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. Bipedal locomotion C. collaris are known for their bipedal locomotion–the ability to run on their two hind legs–and can sprint at incredible speeds of up to 24 kilometers per hour; this behavior is usually observed when trying to escape predators. Like many other lizards, including the frilled lizard and basilisk, the collared lizard can run on its hind legs, and is a relatively fast sprinter. Record speeds have been around , much slower than the world record for lizards () attained by the larger-bodied Costa Rican spiny-tailed iguana, Ctenosaura similis. Geographic range and habitat 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. 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. 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, C. collaris 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