Anoles, iguanas, and relatives

(Iguanidae)

Class Reptilia

Order Squamata

Suborder Sauria

Family Iguanidae

Thumbnail description
Small to large lizards, the majority of which are terrestrial and oviparous, that are marked by pleurodont teeth, which lie in inner-jaw grooves rather than in sockets

Size
1.6–30 in (30–750 cm) in snout-vent length (svl), and some have tails reaching twice the svl

Number of genera, species
69 genera; approximately 900 species

Habitat
Diverse, with most species occurring either in arid locales or wooded habitats

Conservation status
Extinct: 2 species; Critically Endangered: 6 species; Endangered: 4 species; Vulnerable: 12 species; Lower Risk/Near Threatened: 1 species; Data Deficient: 17 species

Distribution
Mainly a New World family, extending into much of North America, throughout Central America, and into South America; some species exist in other areas, including Madagascar and the islands of Polynesia

Evolution and systematics

The Iguanidae is a large family of some 860–900 species and nearly 70 genera. The iguanids comprise eight subfamilies:

• Corytophaninae, the casquehead lizards of Central America
• Crotaphytinae, the leopard and collared lizards
• Hoplocercinae, a small assemblage of South American tropical lizards
• Iguaninae, the true iguanas and spinytails
• Oplurinae, the Madagascar iguanas
• Phrynosomatinae, the tree, side-blotched, sand, spiny, and horned lizards
• Polychrotinae, the anoles
• Tropidurinae, the ground lizards of Neotropical South America and the Antilles Islands of the West Indies

The Iguanidae family is most closely related to the families Agamidae of Africa, Asia, and Australia, and the family Chamaeleonidae, mainly of Africa and Madagascar. These three families, collectively grouped as Iguania, diverged within the snake and lizard lineage very early in their evolution. Some taxonomists now classify each Iguanidae subfamily as a separate family, in which case the endings of the sub-family names listed above end in "-idae" rather than "-inae."

Physical characteristics

This large family contains species with varied appearances. Members of the Iguanidae family range from squat, toadlike horned lizards (Phrynosoma spp.) that fit in the palm of a hand, to iguanas (Iguana spp.) that are as long as a man is tall, and long-tailed and sleek anoles often seen climbing on a window screen. However, the family does have one characteristic that sets it apart from the other Iguania families. That trait is pleurodont teeth, which lie in inner-jaw grooves rather than in sockets.

The subfamilies within Iguanidae can be described in more detail. Members of the Iguaninae include the green iguana (Iguana iguana) and marine iguana (Amblyrhynchus cristatus). The typical iguanine is an imposing beast with a strong, muscular tail and (in males) a row of noticeable spines down the center of the back.

The corytophanines and polychrotines are slender-bodied lizards with long tails and long limbs. Corytophanines are generally the larger of the two, ranging in size from about 12 to 25.5 in (30.5 to 64.8 cm), compared to the 3–16 in (7.6–40.6 cm) range in the anole subfamily. The most obvious difference is the casque, or helmet, seen in the Corytophaninae subfamily. The casque is actually a tall fin on the top of the head. Corytophanines also generally have exaggerated dorsal and tail fins.

The crotaphytines and phrynosomatines are the typical lizards associated with southwestern United States. The former, which include the collared and leopard lizards, are quick, long tailed, and fairly large headed. The leopards are noted, and named, for their abundant dorsal spots, and the collared lizards usually display incomplete neck bands. The phrynosomatines are more diverse, and include more hefty-bodied species. Perhaps the most well-known phrynosomatines are the horned lizards (Phrynosoma sp.), which are often mistaken for toads because of their wide bodies and very short limbs.

The final three groups of Iguanidae are the hoplocercines, oplurines, and tropidurines. They are all small to moderately sized lizards. The first group has spiny scales; the second and third groups are distinguished more by geographic distribution (Madagascar for the second, and extreme South American areas for the third) than their appearance.

Distribution

Iguanids are largely lizards of the Western Hemisphere. They range from far southwestern Canada, into much of the United States, throughout Central America and the West Indies, and in almost all of South America except the southwestern edge. Some, like the iguanines, have wide ranges, with representatives from the southwestern United States, Central America, the northern half of South America, and the Galápagos Islands. Others, like the hoplocercines, are more restricted, with species occurring only in tropical South America.

The exceptions to the Western Hemisphere rule are the oplurines, which occur in Madagascar off the southeastern coast of Africa, and a few other species, such as Brachylophus species, that live on the Fiji Islands.

Habitat

Iguanids are almost all land-dwelling lizards. Many species, including most of the iguanines, crotaphytines, and phrynosomatines, prefer arid areas. These desert dwellers often seek sites with at least some vegetation, rocks, or other cover to provide escape routes from predators. Other iguanids seek a wooded habitat, with some, like many corytophanines, living in rain-forests. Within these varied habitats, iguanids may be either terrestrial or arboreal, with some switching between the two depending on time of day and outdoor temperature. The most unusual habitat among the iguanids is that of the well-known marine iguana of the Galápagos Islands. This lizard actually frequents salt water, where it forages marine algae to fill its diet.

