Influence of Supplemental Feeding on a Vole Population

Densities and demography of prairie voles (Microtus ochrogaster) vary widely in different habitats, and dramatic, cyclical changes in population densities occur. We provided high quality supplemental food (rabbit pellets) to a population in relatively unfavorable habitat (an old bluegrass pasture) to test the hypothesis that differences in food quality can account for those trends. Throughout the winter the experimental population showed higher breeding intensity, better adult survival, and higher body growth rates than the control population. As a result, the supplemental population reached densities (135/ha) 50% higher than those of the control population (90/ha). Moreover, body growth, litter size, and density remained higher in the supplemental population during the following spring and summer. However, supplemental feeding did not prevent or delay declining densities that occurred in late summer and autumn in both populations. We conclude that quality of available food influences the amplitude of population fluctuations of the prairie vole, but some other factor(s) must initiate the periodic declines.