Population Dynamics of the Cotton Rat in Southeastern Virginia

Abstract: We used monthly live trapping for 2.5 years to evaluate the life-history features of the most common small mammal, Sigmodon hispidus (hispid cotton rat), in an old field at its northern limit of distribution on the Atlantic coast. Peak densities, achieved in late autumn or early winter, were among the highest recorded for the species and were more typical of marginal populations rather than of central ones. Unlike some other marginal populations, hispid cotton rats in eastern Virginia did not lose significant body mass over the winter (when few juveniles were present) and survival in winter was not significantly different from other seasons. Our study provides support for the presence of spring and autumn cohorts, with long-lived animals being drawn almost entirely from the latter.