Experimentally Induced Habitat Shifts by Hispid Cotton Rats (Sigmodon hispidus): Response to Protein Supplementation

Abstract

Hispid cotton rats (Sigmodon hispidus) occupy habitat patches nonrandomly on the Texas coastal prairie. We addressed the hypothesis that this pattern of habitat occupancy was influenced by nutrient content of habitat patches. Because availability of protein varied among habitat patches and amount of protein available in monocot patches was insufficient for reproduction, a specific objective was to determine whether animals would shift their habitat affinity toward monocot patches when protein was experimentally increased. We also tested whether overhead cover affected selection of habitat. Experiments were conducted in enclosures open to field weather conditions. Quadrants in these enclosures contained vegetation from monocot (i.e., low protein content, 4%) or mixed (i.e., high protein content, 11%) habitat types. In addition, quadrants received treatments of high or low cover and artificial diets containing either 0 or 15% protein. Hispid cotton rats selected quadrants containing high cover and supplemental food with 15% protein. The greatest increase in occupancy was in monocot habitats supplemented with 15% protein and where cover was low. Thus, nutritional content of habitat patches affects habitat occupancy by this herbivore, and cotton rats balanced risk against reward.