Description: C. collaris can grow up to 8 to 15 inches in total length (including the tail), with a large head and powerful jaws. Males have a blue-green body with a light brown head. Females have a light brown head and body. C. collaris exhibit a wide range of physical characteristics, particularly in coloration and spotting patterns, and this phenotypic variability may be attributed to a combination of differences in population, social organizations, or habitat. They are a sexually dichromatic lizard species with the adult males being more vivid and colorful than the females. Male dorsal and head color tend to range from green to tan and yellow to orange respectively, while females, overall, possess more muted body pigmentations, varying from brown to gray. However, when reproductively active during breeding seasons, females undergo a rapid color change, in which faint orange spots on their heads increase in brightness; this orange spotting reaches a maximum during egg maturation but gradually fades again after expulsion from the female’s oviduct as she lays her eggs. Both males and females have two distinct black bands around their neck, providing additional context to their name, the common collared lizards.

Similar to adult females, juveniles also exhibit dull body colorations compared to adult males, but a key distinction is that the young have pronounced, dark brown markings that eventually fade as they grow and mature. Consequently, juvenile collared lizards lose this sharp cross-band pattern, and their features drastically change to resemble those of either adult males or females.

Moderate in size, C. collaris have disproportionately large heads and long hind limbs. It can reach a length of 14 inches, including the tail, with males being larger than females. Hence, they are sexually dimorphic, and adult males exhibit larger and more muscular heads than females, which tend to vary in size. Used as a weapon during male combat, the head dimensions play a key role in determining dominance, territoriality, fitness, as well as mating success. In general, bigger heads are associated with greater jaw strength and thus, bite force.

Habitat: C. collaris is distributed across the Southwestern United States and extend to Northern Mexico as well. Individuals occupy a range of different habitats from rocky desert landscapes to grasslands, but they often prefer to inhabit mountainous regions with high environmental temperatures for optimal thermoregulation. In addition, the hilly topography allows these keen and highly alert lizards to stay hidden between rocks, despite their flamboyant features, and look out for potential predators or territory intruders from the top of elevated platforms.

Range: C. collaris is chiefly found in dry, open regions of Mexico and the south-central United States including Arizona, Arkansas, Colorado, Kansas, Missouri, New Mexico, Oklahoma, and Texas. The full extent of its habitat in the United States ranges from the Ozark Mountains to Western Arizona.

Found in these States: AR | AZ | CO | IL | KS | NM | MO | OK | TX | UT

Diet: As obligate carnivores, they consume insects and small vertebrates as their main diet. While they may occasionally ingest plant materials, it is not preferred. They feed on a variety of large insects, including crickets, grasshoppers, spiders, moths, beetles, and cicadas, along with other small lizards and even snakes. As plants do not provide enough nutrients for constant body weight maintenance, cannot survive solely on an herbivorous diet. Their stomachs are too small to accommodate the amount of flowers, shrubs, herbs, etc. that would be needed to maintain a constant body weight. Thus, they are considered obligate carnivores, requiring nutrients from arthropods or other small reptiles.

Diet can also vary depending on age, sex, as well as seasonal changes. In the case of younger lizards, they consume the same kinds of foods, specifically insect species, that adults do, but since younger lizards and adults differ in body size and weight, the amount of food intake tends to vary. On the other hand, male and female adults are similar in terms of their sizes and the amounts of food ingested but exhibit drastic differences in the kinds of foods that they eat. From an evolutionary standpoint, these sexual differences in diet may act to reduce intra-species competition for resources, whereby females and males do not need to fight for the same type of food. Moreover, changes in season can drastically affect their diets as well.

Reproduction: The reproductive season starts in mid-March to early April and concludes in mid-July. Females and smaller individuals emerge first from hibernation with males following around two weeks later. Though lizards are considered mature and may breed following their first hibernation, those that are two years and older exhibit greater reproductive success due to their larger size. In late May, courtship occurs between adult males and females. Subsequently, mature females, typically two years and older, produce their first clutches and lay them in a burrow or under a rock about two weeks after copulation. They may then go on to produce second and sometimes even third clutches throughout June until mid-July. The eggs are incubated in a temperature dependent manner, and the incubation period may vary from 50 to 100 days. On average, clutch size can range from 4 to 6 eggs, but larger, older females can produce more. By August, adults begin to hibernate again, and juveniles do the same after hatching. The earliest of the clutches can hatch in mid-July and later ones follow until mid-October. Upon hatching, juveniles are fully developed and behave independently of their parents, as the C. collaris do not exhibit any parental care in offspring.

During courtship rituals, a male or a female lizard approaches the opposite sex within 1 body length and subsequently engages in various behavioral patterns, which include either individual superimposing its limbs, torso, or tail over its partner, mounting the dorsum of the other lizard, males nudging females with their snouts or grasping them with their jaws, and mutual displays. These mutual displays involve a complex set of movements and behaviors, unique to each sex. Males flex their forearms up and down and extend their dewlaps while females also extend their dewlaps and raise the base of their tails to signal receptivity. Ultimately, at the end of this courting process, both sexes walk in circles, making sure to remain within 1 body length of one another throughout.

Status: Crotaphytus collaris is assessed as Least Concern because this species is widely distributed and is represented by many stable populations. It faces no major threats at present.

Subspecies: Four, all are found in the United States:
   Yellow-headed Collared Lizard (Crotaphytus collaris auriceps)
   Western Collared Lizard (Crotaphytus collaris baileyi)
   Eastern Collared Lizard (Crotaphytus collaris collaris)
   Chihuahuan Collared Lizard (Crotaphytus collaris fuscus)

Taxonomy: