Greater Earless Lizard (Cophosaurus texanus)

Greater Earless Lizard (adult male). Photo by Young Cage

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Description

In 1957, a high school friend and I tried to drive my old ’38 Plymouth coupe up the sandy road along the flood plain of the Verde River north of Fort McDowell. We made it to the mouth of Camp Creek, but there the tires began to sink into the sand. The car became bogged down to the axel, bringing our herpetological expedition to an abrupt halt. While digging the vehicle out, I was surprised to see what looked like a Zebra-tailed Lizard (Callisaurus draconoides) perched on a ledge in the canyon. I managed to noose the lizard and observed that it lacked external ear openings.

Photo by Erik Enderson

Figure 1. Greater Earless Lizard (Cophosaurus texanus) in a challenge display. Note the ventrally banded tail and the posterior position of the lateral bars. Photo by Erik F. Enderson. Pima Co., Arizona.

This was my introduction to the animal we now call the Greater Earless Lizard (Cophosaurus texanus; Figure 1). I had not previously encountered the species on my field trips into the Sonoran Desert near Phoenix and became curious about its distribution in the region. Searching rocky habitats, I found it along the slopes of what I then called the “peninsular ranges”, montaneridges such as the Mazatzal and Bradshaw mountains that extend south from the high country bordering the Mogollon Rim. I also encountered the species in some of the outlying desert ranges of Maricopa Co., such as Black Mountain near Cave Creek, the McDowell and Superstition mountains, and even the Harquahala Mountains. Climbing to the top of these desert ranges, I found relicts of montane vegetation, including scrub oak, silk tassel, and juniper. I theorized that in central Arizona, the Greater Earless Lizard was restricted to riparian areas and mountain ranges that are now, or were in the Pleistocene, connected to the higher elevations by corridors of chaparral or woodland.When I arrived as a freshman at the University of Arizona, Charles Lowe explained to me that this is a well-known biogeographic pattern applicable to many species of our fauna and flora. Eventually, the occurrence of chaparral and woodland vegetation on the peaks of the Arizona desert ranges was summarized by Brown (1978) for the current era and by Van Devender (1990) for the past 40,000 years (based on packrat middens). But the biogeography of Cophosaurus in the state has received little attention.

The Greater Earless Lizard bears a remarkable similarity to the Zebra-tailed Lizard, although it differs in lacking external ear-openings and in having the dark lateral bars located more posteriorly (Figures 1 and 2). The two also share a peculiar behavior, that of arching the tail over the back and wagging it side to side before fleeing.

Dial (1986) conducted a field study of tail-wagging behavior in Cophosaurus texanus and compared it with the Keeled Earless Lizard (Holbrookia propinqua). The Greater Earless Lizard occurs in less dense populations, has a tail with conspicuous black and white ventral bands, and, when approached, displayed tail-wagging 54% of the time before fleeing. The Keeled Earless Lizard has denser populations, lacks conspicuous tail bands, and did not display tail-wagging before fleeing. Dial (1986) concluded that tail-wagging in Cophosaurus is a signal directed at predators rather than conspecifics, a conclusion reached independently by Hasson et al. (1989) for the behavior in Callisaurus.

Figure 2. Greater Earless Lizard (Cophosaurus texanus). Note the absence of external ear openings. Photo by Erik F. Enderson. Pinal Co. Arizona.

Figure 2. Greater Earless Lizard (Cophosaurus texanus). Note the absence of external ear openings. Photo by Erik F. Enderson. Pinal Co. Arizona.

In enclosures, Greater Earless Lizards displayed tail-wagging less frequently than Zebra-tailed Lizards (Clarke 1965). In the field, Cophosaurus allowed closer approach and fled shorter distances than Callisaurus (Bullova 1994). Besides its use as a signal to predators, the tail functions in locomotion and its loss was found to significantly reduce sprint speed in the species (Punzo 1982). These two tail-wagging species have complementary geographic distributions, Cophosaurus being centered in the Chihuahuan Desert and Callisaurus in the Sonoran, Mohave, and Great Basin Deserts. But they occur in close proximity along a zone extending diagonally from southwestern New Mexico to northwestern Arizona. In this area of geographic overlap they are often segregated by habitat, Greater Earless Lizards predominating on rocky bajadas and in riparian areas, Zebra-tailed Lizards on the more sparsely vegetated desert flats and in arroyos. Perhaps the best example of this habitat and micro-geographic separation is in Sabino Canyon (Santa Catalina Mountains, Pima Co.), where the overlap between the two is surprisingly minimal (see Map 10 and discussion in Lazaroff et al. 2006).

