Great Basin Naturalist Volume 45 Number 4 Article 4 10-31-1985 Snakes of western Chihuahua Wilmer W. Tanner Brigham Young University Follow this and additional works at: https://scholarsarchive.byu.edu/gbn Recommended Citation Tanner, Wilmer W. (1985) "Snakes of western Chihuahua," Great Basin Naturalist: Vol. 45 : No. 4 , Article 4. Available at: https://scholarsarchive.byu.edu/gbn/vol45/iss4/4 This Article is brought to you for free and open access by the Western North American Naturalist Publications at BYU ScholarsArchive. It has been accepted for inclusion in Great Basin Naturalist by an authorized editor of BYU ScholarsArchive. For more information, please contact [email protected], [email protected]. SNAKES OF WESTERN CHIHUAHUA Wilnier W. Tanner' Abstract —This is a report on the snakes of western Chihuahua that were taken at intervals from 1956 to 1972. At no time did we attempt to colleet east of Highway 45, rather expending our time in the foothills, valleys, and desert ranges east of the mountains and in the highlands of the Sierra Madre Occidental. Reference is made to reports on the geological and ecological aspects of the area as a whole, but without a major attempt to duplicate previous studies. A brief gazetteer and a map are included as guides. To provide orientation to the area traversed by the John Cross expeditions, a map of the lower Rio Urique and Rio San Miguel is also included. From the area studied, 28 genera and 51 species are listed, with three new subspecies described: two worm snakes (Leptotyphlops huinilis chihuahuaensis and Leptotyphlops diilcis sitpraocularus) and a garter snake (Thatnnophis rufipunctatus ttnilabialis). For a number of species it became necessary to expand the study into populations from adjoining states in Mexico and the United States. Such species as T. rufipunctatus and R. hesperia are examples. Where data were available systematic relationships were implied, as well as ecological and biological data. This study is an outgrowth of a series of der. He suggested that perhaps one of the herpetological investigations and a number of areas most neglected was the state of Chi- conversations with individuals who have huahua. spent many years in various parts of Mexico. I Preliminary studies from the small collec- was constantly enthused with the idea of tion that then existed at Brigham Young Uni- spending time in Mexico, and, upon my ar- versity (BYU) indicated there were a number rival at the University of Kansas in 1946, of relationships, particularly as I understood where I became associated with Dr. Edward them in the serpents, that must yet be under- H. Taylor, I was even more motivated by his stood not only from the standpoint of taxon- constant references to the fabulous herpeto- omy, but also from the standpoint of geo- logical fauna of this neighboring country to the graphical distribution. Also, a small collection south. My association with the plethodontid made by Dr. D Eldon Beck in 1931 included a salamanders, which through the courtesy of juvenile skink from the vicinity of Colonia Dr. Taylor served as the subject of my disser- Garcia. It was not possible to key this speci- tation, demonstrated there were new species men to any of the materials described and and subspecies to be discovered. The thrill of discussed by Taylor (1936) and others, and it discovering the new genus Lineatriton left was eventually found to represent a new spe- httle doubt in my mind that someday I must cies (Tanner 1957). My visits with some of the visit the area and become more involved in students from the Mormon colonies in north- understanding the herpetological faunas of ern Chihuahua convinced me they were fa- this fascinating republic. miliar with a fauna that was unique to that I remember distinctly a conversation with area, and certainly not one that was commonly Dr. Taylor during my visit to the University of understood by most of the herpetologists with Kansas in 1952, at which time I was trying to whom I had visited. Thus, in May 1956, in prepare for my first adventures into Mexico. company with Mr. Verl Allman and my oldest After we discussed some of the problems that son, Lynn, we spent a month in northern seemed pertinent to my understanding of the Chihuahua, spending most of our time in the faunas extending from Mexico into the south- area of Nuevo Casas Grandes and Colonia western U.S., he advised me emphatically to Juarez, with one trip into the mountains of not worry about getting into the central and western Chihuahua at Three Rivers (Tres southern parts of Mexico, but to start collect- Rios) on the Rio Bavispe. ing as soon as I had crossed the Mexican bor- Each year, from then until 1972, trips were Life Science Museum, Brigham Young University, Provo, Utah 84602. 