Behavior

Iguanids are frequently seen stretched out on a rock or otherwise basking in the morning sun. This behavior falls under the heading of thermoregulation. Because lizards are poikilothermic, or "cold blooded," they engage in basking to raise their body temperature to prepare for the day's activities of feeding, perhaps breeding, and evading ever-present predators. Many iguanids spend the night in burrows and emerge each morning to find a sunny spot and raise their internal temperature. As the day gets hotter, ground-dwellers will move into shadier spots so they do not overheat. The more arboreal species may move from a basking spot on an outer tree limb or the sunward wall of a house to the inner branches of a tree or shrub, or closer to the ground where the temperature is lower.

The typical iguanid spends the day in a high state of alert, as predators abound, particularly for the small- and medium-sized

species. Many iguanids are cryptically colored and patterned, and are best served by remaining still when a predator passes. Others are quick runners and dash off almost immediately after they spot an animal that is even remotely threatening. Favorite hiding places for these runners are crevices between or under rocks, tangles of vegetation, or anything else that provides adequate cover. Some, like the zebratailed lizard (Callisaurus draconoides), start and stop while running or abruptly change direction when momentarily out of view to confound their pursuer. Various lizards, including Uma species, conceal themselves by squirming under the sand. A few inflate their bodies to avert capture. Common chuckwallas (Sauromalus obesus) are well known for this practice, and inflate their bodies when hiding in a narrow crevice. The enlarged size makes them nearly impossible to extract. The horned lizards also puff up their bodies, but the result is an erection of their numerous spines, an excellent deterrent against biting predators. Several species of these small lizards will go a step further if the attacker is persistent, and squirt up to one-third of their blood supply out of their eye pores. Foxes and coyotes, who are the most common recipients of this behavior, seem to find the blood distasteful and release the lizards.

Another unusual predator-avoidance strategy is employed by the so-called Jesus Christ lizards (Basiliscus sp.) that appear to "walk on water" while making their escape. Normally terrestrial, the basilisks drop into the water when threatened and race on their hind legs across the water surface. Studies have shown that fringes on the hind toes trap a bubble of air beneath their feet and keep them from sinking if they are running quickly enough. Basilisks have been known to race across water as far as 100 ft (30.5 m). Numerous other iguanids engage in bipedal running, and some are very quick sprinters, but none run across the water like the basilisks.

Behaviors between members of the same species also vary among the iguanids. Territoriality is prevalent, and many species exhibit stereotyped behaviors, such as doing repeated "push-ups" or marking their turf with secretions from femoral pores, to defend specific areas for feeding or breeding. In many species, territoriality becomes more pronounced when food resources are low. In some cases, dominance hierarchies may develop. Research on green iguanas (Iguana iguana) has shown that dominant males typically have higher levels of testosterone, as well as particularly strong jaws and enlarged femoral pores. These males were able to attain and defend prime territories against other males, and also to attract more females.

Among many species, including Cyclura carinata and Sauromalus obesus, territoriality becomes more pronounced during the breeding season. The males of some species captivate potential mates by certain actions. One of the most noticeable mating displays is the flaring of the throat fan, or dewlap, which is often seen in anoles (Anolis sp.). Anoles also flare the dewlap during territorial displays, which may include head bobbing and posturing.

Feeding ecology and diet

Most iguanids are either insectivorous or herbivorous, with the larger lizards tending toward a completely vegetarian diet. The iguanines, for instance, are primarily herbivorous as

adults, but the young also eat arthropods. Some members of this family, such as Gambelia species, will eat other lizards, and a few species are cannibalistic.

The insectivorous iguanids typically either stalk their prey or wait in ambush, particularly if the lizard is cryptically colored. After striking out at an insect or other arthropod, most lizards swallow the prey quickly. The common side-blotched lizard (Uta stansburiana) engages in the unusual practice of banging the prey on the ground several times before consuming it. Horned lizards are distinguished by their diet, which consists almost wholly of ants. These small lizards must eat considerable numbers of ants to gain adequate nutrition. Since ants produce formic acid to deter predators, the lizards may smell of formic acid as a result.

Reproductive biology

Most iguanids lay eggs, but a few give birth to live young. These include some Phrynosoma, Sceloporus, and Leiolamus species, as well as Corytophanes percarinatus. The number of eggs ranges widely. Many iguanids, such as the green anole (A. carolinensis), lay only one or two eggs at a time, but others lay dozens. The horned lizard (P. cornutum) commonly lays 24 eggs, but the number sometimes reaches more than 36 per clutch. A green iguana female may lay more than 60 eggs at a time.

In many species, optimal environmental conditions can spawn additional clutches. For example, some Dipsosaurus, Crotaphytus, and Gambelia species that live in cooler climates have only one clutch each year, while warmer-climate populations may have two, three, four, or more clutches.

Parental care among most iguanids is either nonexistent, or is restricted to simply burying the eggs or engaging in short-term nest guarding. The iguanines are most known for nest guarding. The rhinoceros iguana (Cyclura cornuta cornuta), for example, lays from two to nearly three dozen eggs, then tenaciously guards her nest for several days. The Jamaican iguana (Cyclura collei) guards her nest for up to two weeks. Among the iguanines, nest-guarding behaviors may range from displays to physical attacks.