Smith et al. (1987) compared the ecology of Greater Earless Lizards with that of Zebra-tailed Lizards at Burro Creek (Mohave Co.) and found a high degree of niche overlap in macrohabitat, time of activity, and food habits. Niche overlap was low (0.57) for microhabitat, with Cophosaurus predominating on rocks in riparian areas. The Greater Earless Lizard was found to have a slightly smaller average body size and clutch size than Callisaurus. In the area of San Simon Cienega in extreme western Hidalgo Co., New Mexico, both species were found mainly at sites having little vegetation cover (Baltosser and Best 1990).

The mean body temperature of active Greater Earless Lizards at Burro Creek was 38.5°C (101.3°F) and did not differ significantly from that of Callisaurus. Lowe et al. (1971) found the species to have a freezing temperature of -0.65°C (30.8°F) and a supercooling limit of -6.65°C (20°F). Ramsey (1948) found 5 individuals hibernating together under 7.6 cm (3 in) of shale.  Reproductive ecology of the Greater Earless Lizard was thoroughly studied near San Angelo, Texas, by Ballinger et al. (1972) and Schrank and Ballinger (1973). The reproductive season extended from early April to mid August. Clutch size was found to be positively correlated with body size and averaged 6.1 eggs. Larger females produced earlier clutches that contained larger eggs and a greater number of eggs. Three or four clutches may be laid in a year, yielding a reproductive potential of ca 18 eggs. Females mature at ca 50 mm (1.97 in) SVL and may breed in their first year.

During the reproductive season fat bodies become progressively depleted in both females and males. These authors, together with previous work by Cagle (1950), clearly established that in central and west Texas, the Greater Earless Lizard is an early maturing, short-lived species with a high reproductive effort.

Subsequent studies in the Big Bend region of Texas (Howland 1992, Punzo 2000, 2007), in the Chihuahuan Desert of Coahuila (Punzo 2007), and in Arizona (Vitt 1977, Smith et al. 1987) indicate that in these more arid habitats, energy limitations may severely reduce clutch size and reproductive potential. At Burro Creek, Cophosaurus clutches contained fewer eggs and relatively smaller eggs than those of Callisaurus, suggesting the Greater Earless Lizard may be more negatively impacted by arid environments (Smith et al. 1987). Sugg et al. (1995) presented evidence that thesmaller body size of female Cophosaurus compared to males may be a result of reproductive energy expenditure rather than sexual selection.

Diet is quite broad and varies with season and locality. Among the 12 orders of arthropods consumed, the greatest volume was found to be Orthoptera at Burro Creek (Smith et al. 1987); Lepidoptera larvae in the Bolson de Mapimi (Maury 1995); Orthoptera and Lepidoptera larvae in south central Texas (Durtsche 1997); and Coleoptera and Lepidoptera larvae in Trans-Pecos Texas and the Chihuahuan Desert of Coahuila (Punzo 2007). No significant differences in diet between the sexes or between juveniles and adults were detected (Durtsche 1997).

Castañeda et al. (2005) observed a female Cophosaurus texanus eat a small male of the same species and also found limb fragments of Couch’s Spiny Lizard (Sceloporus couchii) in the stomach of the lizard. MataSilva et al. (2006) observed an individual die after consuming two honey bees (Apis melifera). Perhaps the strangest record is that of Kesson and Ross (2001) who observed a Greater Earless Lizard basking on the carcass of a Domestic Swine (Sus scropha) and eating dermestid larvae.

The Greater Earless Lizard has been recorded as a host for 5 species of gastrointestinal helminth parasites (Gambino 1958, Specian and Ubelaker 1974, Goldberg and Bursey 1992). Documented predators include the Sonoran Whipsnake (Coluber bilineatus; Camper and Dixon 2000, Enderson and Bezy 2003), Striped Whipsnake (Coluber taeniatus; Camper and Dixon 2000), Loggerhed Shrike (Laurus ludovicianus; Reid and Fulbright 1981, Clark 2011), Greater Roadrunner (Geococcyx californianus; Dial 1986), and the lycosid spider (Arctosa littoralis; Whiting et al. 1991).

Population density of the species appears to vary extensively with geography and year, ranging from 107 lizards/ha at Big Bend (Howland 1992, Punzo 2000, 2007) to 20 lizards/ha in wet years and 10 lizards/ha in dry years at Las Cruces (Whitford and Creusere 1977).

