Collared lizards of the genus Crotaphytus are among the most colorful lizards in North America. They get their name from the pair of black collars that circle the back of the neck. All of the genus Crotaphytus have these collars, though they vary in size and shape between the different species. Collared lizards are characterized by a large head, skinny neck, and a large body with a long skinny tail. There are two forms of collared lizards, the collaris form and the insularis form. The collaris form has a blunt snout, a round tail, and green or blue coloration in males. Both sexes have black oral melanin in which they use during the defense behavior of mouth gaping. The insularis form has a long snout and a wedge shape tail. They lack the oral melanin. Males lack the bright coloration but have enlarged inguinal patches. Axtell (1972) suggested that the insularis forms are primitive character states. The rear limbs of collared lizards are longer than the front limbs, giving them the appearance of a small T-rex. There is strong sexual dimorphism between male and female collared lizards. The maximum size in males is between 111mm to 125mm depending on the species. The maximum size for females is 97mm to 108mm, again depending on the species. Males are the more colorful of the sexes. Their size and coloration evolved due to their territorial behavior and their reliance on vision. Collared lizards were first described in Edwin James' account of Expedition to the Rocky Mountains in 1823. Thomas Say, a member of that expedition, collected and described them as Agama collaris. In 1842, Holbrock placed collared lizards in the new genus Crotaphytus. Until recently, leopard lizards were also included in this genus. They have since been placed in the genus Gambelia. In 1989 Frost and Etheridge put these two genera in the iguanian family Crotaphytidae. With the discovery of new species, scientific names of collared lizards have changed many times. Currently they have been divided into at least eight or nine species.

Crotaphytus reticulatus is a tan to brown lizard with reticulations covering most of its dorsum, limbs, and tail. Some of these reticulations are filled with black pigmentation. Unlike the rest of Crotaphytus, there is no color difference between males and females except during the breeding season. During this time males develop a bright yellow coloration on their chest. The collars on C. reticulatus are faint and the anterior collar is complete ventrally. The dewlap, or gular area is a greenish gray with black pigmentation in the center. The gular area of the female is white to yellow without the black pigmentation in the center. Collared lizards have small pockets at the base of the tail and folds of skin above the front legs. Mites and chiggers gather in these areas. C. reticulatus lacks post-femoral mite pockets that are present in the rest of the genus. This suggests that this genus broke away from the ancestral group first. C. reticulatus has black oral melanin and black femoral pore secretions, the rest of the genus, except C. antiquus, has gray secretions.
Of all the Crotaphytid species, C. reticulatus is the only species that is not restricted to rocky habitat. It is native to the Tampaulipan biotic province, a thornscrub desert, of southern Texas and adjacent Mexico. C. reticulatus spends its life on the ground much like a close relative the leopard lizard. When threatened, it will take refuge in rodent borrows and under brush. This species range is declining due to habitat destruction and possibly climate change. The reticulated collared lizard is the only Crotaphytid species in the United States that is protected from collecting.

