Record Details

Sylber, Charles K
Feeding habits of the lizards Sauromalus varius and S. hispidus in the Gulf of California
Journal of Herpetology
Journal Article
Sauromalus hispidus;Sauromalus varius
The feeding habits of adult Sauromalus hispidus and adult Sauromalus varius were studied on four islands in the midriff region of the Gulf of California, Mexico. Diets were determined by examining a total of 1875 fecal pellets from four islands during the summer, fall and spring of 1979-1980. Results of a point frame technique demonstrated that the diet of S. varius consisted of 22 plant species and 12 plant families whereas that of S. hispidus was made up of 35 plant species and 20 plant families. Chuckwallas ate a strictly vegetarian diet, preferring shrubs over forbs, cacti, and grasses or leaves over flowers, fruits, seeds, and stems. No plant parts from halophytic species were found in the pellets. Plant trophic diversity in the diet was highest on Isla San Esteban and lowest on Isla Mejia. Examination of the fecal pellets also revealed that they contained gravel and sand. Some gravel and sand were ingested by the lizards on all 25 of the study sites. The consistency with which gravel was found in the fecal pellets from all sites and every season, suggests that these lizards had intentionally ingested this material as a part of their food regime. No correlation was found between the plant frequencies at the sites and the plant frequencies in the pellets. Neither species of giant chuckwalla appears to seek out plants based on the plant's relative abundance.