Influence of Red Fox Predation on a Local Population of Small Rodents I. Population Fluctuation in Small Rodents

Abstract

In order to study the effect of predation on a rodent population, it is necessary to estimate accurate numbers of living rodents and of those consumed by predators. As a first step, the author studied population changes in small rodents for the 5 years from 1974 to 1978 in Koshimizu in eastern Hokkaido, Japan. The number of rodents and their biomass were estimated as available food sources for foxes. Definite seasonal variations in the number of rodents were found but there was no remarkable outbreak. Some factors which cause erroneous estimation of rodent numbers are also discussed.