Conservation status

The 2002 IUCN Red List includes 2 iguanids as Extinct, 6 as Critically Endangered, 4 as Endangered, 12 as Vulnerable, 1 as Lower Risk/Near Threatened, and 17 as Data Deficient. The extinct species are both tropidurines: Leiocephaluseremitus and L. herminieri. In addition, other iguanid species that are not listed by the IUCN are declining in either number or range due to overcollecting or habitat disruption and destruction. Introduced species also may play a role in these declines. For example, numbers of horned lizards in southern California have dropped in association with the proliferation of Argentine ants, which are replacing the native ants that make up the bulk of the lizards' diet.

A number of conservation activities are under way to protect threatened iguanids. For example, the Jamaican iguana (Cyclura collei), was believed extinct until a dead lizard was found in 1970 and a second individual, this time a living male, was discovered 20 years later. Since that time, the Jamaican Iguana Research and Conservation Group formed to survey the lizard's present habitat, which is now limited to a small peninsula west of Kingston. The population, estimated at about 100 individuals, is faced with several threats in the wild, including predation of the eggs (and likely the young) by the Indian mongoose (Herpestes javanicus [=auropunctatus]). Researchers now hope to boost the population by gathering eggs from the wild and rearing the hatchlings at the Hope Zoo in Jamaica until the lizards are large enough to avoid predation. The Natural Resources Conservation Authority is also taking measures, including promoting the designation of the area as a national park, to protect the lizard's current habitat from deforestation and development. Other proposals include introducing the lizards to areas such as Great Goat Island, which supported a population of Jamaican iguanas through the middle of the twentieth century.

Another at-risk iguanid is the Turks and Caicos iguana (Cyclura carinata carinata), which is native to these islands north of Haiti and the Dominican Republic. The lizards were once widespread, but the population is now estimated to number about 30,000 adults, and these are restricted to the smaller islands. Introduced mammals are the largest threat. Cats and dogs prey on the lizards, and now-wild livestock competes with the mainly herbivorous lizards for vegetation. Habitat destruction is also taking a toll. In an attempt to prevent the continued decline of the lizard population, the National Trust for the Turks and Caicos Islands worked with the government to draft legislation protecting the lizards from additional introduced mammals. The trust has also trapped cats in vulnerable areas. Other efforts include recently installed viewing platforms to keep tourists away from the lizards, the introduction of tourist fees to support further conservation efforts, and new educational programs to spread the word about the lizards and their plight.

Significance to humans

Many iguanid lizards are prized as sources of food meat, particularly in the southwestern United States and Mexico. They are also a mainstay in the pet lizard trade. Perhaps most importantly, they are valued by nature lovers, who can spend hours watching the antics of the lizards.

Species accounts

List of Species

Common collared lizard

Crotaphytus collaris

subfamily

Crotaphytinae

taxonomy

Crotaphytus collaris Say, 1823, Verdigris River, Oklahoma. Six subspecies are recognized.

other common names

English: Mountain boomer, yellowhead collared lizard, western collared lizard, eastern collared lizard, Chihuahuan collared lizard, Sonoran collared lizard; French: Lézard à collier; German: Halsbandleguan; Spanish: Lagartija de collar.

physical characteristics

Collared lizards are sturdy-looking lizards with a large head, long, round tail, and two dark, often-broken rings around the neck. The body ranges from yellowish green to blue, olive, or grayish brown, is dotted with small whitish spots, and is sometimes tinged with orange. Males are typically more brightly colored than females. Adults may reach 14 in (35.5 cm), with the tail comprising two-thirds of that length.

distribution

Collared lizards are found in the central and west-central United States and into northeastern Mexico.

habitat

These lizards prefer hilly, rocky glades and prairies with little shade.

behavior

These are exceptionally cautious lizards that need little provocation to run (often on two feet at high speed) to hiding places under and between rocks. They are aggressive when cornered, and will either bite, or show their intent to bite by gaping at the attacker. Despite the common name of mountain boomer, these lizards are silent.

feeding ecology and diet

Collared lizards stalk or ambush various insects and spiders, along with occasional small lizards. They are known to wave their long tails before snapping out at their prey.

reproductive biology

The breeding season of the collared lizard is in May and June. In July, females lay about a half dozen eggs per clutch, either in a burrow beneath rocks or buried several inches deep in the sand. Some females, particularly those in warmer climates, have two clutches per year. The eggs hatch two to three months later.

conservation status

Not listed by the IUCN.

significance to humans

None known.

