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Western Banded Gecko (Coleonyx variegatus)

Order: Squamata
Family: Gekkonidae (gekkos)
Spanish name: salamanquesa de franjas

Distinguishing Features

This delicate-looking lizard seldom exceeds 3 inches in length, excluding the tail. It has moveable eyelids and large eyes with vertical pupils. The small body scales are granular and soft; the toes are slender. There is a constriction at the base of the otherwise bulky tail. The tail is about as long as the body with indistinct rings. Between the pairs of legs are dark brown crossbars on a pale yellow, pink, tan, or cream background. The eyelids are edged in white. The head and body are mottled with light brown. The belly is somewhat translucent. Males have prominent spurs on either side of the body at the base of the tail.

Range

The western banded gecko occurs in the Mohave and Sonoran deserts.

Habitat

The western banded gecko is found in open arid deserts and desert grassland, in canyons and on hillsides. It is usually associated with rocks or other shelters, but is also is found in sandy arroyos and dunes.

Life History

Active principally at night, western banded geckos can be seen crossing roads during the summer. It has been suggested that their gait and carriage mimics that of the scorpions of the genus Hadrurus that share the same habitat. If disturbed, the gecko will wave its tail to divert attention of a would-be predator away from its head and body. The tail has specialized fracture planes that allow it to easily break off. Blood vessels close off rapidly to prevent much blood loss and the writhing tail is left behind. This may allow the lizard to escape predation; its tail is very rapidly regrown. However, the regenerated tail consists of cartilaginous material that lacks fracture planes; it is also shorter than the original and has different color patterns and scales.

The tail of the gecko serves as more than a way of escaping predation. It also stores food and water that the animal uses during lean times, including winter dormancy. Regrowing the tail is energetically expensive and the loss of the tail can put the survival of the lizard in jeopardy—especially if it was lost just before the onset of winter.

Banded geckos feed on a variety of invertebrates including beetles, spiders, grasshoppers, sowbugs, termites, and solpugids. Two eggs are laid in late spring, with females laying 2 clutches a year. After 6 weeks, the eggs hatch into 1 inch (2.5 cm) long lizards.

Comment

This small lizard is often mistaken for a young Gila monster due to the similarity of the pattern. A banded gecko can be distinguished from a Gila monster by its small size (young Gila monsters are around 6 inches; 15 cm) and the lack of bead-like scales on the back. Banded geckos may emit a squeak when captured.

Whiptails (Cnemidophorus spp.)

Order: Squamata
Family: Teiidae (whiptails)
Other common name: racerunner
Spanish name: huico

Distinguishing Features

Whiptails are long, slender lizards with pointed snouts and extremely long tails. Snout-vent lengths range from 2¾ inches (69 mm) to 5¼ inches (137 mm) among the various species of whiptails. Giant spotted whiptails (C. burti), with tails longer than their bodies, can have a total length of over a foot. Color tends to be tan, olive, or brown with lighter stripes and/or spots of yellow or white. Male western whiptails (C. tigris) may have very dark forelimbs, throats and upper torsos. Whiptails have large, square belly scales arranged lengthwise and transverse rows. The scales on the upper part of the body are very small and granular in appearance.

Western whiptail
Range

Whiptails are found throughout the Sonoran Desert region from sea level up to 8000 feet (2440 m).

Habitat

These lizards occupy low desertscrub through grasslands, woodlands and pine forests. They are often found under rocks or nosing around leaf litter.

Life History

Whiptails feed on a variety of terrestrial invertebrates and occasionally on smaller lizards. Most species reproduce sexually and lay 1 or more clutches of 1 to 6 eggs in late spring or early summer. However, in Arizona approximately 60 percent of whiptail species are parthenogenetic, meaning that they reproduce asexually. These species, such as the Sonoran spotted whiptail (C. sonorae), consist entirely of genetically identical females that lay unfertilized eggs, creating a population of clones. Oddly enough, many of the behaviors exhibited by sexually reproducing species are expressed by these parthenogenetic lizards. Females will engage in pseudocopulation and mount and bite other females. Apparently this triggers hormonal changes necessary for ovulation and egg laying. Eggs typically take 60 to 75 days to hatch regardless of reproductive style.

