Southwestern Fence Lizard – Tucson Herpetological Society

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Southwestern Fence Lizard (Sceloporus cowlesi)

[/vc_column_text][gap size=”12px” id=”” class=”” style=””][/vc_column][/vc_row][vc_row][vc_column width=”1/2″][vc_single_image image=”1286″ img_size=”large” alignment=”center” style=”vc_box_rounded”][vc_column_text]Photo by Robert L. 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=”1872″ img_size=”medium” alignment=”center” onclick=”img_link_large”][vc_column_text]Photo by Robert L. 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=”1873″ img_size=”medium” alignment=”center” style=”vc_box_rounded” onclick=”img_link_large”][vc_column_text]Southwestern Fence Lizard, Cochise Co., AZ. 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=”1874″ img_size=”medium” alignment=”center” style=”vc_box_rounded” onclick=”img_link_large”][vc_column_text]Southwestern Fence Lizard, recent hatchling, Cochise County, 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=”1875″ img_size=”medium” alignment=”center” style=”vc_box_rounded” onclick=”img_link_large”][vc_column_text]Southwestern Fence Lizard, western Dragoon Bajada, 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 Southwestern Fence Lizard (Sceloporus cowlesi) is a small (< 75 mm SVL) spiny lizard. The tail length is about equal to SVL. In our area, the background coloration of the dorsum is gray, brown, or tan, with a light dorsolateral stripe on each side, a brown or gray mid-dorsal stripe, and light and dark spots between the mid-dorsal and dorsolateral stripes. These lizards can appear quite dark when cold, but the overall pattern lightens as the lizard warms up. The ventral surface is whitish-gray. Males have prominent blue patches on each side of the abdomen and throat that are often edged with black. These blue markings are faded in adult females and juveniles of both sexes. Males have enlarged post-anal scales and 12-21 femoral pores on each thigh. The scales upon which the femoral pores reside are not notched (Babb and Leaché 2009, Rorabaugh and Lemos-Espinal 2016).

The Southwestern Fence Lizard is a member of the Sceloporus undulatus complex, which includes ten species distributed across the United States and Mexico (Wiens et al. 2010). In Arizona, the complex also includes the similar Plateau Lizard (Sceloporus tristichus), which is distributed generally to the north and west of the range of the Southwestern Fence Lizard. It also includes the Striped Plateau Lizard (S. virgatus), which occurs in the Chiricahua, Peloncillo, and Dos Cabezas mountains in Arizona, and a number of ranges in northeastern Sonora within the 100-Mile Circle. The abdomen of the Striped Plateau Lizard is unmarked, the scales upon which the femoral pores reside are notched posteriorly, it is slightly smaller (< 70 mm SVL), and it only occurs in montane woodlands, whereas in our area, the Southwestern Fence Lizard is only known to be a species of valleys and bajadas (but see below concerning ranges north of Interstate 10). Unfortunately, where the ranges of the Plateau and Southwestern Fence lizards come together, both are typically striped lizards with indistinguishable patterns, and there are no morphological characters that definitively distinguish between the two. But they are genetically distinct. The similar Slevin’s Bunchgrass Lizard (Sceloporus slevini) lacks the blue patches on the throat and the lateral scale rows are parallel to the dorsal scale rows instead of oblique (slanting upwards) as in other Arizona Sceloporus. The tail of Slevin’s Bunchgrass Lizard often has a dark, mid-dorsal stripe, as well.

Range wide, the Southwestern Fence Lizard occurs in portions of eastern Arizona and northeastern Sonora, east through much of New Mexico and northern Chihuahua to western Texas (Babb and Leaché 2009, Lemos-Espinal 2015). Leaché and Cole (2007) provide the best map of the distributions of the Plateau and Southwestern Fence lizards in Arizona, based on genetic analysis. From that analysis, all confirmed Plateau Lizard populations lie north of the Gila River. The farthest south populations in Leaché and Cole’s analyses are from Oak Flat between Superior and Globe, and the Pinal Mountains. The Southwestern Fence Lizard is known to occur in the valleys of southeastern Arizona, but also above the Mogollon Rim from about 20 miles south of Sanders to near Springerville. In an area from about Holbrook to Snowflake, forms of the Plateau Lizard hybridize with the Southwestern Fence Lizard (Leaché and Cole 2007, Leaché 2011). Leaché and Cole (2007) did not have samples west of the Sonoita Valley in the border region; however, several specimens of the Southwestern Fence Lizard have been collected from the Santa Cruz River Valley south of Tucson, as well as a few from south of Arivaca. UAZ 42541 was collected 1.5 mile southwest of Patagonia. No records are known from the San Rafael Valley. Leaché and Cole (2007) show an outlier at Oracle, Pima County. There are only two localities for Sonora: UAZ 36545 from “6 mi S of Naco along dirt rd to Cananea Rd” and two sight records from 5.4 km NE of Cananea (Rorabaugh et al. in press), although the species has likely been overlooked in other northeastern Sonora valleys (Rorabaugh and Lemos-Espinal 2016).