Long-nosed leopard lizard

Gambelia wislizenii

subfamily

Crotaphytinae

taxonomy

Gambelia wislizenii Baird and Girard, 1852, Sante Fe, New Mexico. Four subspecies are recognized.

other common names

English: Leopard lizard, small-spotted lizard, Cope's lizard, Lahontan Basin lizard, pale leopard lizard; French: Lézard léopard; German: Leopardleguan; Spanish: Cachora leopardo.

physical characteristics

Long-nosed leopard lizards have dark-gray to black spots covering a light-gray to olive-gray back and tail. The coloration varies between individuals, and depending on temperature, even in the same lizard. These lizards frequently sport a series of white bands on the back and tail, and females often develop orange splotches along the sides during breeding season. Adults can reach 17 in (43 cm), including a long tail that makes up slightly more than two-thirds of the total length.

distribution

Long-nosed leopard lizards occur from the west-central United States to north-central Mexico.

habitat

These lizards live in flat desert areas with little vegetation.

behavior

To escape predators, long-nose leopard lizards will either race (often on two feet) into burrows or dash to the cover of lowlying

vegetation. Cornered or captured lizards become aggressive and will bite their attacker.

feeding ecology and diet

The long-nosed leopard lizard is a diurnal species that stalks its meals of insects and spiders, frequently lunging airborne after a tasty arthropod. It will also eat other lizards, including those of its own species.

reproductive biology

The breeding season of the long-nosed leopard lizard runs through May. In July, a female will lay about two to four eggs, although clutches of nearly a dozen are possible. Individuals in warmer climates may lay a second clutch. The eggs hatch within one to two months.

conservation status

Not listed by the IUCN.

significance to humans

None known.

Cape spinytail iguana

Ctenosaura hemilopha

subfamily

Iguaninae

taxonomy

Ctenosaura hemilopha Cope, 1863, Cape St. Lucas, Baja California. Five subspecies are recognized (some taxonomists list six).

other common names

English: Northern false iguana, spiny-tailed iguana; French: Iguane communà queue espineuse; German: Schwarze Leguane; Spanish: Iguana del Cabo.

physical characteristics

Cape spinytail iguanas are large, stocky, wrinkly-looking lizards, with a strongly ridged tail and crest of scales running along the top of the back. The crest is more pronounced in males than females. Adults can reach 3 ft (0.9 m) in total length, including their long tails, which can extend about one and a half times the length of the body.

distribution

These iguanas occur in northwestern Mexico, including the state of Sonora, and on islands in the Gulf of California.

habitat

Cape spinytail iguanas live in areas with numerous rocky crevices and frequently with some trees.

behavior

Cape spinytail iguanas are territorial, and the males form dominance hierarchies when habitat is limited. Although they will fight back aggressively with their strong legs, jaws, and tail if cornered or handled, they usually opt to run into a rock crevice for cover when they feel threatened.

feeding ecology and diet

These lizards are diurnal, and herbivorous, dining on flowers, fruits, and leaves of native vegetation. They occasionally eat invertebrates.

reproductive biology

These colonial lizards typically form groups with one lead male, several subordinate males, and a harem of females who are dominant to the subordinate males. They are oviparous, laying two dozen or more eggs in one clutch per year. The eggs hatch in about three months.

conservation status

Not listed by the IUCN.

significance to humans

These lizards are sold as pets and are a minor source of food for humans.

Desert iguana

Dipsosaurus dorsalis

subfamily

Iguaninae

taxonomy

Dipsosaurus dorsalis Baird and Girard, 1852, Colorado Desert, California. Four subspecies are recognized.

other common names

English: Northern crested lizard, crested lizard, desert lizard; French: Iguane du désert; German: Wüstenleguan; Spanish: Iguana del desierto, cachoron guero.

physical characteristics

Desert iguanas are robust lizards with a crest of raised, enlarged scales along the top of the back. They have whitish bellies, slate-colored backs that are spotted with white, and striped tails. Males have reddish, posterior markings. Adults can reach 15 in (38 cm) long, including a tail that is almost twice as long as the body.

distribution

Desert iguanas occur in the southwestern United States and northwestern Mexico, including islands in the Gulf of California.

habitat

These lizards live in open desert, often amidst scrubby bushes, where they occupy burrows and rock crevices.

behavior

Like the chuckwallas, desert iguanas will scurry into a crevice when threatened and puff up their bodies to avert being extracted by a predator.

feeding ecology and diet

Desert iguanas are diurnal, primarily herbivorous lizards that feed on the foliage and fruit of bushes and other desert plants, but will also eat invertebrates. They are territorial over feeding areas.

reproductive biology

The breeding season of the desert iguana runs from spring to midsummer. Females typically lay three to eight eggs from early to late summer, and under optimum conditions may have a second clutch.

conservation status

Not listed by the IUCN.

significance to humans

None known.

