Early behavioral research on populations

Abstract

Research on populations of rats (Rattus norvegicus) in Baltimore beginning in 1943 suggested the hypothesis that aggressive behavior could regulate the numbers in a city block where food and shelter were adequate. A program of experiments using wild rats or laboratory mice justified publication of the aggressive behavior hypothesis in 1949. Continued research by Davis, Calhoun, Christian and graduate students showed that the number of rats in a city block returned towards an asymptote after a reduction in number, and that the introduction of alien rats was followed by a decline. Communication about the level of population was achieved by signals (visual, olfactory, auditory and tactile) that determined social status. Rates of reproduction declined and rates of mortality increased as the population increased. Various physiological mechanisms were explored but the mechanisms of communication were little studied before 1955. © 1987 by the American Society of Zoologists.