Altitudinal Variation in the Annual Cycle and Life History of the Golden-mantled Ground Squirrel (Spermophilus lateralis)

DOCTORATE DISSERTATION: How does the golden-mantled ground squirrel contend with the severe restriction in time available for reproduction and growth? The answer may emerge from examination of the correlation between the length of the active season and other characteristics of the species. The snow-free season diminishes from low to high elevations. In response, the duration of the above-ground active season of the golden-mantled ground squirrel would be expected to decrease. The restriction of such a critical resource may have resulted in at least 2 sets of adaptive modifications. 1. The physiological control of the time of spring emergence and fall immergence in the annual cycle may have been adjusted to seasonal constraints. 2. Life history aspects, such as age of first reproduction, litter size, and survivorship, may have been altered by selection under different climatic regimes. The research reported here tested for the natural occurrence of these variations, whether they be genetically or merely phenotypically based. III. Within the subspecies Spermophilus lateralis chrysodeirus, (the researcher) tested for geographical and temporal variation in the schedule of springtime emergence, reproduction, and fall immergence. IV. This section describes variation in several demographic features of the golden-mantled ground squirrel, a hibernator, over a climatic gradient.