Boreal.—Each of the 12 species listed below is of northern distribution, is dependent, at the latitude of Colorado, upon the habitat provided by areas of high altitudes, and is near its southern zonal limit on the Grand Mesa. The 12 species are: Sorex cinereus, Sorex palustris, Sorex vagrans, Ochotona princeps, Lepus americanus, Marmota flaviventris, Spermophilus lateralis, Clethrionomys gapperi, Phenacomys intermedius, Microtus longicaudus, Microtus montanus, and Zapus princeps. Thomomys talpoides may be considered in this category also, although it is less restricted in range and habitat than most of the other species listed as boreal. These thirteen species make up almost half of the twenty-seven species known from the Grand Mesa.
Wide-spread.—Species in this category are those that are widely distributed in the western United States and that occur in Colorado in both the mountains and the lower more arid intermontane areas. Some of these species are differentiated into subspecies, one of which inhabits the mountains and another the lowlands. Wide-spread species that do not have subspecies in the lowlands different than the subspecies in the mountains or that are represented by too little material from the Grand Mesa to be evaluated critically are Myotis evotis, Myotis volans, Spermophilus variegatus, Eutamias quadrivittatus, Castor canadensis, Ondatra zibethicus, Erethizon dorsatum, Mustela frenata, Taxidea taxus, Mephitis mephitis, and Odocoileus hemionus. Three other wide-spread species are differentiated into lowland and highland subspecies; two of these species, Eutamias minimus and Peromyscus maniculatus, are represented on the Grand Mesa by the darker subspecies of the mountains. The third species, Neotoma cinerea, is represented by two individuals from below the actual rim of the mesa; they are intergrades between the lowland and highland subspecies.
Species of southern distribution, that are dependent at the latitude of Colorado upon the habitat provided by areas of lower altitudes, and that are here in Colorado near their northern limit comprise a third category that is not represented in the list of mammals from the Grand Mesa although such characteristic species as Ammospermophilus leucurus, Perognathus apache, and Dipodomys ordii occur as near as Grand Junction.
Approximately 55 per cent of the species of the mammalian fauna are boreal; no species of Sonoran affinities finds haven on the Grand Mesa.
Transmitted January 22, 1959.
27-7472
Transcriber's Notes
Page [407]: Rejoined the remainder of the last paragraph, originally
found on page 409.