The sagebrush lizard or sagebrush swift (Sceloporus graciosus) is a common species of phrynosomatid lizard found at mid to high altitudes in the western United States. It belongs to the genus Sceloporus (spiny lizards) in the Phrynosomatidae family of reptiles. Named after the sagebrush plants near which it is commonly found, the sagebrush lizard has keeled and spiny scales running along its dorsal surface.
The sagebrush lizard is similar to the western fence lizard, another Sceloporus species found in the western US. The sagebrush lizard can be distinguished from the western fence lizard in that the former is on average smaller and has finer scales. The keeled dorsal scales are typically gray or tan, but can be a variety of colors. The main (ground) color is broken by a lighter gray or tan stripe running down the center of the back (vertebral stripe) and two light stripes, one on either side of the lizard (dorsolateral stripes). S. graciosus will sometimes have orange markings on its sides.
Three regional races of the sagebrush lizard are recognized: the southern sagebrush lizard lives in Southern California, and the western and northern races are found in many western states, including Nevada, Oregon, Idaho, Colorado, Montana, Washington, New Mexico, Utah, Wyoming, North Dakota, South Dakota, Nebraska, and Arizona.
Physical description
The sagebrush lizard is usually snout-to-vent length (SVL) when fully grown. Hatchlings are about SVL. The sagebrush lizard looks very similar to the western fence lizard, but differs in that it is typically smaller and has an increased number of scales. In appearance, sagebrush lizards are grey, brown or olive, with hints of blue or green on the dorsal surface during the light phase, and they often have irregular banding patterns on the body and tail. They also often display a black bar on the shoulder, and a light lateral and dorsolateral line on both sides. The scales on the rear portion of the thigh are small and granular, while the armpit and lateral surface of the body is often rust-colored. Females have white or yellow bellies, and males have distinctive blue patches on the abdomen and throat, although the throat patch can be absent. Males also have enlarged postanal scales, and two areas of swelling at the base of the tail. During the breeding season, males may develop orange breeding colors. Young lizards look similar to adults, but lack the dark blue markings.
Elevation-dependent variation in growth rate
In SW Utah, the sagebrush lizards exhibit unexpected growth patterns. Lizards who live in higher elevations grow faster than lizards who live in areas that are at lower elevations, even though the lizards that live at higher elevation have shorter daily and seasonal activity. It is hypothesized that the differences in growth is because lizards at a higher elevation have lower resting metabolic expenditure compared to those at a lower elevation. When these metabolic rates were measured and compared in lizards from both elevations, the resting metabolic rates were found to be lower for lizards at a higher elevation and higher for lizards at a lower elevation. For the lizards at a lower elevation, the daily resting metabolic expenditure was 50% higher which means 12.5% more energy that could be used for growth was being used up in comparison to higher elevation lizards.