Herps

Based on collections and published reports, the herpetofauna of mainland Sonora, México, includes 37 amphibian and 139 reptile species. An additional two amphibian and five reptile species have been taken very near the Sonoran border in contiguous habitats in Arizona, Chihuahua, or New Mexico, and almost certainly occur in Sonora, as well. This compares to 15 amphibian and 95 reptile species documented in the last summary of Sonora's herpetofauna, published in 1945. Five taxa have been introduced, and one species is known to have been extirpated from Sonora.

The pine-oak woodlands of the Sierra Madre Occidental of Mexico extend for about 1100 km from the northern end ofthe Sonoran-Chihuahuan border southward to the region ofthe common borders of Zacatecas, Nayarit, and Jalisco. On the eastern side of the sierra the pine-oak woodlands grade into mesquite-grassland on the Mexican Plateau in the foothills. The steep escarpment on the west and its deep barrancas allow for complex interdigitation of the pine-oak woodland vegetation and the tropical deciduous forests in the lowlands.