An Eleven Year History of a Sigmodon Population

While general observation has indicated that annual fluctuations in population density of rodents in southern United States are less “cyclic,” i.e., peaks less regular, than is the case in the classic northern four-year cycles, few long-term observations have been made on populations in stable habitats. The possibility of a north-south difference in the nature of population oscillations has an important bearing on current theories of “cycles.” For the past eleven years trapping has been carried out according to a consistent plan in an old field where habitat features have been relatively constant. The field is located near Athens, Clarke County, Georgia in the Piedmont section of the state. The cotton rat, Sigmodon hispidus, comprised the great bulk of the readily trappable small mammal population in the old field, which is in a stage of vegetative succession favorable to the species. (Cotton rats occurring in Georgia except for the coastal...