Crotaphytus collaris has the largest distribution of all Crotaphytus species. It is the most common species found in the pet trade. C. collaris is the most generalized of all the collared lizards and has adapted to many different habitats. C. collaris is divided into five subspecies. The eastern collared lizard, C. c. collaris, ranges from the Ozarks of southern Missouri and Arkansas, westward through the plains of Kansas, Oklahoma, Texas, and into eastern New Mexico. Here it comes into contact with the western collared lizard, C. c. baileyi. C. c. baileyi is similar in color to C. c. collaris, yet C. c. baileyi has a slightly longer snout and separate supraorbital scales. C. c. collaris usually has fused supraorbital scales. C. c. baileyi occurs from western Arizona, eastward into central New Mexico, where it intergrades with C. c. collaris and C. c. fuscus. In western Arizona two hybrid zones have been discovered where C. c. baileyi comes into contact with the Mojave collared lizard, C. bicinctores (Axtell, 1972)(Montanucci, 1983). C. c. fuscus, the Chihuahuan collared lizard, ranges from south-central New Mexico east to Texas, southward into northern Mexico. C. c. auriceps, the yellow headed collared lizard, is found in east central Utah and western Colorado. This subspecies is similar in coloration to C. c. baileyi except the yellow on the head extends on the chin down to the dewlap. In C. c. baileyi this area is white. C. c. auriceps intergrades with C. c. baileyi between the Colorado River in Utah and the Painted Desert area of Arizona. C . c. melanomaculatus, the black spotted collared lizard, is a newly described subspecies that inhabits the Mexican states of Coahuila, Zacatecas, Nuevo Leon, San Potosi and the southwestern edge of Tamaulipas.
Crotaphytus collaris is characterized by a round cylindrical tail and a broad head with a blunt snout. Like C. reticulatus, C. collaris has black oral melanin. Dorsal coloration varies greatly in this species. In some population it is green while in others it is blue to turquoise. C. c. fuscus lacks the greens and blues and is brown to tan. Some males have yellow bands across the dorsum. Females are greenish to brown and are not as bright as the males. Gular coloration also varies. Most western populations have green to blue dewlaps while eastern populations have yellow or orange dewlaps. This species lacks the black pigmentation in the center of its dewlap. Females usually have a plain white dewlap, but some individuals will have small spots in the gular area. A pair of collars are always present. In this species, the anterior collar doesn't connect in the gular area as it does in the rest of Crotaphytus. In some populations, C. collaris has black patches or spots on its sides, in front of the rear legs. These spots are not as large as the inguinal patches that are found in the rest of the genus. Males have enlarged postanal scales and some females will have a small dark spot, or a pair of spots, on each side of the vent. Most of C. collaris has white spotting covering the dorsum. C. c. melanomaculatus is between the ranges of C. collaris and C. reticulatus and completely surrounds the isolated species, C. antiquus. C. c. melanomaculatus shares charateristics of C. collaris, C. antiquus and possibly C. reticulatus, therefore it is probably a product of hybridization between these lizards over a long period of time(Montanucci 1974, and Axtell and Webb 1995). C. c. melanomaculatus has greenish and yellow pigmentation on the trunk and limbs with several black spots or bars forming bands across the dorsum. The femoral pores are gray or only lightly pigmented and the dewlap color is bluish gray without a black center. It lacks the black inguinal patches found in C. antiquus, and has the black oral melanin. An active hybrid zone hasn't been found, so the origin of these lizards needs further study.

Crotaphytus nebrius, the Sonoran collared lizard, has been considered a subspecies of C. collaris (Axtell and Montanucci, 1977). It shares characteristics from both the collaris and the insularis groups. In the early 1970's, Axtell believed that C. nebrius was an intergrade between C. collaris and Dickerson's collared lizard, C. dickersonae in the Guayamas, Mexico area. They occur on parallel mountain ranges there but do not intergrade. There is no current intergration or overlap with C. collaris were their ranges near each other. C. nebrius has tan to yellow dorsal coloration with white spotting on the back and sides. These spots are generally larger than the white spots found on C. collaris. This species lacks the blues and greens found in C. collaris. The gular area is gray to brown in males, and either plain or lightly marked in females. Oral melanin is present in this species. Both collars are present with the anterior collar complete ventrally. Inguinal patches are fixed in males of this species. C. nebrius is one of the smallest members of the genus.
C. nebrius inhabits most of Sonora Mexico. It crosses into the United States on the north to south trending mountain ranges in southwestern Arizona. The Gila River forms a boundary between this species and C. bicinctores, the Mojave collared lizard. Since there are no mountains reaching up from Sonora to the Gila River near the Sentinel Plain, C. nebrius isn't found there. This is the only place where C. bicinctores has become established south of the river.