615 616 Great Basin Natufl\list Vol. 45, No. 4 made into Chihuahua at various times during more complete study and review of the Chi- the summer from May into October. My com- huahuan Desert see Morafka (1977). panion in 1957 and on through the next three Ecologists have established various life years was Dr. Gerald W. Robison. Perhaps zones in northern Mexico that have included the three most noteworthy trips were made in the state of Chihuahua. Perhaps the report 1957, 1958, and 1960, during which times compiled by Leopold (1950) and summarized much of the mountain area west of Colonia by Knobloch and Correll (1962) gives a gen- Juarez and west of Ciudad Chihuahua was eral overview useful to an understanding of visited. The trip in 1958 reached its climax at the diverse biotic zones encountered in this the mining town of Urique on the Rio Urique state. in the Barranca del Cobre. Knobloch and Correll (1962) summarized these zones as follows: In 1960 an extended trip was made into the 1. Boreal forest: rare, found only at barranca country, where we visited the min- 3000-3200 m (Cerro Mohinara). ing town of Maguarichic, and thus were in the 2. Pine-oak forests: ranging from pure pine vicinity of the area collected by Dr. Irving W. forests to mixed pine/oak and scrub oak. Knobloch (Taylor and Knobloch 1940). Other 3. Chaparral: mostly shrubs and small trips will be mentioned as it becomes impor- trees other than oak. tant to do so, but it should be noted that the 4. Mesquite-grassland: the short grass emphasis on our biological surveys was to plains, mesquite shrubs and grasslands cover as best we could in the time available to east of the Sierras. us the area west of Highway 45 that extends 5. Desert: cactus-euphorbia-yucca and from Ciudad Juarez south to Parral. The only creosote bush. important area that we were not able to visit 6. Tropical deciduous forests: short thorn was the area southwest of Parral across the forests of the western barrancas. headwaters of the Rio Conchos and into the Chihuahua may best be considered a headwaters of the Rio San Miguel, and the steppe desert, in which there is no certainty as tableland area near Guadalupe y Calvo. We to when or how much precipitation may occur were, however, fortunate in having received a in any given year or at any locality. At times collection from Mr. John Cross as he tra- during July and August, heavy rains occur, versed the area southeast of Guachochic and producing heavy runoff in local streams, but then boated down the Rio Verde and San this is not always widespread nor constant. Miguel rivers to their junction with the Rio Thus, Chihuahua has much dry terrain and Urique. Mr. Cross also provided some speci- there are many small or intermittent streams mens from the Urique River north of the town during most of the year. During the rainy of Urique. Figure 8 indicates the extent of his season streams may be in flood for a short travels. time, requiring traffic in local areas to wait for The state of Chihuahua is 245,612 square the streams to recede. We encountered these km and is the largest state in the Mexican conditions several times, but usually for only a republic. Its territory is approximately 12.5% few hours or, at most, a day. of the total area of Mexico. Within the state The heavy runoff" in the desert \ alleys and are many diverse ecological habitats ranging mountains rutted the roads, most of which from deserts in the eastern and central areas were dirt, exposing rock and making tra\'el off to subtropical areas in the southwest barran- the main highways difficult and hazardous. cas. As should be expected, the vegetation is Because of the rugged Sierra Madre Occiden- very diverse, from desert and dime floras in tal, which extends through most of western the eastern deserts to the pine-oak forests in Cvhihuahua,, few roads are available, and the western mountains. Between these ex- these often in poor condition. Roads in the tremes are the multitude of ecological niches mountains were passable, particularly where that change with the seasons from dry, rock\-, mining or lumber companies were operating; scrub, brush foothills to helds of waving however, if these companies closed or moved, grasses and other flowering plants after the the roads soon deteriorated. Furthermore, summer rains have renewed the area. For a most traffic was from the mountains eastward October 1985 TANNER: Snakes of Western CiiHiUAHUA 617 since the abrupt escarpment and the deep 1. The bajados, gentle slopes in the eastern canyons on the west Hmited travel to means section of the country, including the lower other than a car.