Common chuckwallas (Sauromalus ater) in urban preserves: Do food plants or crevice retreats influence abundance?

Understanding anthropogenic effects on key habitat features for reptile populations is critical to ongoing conservation efforts in urban regions. We surveyed habitat features associated with populations of the Common Chuckwalla (Sauromalus ater) in preserves of the Phoenix Mountains and adjacent areas near the Phoenix Metropolitan region during spring and fall, 2009. Extending prior work with fecal count indices, we assessed current population levels as indicated by fecal counts in relation to variation in abundance of preferred food plants and availability of rock crevice refuges. Our results revealed an association between fecal counts and presence of six favored food plants, but not number of crevices or overall plant density. These six plant species, previously established to influence female selection of male territories, were uncorrelated with plant density. A secondary analysis indicated that overall plant diversity was strongly correlated with fecal counts. Our survey results suggest that Common Chuckwalla populations are stable in these island preserves, and that the presence of particular plant foods may be critical to their persistence.