Red-backed Whiptail – Tucson Herpetological Society

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Red-backed Whiptail (Aspidoscelis xanthonota)

[/vc_column_text][gap size=”12px” id=”” class=”” style=””][/vc_column][/vc_row][vc_row][vc_column width=”1/2″][vc_single_image image=”1312″ img_size=”large” alignment=”center” style=”vc_box_rounded”][vc_column_text]Red-backed Whiptail, Organ Pipe Cactus National Monument, AZ. 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=”2017″ img_size=”medium” alignment=”center” onclick=”img_link_large”][vc_column_text]Red-backed Whiptail, Organ Pipe Cactus National Monument, AZ. Photo by Larry Jones[/vc_column_text][gap size=”12px” id=”” class=”” style=””][/vc_column_inner][vc_column_inner width=”1/2″][vc_single_image image=”2018″ img_size=”medium” alignment=”center” style=”vc_box_rounded” onclick=”img_link_large”][vc_column_text]Red-backed Whiptail, Ajo Mountains, Organ Pipe Cactus National Monument, 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 Red-backed Whiptail (Aspidoscelis xanthonota) is a fairly large (< 114 mm SVL) whiptail with large plate-like scales on the pointed head, and an elongated body and tail. The scales on the central rear surface of the forearm (postantebrachial scales) are distinctly enlarged. This lizard goes through considerable ontogenetic or developmental changes in coloration and pattern as it ages. Juveniles have 6-7 light stripes on the neck and body, and light spots in the dark fields between the stripes. The juvenile tail is slate-blue or slate-gray, usually with at least faint blue tinting. As the lizards age, the stripes fade and the spots usually become more prominent. The spots may be faded in some individuals. The dorsum also becomes dark brown to rusty orange as the lizards age, sometimes with blue or slate-blue on the sides, limbs, tail, and head. The rusty-orange coloration does not, or only slightly extends onto the sides of the body. The adult tail is yellowish-brown to dark brown, sometimes with a blue tint.

The only other whiptail that occurs broadly throughout the range of the Red-backed Whiptail is the Tiger Whiptail (Aspidoscelis tigris). The scales on the central rear surface of the forearm are not enlarged, there is often black pigment on the throat and chest (not so in the Red-backed Whiptail), and the adult dorsal pattern in our area is a dark reticulation on the back and tiger banding on the sides. The only blue likely to be seen on the Tiger Whiptail is on the tail of young juveniles, which at that age can be mistaken for Red-backed Whiptails. However, they have 4-6 light stripes on the body and usually some trace of the adult barring on the sides. The Sonoran Spotted Whiptail (A. sonorae) occurs with the Red-backed Whiptail at Martina Mountain in Pima County and perhaps elsewhere. That species is unisexual (all female), the young juveniles have six light stripes on the back with no spots in the dark fields between the stripes, older individuals retain at least some striping and most adults have six distinct stripes. Only rarely does a Sonoran Spotted Whiptail show blue coloration, and throughout life the tail is brown, tan, or tan-orange, sometimes with an olive hue towards the tip. Furthermore, the Sonoran Spotted Whiptail grows to a maximum of only 93 mm SVL. The Giant Spotted Whiptail (A. stictogramma), which was until recently considered conspecific with the Red-backed Whiptail, occurs to the east and south of the range of the Red-backed Whiptail, but in some populations can closely resemble A. xanthonota, particularly older adults. Younger lizards usually have orange tails and if reddish-brown occurs on the back, it can extend onto the sides. The Giant Spotted Whiptail also grows to a larger size (< 140 mm SVL).

The Red-backed Whiptail is an inhabitant of Sonoran desertscrub and relictual mountain top semi-desert grasslands, often within unusual plant communities. It is a species of the higher desert mountains, often on north-facing slopes or mesic canyons, but it occasionally follows drainages or mesas out onto the upper bajadas, such as at the mouth of Alamo Canyon in Organ Pipe Cactus National Monument. The elevational range is 396-1,402 m. This desert sky island lizard has been found in many of the larger mountain ranges south of the Gila River in Arizona from the Agua Dulces and the southern end of the Growler Mountains east to Martina Mountain about 14 km west of Three Points, and north to the Sierra Estrellas and Table Top, Cimarron, and the Sand Tank mountains. In Sonora it has been documented from the Sierras Cubabi, La Gloria-Cerro El Alamo, and San Manuel between Sonoyta and Caborca. It likely occurs elsewhere in Sonora to the north and east of those ranges, and will likely be found in other higher ranges in Arizona, such as the Santa Rosa and South Comobabi mountains and perhaps the western slope of the Baboquivari Mountains on the Tohono O’odham Nation lands, and the Sauceda and Batamote mountains northeast of Ajo.

This is an active, diurnal species, and like other whiptails, is often found methodically poking and digging under shrubs or at the base of grasses for insect prey. It tends to move rapidly between bushes or grass clumps, but may stop to bask in the dappled light under shrubs. It has been found active from April into October, and is most frequently observed in the morning hours. Its reproductive behavior is poorly known; however, mating has been observed in June, and if similar to other desert whiptails, hatchlings likely appear in mid- to late summer. The closely related Canyon Spotted Whiptail produces clutches of 3-10 eggs. The diet has not been studied, but the Red-backed Whiptail likely consumes a variety of arthropods, and possibly small lizards.

Until recently, this lizard was known as Cnemidophorus burti xanthonotus, and much of the literature on the species is under that name. With a valid Arizona hunting license, 20 Red-backed Whiptails can be collected per day or possessed, in aggregate, alive or dead, except that take of these lizards is prohibited without specific authorization in protected areas, such as Tohono O’odham Nation lands, Organ Pipe Cactus National Monument, and Cabeza Prieta National Wildlife Refuge, which collectively, cover most of the range of the species in Arizona. The conservation status of this lizard has not yet been assessed by the IUCN; however, the Red-backed Whiptail is an inhabitant of unusual, relictual communities and mesic, north-facing slopes and canyons. If climates continue to warm and dry out, as predicted by climate change models, this species could decline or be eliminated from some areas.

Red-backed Whiptail (Aspidoscelis xanthonota)

Description

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