Common chuckwalla

Sauromalus obesus

subfamily

Iguaninae

taxonomy

Sauromalus obesus Baird, 1858, Fort Yuma, Arizona. Four sub-species are recognized. Discussions are underway over the placement of this species under the name Sauromalus ater.

other common names

English: Glen canyon chuckwalla, western chuckwalla, chuck, chuckawalla, iguana; French: Chuckwalla; German: Chuckwalla; Spanish: Chacahuala.

physical characteristics

Chuckwallas are robust lizards, with many loose folds of skin on the body, and a tail that stretches as long as the body. Their body color varies geographically, from the common grayish brown hue to brownish red and black. They are also known to change colors in response to environmental conditions. Males typically have dark heads and forelimbs. Females and juveniles are commonly distinguished by some banding, but adult males in some areas are also banded. Adults can reach 16–18 in (41.6–45.7 cm) in total length.

distribution

These lizards occur in the southwestern United States to northwestern Mexico, including parts of Arizona, Nevada, Utah, the Mojave and Sonoran Deserts, and in Baja California.

habitat

Chuckwallas prefer a rocky desert setting with plenty of crevices and other small hiding places.

behavior

These are quick lizards with a proficient predator-avoidance strategy. When pursued or otherwise threatened, a chuckwalla will race into a crevice, take a deep breath, and inflate its body so that extraction from the point of entry is nearly impossible. They spend the winter deep within rock crevices, but individuals will occasionally poke a nose outside on a particularly warm day. Chuckwallas are sometimes territorial.

feeding ecology and diet

Chuckwallas are herbivorous and feed diurnally, foraging for vegetation after warming up by basking in the desert sun. Limited food resources can negatively affect their growth rate.

reproductive biology

Mating among the chuckwallas begins in the spring. About two months later, each female lays five to 16 eggs (usually fewer than 10) in depressions or tunnels under stones. The young typically hatch in early fall.

conservation status

Not listed by the IUCN.

significance to humans

These lizards are used in the pet trade and are also a minor source of human food.

Zebra-tailed lizard

Callisaurus draconoides

subfamily

Phrynosomatinae

taxonomy

Callisaurus draconoides Blainville, 1835, northern Baja California. Nine subspecies are recognized.

other common names

English: Gridiron-tailed lizard, northern zebra-tailed lizard, western zebra-tailed lizard, eastern zebra-tailed lizard, Nevada zebratail, Mojave zebratail; German: Zebraschwanzleguan; Spanish: Lagartija cachora, perrita.

physical characteristics

Zebra-tailed lizards are speckled, light gray to brown lizards with particularly long forelimbs and a flat, broadly banded tail. The dark tail bands continue on to the light-colored ventral tail, where they are particularly noticeable. Males typically are distinctly blue on the belly, and display a pink throat fan during breeding season. Adults reach about 10 in (25.4 cm) in total length, with the tail about one and a half times as long as the body.

distribution

These lizards occur in the southwestern United States, northwestern to west-central Mexico.

habitat

The zebra-tailed lizard prefers a sand or gravel substrate in desert canyon washes, scrubby plains, and other areas that are dry for much of the year.

behavior

This wary species is noted for its swiftness. When threatened by a predator, the zebra-tailed lizard will arch its tail over its back and wave the particularly conspicuous ventral banding at the pursuer. As the predator's attention is drawn to that location, the lizard speeds off to cover in a dizzying pattern of stops, starts, and sharp turns.

feeding ecology and diet

This mainly diurnal lizard will consume tender spring vegetation, but mostly feeds on insects and spiders. A sit-and-wait hunter, it may suddenly leap at prey, sometimes jumping a foot or more to secure its meal.

reproductive biology

Male zebra-tailed lizards flare the throat fan during the breeding season. During the summer, females typically lay two to six eggs per clutch, and a female may have up to five clutches in one year.

conservation status

Not listed by the IUCN.

significance to humans

None known.

Common lesser earless lizard

Holbrookia maculata

subfamily

Phrynosomatinae

taxonomy

Holbrookia maculata Girard, 1851, opposite Grand Island, Platte River, Nebraska. Nine subspecies are recognized.

other common names

English: Mountain earless lizard, speckled earless lizard, band-tailed earless lizard, bleached earless lizard, Bunker's earless lizard, Huachuca earless lizard, eastern earless lizard, northern earless lizard, western earless lizard, spotted lizard; Spanish: Lagartija.

physical characteristics

Common lesser earless lizards are gray, with rather regular dark blotches down the back and onto the sides and tail. They lack the ear openings typical of other lizards. Males have orange to red throat patches. Adults average about 5 in (12.7 cm) in total length, including a tail that is about as long as the body in males and slightly shorter in females. Subspecies have slightly different scalation patterns.

distribution

These lizards occur in the central United States as far north as Nebraska and Wyoming, and also in northern Mexico.

habitat

Lesser earless lizards live in sandy, open areas with sparse vegetation that provides shady retreats.

behavior

These are quick lizards that race between burrows or the shade of a bush during the day. The males are often territorial. As the breeding season progresses, the females become more vividly colored, eventually developing a bright yellow head and reddish-orange sides and hind legs. The males use a series of rapid head bobs to court females who are just beginning to show the breeding coloration. Later-season, high-intensity coloration appears to signal the end of a female's receptivity to the male's approach.

feeding ecology and diet

The diet of the lesser earless lizard consists of insects, especially grasshoppers and ants, and spiders. Occasionally it will eat other, smaller lizards.

reproductive biology

Breeding in the lesser earless lizard occurs in early summer. About two months later, the females lay between three and 11 eggs in an underground burrow. Younger females have one clutch per year; older females may have a second clutch.

conservation status

Not listed by the IUCN.

significance to humans

None known.

