Description
Head large, sometimes bright yellow; tail long; two incomplete black collars around narrow neck; upper side with smooth granular scales, turquoise to greenish to brown with numerous small light spots in adult; toes of adults yellow in western Colorado; lining of pharynx usually black; maximum total length about 36 cm. Mature male: bulge of hemipenes evident at base of tail; throat with dark spots or circles (pale reticulation), most evident in western Colorado, or throat yellow to orange (southeastern Colorado); head especially large; enlarged postanal scales and femoral pores. Mature female: orange-red bars or spots on sides of body and neck during breeding season; orange spots on the sides of reproductive females attain maximum brightness prior to ovulation and 10-13 days before egg laying; throat unmarked or faintly spotted. Juvenile: dorsum with wide dark bands or rows of large dark spots separated by narrow light lines, sometimes with red/orange spots on neck and sides of chest. Hatchling: 31-42 mm snout-vent length, often about 40 mm. Source: Hammerson (1999).
Diagnostic Characteristics
Differs from all other species of CROTAPHYTUS by the absence of dark brown or black pigmentation in the gular fold of adult males (McGuire 1996, which see for further information).
Habitat
The habitat consists of rocky areas with sparse vegetation and encompasses open woodlands, bunchgrass areas, canyons, gullies, slopes, and mesa tops (Degenhardt et al. 1996, McGuire 1996, Bartlett and Bartlett 1999, Hammerson 1999, Johnson 2000, Stebbins 2003, Trauth et al. 2004). When inactive, these lizards hide under rocks or in crevices. Eggs are laid under large rocks or in burrows (Collins 1982).
Ecology
In Oklahoma, density was 6.4 dominant males per ha; including subordinate males, density was 17.2 males per ha (Stone and Baird 2002).
Reproduction
Eggs laying occurs in June-July in Kansas, mainly May-June in west-central Texas. Clutch size usually is 4-11. IReproductive females produce a single clutch annually in the northern part of the range, often 2 clutches in the south. Young-of-year first appear in early August in Missouri (Copeia 1992:968-990) and Colorado (Hammerson 1999). Individuals become sexually mature in their 1st or 2nd year (1st year in areas with long growing season). In Oklahoma, males established all-purpose territories (and presumably became reproductively active) when they were two years old (Stome and Baird 2002).