Comparing permeability of matrix cover types for the marsh rice rat (Oryzomys palustris)

Abstract

Matrix land cover types differ in permeability to animals moving between habitat patches, and animals may actually move faster across less-suitable areas. Marsh rice rats are wetland specialists whose dispersal crosses upland matrix. Our objectives were to (1) compare matrix permeability for the marsh rice rat among upland cover types, (2) compare permeability within versus outside perceptual range of the wetland, and (3) explore intrinsic and extrinsic features influencing matrix use and permeability. We quantified permeability of grassland, crop field, and forest to the marsh rice rat during 2011–2012, by marking rats in wetlands and estimating the slope of capture rate versus distance (0–95 m) into the matrix. We also compared permeability within (0–15 m) and beyond the perceptual range of rice rats, and tested whether age, sex, time, water depth, rice rat abundance, and vegetation density influenced matrix use and permeability. Permeability was greater for soybean fields than grassland or forest but did not appear to differ within versus beyond rice rats’ perceptual range. Matrix capture rates were higher early in the study and in times and locations with thick ground vegetation and high rice rat abundance in the wetlands. Rice rats captured in the matrix were younger than those in wetland patches. Our findings expand known matrix use by marsh rice rats, and support permeability being high in matrix types dissimilar to suitable habitat. Studying individual movements will help identify mechanisms underlying enhanced permeability in crop fields.