Cophosaurus was considered to be most closely related to Callisaurus by Earle (1961) based on anatomy of the middle ear. This is an intriguing hypothesis: the two Southwestern lizard species with banded tails, tail-waging behavior, similar body forms, broadly overlapping ecological niches, and complementary geographic distributions might be nearest relatives (sister species). In this hypothesis the loss of external ear openings may have occurred independently in Cophosaurus and Holbrookia. However, subsequent studies of anatomy (e.g., Cox and Tanner 1977), allozymes (de Queiroz 1992), and mitochondrial DNA sequences (Wilgenbusch and de Queiroz 2000) place Cophosaurus as the nearest relative of Holbrookia, indicating a single loss of the external ear opening within the sand lizards.

Troschel (1852) described Cophosaurus texanus from “der deutschen Colonie Neubraunfels am der Guadalupe im westlichen Texas” [New Braunfels, Guadalupe River, Comal Co., Texas]. The paper is dated 1850 but was not published until 1852. The name Cophosaurus is derived from Greek, meaning “deaf lizard”, in reference to the lack of external ear openings. Peters (1951) recognized three subspecies, with C. texanus scitulus (Chihuahuan Greater Gearless Lizard; type locality Cañada del Oro, 16 mi N Tucson) occurring in Arizona and western New Mexico. Analyses of DNA sequences demonstrate considerable geographic structure in the species, with the most divergent populations found near Eagle Pass, Texas, and in Mexico (Blaine 2008).

Figure 3. Geographic distribution of the Greater Earless Lizard (Cophosaurus texanus) in Arizona.

Figure 3. Geographic distribution of the Greater Earless Lizard (Cophosaurus texanus) in Arizona.

The Greater Earless Lizard ranges across northern Mexico from southern Tamaulipas to northeastern Sonora and north into the U. S. to northern Texas, New Mexico, and Arizona. In Arizona, the species is widely distributed below the Mogollon Rim, but is absent in the southwestern part of the state (Figure 3). In southeastern Arizona it appears to occur on the bajadas of virtually all the Madrean ranges as well as in the Chihuahuan Desert and along the San Pedro River from near Hereford to its confluence with the Gila River. It may be absent from parts of the Sonoita grasslands (Santa Cruz Co.), Sulphur Springs Valley (Rosen et al. 1996), and southern San Bernardino Valley (Cochise Co.). Its apparent western limits of distribution in the state (Figure 3) extend northwest from the Pajarito Mts. (Peters 1951; Santa Cruz Co.), though the Santa Rita Mts., Rincon Mts., Santa Catalina Mts. (Pima Co.), Tortolita Mts., Black Hills, Tortilla Mts., Gila R. at Cochran, Superstition Mts. (Pinal Co.), McDowell Mts., Cave Creek (Van Denburgh and Slevin 1913), Wickenburg (Gates 1957; Maricopa Co.), Congress (Williams and Chrapliwy 1958), Santa Maria R., Burro Ck. (Smith et al. 1987; Yavapai Co.), Aquarius Cliffs (Duellman 1955), Cottonwood Mts., and Hualapai Mts., to the Cerbat Mts. (Jones et al. 1981; Mohave Co.). An apparently isolated population is found in the Harquahala Mts. (Williams 1960; Maricopa and La Paz Cos.).

The species occurs remarkably far north in Arizona, apparently ranging to the Blue River at Alder Creek (Greenlee Co.), Upper Eagle Creek (Graham and Greenlee cos.), the confluence of the Black River and White River (Hulse 1973), Cherry Creek near Young, Verde River N of Payson (Gila Co.), Perkinsville, Santa Maria Mts. (Yavapai Co.), Sedona (Coconino Co.), and Cerbat Mts. (Mohave Co.).

Acknowledgments.

For assistance with museum records, I thank George Bradley, University of Arizona Museum of Natural History (UAZ); Neftali Camacho, Natural History Museum of Los Angeles County (LACM); Thomas Dowling, Arizona State University (ASU); and Brad Hollingsworth, San Diego Natural History Museum (SDNHM). I also thank Erik Enderson for use of his photographs and Kit Bezy and Kathryn Bolles for helpful suggestions on a previous version of this paper.

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Author: Robert Bezy

Originally published in the Sonoran Herpetologist 2011 24(5):42-46

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