COMPARISON OF DIETS OF TWO SYNTOPIC LIZARDS, ASPIDOSCELIS MARMORATA AND ASPIDOSCELIS TESSELATA (TEIIDAE), FROM THE NORTHERN CHIHUAHUAN DESERT OF TEXAS

We compared types and volume of prey in the diets of two whiptail lizards (Teiidae), Aspidoscelis marmorata (a bisexual species) and A. tesselata (a unisexual species) that occur syntopically in a Chihuahuan Desert landscape on Indio Mountains Research Station, Hudspeth County, Texas. Because their home ranges overlap extensively, we hypothesized that there would be dietary resource partitioning between the two species. Stomach contents of 69 A. marmorata and 21 A. tesselata included only arthropods. Aspidoscelis marmorata used 14 orders of arthropods for prey, while A. tesselata used eight orders. Isopterans (termites) were the principal food for both species by count (93.5 and 83.8% in male and female A. marmorata, respectively; 94.6% in A. tesselata). By volume, Homoptera (37.8 and 10.3%), Araneae (11.9 and 54.1%), Orthoptera (18.0 and 0.9%), and Isoptera (16.6 and 3.6%) composed 84.3 and 68.9% of the diet of male and female A. marmorata, respectively; whereas Orthoptera (29.8%), Homoptera (29.7%), Araneae (16.6%), and Isoptera (16.2%) were 92.3% of the diet of A. tesselata. The hypothesis that syntopic A. tesselata and A. marmorata were partitioning food resources on the study area was not supported; both species are opportunistic feeders that consume similar food types.