Ranches are being converted to low density exurban housing developments in the southwestern United States, with potentially significant but little studied impacts on biological diversity. We counted lizards in a grassland and mesquite/oak savanna in southeastern Arizona, along 48 transects evenly divided among landscapes that were grazed by livestock, embedded in housing developments, both or neither. Terrestrial lizards as a group (mostly Aspidoscelis uniparens and Holbrookia maculata) were scarce in developed areas, especially where homeowners kept livestock. Combined counts of lizards (Sceloporus clarkii, Sceloporus undulatus and Urosaurus ornatus) associated with three dimensional substrates did not differ among landscape categories. Roadrunners (Geococcyx californianus), known predators of terrestrial lizards, were more common in developed areas, especially those that were grazed. These results are consistent with the hypothesis that the relative scarcity of terrestrial lizards in developed landscapes was due to increased predation by roadrunners, but predation by other species, especially domestic pets, may also have been important.