The Ecology of the Desert Iguana Dipsosaurus Dorsalis

The genus of iguanid lizards known as Dipsosaurus is a small group of mediumsized, rather robust forms found in southwestern North America. The genus is related to the genera Ctenosaura and Iguana. The resemblance is striking when the young of each of these genera are compared. Like others of this group, Dipsosaurus has a mid-dorsal longitudinal row of enlarged scales, but unlike the most closely related genera, the scales are not greatly produced into a crest in adult males. I have adopted the vernacular name desert iguana for Dipsosaurus dorsalis. The ecology of the lizards of the genus Dipsosaurus is very poorly known although it is one of the most common desert creatures in the southwestern United States and western Mexico. Smith (1946), in discussing the United States form, Dipsosaurus d. dorsalis, says: "Almost nothing is known of the breeding habits and life history of this species." Equally little is known of the Mexican forms. Opportunities to observe Dipsosaurus were afforded me during the spring and early summer months of 1947-50. Observations were made over most of the range of the genus, including Baja California, Sonora, California, Arizona and Nevada. The dorsal color pattern of Dipsosaurus is composed of a black or brown reticulum superimposed over a white or pinkish background, sometimes forming definite longitudinal lines, indefinite vertical bands, or rounded or irregular ocelli (Fig. 1). The ventral surface of the desert iguana is usually white or grey. During breeding season both males and females show longitudinal latero-ventral patches of pinkish grey, brownish red, or brownish orange. The coloration of these patches and of the dorsal markings is quite variable geographically, there being marked adaptation of dorsal coloration to soil color in some localities (e.g., Algodones Dunes, Imperial County, California). The lizards of the genus Dipsosaurus occupy lowland habitats at least as far