. Fig. 42. Detailed map of Larimer and Boulder counties and parts of adjacent counties, showing dis- tribution of Eutamias quadrivittatus (closed circles) and Eutamias umbrinus (open circles). The fine, irregular north-south line is the 8000-foot contour. Localities plotted are identified with an asterisk in respective lists of specimens examined. ranges approach. In the mountains of north- ern and central Colorado, E. quadrivittatus is consistently found at lower elevations. A simi- lar relationship exists between the Uinta and Colorado chipmunks on the Western Slope. In areas where only a si
. Fig. 42. Detailed map of Larimer and Boulder counties and parts of adjacent counties, showing dis- tribution of Eutamias quadrivittatus (closed circles) and Eutamias umbrinus (open circles). The fine, irregular north-south line is the 8000-foot contour. Localities plotted are identified with an asterisk in respective lists of specimens examined. ranges approach. In the mountains of north- ern and central Colorado, E. quadrivittatus is consistently found at lower elevations. A simi- lar relationship exists between the Uinta and Colorado chipmunks on the Western Slope. In areas where only a single species of large chipmunk occurs, that species is found to have a wider altitudinal range. In southwestern Colorado, for example, E. quadrivittatus is recorded from localities above 10,000 feet; in Larimer and Boulder counties, records are consistently below 8000 feet. Likewise, in north-central Colorado, E. umbrinus occurs mostly above 8500 to 9000 feet, but in the White River Valley, where the species is re- moved from the range of other large chip- munks, records are available as low as 6500 feet. This pattern is illustrated elsewhere in Colorado by comparison of lists of specimens examined. The known distributions of the two species in question in north-central Colorado are il- lustrated in figure 42. The fine, irregular north-south line in the figure is the 8000-foot contour. It is noteworthy that this is the approximate elevation at which open wood- land cedes dominance to closed coniferous forest. Long and Cronkite (1970) presented distributional data on the two species in a zone of near sympatry in Gunnison and Chaf- fee counties. Long and Cronkite (1970) remarked on the large size of two specimens from the vicinity of Bondad, La Plata County. Ex- ternal measurements of these two specimens (a young adult male and an adult female, KU 34693 and 34692) are, respectively, 249, 241; 102, 112; 34, 36; 18, 18. Representative cra- nial measurements are presented in table 9
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Keywords: ., bookcentury1900, bookcollectionbiodiversity, booksubjectmammals