Texas horned lizard

Phrynosoma cornutum

subfamily

Phrynosomatinae

taxonomy

Phrynosoma cornutum Harlan, 1825, Great Plains, east of the Rocky Mountains. No subspecies are recognized.

other common names

English: Horned toad, horny toad, San Diego horned lizard, California horned lizard; French: Lézard crapaud ou cornu; German: Texas-Krötenechse; Spanish: Torito de la Virgen.

physical characteristics

Texas horned lizards are squat and spiny, with a short tail and two large occipital "horns" on the head. They also have a large blotch on either side of the neck, and large, dark spots on the back. The general body color is brown, sometimes with a yellowish or reddish tint, but color varies with external temperature. Adults are typically about 3 in long (7.6 cm), but some may reach 5 in (12.7 cm).

distribution

Texas horned lizards occur in the west-central United States, and in northern Mexico.

habitat

These lizards are found nearly anywhere throughout their range where it is dry, flat, and sparsely vegetated.

behavior

Texas horned lizards are diurnal. They peculiarly squirt blood from their eyes. This behavior may be observed while the lizard is shedding, or when it is seriously threatened. Other defensive tactics include hissing, inflating the body, and erecting the horns at an attacker.

feeding ecology and diet

Ants are the primary component of the diet of the Texas horned lizard, although the lizards will also eat other arthropods. They drink by gathering raindrops on their back, then channeling the drops through their scales and into the mouth.

reproductive biology

Texas horned lizards mate in spring, and females lay an unusually large number of eggs (two to three dozen) which they bury about 6 in (15.2 cm) deep. The young typically hatch in July and early August.

conservation status

Not listed by the IUCN, but the species has disappeared from about one-half of its historical range. Their disappearance coincides with a loss of habitat, as well as a proliferation of fire ants. Fire ants have displaced harvester ants, a mainstay of the lizard's diet.

significance to humans

An unusual and well-known reptile, it is the state reptile of Texas.

Mountain spiny lizard

Sceloporus jarrovii

subfamily

Phrynosomatinae

taxonomy

Sceloporus jarrovii Cope, 1875, Southern Arizona. Eight sub-species are recognized.

other common names

English: Yarrow's spiny lizard; French: Lézard épineux, lézard de palisades; German: Jarrov Zaunleguan; Spanish: Lagartija espinosa de Yarrow.

physical characteristics

Mountain spiny lizards are robust lizards with finely patterned skin. The dorsal body is dark gray to black and has large scales, each of which contains a central, white dot. The male's belly and sides range from blue to black to gray; the female's belly is usually whitish. The overall coloration of these lizards can vary depending on environmental conditions. Adults can reach about 9 in (23 cm) long, with the tail making up one-half to three-fifths of that length.

distribution

These lizards occur in the western United States to northwest and west-central Mexico.

habitat

Mountain spiny lizards are found in mountainous areas at elevations between 5,000 and 10,000 ft (1,520 and 3,050 m). They prefer rocky, well-forested areas.

behavior

These lizards engage in extended morning basking periods, and are less wary than most other lizards. They are territorial and will defend larger areas when food is limited. During lean times, they may also alter their diet and become less active.

feeding ecology and diet

Mountain spiny lizards eat insects and spiders, as well as lizards, including other mountain spiny lizards.

reproductive biology

Most lizards lay eggs, but mountain spiny lizards bear live young, which are born in the spring. The gestation period is about five months, but since females can store sperm, breeding can occur several months earlier. A typical litter ranges from five to eight, but a few more or less is not unusual.

conservation status

Not listed by the IUCN.

significance to humans

None known.

Coachella Valley fringe-toed lizard

Uma inornata

subfamily

Phrynosomatinae

taxonomy

Uma inornata Cope, 1895, Colorado Desert, Riverside County, California. No subspecies recognized.

other common names

English: Coachella uma, Coachella sand-lizard; German: Fransenzehenleguan.

physical characteristics

Coachella Valley fringe-toed lizards are light gray with delicate black speckles on the back and dorsal tail. These speckles may appear as black-outlined, white circles with small, black, central dots. The speckles typically run together to form discontinuous, lateral stripes that extend from the head to about the middle of the body. The Coachella Valley fringe-toed lizard is also distinguished by a fringed fourth toe. Adults can reach about 13 in (33 cm) in total length, of which one-half to two-thirds may be tail.

distribution

These lizards occur only in the Coachella Valley in southern California's Riverside County.

habitat

Coachella Valley fringe-toed lizards live in dunes and other desert areas with loose, sandy soil and some low vegetation.

behavior

When not scurrying about the dunes, this lizard is either hiding in a bush or a burrow, or buried in the sand. It accomplishes the latter avoidance tactic by maneuvering its hind limbs and body (so-called sand swimming) to wiggle itself down into the substrate.

feeding ecology and diet

Primarily insectivorous, these diurnal lizards occasionally eat vegetation.

reproductive biology

Female Coachella Valley fringe-toed lizards lay one to four eggs from late spring to early fall.

conservation status

Listed as Endangered by the IUCN.

significance to humans

None known.

