herpetological Review 37(2):154-157.

Walker, J.M., and J.E. Cordes. 2011. Taxonomic implications of color pattern and meristic variation in Aspidoscelis burti burti, a Mexican whiptail lizard. Herpetological Review 42(1):33–39.

Author: Jim Rorabaugh

 

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