An Investigation of Competition in Natural Populations of Mice

Abstract

Three approaches were used to study interactions between Peromyscus polionotus and Mus musculus: (1) a 15-month study of natural populations in six 3.5-acre grids located in a large abandoned field on the AEC Savannah River Plant Reservation which is located on the Upper Coastal Plain of South Carolina, (2) a comparison of behavior and food requirements of the mice in the laboratory, (3) a 7-month study of the 2 species confined to a one-acre enclosure located in the field. No evidence of aggressive competition (fighting, etc.) was obtained but Mus was definitely at a disadvantage in competition for food when population density was high or when the 2 species were confined in the enclosure. It is postulated that the migratory behavior of Mus is a mechanism which reduces competition between it and the more sendentary Peromyscus enabling both species to coexist in the same habitat even when Mus appears to be less well adapted to the Upper Coastal Plain environment.