Comments

Lizards’ behavioral habits vary considerably. Some are day active. Others, such as most geckos, are nocturnal. Some are sit-and-wait predators, while others are active foragers. Whiptails fit the latter description in the extreme. Beyond actively foraging, they forage intensely for prey, often at a frenetic pace.

When they are on the move under plants or through leaf-litter, their jerky, start-stop movements create unmistakable and unique sounds. Someone familiar with whiptail lizards can often locate and identify a whiptail from auditory cues alone.

Lizard Displays

Most Sonoran Desert lizards use a variety of behaviors in a purely social context. Displays to establish dominance or territory or to aid in courtship are common. Though many species are similar in their behavioral repertoires, each species’ behaviors are unique to that species. They may differ only slightly, such as with head-bobs, where the number of or intensity of them may be the only difference. Then again, some are vastly different. The open-mouthed gape and vertical extension of the body and throat of collared lizards, which serve as a challenge from one male to another, appear quite different from the four-legged push-ups accompanied by the display of the brightly colored dewlap of tree lizards, though both serve the same purpose.

Some of these displays are used only within a species, while others may be used between species. Aggressive male collared lizards will display to establish dominance over just about any other lizard they can intimidate. Often, agonistic (aggressive) behaviors are ritualized display between males. These behaviors serve to reduce physical contact and the potential for injury to either animal.

An inventory of a species’ repertoire may include gaping, lunging, chasing, biting, inflation of the body or throat, head bobs, and push-ups, as well as subtler shudders of the body. Some of these actions will be used only between males, while others facilitate courtship. What may superficially resemble agonistic push-ups may actually be a subtler shudder of the fore-body, which a male uses to court a female.

Taking a closer look at how lizards interact with one another can be fascinating entertainment, as well as a way to give the observer a better understanding of how animals that cannot speak actually communicate desire, intent, and need to each other.

Gila Monster (Heloderma suspectum)

Order: Squamata
Family: Helodermatidae (venomous beaded lizards)
Spanish name: escorpión

Distinguishing Features

The Gila monster is a large, heavy- bodied lizard reaching a little over 1¼ feet in length. The head is large, with small, beady eyes; the tail is short and fat. The family name Helodermatidae means “warty skin,” referring to the beaded look of the dorsal scales, due to the presence of osteoderms (small bones) under the scales. The lizard is bright pink and black, usually in a reticulated pattern, but in a banded pattern in some populations.

Range

The bulk of this lizard’s range is in western and southern Arizona, continuing to southern Sonora, Mexico, but it can also be found in extreme southeastern California, southern Nevada, extreme southwestern Utah, and southwestern New Mexico.

Habitat

The Gila monster is most commonly found in mountain foothills dominated by saguaros and palo verde trees. It also uses washes that extend down into valleys. It may use burrows dug by other animals, or construct burrows of its own.

Life History

Gila monsters prey on newborn rodents, rabbits, and hares, though ground nesting birds and lizards, as well as eggs from birds, lizards, snakes and tortoises are also eaten. Young Gila monsters may consume as much as 50 percent of their body weight in one feeding, while adults are capable of consuming 35 percent of their body weight in a single feeding. They are active mainly during the day from March through November, and may be seen basking at the entrances to their shelters in winter and early spring. Hibernation takes place from the end of November through February. Some sources estimate they spend up to 98 percent of their time in their subterranean shelters. Generally an animal occupies two burrows over the course of a year, one from autumn through early spring and another during the warmer spring and summer months. The latter burrow is usually in or near a bajada, while a higher elevation, foothill burrow is used when cooler temperatures arrive. Little is known about reproduction in the wild. An average of 5 eggs, but as many as 12, may be laid in late summer. In southern Arizona, Gila monsters breed in May and June, with eggs laid in late June through mid August. The eggs incubate and develop from fall to early spring; young appear the following April through June. There is no other known egg-laying lizard in North America where eggs over-winter and hatch the following year.