Crotaphytus antiquus (Axtell and Webb,1995) is a newly described species of collared lizard found in southwest Coahuila, Mexico. Axtell and Webb named this lizard according to their theory that this was the most ancestral-like species of the genus Crotaphytus. This lizard is only found in the Sierra de San Lorenzo, Sierra Texas, and Sierra Solis. These three small, isolated mountain ranges are completely surrounded by C. collaris, yet this species shares most of its characteristics with the insularis group. In males, the anterior collar is complete ventrally, there is black pigmentation in the center of the dewlap, a laterally compressed tail, and black ingiunal patches. C. antiquus lacks the blue and green dorsal coloration and the black oral melanin found in C. collaris. C. antiquus has a brown dorsal coloration. In both males and females, the limbs and dorsum are covered with reticulations. Adult males have seven to eight rows of reticulations that are filled with black pigmentation. Females and young males lack this coloration. Besides sharing a reticulated body pattern with C. reticulatus, they both have jet black femoral pores. One characteristic that separates this species from the rest of Crotaphytus is a row of scales separating the supraorbital semicircles. The two supraorbital semicircles almost always touch each other on the top center of the head in all the other species. In C. collaris collaris these scales are usually fused together where they touch. More research is needed to determine if this lizard is an ancient species or a more recent hybrid.

Crotaphytus dickersonae has a very small range in the coastal mountains of Sonora, Mexico, between Punta Cirio and Bahia Kino. It is also found on the Isla Tiburon in the Sea of Cortez. This lizard has many characteristics of the collaris and the insularis groups. Its ancestors may have been hybrids of both forms. The dorsal coloration is a vibrant cobalt blue without any yellow as in C. collaris. The dorsum is covered with white spots and the collars are complete dorsally. The anterior collar is complete ventrally. In males the gular area is gray with a black center and enlarged inguinal patches are present. Females lack the gular coloration and the inguinal patches. The body shape of C. dickersonae is like the insularis form. Males have a laterally compressed tail and an elongated snout. Montanucci, Axtell, and Dessauer found that genetically, C. dickersonae is more similar to C. collaris than it is to the insularis group. More study is needed to find the origin of this beautiful species.

Crotaphytus vestigium, the Baja collared lizard, occurs on the eastern escarpment of the peninsular mountains of southern California, southward to the Sierra San Pedro Martir of Baja Mexico. In the southern portion of its range, it can be found on both sides of the peninsula. These lizards can be found basking on rocks when the temperature in the shade is well over 100 degrees. They are a little more wary and harder to approach than C. collaris. C. vestigium has an elongated snout. McGuire theorizes that the elongated snout found in the insularis group and C. dickersonae, could have evolved to help catch vertebrate prey such lizards. Males have a laterally compressed tail and enlarged inguinal patches. The compressed tail and inguinal patches are believed to be male display features. A laterally compressed tail makes the lizard appear larger. In males the gular area is grayish blue with a black center. Reticulations extend from the dewlap to just under the eyes. Females usually have a yellow gular area without the dark center or the reticulations. C. vestigium lacks the oral melanin and doesn't gape its mouth as a defense reaction. The collars of C. vestigium do not connect mid-dorsally. In some individuals the posterior collar is faint or nonexistent, and the anterior collar is complete ventrally. The dorsum is olive gray to tan with white dashes, spots, and bars. In C. vestigium the bars are often wavy and sometimes offset mid-dorsally. This is one of the largest members of the genus.
C. insularis, a very close relative to C. vestigium, occurs on Isla Angle de La Guarda in the Sea of Cortez. Its body shape and physical characteristics are very similar to C. vestigium. The collars are noticeably reduced in this species and the posterior collar is almost always absent. Adult males have a green tint to the ventro-lateral area, but some C. vestigiums also have this coloration. C. insularis has the spots and dashes on its dorsum, but lacks the wavy transverse body bars found in C. vestigium. More study of this species is needed to determine if it is indeed a true species or a subspecies of C. vestigium.
Crotaphytus grismeri is a species described by McGuire in 1994. It is a brown lizard with white spotting much like C. bicinctores, except that males lack the rust colored dorsal bars. The collars are complete or nearly complete mid-dorsally and the anterior collar is complete ventrally in the gular area. There is green pigmentation on the white bars between the collars. This species lacks oral melanin. Like the rest of the insularis group, males have an elongated snout, laterally compressed tail, and enlarged inguinal patches. The gular area is bluish gray with a black center. Females lack the dewlap coloration and subadult females have a burnt orange tail, which is not found in the rest of Crotaphytus.
This species is one of the smaller lizards of the genus. C. grismeri inhabits the Sierra de las Cucapas and Sierra el Major mountains in northern Baja Mexico. These lizards appear to be a sister taxon to C. bicinctores but as with the rest of the Crotaphytus genus further study is needed.

