Common collared lizard

The common collared lizard, known scientifically as Crotaphytus collaris, is a striking reptile found in North America.

This species is a member of the Crotaphytidae family. It is highly recognized for its distinct appearance, specifically the black bands around its neck. These bands resemble a collar, which is how the lizard earned its common name. These lizards play an important role in their ecosystems as active predators. They are found in dry, open regions across the Southwestern United States and Northern Mexico. Their range includes states such as Arizona, New Mexico, Texas, and Oklahoma.

These lizards possess unique physical traits that help them survive in harsh environments. They are characterized by disproportionately large heads and long hind limbs. This body structure supports bipedal locomotion, which is the ability to run on two hind legs. By using this method, they can sprint at speeds up to 24 kilometers per hour. This rapid movement is a vital defense mechanism used to escape predators. While they are fast, they are not the fastest lizards globally. For example, the Costa Rican spiny-tailed iguana holds a much higher speed record.

There is significant variety within the species, known as phenotypic variability. This variety can be caused by differences in habitat, social organization, or population. Scientists recognize five valid subspecies of the common collared lizard. These include the yellow-headed collared lizard and the black-spotted collared lizard. One subspecies, Crotaphytus collaris baileyi, is named in honor of the American mammalogist Vernon Orlando Bailey. Each subspecies may show different patterns of spotting or coloration depending on its specific environment.

Coloration in this species is sexually dichromatic, meaning males and females look very different. Adult males are quite vivid, often featuring blue-green bodies and yellow or orange tones. They may also have yellow stripes on their tails and backs. In contrast, females possess more muted pigmentations, such as gray or brown. However, females undergo a rapid color change during breeding seasons. Faint orange spots on their heads become much brighter as their eggs mature. These spots gradually fade after the female expels the eggs from her oviduct.

Physical size also differs between the sexes, a trait called sexual dimorphism. Males are generally larger than females and possess more muscular heads. These large heads serve as important tools during male combat. Head size is a key factor in determining a male's dominance and mating success. Larger heads are typically associated with greater jaw strength and higher bite force. This physical advantage helps males defend their territories and protect their harems of females.

Collared lizards are obligate carnivores, meaning they must eat meat to survive. Their small stomachs cannot hold enough plant material to maintain their body weight. Therefore, they rely on nutrients from arthropods and small vertebrates. Their diet includes large insects like grasshoppers, beetles, moths, and cicadas. They also consume spiders, crickets, and even other small lizards or snakes. Interestingly, diet can vary between males and females to reduce intra-species competition. This allows them to share the same habitat without fighting over the exact same food sources.

Social behavior in males is highly complex and revolves around territoriality. Males are very active, engaging in displays, chases, and fights to protect their resources. They often use social displays, such as trunk elevations and dewlap extensions, to avoid violent combat. These displays allow them to advertise superiority to rivals from a distance. Interestingly, they show less aggression toward neighbors they recognize. They reserve their most intense hostility for strangers who enter their territory.

Reproduction follows a specific seasonal cycle from mid-March to mid-July. Females usually emerge from hibernation first, followed by males about two weeks later. Mature females, typically two years or older, lay clutches of four to six eggs. These eggs are placed in burrows or under rocks for incubation. The incubation period is temperature dependent and lasts between 50 and 100 days. Once the juveniles hatch, they are fully developed and live independently. The parents do not provide any care for their offspring.