Comments

Gila monsters are one of only two venomous lizards known to occur in the world. The other, the beaded lizard (Heloderma horridum), is found in southern Sonora and further south in thornscrub and tropical deciduous forest.

Venom is produced in glands in the lower jaw and expressed along grooved teeth as the animal bites. Once the lizard bites, it generally holds on and chews more of the venom into its victim. Though the bite is rarely life-threatening to humans, it may cause pain, edema, bleeding, nausea and vomiting. A Gila monster’s venom is believed to be a defensive weapon. The animal probably does not need venom to subdue its defenseless prey and the intense pain caused by the venom readily causes a predator to change its mind. Before biting, the lizard will hiss, gape, and back away from its would-be attacker. If these efforts fail, it will bite with amazing speed. Gila monsters should not be handled!

Reptiles, especially venomous ones, are often poorly understood and greatly feared. With the Gila monster this combination has led to misinformation and the generation of many myths. Interesting but untrue are stories about how the Gila monster is venomous because it lacks an anus and “all that stuff went bad in there.” Or about how “once they bite down, they can’t let go until sundown,” or “if one bites you, don’t worry, it has to turn upside down to get the venom in you.” In 1952 the Gila monster became the first venomous animal in North America to be afforded legal protection; it is therefore illegal to collect, kill, or sell them in Arizona. Though it is an animal with a fairly large range, it has a spotty distribution primarily clumped around mountain ranges.

Dr. Ward’s Prescription

Dr. Ward, of Phoenix, an old practitioner in the valley, says: “I have never been called to attend a case of Gila monster bite, and I don’t want to be. I think a man who is fool enough to get bitten by a Gila monster ought to die. The creature is so sluggish and slow of movement that the victim of its bite is compelled to help largely in order to get bitten.”

                     —Arizona Graphic September 23, 1899

Desert Iguana (Dipsosaurus dorsalis)

Order: Squamata
Family: Iguanidae (iguanid lizards)
Spanish names: porohui, lagartijo

Distinguishing Features

This medium-sized lizard with a blunt head and long tail reaches a length of 16 inches (40 cm), including the tail. It is pale gray or whitish with a tan or brown reticulated pattern on the back and sides. Down the center of the back is a row of slightly enlarged, keeled scales. Rows of brown spots are on the tail, which is as long as the body from snout to vent. The belly is pale. During the breeding season, in both sexes, the sides become pinkish.

Range

This heat-loving, desert dweller occurs in southeastern California, southern Nevada, southwestern Utah, and western and south-central Arizona in the United States. The Mexican distribution includes eastern and southern Baja California, northwestern Mexico, and some of the Gulf of California islands. The range of the desert iguana is largely contained within the range of the creosote bush.

Habitat

This lizard is most common in dry, sandy areas dominated by creosote bush. It can also be found in rocky streambeds up to 4000 feet (1200 m). In the southern portion of its range this lizard lives in arid subtropical scrub and tropical deciduous forest associations.

Life History

Desert iguanas emerge from hibernation in mid-March. Breeding occurs in April and May with 2 to 10 eggs laid from late May to early July. Hatchlings emerge late July through August. Desert iguanas may lay 2 clutches of eggs a year under the right conditions. This lizard is extremely tolerant of high temperatures and can be seen active during mid-day even in the hottest summers.

Primarily herbivorous, the desert iguana crawls into the branches of creosote bushes and other shrubs to feed upon the leaves and flowers. Additionally, it eats insects, carrion, and fecal pellets of its own species, which aids in the digestion of plant cellulose by establishing the proper gut fauna.

Studies have shown that secretions from the femoral pores (on the underside of the thighs of the rear legs) fluoresce and that the lizard has vision in these wavelengths. So, besides using these secretions as scent markings, they may also serve as visual indicators of a desert iguana’s presence.

Though desert iguanas seem to prefer open, relatively flat habitat, they rely heavily on the creosote bush in these areas for a number of needs. This plant provides some of the lizard’s diet (flowers), and the lizard burrows around and under the plant’s roots to avoid thermal extremes and predation.