Often referred to as the Mojave or Great Basin collared lizard, Crotaphytus bicinctores has the largest range of the insularis group. It occurs from southern Idaho and Oregon, southward through Nevada and western Utah, to the deserts of western Arizona and California. C. bicinctores intergrades with C. collaris baileyi in northwestern Arizona and comes into contact with, but doesn't intergrade with C. nebrius along the Gila River in southwestern Arizona. In southern California, C. bicinctores is separated from C. vestigium by the San Gorgonio pass. There is no evidence of intergration between these two species (Sanborn and Loomis, 1979).
C. bicinctores is a brown lizard with small white spots on the dorsum. Males have rust colored bars across their dorsum and their dewlap is bluish with a black center. Reticulations are present from the dewlap to under the eyes. Females color and patterns are the same as in males but without the rust colored bars across the back. Their dewlaps are white or lightly marked. The collars are complete or nearly complete mid-dorsally. The anterior collar is complete ventrally. As with the rest of the insularis group, males have elongated snouts, laterally compressed tails, and large inguinal patches. It also lacks oral melanin.

The speciation of Crotaphytus is directly related to plate tectonics and the formation of mountain ranges. Ancestral collared lizards probably evolved during the Miocene epoch. During this time, there was a north to south trending volcanic arc extending along the west coast of North America. From 20 to12 million years ago the Baja peninsula was a part of mainland Mexico. Underlying forces responsible for the basin and range topography of western North America, formed a deep basin where the Pacific plate once subducted beneath the North American plate. About 13 million years ago, the ocean invaded this basin. By 6 million years ago, it had reached the San Gorgonio pass area near Palm Springs, California. These events probably separated ancestral C. dickersonae from ancestral C. antiquus. Ancestral C. antiquus, C. collaris and/or C. nebrius was already established in the Sierra Madre Occidental. It is not known if there was suitable habitat in this basin for C. dickersonae to cross over to the volcanic arc or if the lizards dispersed over water as the ocean invaded. In any case, ancestral C. dickersonae became isolated on this arc. Around 5.5 million years ago, the former subduction zone began to split as a transform fault developed. This split the volcanic arc, leaving parts of it on the North American plate and parts of it on the Pacific plate. A spreading center developed and the Baja peninsula began on its northwestern journey. This left ancestors to the insular stock on the peninsula. It is probable that as Baja broke away, C. bicinctores and C. grismeri dispersed to their present locations. Since the gulf was present during this time, these lizards most likely crossed over water. There is evidence that the Sierra de las Cucapas and Sierra el Mayor mountains existed as a Pliocene island (Gastil, 1983). Chuckwallas and collared lizards are the only saxicolous reptiles found on these mountains. Both are well suited for over water dispersal (Grismer, 1994). As the peninsula drifted away from the mainland, C. vestigium evolved on this narrow mountain block. Around 1 million years ago, the axis of the spreading center shifted from the east side of Isla Angle de La Guarda to the west side of the island. This event displaced the island 20 kilometers to the east (Phillips, 1968). C. insularis either went with this island or dispersed over water to the island (McGuire, 1994).
C. collaris probably originated in northern Mexico and migrated north as the climate warmed. C. c. fuscus moved into its present range in New Mexico and C. c. collaris spread east to the Great Plains area from there. C. c. baileyi migrated into Arizona, then north to the Upper Colorado River Basin of eastern Utah and western Colorado. North of the Colorado River and along its drainages, a distinct population has formed. C. c. auriceps has evolved far from the main C. c. baileyi populations in cental Arizona, and may be the youngest of the collaris subspecies( Ingram and Tanner, 1971).
On the eastern side of the Sierra Madre Occidental, C. reticulatus probably broke away from the ancestral C. collaris before C. dickersonae did. Mountain building activity may not have played an important role in C. reticulatus' divergence, since it is not restricted to rocky habitat. Changes in the climate may have been the separating factor. C. reticulatus prefers a slightly wetter climate than the xeric condition preferred by C. collaris. Between 2000 and 4000 years ago, the climate became drier and this may have caused C. reticulatus to retreat eastward. C. reticulatus may have left scattered populations behind which were absorbed by C. collaris as it moved into the area. This could explain the origin of the C. collaris melanomaculatus which occurs between the present day ranges of C. collaris and C. reticulatus (Montanucci, 1974). Another theory on the origin of C. melanomaculatus, is that C. antiquus occupied a larger range than it currently does. Advancing C. collaris entered the range of C. antiquus from the north and absorbed some of their genes as they advanced further southeast to the mountains of Zacatecas, Nuevo Leon, and San Luis Potosi (Axtell and Webb,1995).

