An Experimental Attempt to Produce a Mouse Plague

Abstract

In earlier papers about this population of house-mice, Mus musculus L. (Newsome 1969a, b) it was concluded that numbers were limited by lack of suitable soil for burrowing and by the food supply, in that order. During the 6 years of the study so far, mice have always multiplied in summer, the season when food is abundant, only to have their numbers checked if the soil dried out and was too hard for burrowing. Autumn rains always provided plenty of opportunity for burrowing, but they also germinated any seed left from the summer; so food was scarce and numbers fell. It was suggested in those papers that mouse plagues would arise should the soil be suitable for burrowing at the same time as food abounded. This paper describes an experiment to induce a plague on small plots in a reed-bed. The soil there, being sandy, is fairly well drained and not readily subject to water-logging (Newsome 1969b), a condition that quickly rids the adjacent wheatfields of mice early in winter because soil there is clayey (Newsome 1969a). So the reed-bed should provide an abundance of homesites in winter, and mice should multiply greatly given enough food, thereby reversing the annual cycle of rising numbers in summer and falling numbers in winter. Besides describing the consequence of artificially removing shortage of food, this paper also examines demographic changes imposed by shortage of burrowing sites. It has been suggested elsewhere (Newsome 1969b) that in such circumstances social conflicts arise to act as a servo-mechanism to curb breeding and promote dispersal, especially of the young.