Chuckwalla (Sauromalus obesus)

Order: Squamata
Family: Iguanidae (iguanid lizards)
Spanish name: iguana

Distinguishing Features

The chuckwalla is a large, bulky lizard reaching nearly 16 inches (40 cm) with folds of loose skin on the sides of its body. The color varies between sexes and with the age of the individual. Adult males have black heads and forelimbs; their trunks may be black, red, orange, gray, or yellow. Females and juveniles may have gray or yellow banding.

On the inside of the male’s thigh are well-developed femoral pores, which are small openings that allow secretions to be exuded. These secretions are thought to be a way of marking areas.

Range

A resident of southwestern deserts in the United States and Mexico, the chuckwalla is found in southeastern California, southern Nevada, southwestern Utah, western Arizona, eastern Baja California, and northwestern Mexico.

Habitat

Strictly a rock dweller, the chuckwalla is found in rocky outcrops, lava flows, and rocky hillsides of the Great Basin, Mohave and Sonoran deserts.

Life history

This herbivorous lizard emerges from hibernation in mid to late February, although it may be seen in rock crevices close to the surface on any warm winter day. During the active season, it emerges in the early morning to bask in the sun. It is active in temperatures as high as 102ºF (39ºC). When disturbed it seeks shelter in rock crevices and gulps air, wedging itself in a crack, thus making it extremely difficult for predators to extract it. During summer an average of 6 eggs are laid; hatchlings emerge in late September. The chuckwalla feeds mainly on annuals, but also eats perennials; it will consume insects on occasion.

Comments

If food resources are abundant, large male chuckwallas become territorial during certain parts of the year. Below the “tyrant”male, the other males will set up a dominance hierarchy based on size. When food is scarce, no territoriality is exhibited and some males form a hierarchy centered around food resources rather than the size of the animal. Often in these lean times, reproduction will not occur.

Common Collared Lizard (Crotaphytus collaris)

Order: Squamata
Family: Iguanidae (iguanid lizards)
Other common names: mountain boomer
Spanish name: lagartija de collar

Distinguishing Features

This is a medium-sized lizard reaching nearly 10 inches (25 cm) in total length; males are larger than females. The head is large. Two black collars around the neck give the lizard its name. The small body scales have a ground color of tan, bright green, olive, brown, bluish or yellowish with many light spots and dark crossbands. The belly is whitish. Juvenile collared lizards have distinct banding that slowly fades as the animal matures. The adult male is usually very green with dark spots on the throat. Adult females are only slightly green. In breeding season spots and bars of bright red or orange appear on the sides of the female’s body and neck indicating that she is pregnant; these fade after egg deposition. Color varies among the different populations throughout the range.

Range

The collared lizard is widespread throughout the western United States. In the Sonoran Desert, it is found in Arizona, southeastern California, and northern Mexico, including eastern Baja California.

Habitat

Collared lizards are found in rocky areas of a variety of habitats: pinyon-juniper, sagebrush, desertscrub, and desert grassland. They are usually in areas with open vegetation.

Life History

Collared lizards are capable of running swiftly on their hind legs, the body held off the ground at a 45° angle, with tail and forelimbs raised. The stride is up to 3 times the length of the body. They do not lose their tails easily, as they are useful in maintaining balance as the lizards sprint on hind legs. Speed facilitates the capture of prey by these visually oriented lizards. They have large heads with strong jaw muscles that allow them to get a powerful grip on large prey such as lizards. Though fairly bold, if confronted by a predator, collared lizards quickly dive into rock crevices to avoid being eaten.

These lizards often sit on large rocks basking in the sun and looking out for other individuals or food. Males are highly territorial and have stereotypical head-bobbing and push-up displays. Collared lizards primarily eat grasshoppers, but also eat other insects as well as lizards, including their own species. In early summer females lay 1 to 13 eggs; they are capable of reproducing more than once a year. Hatchlings emerge in late summer and early fall.

