Chihuahuan Spotted Whiptail – Tucson Herpetological Society

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Chihuahuan Spotted Whiptail (Aspidoscelis exsanguis)

[/vc_column_text][gap size=”12px” id=”” class=”” style=””][/vc_column][/vc_row][vc_row][vc_column width=”1/2″][vc_single_image image=”1303″ img_size=”large” alignment=”center” style=”vc_box_rounded”][vc_column_text]Chihuahuan Spotted Whiptail, Jeff Davis Co., TX. Photo by Larry Jones[/vc_column_text][/vc_column][vc_column width=”1/2″][vc_row_inner][vc_column_inner width=”1/2″][vc_single_image image=”1967″ img_size=”medium” alignment=”center” onclick=”img_link_large”][vc_column_text]Chihuahuan Spotted Whiptail, Chiricahua Mtns, AZ. Photo by Jim Rorabaugh[/vc_column_text][gap size=”12px” id=”” class=”” style=””][/vc_column_inner][vc_column_inner width=”1/2″][vc_single_image image=”1968″ img_size=”medium” alignment=”center” style=”vc_box_rounded” onclick=”img_link_large”][vc_column_text]Chihuahuan Spotted Whiptail, Chiricahua Mtns, AZ. 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 Chihuahuan Spotted Whiptail (Aspidoscelis exsanguis) is a moderately-sized, striped and spotted whiptail. The maximum SVL is 107 mm (Cordes and Walker 2016), but most are less than 100 mm SVL. This is a parthenogenetic, all female, triploid species that arose when a diploid, all-female species back-crossed with a bisexual ancestor. Authors do not agree entirely on the species involved in these hybridization events, but the list includes the Little Striped Whiptail (A. inornata), Plateau Spotted Whiptail (A. scalaris), Giant Spotted Whiptail (A. stictogramma), and the Western Mexico Whiptail (A. costata) (Reeder et al. 2002). There are 6 (rarely a 7th median) light dorsal stripes that fade with age, but are always visible on the neck. In the dark fields between the light stripes are many small, light spots that also overlay the light stripes. Light spots atop the hind limbs and towards the rear of the dorsum are generally brighter than the anterior spots. Hatchlings and juveniles have more distinct light dorsal stripes and fewer and less discernable light spots, or the light spots may be absent. The venter of adults and juveniles is milky white. The latter half of the tail is greenish-gray in adults, and blue or green in juveniles (Lowe 1956, Degenhardt et al. 1996, Babb 2009).

The scales on the central rear surface of the forearm (postantebrachial scales) and the mesoptychial scales across the throat are distinctly enlarged and angular in shape. There are 62-86 granular scales around the mid-body, and 2-8 scales between the paravertebral stripes anteriorly. In most specimens, enlarged pre-anal scales number three, but some have a different arrangement of these scales (Cole et al. 2016, Rorabaugh and Lemos-Espinal 2016).

This species resembles other striped and spotted whiptails. It differs from the Sonoran Spotted Whiptail (A. sonorae) and Gila Spotted Whiptail (A. flagellicaudus) in having more, small light spots, some of which overlap the light stripes, and light spots on the dorsal surface of the hind legs (reticulate in the Sonoran Spotted and Gila Spotted whiptails). The Sonoran Spotted Whiptail is smaller (< 89 mm SVL), the dorsum is less heavily spotted, and the light spots do not usually impinge on the light dorsal stripes. The tail of the Sonoran Spotted Whiptail is brown, tan, or orange-tan. In the Gila Spotted Whiptail, the six or seven light stripes are brighter anteriorly, the tail is greenish or bluish, and it typically has two pre-anal scales. The Gila Spotted and Sonoran Spotted whiptails were considered conspecific with the Chihuahuan Spotted Whiptail until C.H. Lowe and J.H. Wright split them into separate species (Lowe and Wright 1964).