Lizards from the Santa Catalina and Rincon mountains are sometimes referred to as Plateau Lizards (Brennan and Holycross 2006, Flesch et al. 2010), but they could be montane populations of the Southwestern Fence Lizard. The same can be said for lizards of this complex from the Pinaleño and Santa Teresa mountains. Recognizing this problem, Bezy and Cole (2014) referred Sceloporus undulatus complex lizards from all four ranges to the Southwestern Fence Lizard, but noted there may very well be cryptic montane and lowland forms that need to be teased apart. We will have to await further genetic analysis to know which Sceloporus species occurs in the Santa Catalina, Rincon, Pinaleño, and Santa Teresa mountains.

In the 100-Mile Circle, the Southwestern Fence Lizard is only known to be a species of valleys and bajadas vegetated with Chihuahuan desertscrub, semi-desert grassland, Plains grassland, and oak savanna. They are also known to occupy riparian woodlands (Corman 1988, Bateman and Chung-MacCoubrey 2012). If lizards in the four ranges north of Interstate 10 are, indeed, Southwestern Fence Lizards, then the species also occurs in a variety of montane woodlands, from oak woodlands upslope through pine and pine-oak woodland, and mixed conifer forest. Outside of the 100-Mile Circle, this species is known to inhabit chaparral and montane woodlands, as well.

The Southwestern Fence Lizard breeds in the spring and summer, and eggs are laid from May into August. In a desert grassland 17 km north of Lordsburg, New Mexico, females were found to lay at least four clutches per year with a mean clutch size of 9.9 eggs (Vinegar 1975). Lizards in that population matured at 54 mm (females) and 50 mm (males) SVL. Females matured in 11-14 months. The first hatchling was seen 28 July. Hatchlings measure 21-24 mm SVL and resemble small adults (Vinegar 1975, Bateman and Chung-MacCoubrey 2012). In a sample of Southwestern Fence Lizards from New Mexico, Goldberg (2015) noted the smallest mature male was 45 mm SVL. He also noted clutch sizes of 4-12 (mean=8.3, n=29). On the Río Grande in central New Mexico, Southwestern Fence Lizards survived for as long as five years, and most achieved maturity in their second summer, although a few were 60 mm SVL in their first year before the winter cool down (Bateman and Chung-MacCoubrey 2012). In that study, hatchlings were present from May into mid-September. At his study site near Lordsburg, Vinegar (1975) surmised that the greatest source of mortality was predation by snakes, Long-nosed Leopard Lizards, Red-tailed Hawks, Roadrunners, and Loggerhead Shrikes.

These lizards are often quite common where they occur (Babb and Leaché 2009). In the Sulphur Springs Valley of Cochise County, it was “perhaps the second most frequently seen lizard in the valley, where it lives on the ground near dense grass or scrub, on shrubs, and on and around, or under, human-made debris. Especially conspicuous at corrals and ruins. Also seen occasionally on rocks.” The most frequently encountered lizard was the Desert Grassland Whiptail (Aspidoscelis uniparens, Rosen et al. 1998). On the western bajada of the Dragoon Mountains the Southwestern Fence Lizard was common in all habitats (Chihuahuan desertscrub, large arroyos, and an ecotone between semi-desert grassland and Chihuahuan desertscrub, Rorabaugh 2017).

At White Sands National Monument in New Mexico, important dietary items included Hymenopterans (sawflies, wasps, bees, and ants; 38% by volume) and beetles (32% by volume). A hatchling Little Striped Whiptail (Aspidoscelis inornata) was also found in a stomach (Dixon and Medica 1966). These lizards are sit and wait predators, darting from perches and resting places to grab small prey (Babb and Leaché 2009). On the upper San Pedro River, Corman (1988) characterized the Southwestern Fence Lizard as a ground forager that would also use downed litter and lower trunks and limbs of mesquite. It was most common where dense cover occurred and “totally absent where ground cover is scarce”.

The Southwestern Fence Lizard is listed as a species of least concern on the IUCN Red List. With a valid Arizona hunting license, 20 can be taken per day or held in possession, alive or dead, except in protected areas such as National Park Service units. Although eliminated from urban areas, where intensive mining occurs, and other areas of severe human disturbance, there is no reason to believe the species is declining in wild or semi-natural areas.

Much of the literature on this species is under the name Sceloporus undulatus cowlesi, although former populations of S. u. consobrinus and S. u. tristichus are also included under the current S. cowlesi as used herein.

Southwestern Fence Lizard (Sceloporus cowlesi)

Description

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