Spiny Lizards

desert spiny lizard (Sceloporus magister)
Clark spiny lizard (Sceloporus clarkii)

Order: Squamata
Family: Iguanidae (iguanid lizards)
Spanish name: cachora

Distinguishing Features
Desert spiny lizard

These are medium to large lizards with snout-vent lengths ranging from 2¼ to 5¼ inches (63 to 138 mm). These robust lizards have keeled, pointed scales. Background color is usually subdued gray, tan, or blue with a striking wide, purple stripe down the back and single yellow scales scattered on the sides (S. magister), or scattered turquoise scales mixed with tan and brown on the back and sides (S. clarkii). Both species have a dark collar under or around the neck; males have vivid blue throats and under-bellies. Females develop orange to red heads during the breeding season.

Range

S. magister occurs in 6 western states including almost all of Arizona; it occurs east to Texas and south to Sinaloa, Mexico; it is found from sea level to 5000 feet (1520 m). S. clarkii is found in central to southeastern Arizona, southwestern New Mexico, and south to northern Jalisco, Mexico, from sea level to around 6000 feet (1830 m).

Clark spiny lizard
Habitat

S. magister and S. clarkii overlap in their use of arid to semiarid regions, lower mountain slopes, and subtropical thornscrub. S. magister, primarily an inhabitant of desertscrub and thornscrub, is found mainly on the ground in rocks and, less frequently, in trees. S. clarkii prefers trees, but also inhabits rocky areas with large boulders; it ranges from rocky Sonoran desertscrub into oak woodland. This species also occurs in tropical deciduous forest and oak-pine forest in Chihuahua, Mexico.

Life History

These two species are insectivorous. Both lay 4 to 24 eggs in the summer (into early fall for S. clarkii) which take 60 to 75 days to hatch.

Comments

Like many other lizards, spiny lizards exhibit metachromatism, which is color change as a function of temperature. When it is cooler, colors are much darker than when the temperature is high. Darker colors increase the amount of heat absorbed from the sun and lighter colors reflect solar radiation.

Meeting One’s Match

Collared lizards can be quite pugnacious. In fact we had a male in one of our enclosures that routinely visited all other similar-sized lizards, just to make sure they knew exactly who was in charge.

When we introduced a male desert spiny lizard to this enclosure, the collared lizard quickly ran over to assert himself. However once he was within a few inches of the spiny lizard he seemed to realize how large this newcomer was. The two lizards took positions next to each other, bodies parallel, then sized up one another with sidelong glances. Eventually they took off in opposite directions. Apparently neither felt superior enough to press the issue.

                                                                                     —Craig Ivanyi

Tree Lizard (Urosaurus ornatus)

Order: Squamata
Family: Iguanidae (iguanid lizards)
Spanish name: cachora, lagartija

Distinguishing Features

A small, up to 2½ inch (56 mm), black, dark brown, tan, or gray lizard, often with a rusty area at the base of the tail. The ground color of this slim-bodied lizard is broken with a dusky pattern of blotches and/or crossbars. There are two bands of enlarged scales down the middle of the back, separated by a strip of smaller scales. Adult males have bright blue or blue-green belly patches that have a metallic sheen. The color of the throat varies from yellow to green or blue-green. The throat of females can be white, orange, or yellow.

Range

This species occurs from southwestern Wyoming to southern Sinaloa and northern Coahila, Mexico, and from the Colorado River east to central Texas. It is found from sea level to 9000 feet (2770 m).

Habitat

This arboreal lizard most commonly lives in riparian zones in mesquite, alder and cottonwood, but it also is found on non-riparian oak, pine, and juniper. The tree lizard is also found on some non-native trees such as eucalyptus and tamarisk, and in some treeless areas; it is often very abundant on granite boulder piles. Color and pattern serve it well in avoiding detection by would-be predators.

Life History

The tree lizard eats insects and spiders. It reproduces 1 to 6 times per year, laying 2 to 13 eggs per clutch from March through August.

Comments

Secondary sexual traits, such as the brightly colored throat fold (dewlap) of the tree lizard, are often considered to play a part in mate selection (as well as in male-male competition). The theory is that females choose males based on physical or behavioral traits (dewlap color, body size, frequency of and intensity of social display or courtship) that they equate with “fitness” (superior reproductive success). Recent research on tree lizards, however, has failed to support this theory: female tree lizards did not seem to prefer one throat color over another, nor did they necessarily select the largest or most vigorous males. Instead, females may first select a suitable territory and then select a male whose range overlaps their territory.

