USE OF COASTAL WETLANDS BY HISPID COTTON RATS (SIGMODON HISPIDUS)

Abstract

Hispid cotton rats (Sigmodon hispidus) occur primarily in grass-dominated habitats. These habitats abut tidal wetlands along the Gulf and Atlantic coasts of the United States occupied by the marsh rice rat (Oryzomys palustris). Few data document whether cotton rats also occupy wetlands and whether interspecific interactions exist with rice rats. We used livetraps to sample 4 grids that each encompassed wetland and upland habitats near Galveston, Texas. Cotton rats occurred in both upland and wetland habitats. Density of cotton rats was lower in wetlands; their residence time was less in wetlands, which perhaps indicated poorer survival or movement to uplands. Sex ratio, proportion reproductive, and age structure, however, did not differ between upland and wetland habitats. Density of cotton rats and rice rats was negatively correlated. Such density compensation coupled with differences in diel activity and diet minimizes potential for interspecific competition.