Collared lizards emerge from hibernation during March and April. Follicular development has begun in females by early April (Ferguson, 1976). Orange to red bars and spots appear on her neck and sides. This coloration, which can appear overnight, is visual signal to the male lizards that the females are ready to mate. Around the same time, testes size in male lizards increases and continues to increase until early June (Trauth, 1979). Collared lizards are very territorial. Adult male lizards defend several female lizards that share his territory. They will defend their territories by high rates of displays. If a male lizard enters another male's territory, the defending male arches its back, compress its sides in an attempt to appear large and fierce. He will then do a series of pushups. C. collaris ' pushups are so powerful that its front feet often come off the ground. If this doesn't deter the trespasser, the defending male chases the intruder off. Hatchling and yearling males don't defend a territory, but will take on a submissive behavior in order to stay within adult males' territories. This could give them the opportunity to inherit territories and mates (Baird, Acree, and Sloan, 1996).
Male lizards will approach a female and do a series of rapid headbobs. The lizards circle each other, both of them bobbing their heads. The male will grab the female by the back of her neck and attempt to mate. The female becomes submissive if she is ready. If she is not ready or already gravid, she will twist her body and roll him off. Sometimes the female lizard climbs on the males back to subdue his advances.
The breeding season last until June. Once the eggs are laid, female lizards aggressively defend the nesting site (Yedlin and Ferguson, 1973). Her breeding coloration also fades. This coloration becomes vibrant again if there is another clutch. In the northern part of their range, female collared lizards produce only one clutch. In the south, they produce two to four clutches. Clutch size ranges from one to thirteen. There is a positive correlation between body size and clutch size (Ballinger and Hipp, 1985). The average clutch size is about six. Eggs are usually deposited under rocks and will hatch in about 40 to 60 days.
Hatchlings appear from July to September. By late August to early September, adult lizards usually start their hibernation. This leaves the hatchlings with less competition for resources. The young lizards eat anything that it can get their mouth around. This insures survivalship over the winter. Young male lizards often have orange bars across their dorsum similar to breeding females. This is to deter adult male aggression until the young lizard can find its own territory. Collared lizards are usually sexually mature during their first spring, but females usually won't mate with a yearling males (Baird, Acree, and Sloan, 1996). Lizards from colder areas may not reproduce until their second season. Males reach their maximum size by the age of three. Females continue to grow very slowly their entire lives (Sexton, Andrews, and Bramble, 1992).
Collared lizards emerge each morning to bask on prominent rocks in their territory. Once they reach their preferred body temperature, they begin to forage for insects. They are very agile and can easily snag flying insects out of mid-air. Before rushing down on their prey they will do a series of head bobs and cat-like tail wags. Collared lizards occasionally feed on plant matter and vertebrate prey, such as lizards and small rodents (McAllister and Trauth, 1982).
Collared lizards have excellent eyesight and are difficult to approach. The best way to get close, is to scan boulders far ahead of you with binoculars. The lizards are usually already looking back at you by the time you spot them. When approaching these lizards, do so very slowly. You can get within a few feet if you move slowly and don't startle them. If you get too close they'll dash under rocks, often running on their hind legs. Their tails are used to balance when running bipedally, and it doesn't break off easily like most other lizards. It will only grow back if just the tip is broken off . When hiding under rocks or sleeping, they will coil their tail to keep from being pulled out by it. These lizards are very aggressive when cornered. They will hiss and leap at you in an attempt to bite. Once they get a hold of you, they will hold on.

