Population Ecology of the Prairie Vole, Microtus ochrogaster, in the Western Mixed Prairie of Nebraska

Meserve, Peter

Populations of prairie voles were studied on two grids of 4.1 and 3.7 acres in the western mixed prairie of Scotts Bluff National Monument, Nebraska. This xeric prairie, with a mean annual precipitation of 36.6 cm, is dominated by mid and short grasses. Over three seasons, 1968-69, live-trapping revealed population densities of one to 14 voles per acre. The mean trap-revealed home range was .22 acres during the summer of 1968. Correlation of trapping results with known distribution of plants found in fecal samples suggests home ranges as large as .34 acres for some individuals. In general, population densities for the prairie vole in western Nebraska are considerably lower than reported in the mesic tall-grass prairie of eastern Kansas and somewhat lower than reported in the mesic mixed prairie of west-central Kansas. Home ranges in western Nebraska are considerably larger than those reported in the tall-grass prairie. Lower population densities may result from lower precipitation and, indirectly, from the sparser cover and decreased productivity characteristic of the western mixed prairie. Previous studies have documented the importance of precipitation in affecting available food supply and reproduction of voles. Year-round reproduction is supported by indirect evidence, and the populations showed a decline in numbers of juveniles and an increase in mean body weight through late summer, winter and early spring. Fecal analysis indicates that voles eat green succulent grasses and sedges, and show seasonal preferences dependent on the characteristic growth patterns of the most abundant plants. The food in winter is similar to that of summer, indicating a dependence on cached food, while that of spring is most different, reflecting the shifts in preference to various rapidly growing grasses and sedges. Stations with good cover had a significantly larger number of captures and individuals per station on one plot but not the other. This may have been due to the greater uniformity of the latter plot. There was no evident correlation between the location of specific grasses important for food and the distribution of captures for voles.

Population Ecology of the Prairie Vole, Microtus ochrogaster, in the Western Mixed Prairie of Nebraska

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