Horned Lizards (Phrynosoma spp.)

Order: Squamata
Family: Iguanidae (iguanid lizards)
Other common names: horny toad
Spanish name: camaleón

Distinguishing Features
Regale horned lizard

Up to 10 species of horned lizards occur in the Sonoran Desert region, from the 2¾ inch (69 mm) long round-tailed horned lizard (P. modestum) to the 5 inch (127 mm) long Texas horned lizard (P. cornutum). With squat, flat, toad-like bodies (Phrynosoma means “toad-body”) and thorn-like projections at the rear of their heads, horned lizards are easily distinguished from other lizards. The projections differ in size and arrangement from one species to another. Along the sides of the body, fringe-like scales occur in one row, two parallel rows, or they may be absent. Males have enlarged post-anal scales, and during the breeding season, a swollen tail base.

Range

Horned lizards are found throughout the Sonoran Desert region from near sea level up to 11,300 feet (3440 m). Some species are widespread, such as the round-tailed and Texas horned lizards which occur in several U.S. and Mexican states, while the flat-tailed horned lizard (P. mcalli) is restricted to southwestern Arizona, extreme southeastern California, a small part of northeastern Baja California and the upper neck of northwestern Sonora, Mexico.

Habitat

Horned lizards are found in extremely diverse habitats. The flat-tailed horned lizard occurs in areas of fine sand, while the short-horned lizard (P. douglassii) is found in shortgrass prairie all the way up into spruce-fir forest. The most common species in the Arizona Upland subdivision is the regal horned lizard (P. solare), which frequents rocky or gravelly habitats of arid to semiarid plains, hills and lower mountain slopes.

Life History

The diet of some horned lizards consists of specific insects, while other species are more catholic in their tastes. Not only does P. solare prefer ants, it has a strong preference for harvester ants, which may make up to 90 percent of its diet. As diets go, ants are low return items because so much of their body consists of indigestible chitin. Thus, the regal horned lizard must eat a great number of ants to meet its nutritional needs. This diet requires space, which is why the stomach of the regal horned lizard may represent up to 13 percent of its body mass.

Ant-eating horned lizards usually capture their prey with their sticky tongues rather than grabbing it with their jaws. In addition, they have modified skeletal morphologies, such as shorter teeth and reduced diameter of the bones of the lower mandible.

Horned lizards are no exception to the general rule that lizards are not attracted to dead insects as food—the ants must be alive and moving for the lizard to show interest in them as prey. Harvester ants can bite and have a potent venom, but apparently this has little effect on the esophagus or stomach of the lizard. However, when faced with swarming ants the lizard will make a hasty retreat, for these little invertebrates can kill an adult horned lizard.

Most species of horned lizards lay eggs between May and August, with clutches ranging from 3 to 45 depending on species. Even with such high numbers of eggs only around 2 from each clutch will reach sexual maturity. The short-horned lizard bears live young. This is considered an adaptation to living at higher elevations, where eggs may be at risk due to low temperatures, and egg development might be slowed considerably.

Comments

The body form and armor of the horned lizard cost it speed and mobil-ity, but they confer great advantages as well. Small animals, such as snakes, have more difficulty with a horned lizard’s wide, thorny body than with a smooth, slender lizard. In fact, when confronted by a snake, a horned lizard will continually present the largest part of its body to the snake. Some horned lizards are difficult to distinguish from rocks; thus they avoid detection by would-be predators. In response to a threat, a horned lizard may play dead, or it may run away and then suddenly turn around to face its attacker, hissing or vibrating its tail in leaf litter. Several species can rupture small capillaries around their eyes and squirt a bloody solution at would-be predators. These fluids, beyond coming as a surprise, can be irritating to the mucous membranes of some predators.

