Counting marmots…
Since pocket gophers use their incisor teeth to excavate rather extensive burrow systems in hard soil, their rate of incisor growth and attrition is unusually high (Howard and Smith, 1952). The purpose of this study was to compare the rates of incisor growth of pocket gophers from different habitats, and to determine the extent to which extrusive incisor growth is a subspecific adaptation to local habitat conditions. I am grateful to Drs. Ernst Mayr and Richard M. Hansen for suggestions during the preparation of the manuscript, and to Dr. Elmer Remmenga for advice on statistical procedures. Methodsand materials.—The pocket gophers used in this study were collected from two ecologically different localities, each within the range of a different subspecies of Thomomys talpoides. One of the localities, Black Mesa, is located on the western slope of the Rockies about 27 miles west of Gunnison in Gunnison County, Colorado. The elevation of this locality is approximately 10,000 feet, the growing season is short and, although there is a fairly heavy winter snowfall, the total annual precipitation is low. The Black Mesa sample was taken from mountain meadows in which the vegetation is predominantly grasses and mixed forbs and the soil is relatively coarse and shallow.
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