Diet comparison between two syntopic teiid lizards, Aspidoscelis marmorata and Aspidoscelis tesselata, in the northern Chihuahuan Desert

The purpose of this study was to compare prey types and prey volume between the diets of two whiptail lizards (Teiidae), Aspidoscelis marmorata (a bisexual species) and A. tesselata (a unisexual species), that occur syntopically on the Indio Mountains Research Station (IMRS), Hudspeth County, Texas, which is located in a Chihuahuan Desert landscape. Because their home ranges overlap extensively, it was hypothesized that there would be resource partitioning in the diets between the two forms. Stomach contents of 69 individuals of A. marmorata and 21 individuals of A. tesselata were examined and determined to contain only arthropods. Taxa consumed by A. marmorata included species in 14 orders, while species in eight orders were consumed by A. tesselata. Both species eat primarily individual isopterans (92.7% in A. marmorata; 94.5% in A. tesselata). By volume, Homoptera (30.3%), Araneae (23.2%), Orthoptera (13.3%), and Isoptera (13.0%) compose 80.0% of the diet of A. marmorata; whereas Orthoptera (29.7%), Homoptera (29.7%), Araneae (16.6%), and Isoptera (16.2%) make up 92.2% of the diet of A. tesselata. The results indicated that both species are opportunistic feeders that compete with each other for available food resources. This competition seems to be reflected in differences between densities of the species ( A. tesselata was present in lower densities). However, slight differences in their ecologies and available food resources may have accounted for the coexistence of both species in the study area