Common sagebrush lizard

Urosaurus graciosus

subfamily

Phrynosomatinae

taxonomy

Urosaurus graciosus Baird and Girard, 1852, Southern California. Two subspecies are recognized.

other common names

English: Long-tailed uta, western sagebrush lizard, northern sagebrush lizard, southern sagebrush lizard, brush lizard, Arizona brush lizard; Spanish: Lagartija de Matorral, cachora coluda.

physical characteristics

Sagebrush lizards are light grayish brown lizards with a very long tail. They have a series of thin, dark lines branching across the head and running down the back and sides. The lizards are generally darker in color in the early morning and become lighter as the temperature rises. Blue blotches are

frequently noticeable on the belly. Adults can reach 10.5 in (26.7 cm), including a tail that makes up about 70% of the total length.

distribution

Sagebrush lizards occur in the southwestern United States and in Baja California, Mexico.

habitat

These lizards live among sagebrush and other shrubs, as well as in mesquite and creosote trees, in otherwise open desert areas.

behavior

This lizard is known as a climber and is frequently seen stretched out perfectly still on branches, tree trunks, and other vertical surfaces. When threatened, they scamper into thicker vegetation, or abandon their arboreal habits altogether and run into burrows hidden beneath vegetation.

feeding ecology and diet

Sagebrush lizards mostly eat insects. They do much of their foraging in vegetation, but will venture onto the desert ground when necessary.

reproductive biology

Female sagebrush lizards commonly lay clutches of two to five eggs from late spring to late summer, although clutch sizes of a dozen eggs have been reported. In cooler climates, one clutch is common. Females in warmer climates may lay up to six clutches a year.

conservation status

Not listed by the IUCN.

significance to humans

None known.

Common side-blotched lizard

Uta stansburiana

subfamily

Phrynosomatinae

taxonomy

Uta stansburiana Baird and Girard, 1852, Salt Lake Valley. Six subspecies are recognized.

other common names

English: Northern ground uta, western ground uta, western side-blotched lizard, Nevada side-blotched lizard, northern side-blotched lizard, eastern side-blotched lizard, plateau side-blotched lizard, uta, Stansbury's swift, northern brown-shouldered lizard; German: Seitenfleckleguan; Spanish: Cachora del suelo, Lagartija de manchas lateralis.

physical characteristics

Side-blotched lizards are mostly brown, with five, light-colored, dorsal stripes running from the head at least to the beginning of the tail. These stripes are sometimes indistinct. During breeding season, the males often take on a distinctly bluish hue on the head, tail, top of the back, and sides.

distribution

Side-blotched lizards occur in the western United States, from Washington State south to Baja California and northern Mexico.

habitat

The side-blotched lizard is a wide-ranging species that lives in the flat desert, as well as rocky outcrops, hills, and even mountainous regions. It usually prefers sites with some vegetation.

behavior

Side-blotched lizards have the unusual habit of grasping their prey in their mouths, then beating it on the ground before consuming it. They are less skittish than many other lizards, but if approached too closely, they will run for a burrow, bush, or other cover.

feeding ecology and diet

These lizards are primarily insectivorous, but they are also known to eat other arthropods, including scorpions.

reproductive biology

Breeding in side-blotched lizards begins in early spring, and females commonly lay one to two clutches of three or four eggs each from spring to midsummer. Females in warmer climates sometimes lay up to seven clutches in a single year. Most eggs hatch from June to August. They have unusually speedy development, and the hatchlings reach maturity before the year is out.

conservation status

Not listed by the IUCN.

significance to humans

These lizards help control the population of insects that are agricultural pests.

Green anole

Anolis carolinensis

subfamily

Polychrotinae

taxonomy

Anolis carolinensis Voigt, 1832, Carolina. Two subspecies are recognized.

other common names

English: American chameleon, Carolina anole; French: Anolis de Caroline; German: Rotkehlanolis; Spanish: Anolis verde.

physical characteristics

Slim lizards, green anoles have pointed heads and long tails that can be more than twice the length of the body. They have the ability to switch from their usual green coloration to brown or gray. Males display a conspicuous usually reddish-pink throat fan, known as a dewlap. Adults typically range from 5 to 8 in (12.7 to 20.3 cm) in total length, and about 2.5 in (6.3 cm) from snout to vent. Males are usually longer than females of similar age.

distribution

Green anoles occur in the southeastern United States as far west as Texas and north to Virginia. They are also found in Cuba and on islands in the Caribbean.

habitat

Green anoles prefer moist, vegetated habitats with climbing surfaces, including trees, vines, and bushes, as well as fences and house walls. They are commonly found near the ground, but climb higher to bask.

behavior

Green anoles are territorial, and males exert their dominance by flaring their dewlaps, bobbing their heads, erecting the dorsal skin into a crest, and engaging in stereotypical posturing to enlarge their body image. During the breeding season, males also use their dewlaps to entice females, which appear to choose a mate based on the coloration and possibly the ultraviolet reflectance of the dewlap.

feeding ecology and diet

The diet of the green anole includes small insects and spiders. Diurnal feeders, these lizards typically stalk their prey.

reproductive biology

Breeding occurs from spring to fall. Females typically lay a single egg, and bury it in leaf litter and loose soil. The young hatch five to seven weeks later. Females can continue to lay eggs throughout the long reproductive season, as often as once every two weeks.

conservation status

Not threatened.

significance to humans

These lizards are common in the pet trade.

