Species Removal Effects on Movements of Sigmodon hispidus and Reithrodontomys fulvescens

Abstract

The effects of interspecific interactions on movements of hispid cotton rats (Sigmodon hispidus) and fulvous harvest mice (Reithrodontomys fulvescens) were examined by experimental removal of species. For both Sigmodon and Reithrodontomys, the average distance moved by individuals (AvD,) was greater for males than females. The average distance moved by the population within trap periods (AvD,) was negatively correlated with Sigmodon density only in a field with low resource abundance whereas the AvDp for Reithrodontomys was negatively correlated with density in all fields. Species removal did not affect AvDp of either species. Seasonal differences in AvDp for R. fulvescens suggested an intraspecific effect on movement. Reithrodontomys used the vertical component of the habitat to a significantly greater extent when Sigmodon was present. There was no difference between experimental and control fields in vertical habitat structure, suggesting an interspecific effect of Sigmodon upon movement of Reithrodontomys. Variation in movement may result from differences in available habitat for Sigmodon, but not for Reithrodontomys.