A review of VertNet or even University of Arizona collection data is not very helpful in defining the range of the Chihuahuan Spotted Whiptail in Arizona and the 100-Mile Circle, because many exsanguis specimens were never relabeled as A. sonorae or A. flagellicaudus after the 1964 paper describing the latter two species. However, distribution maps in Brennan and Holycross (2006) and Babb (2009) are reasonably accurate. In the 100-Mile Circle, the species has a limited distribution, occurring in the Chiricahua and Dos Cabezas mountains, Davis Canyon (and probably elsewhere) in the Winchester Mountains, and on the northeastern edge of the Circle in Graham County in the Black Hills and the Gila Box. The population in the Winchester Mountains is apparently isolated (Persons and Rosen 2002); the species should be looked for in the Galiuro Mountains. Outside of the Circle, the species occurs in portions of Greenlee County, the Peloncillo Mountains, and east through much of New Mexico to western Texas, and south to Chihuahua, northwestern Coahuila, and extreme northeastern Sonora.

In Arizona and Sonora, this is primarily a montane and canyon species of oak and pine-oak woodland, extending downslope into semi-desert grassland in places. Elsewhere it occurs in riparian corridors and Chihuahuan desertscrub (Degenhardt et al. 1996, Brennan and Holycross 2006, Rorabaugh and Lemos-Espinal 2016).

Phil Medica (1967) studied a population of the Chihuahuan Spotted Whiptail in south-central New Mexico, where the lizards inhabited a saltgrass, tumbleweed, saltcedar, and saltbush area. Diet included (by volume) Lepidoptera (mostly moths and their larvae) – 28%, beetles (19.7%), grasshoppers, crickets, and their relatives (8.13%), spiders (9.3%), antlions (2.5%), and termites (<1%). A Chihuahuan Spotted Whiptail from Valencia County, New Mexico contained six large caterpillars and beetle larvae (Paulissen et al. 2016). At Fort Bliss, New Mexico, Rocha et al. (2013) watched a Chihuahuan Spotted Whiptail catch and consume an adult tarantula. Like all whiptails, this species is an active forager, and can be seen moving from bush to bush, scratching amidst leaf litter and searching for prey.

In Medica’s 1967 study, females with eggs were only found in late June to July and there was no evidence of double clutching. Mean clutch size was 2.72. An incubation time of 62 days was calculated. Degenhardt et al. (1996) and Babb (2009) say clutch size varies from two to six.

In New Mexico, active lizards preferred a body temperature of about 39⁰C (Medica 1967). In southwestern Texas, mean body temperatures of Chihuahuan Spotted Whiptails were 40.6⁰C (active lizards), 40.9⁰C (lizards in the shade), and 38.5⁰C (basking lizards, Schall 1977).

Bateman et al. (2010) studied Chihuahuan Spotted Whiptails in a riparian forest of cottonwood, saltcedar, and Russian olive on the Rio Grande of New Mexico. Captures of adult whiptails peaked in mid-June and began to decline toward the end of July. Hatchlings first appeared in mid-July and peaked at the beginning of September. Some lizards lived at least three years.

At San Francisco Hot Springs, New Mexico, the smallest reproductive female was 61 mm SVL, and the largest individuals were 93 mm SVL (Taylor and Caraveo 2003). Along the Río Piedras Verdes (1682 m elev) in northeastern Chihuahua, the Chihuahuan Spotted Whiptail was the most commonly encountered reptile (Walker and Lemos-Espinal 2015). At that site, juveniles were 31-60 mm SVL, and adults 61-85 mm SVL. Hatchlings appeared from mid-July into August and grew rapidly until they went dormant in October. Lizards reappeared in April and May and achieved adult size in their second or third active season. Lizards likely lived as long as four years. Based on a low percentage of regenerated tails, Walker and Lemos-Espinal (2015) surmised that predation was relatively insignificant.

This lizard is listed as a species of least concern on the IUCN Red List. With a valid Arizona hunting license, four Chihuahuan Spotted Whiptails can be captured per year or held in possession alive or dead, except that capture without special permits is prohibited in protected areas such as National Park Service units. There is no reason to believe the species is declining in wild areas, although it is eliminated from areas of urbanization and other forms of severe habitat alteration.

Chihuahuan Spotted Whiptail (Aspidoscelis exsanguis)

Description

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