Resources

Books

Burghardt, G., and A. Rand, eds. Iguanas of the World: Their Behavior, Ecology, and Conservation. Park Ridge, NJ: Noyes Publications, 1982.

Campbell, J. A. Amphibians and Reptiles of Northern Guatemala, the Yucatan and Belize. Animal Natural History Series, Vol. 4. Norman: University of Oklahoma Press, 1998.

Cei, J. M. New Species of Tropidurus (Sauria, Iguanidae) from the Arid Chacoan and Western Regions of Argentina. Lawrence: University of Kansas, Museum of Natural History, 1982.

Cogger, H., and R. Zweifel, eds. Encyclopedia of Reptiles and Amphibians. San Diego: Academic Press, 1998.

Conant, R., J. T. Collins, I. H. Conant, T. R. Johnson, and S. L. Collins. A Field Guide to Reptiles & Amphibians of Eastern & Central North America. Peterson Field Guide Series. Boston: Houghton Mifflin Co., 1998.

Crother, B. I., ed. Caribbean Amphibians and Reptiles. San Diego: Academic Press, 1999.

Frank, N., and E. Ramus. A Complete Guide to Scientific and Common Names of Reptiles and Amphibians of the World. Pottsville, PA: NG Publishing Inc., 1996.

Grismer, L. L., and H. W. Greene. Amphibians and Reptiles of Baja California, Including Its Pacific Islands and the Islands in the Sea of Cortês (Organisms and Environments). Berkeley: University of California Press, 2002.

Lee, J. C. A Field Guide to the Amphibians and Reptiles of the Maya World: The Lowlands of Mexico, Northern Guatemala, and Belize. Ithaca, NY: Cornell University Press, 2000.

Milstead, W., ed. Lizard Ecology: A Symposium. Columbia: University of Missouri Press, 1967.

Pianka, E. Ecology and Natural History of Desert Lizards: Analyses of the Ecological Niche and Community Structure. Princeton, NJ: Princeton University Press, 1986.

Pianka, E. R., and L. J. Vitt, eds. Lizard Ecology. Berkeley: University of California Press, 1994.

——. Lizards: Windows to the Evolution of Diversity. Berkeley: University of California Press, 2003.

Savage, J. M., M. Fogden, and P. Fogden. The Amphibians and Reptiles of Costa Rica: A Herpetofauna Between Two Continents, Between Two Seas. Chicago: University of Chicago Press, 2002.

Smith, H. M. Handbook of Lizards: Lizards of the United States and Canada. Ithaca, NY: Comstock Publishing Co., 1946.

Stebbins, R. A Field Guide to Western Reptiles and Amphibians. Boston: Houghton Mifflin Co., 1985.

Periodicals

Bealor, M. T., and C. Krekorian. "Chemosensory Identification of Lizard-Eating Snakes in the Desert Iguana, Dipsosaurus dorsalis (Squamata: Iguanidae)." Journal of Herpetology 36, no.1 (2002): 9–15.

Carothers, J. H. "Dominance and Competition in an Herbivorous Lizard." Behavioral Ecology and Sociobiology 8 (1981): 261–266.

Frost, D. R., and R. Etheridge. "A Phylogenetic Analysis and Taxonomy of Iguanian Lizards (Reptilia: Squamata)." University of Kansas, Museum of Natural History Miscellaneous Publications 81 (1989): 1–65.

Hager, S. B. "The Role of Nuptial Coloration in Female Holbrookia maculata: Evidence for a Dual Signaling System." Journal of Herpetology 35, no. 4 (2001): 624–632.

Hazen-Hammond, S. " 'Horny Toads' Enjoy a Special Place in Western Hearts." Smithsonian 25 (1994): 82–86.

Ramírez-Bautista, A.; O. Ramos Flores, J. W. Sites, Jr. "Reproductive Cycle of the Spiny Lizard Sceloporus jarrovii (Sauria: Phrynosomatidae) from North-Central Mexico." Journal of Herpetology 36, no. 2 (June 2002): 225–233.

Organizations

Iguana Specialist Group of the World Conservation Union (IUCN). Web site: <http://www.iucn-isg.org/index.php>

The International Iguana Society. 133 Steele Rd., West Hartford, CT 06119 USA. Web site: <http://www.iguana society.com>

Other

Pianka, E. R., and W. L. Hodges. Horned Lizards. (cited November 4, 2002). <http://uts.cc.utexas.edu/varanus/phryno.html>

Proliferation of Argentine Ants in California Linked to Decline in Coastal Horned Lizards. February 26, 2002 (cited November 4, 2002). <http://ucsdnews.ucsd.edu/newsrel/science/mclizard.htm>

Leslie Ann Mertz, PhD