Crotaphytus collaris (Say, 1822)

Size

Common collared lizard, scientifically Crotaphytus collaris (Say, 1822), reaches a total length (including the tail) of 8–15 inches (20–38 cm), with a maximum recorded total length of 14 inches.

Body Structure

This moderate-sized lizard has a disproportionately large head, powerful jaws, and long hind limbs. Males are larger than females, and adult males have larger, more muscular heads than females.

Head Function

Head dimensions play a key role as a weapon during male combat, and influence dominance, territoriality, fitness, and mating success; larger heads correspond to greater jaw strength and bite force.

Phenotypic Variation

This species shows a wide range of physical variation, particularly in coloration and spotting patterns, and this phenotypic variability may come from a combination of differences in population, social organization, and habitat.

Sexual Dimorphism

Crotaphytus collaris is both sexually dichromatic and sexually dimorphic.

Adult Male Coloration

Adult males are more vividly colored than females; male body color ranges from green to tan on the dorsum, while the head ranges from yellow to orange. Males typically have a blue-green body with a light brown head.

Adult Female Coloration

Females have a lighter brown overall head and body, with more muted body pigmentation that ranges from brown to gray.

Breeding Season Female Color Change

When reproductively active during the breeding season, females undergo rapid color change: faint orange spots on their heads increase in brightness. This orange spotting peaks during egg maturation, and gradually fades after the female lays eggs and expels them from her oviduct.

Collar Marking

Both males and females have two distinct black bands around their neck, which gives the species its common name of collared lizard.

Juvenile Coloration

Compared to adult males, juveniles have dull body coloration similar to adult females, but juveniles have prominent dark brown markings that fade as they mature. As young lizards grow, they lose their sharp cross-band pattern, and their features develop to match those of adult males or females.

Overall Geographic Range

Crotaphytus collaris is primarily found in dry, open regions of northern Mexico and the south-central and southwestern United States.

U.S. Distribution

In the United States, its known range covers Arizona, Arkansas, Colorado, Kansas, Missouri, New Mexico, Oklahoma, and Texas, extending from the Ozark Mountains to western Arizona.

Habitat Preferences

These lizards occupy a variety of habitats, from rocky desert landscapes to grasslands, and they most often prefer mountainous regions with high environmental temperatures to support optimal thermoregulation.

Habitat Use

Hilly topography lets these alert, observant lizards hide between rocks, even with their bright coloration, and watch for predators or intruders into their territory from elevated vantage points.

Reproductive Season Timeline

The reproductive season for Crotaphytus collaris runs from mid-March to early April, and ends in mid-July.

Hibernation Emergence

Females and smaller individuals emerge first from hibernation, with males emerging roughly two weeks later.

Sexual Maturity

While lizards can reach sexual maturity and breed after their first hibernation, individuals two years old or older have higher reproductive success due to their larger size.

Courtship

Courtship between adult males and females occurs in late May.

Egg Laying

After copulation, mature females (usually two years and older) lay their first clutch of eggs in a burrow or under a rock around two weeks after mating. Females can produce a second, and sometimes even a third, clutch through June until mid-July.

Clutch Size

Clutch size averages 4 to 6 eggs, though larger, older females can produce more eggs per clutch.

Egg Incubation

Incubation length is temperature-dependent, ranging from 50 to 100 days.

Hatching

The earliest clutches hatch in mid-July, and later clutches hatch by mid-October.

Juvenile Independence

Upon hatching, juveniles are fully developed and behave independently; Crotaphytus collaris provides no parental care for offspring.

Hibernation Entry

By August, adults return to hibernation, and juveniles enter hibernation after hatching.