Collared lizards make excellent captives as long as their basic requirements are met. These lizards are very active and you can not give them too much room. Adult lizards should be kept in at least a forty gallon aquarium. These lizards are very territorial, no more than one male and two females should be kept together. Sand makes an excellent substrate. Collared lizards are saxicolous, so rocks piles make natural basking sites. If more than one lizard is to be caged together, make several basking sites. Be careful that the rocks can not come down on the lizards when they dig around them. Like most lizards, collared lizards require ultraviolet light. Use a full-spectrum fluorescent bulb along with a incandescent bulb above the basking site. For healthy and colorful lizards, natural sunlight is a must. Collared lizards like it hot: their basking site should be between 100 and 105 degrees. The rest of their cage should be in the high 80's to 90's (degrees F) during the day. Most individuals will drink from a water bowl, but some wild-caught lizards will only drink from water droplets. Mist the rocks and glass in their enclosure to stimulate drinking every few days. Collared lizards eat a lot and can be fed daily. Crickets are the most convenient food source available. It is best to feed them a variety of insects. It is always fun to watch them catch flying insects in mid-air. Some individuals will also eat lizards and pinkies.
Captive bred lizards make excellent pets. Wild caught lizards don't always do as well. Many die from the stress of being taken from their natural environment. They are usually loaded ticks, chiggers, nematodes, and other parasites (McAllister and Trauth, 1985), and will need to be dewormed. Wild caught lizards will often rub their nose raw trying to escape. If the lizard doesn't adapt, it will go off feed until it is too weak to move. It will lose weight and wither away over a period of several weeks. Once this has started, it is almost impossible or very expensive to turn them around.
Collared lizards are fairly easy to breed in captivity. They must hibernate at least two months but can be left in this state for several months. Two weeks before hibernation, stop feeding them so their entire gastro-intestinal tract will be empty. Failure to completely empty the GI tract will result in colitis abd certain death of the lizard during hibernation. Turn off the heat sources and slowly cool the lizards down to between 50 to 60 degrees. If your room doesn't stay cool enough to induce hibernation, you can hibernate them in coolers. I fill the coolers with several inches of damp sand and with a few flat rocks for the lizards to burrow under. I use blue ice (found in Sportng Goods stores) to cool down the coolers and change it out twice a day. Use a thermometer to regulate the temperature. After hibernation, slowly warm the lizards up by keeping them at room temperature for a day or so, then you can turn up the heat. Start feeding the lizards insects dusted with phosphorus-free calcium fortified with vitamin D3. The females will especially need it for strong egg development. Within a few weeks the female lizards will develop their breeding coloration. After the lizards have mated, the female will start to show bulges near its abdomen. At this time, keep a moist spot in the cage and the female will usually lay the eggs in this spot. When she is ready to lay the eggs, she will begin digging. Check her daily, because she will appear skinny after she has deposited the eggs. The eggs must be removed from the cage. Keep them right side up and place them in an incubator. An incubator can be made from a plastic shoe box with a hole, the size of a quarter, cut in the top for air circulation. Fill the shoe box with about three inches of vermiculite and keep the vermiculite moist but not wet. Put the shoe box in a place were the temperature won't drop below the high 70's at night and won't rise above 90 degrees during the warmest part of the day.. Temperature fluctuations will insure that the hatchlings will be of both sexes. As long as the eggs continue to grow they should be fine, even if they turn an off white to brown. In about 40 to 60 days the eggs should be ready to hatch. It take several hours to more than a day for the hatchling to break free from their eggs. Their umbilical cords will remain attached for several days. Hatchling lizards need natural sunlight in order to develop properly. Without it, they will likely perish. They can be fed week old crickets, but they will eat anything they can get their mouths around. Collared lizards grow very fast and within a matter of weeks they can be fed adult crickets.
There are still many questions about the origin of the collared lizards. This genus should continue to be studied in the lab and in the field. Due to their beautiful colors, individual patterns, and relative tameness; collared lizards will remain popular captives. I welcome any information or questions concerning the genus Crotaphytus.

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