A Comparison of the Herpetofaunas of Ranchos Los Fresnos and El Aribabi in Northern Sonora, Mexico

To compare and contrast herpetofaunas at Ranchos Los Fresnos and El Aribabi in north-central Sonora, Mexico, we conducted herpetological surveys during 2006-2011, contacted others working in these two areas, and queried 27 museums and collections for specimens collected at or near these ranches. Based on this work, nine and seven amphibian, and 27 and 24 reptile species are known to occur at Ranchos El Aribabi and Los Fresnos, respectively. Significant findings at Los Fresnos include presence of presumed Sonora tiger salamanders (Ambystoma mavortium stebbinsi), of which there are only three localities in Mexico; Arizona treefrog (Hyla wrightorum) at several sites; and Mexican gartersnake (Thamnophis eques); and at El Aribabi, Neotropical whipsnake (Coluber mentovarius), a range extension of 144 km, Tarahumara salamander (Ambystoma rosaceum) near the northern edge of its range, and Mexican gartersnake. Both ranches support non-native American bullfrogs (Lithobates catesbeianus) and non-native fishes. Non-native crayfish (Orconectes virilis) are also present at Rancho Los Fresnos. In total, 46 species of amphibians and reptiles were found, 22 of which occur on both ranches. Rancho Los Fresnos supports high grassland species not found at El Aribabi, while a number of typically Sonoran Desert or foothills thornscrub species found at El Aribabi were not encountered at Los Fresnos.