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~University of Kansas Publications~ ~Museum of Natural History~
Geographic Variation in the Pocket Gopher, Cratogeomys castanops, in Coahuila, México
~University of Kansas Publications, Museum of Natural History~
Editors: E. Raymond Hall, Chairman, A. Byron Leonard, Robert W. Wilson
Volume 7, No. 12, pp. 591-608 Published March 15, 1955
~University of Kansas~ ~Lawrence, Kansas~
PRINTED BY FERD VOILAND, JR., STATE PRINTER TOPEKA, KANSAS 1955
Geographic Variation in the Pocket Gopher, Cratogeomys castanops, in Coahuila, México
The plateau pocket gopher, _Cratogeomys castanops_, inhabits open lands from southeastern Colorado southward onto the Mexican Plateau as far south as southern San Luis Potosí and southeastern Zacatecas and southeastward to the Coastal Plain of northern Tamaulipas. This species occurs at elevations from as low as 26 feet at Matamoras in Tamaulipas to as high as 8700 feet in valleys of south-eastern Coahuila. In 1934, Nelson and Goldman (Proc. Biol. Soc. Washington, 47:135-154, June 13, 1934) revised the genus _Cratogeomys_ and decided that six subspecies of _C. castanops_ occurred in Coahuila. In the present account, we describe four previously unknown subspecies from Coahuila, exclude from the state two others recorded from there by Nelson and Goldman, and show that three others named previously from adjacent Mexican states do occur in Coahuila. This makes eleven subspecies now known from that state. From Coahuila Nelson and Goldman had 35 study specimens of _C. castanops_ from seven localities and we have had 234 specimens from 63 localities. Consequently we have been able to define with greater certainty, than formerly was possible, the geographic distribution of _C. castanops_ in this Mexican state and similarly analyze more completely the geographic variation.
Coahuila is near the center of the geographic range of _C. castanops_. The occurrence of 11 subspecies within the state seems to be the result of partial or perhaps, in some cases, total isolation of populations of _C. castanops_ because of the highly dissected topography and the variability of the soil. _Cratogeomys castanops_ is a sedentary animal preferring open plains mantled by suitable soils, preferably sandy in texture, in which the animals can dig their elaborate underground systems of runways. Thin soils of hard texture and rocky soils do not offer optimum habitat for _C. castanops_, and the animals usually are absent or uncommon in such situations. Desert mountains with their thin rocky soils, elevated passes, perpendicular rocky cliffs, and stands of oaks and conifers at higher elevations present impassable barriers for pocket gophers of this species. The Río Grande, bordering Coahuila to the north, in many places flowing through steep-walled cañons, also seems to be a barrier that this fossorial rodent does not cross; distinct subspecies occur on the two sides of the river directly opposite each other (also see Nelson and Goldman, _op. cit._: 143). Smaller streams, such as the Río Salado, Río Nazas and Río Salinas, seem to be unimportant barriers to the passage of these pocket gophers. The food supply of _C. castanops_ seems adequate in most situations and consequently food is unimportant in governing the distribution of this species. Principal foods of _C. castanops_ are fleshy tuberous roots of well-distributed desert shrubs, but in the valleys of the high mountains of southeastern Coahuila, where desert shrubs are absent, roots and leaves of low-growing forbs are eaten.