The large, flat body surface of the horned lizard also works well as a solar collecting panel: at cooler temperatures, the lizard will orient its body to maximize the amount of exposure to the sun. When it gets too hot, the horned lizard will burrow into loose soil. Initially, the lizard uses the scales on the front edge of its lower jaw to literally cut into the earth as it vibrates its head into the ground. Then it will shake and shimmy its body into the soil until almost none of it is above the surface.

"Sand" Lizards

fringe-toed lizard (Uma notata and U. scoparia)
greater earless lizard (Cophosaurus texanus)
lesser earless lizard (Holbrookia maculata)
zebra-tailed lizard (Callisaurus draconoides)

Order: Squamata
Family: Iguanidae (iguanid lizards)
Spanish names: lagartija de las dunas (fringe-toed lizard), lagartija (greater earless lizard), lagartija (lesser earless lizard), perrita (zebra-tailed lizard)

Distinguishing Features

This is a group of small- to medium-sized lizards with wedge-shaped heads and countersunk jaws, smooth granular scales, and dark crescents or bars on the sides of their bellies. Color is usually sandy tan to salmon with irregular spots, blotches, or bars of darker tan to brown. Uma spp. tend to have extensive networks of light spots with dark centers. Aside from the fringe-toed lizard, the species are easily confused. Their defining characteristics are outlined below.

Greater earless lizard
Range

Fringe-toed lizards are restricted to southeastern California, southwestern Arizona, northeastern Baja California, and northwestern Sonora, Mexico. The greater earless lizard is found in southeastern Arizona; southern New Mexico; central, west, and south Texas into Mexico at elevations up to 5600 feet (1700 m). The lesser earless lizard occurs in 5 central to western states, including eastern Arizona, south to Guanajuato, Mexico at elevations ranging from sea level to 7000 feet (2130 m). The zebra-tailed lizard ranges from Nevada and southeastern California through the western half of Arizona south throughout much of Baja California, Sonora and Sinaloa, Mexico at elevations ranging from sea level to 5000 feet (1520 m).

Habitat
Lesser earless lizard

Fringe-toed lizards occur only in low desert areas having fine, loose, sandy substrate. The greater earless lizard seems to prefer rocky bajadas and canyons in upland desert areas with mesquite, ocotillo, palo verde, and occasional creosote bush, in sandy or gravelly soils; it often rests on large rocks. The lesser earless lizard is more of a habitat generalist, occurring in desert grassland, Sonoran desertscrub, pinyon-juniper woodlands, thornscrub, and tropical deciduous forest; it is usually found in open areas with loamy soils. The zebra-tailed lizard is most commonly encountered in canyon bottoms, washes, desert pavement, and hardpan, where plant growth is minimal and there are wide or long stretches of open sandy soil.

Life History

All of these lizards are insectivorous, though some may also eat small lizards. They breed from spring to summer laying between 1 to 15 eggs, with the fringe-toed lizard usually laying fewer eggs than the other species. Eggs take 60 to 75 days to hatch.

Females of several lizard species exhibit color changes during breeding season. The “sand”lizards, for instance, develop bright orange or red areas on the different parts of the body. In some species this indicates readiness for breeding, while in others it is a signal to males that the female has already mated and is gravid (pregnant).

Zebra-tailed lizard
Comments

The fringe-toed lizard with its projecting toe scales, countersunk lower jaw, overlapping eye scales, and nasal valves is ideally suited to its sand dune habitat. Often it will dive into the sand to escape predators or extreme heat.

The zebra-tailed lizard has the peculiar habit of wagging its curled tail, which may serve to visually distract predators by drawing attention away from the lizard’s body and head. If a predator seizes the tail it easily detaches, a process known as autotomy. The tail has built-in fracture planes in the vertebrae to help it readily break off. The lizard grows back a cartilaginous replacement, which is shorter and has a different appearance than the original. Many species of lizards have this ability.

SpeciesEar OpeningsBelly MarksTail Marks
fringe-toedpresent1 large blotchbars present
greater earlessabsent2 crescents behind
midbody
bars present
(underside)
lesser earlessabsent2 crescents midbodybars absent
zebra-tailedpresent2 crescents at or in
front of midbody
bars present
(tail often banded)