AMPHIBIANS OF WESTERN CHIHUAHUA Wilmer W. Tanner ABSTRACT. — This third report on the herpetofauna of Chihuahua deals exclusively with amphibians. The first plethodonid salamander is reported, the species Ambystoma rosaceum is discussed in greater detail than before, and two subspecies are recognized. Spea is elevated from subgeneric to generic rank, and S. stagnalis Cope is removed from synonymy and is recognized as a subspecies of hammondii. The species listed include the following: 2 salamanders and 19 anurans (1 Scaphiopus, 2 Spea, 9 Bufo, 1 Elentherodacttjlus, 2 Hyla, 3 Rana, and 1 Microhyla). Reference is made to various habitats that are associated with elevations arising from lower deserts and extending into the western mountains. The role played by the dry and wet annual cycles is also noted. This is the third report on the herpetology of western Chihuahua (Tanner 1985 [1986], 1987). It deals only with the amphibians. As indicated in the preceding reports, the state of Chihuahua is a large area and includes deserts on the east, steppe foothills and valleys in the central part (north to south), and the north end of the Sierra Madre Occidental in the west. This diverse geographical terrain provides numerous and multiform types of habitat. One wishing to gain a general understand-ing of the terrain of southern and northwest-ern Chihuahua would benefit by reading the account by Goldman (1951), which deals with the explorations of Nelson and Goldman dur-ing the late 1890s. Although their activities did not include exploration of the entire state, they did include considerable travel in north-ern Chihuahua extending into the deserts, mountains, and valleys and to the northeast and west of Casas Grandes. The trip by Gold-man from Parral to Batopilas is replete with descriptions of this extensive area. The cen-tral area west from Ciudad Chihuahua to Madera and southwest to the extensive areas north and west of Creel were not explored. Although these exploratory field trips pro-vided valuable information concerning the general nature of the terrain, faunas, and floras, only a relatively few herpetological specimens were collected and these were de-posited in the U.S. National Museum (Smith-sonian Institution). Thus, it has remained for others to explore and report the rich herpeto-logical faunas of this state. References to other important studies are cited in the first of this series (Tanner 1985 [1986]). One cannot tra-verse this area without becoming enamored with its rugged diversity and beauty. There are few areas where one can stand in a conifer-ous forest on the rim of a mighty canyon and observe an entirely different biome approxi-mately a mile below, where wild figs and man-goes grow along a river, which is in turn sur-rounded by an invading thorn forest from the bench lands of Sinaloa (Fig. 1). The climate in Chihuahua can be character-ized by its cool to cold winters (November into March), dry to very dry springs (March through June), and moderately to heavily rainy summers (July into September), al-though the amounts will vary greatly from location to location and from year to year. The fall months (mid-September and October) are delightful, with warm days and cool nights. As indicated below, the climate and terrain com-bine to provide numerous habitats and a mod-erately rich amphibian fauna. During the dry season (March through June) few amphibians are seen and those only along permanent streams and springs. Much of central Chihuahua is at an elevation be-tween 5,000 and 6,000 feet; and, therefore, it is cool to cold until May with occasional frost during April. It is not until the summer rains come, usually from July to the first part of September, that an abundance of amphibians is seen. A trip from western Durango to Ciu-dad Chihuahua during a rainstorm corre-sponded with the emergence of large num-bers of frogs and toads from areas that had 'Life Science Museum, Brigham Young University, Provo, Utah 84602. 38
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