Cyclic population changes in three mouse species in the same woodland

In two forest areas of West Berlin the population-changes in three mouse species have been investigated over 28 years (1952-1979). Significant changes in absolute density have been established for the Short-Tailed Vole (Microtus agrestis) at 5-year intervals, for the Common Vole (Microtus arvalis) at 4-year intervals, and for the Yellow-Necked Field Mouse (Apodemus flavicollis) at 3-year intervals. The investigations were based on a total of 43,535 small vertebrates, 90% of which had been found in the pellets of breeding Tawny Owls. The remaining 10% belonged to pellets collected in the territories of breeding Long-Eared Owls. It is assumed that, for those prey animals whose percentage in the total prey of a predator is fairly high, the percentage proportionally approximates the real fluctuations in their (absolute) density.