EXPERIMENTALLY-INDUCED HABITAT SHIFTS BY HISPID COTTON RATS (SIGMODONHISPIDUS) - RESPONSE TO PROTEIN SUPPLEMENTATION

Hispid cotton rats (Sigmodon hispidus) occupy habitat patches nonrando mly on the Texas coastal prairie. We addressed the hypothesis that thi s pattern of habitat occupancy was influenced by nutrient content of h abitat patches. Because availability of protein varied among habitat p atches and amount of protein available in monocot patches was insuffic ient for reproduction, a specific objective was to determine whether a nimals 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 enc losures open to field weather conditions. Quadrants in these enclosure s contained vegetation from monocot (i.e., low protein content, 4%) or mixed (i.e., high protein content, 11%) habitat types. In addition, q uadrants received treatments of high or low cover and artificial diets containing either 0 or 15% protein. Hispid cotton rats selected quadr ants containing high cover and supplemental food with 15% protein. The greatest increase in occupancy was in monocot habitats supplemented w ith 15% protein and where cover was low. Thus, nutritional content of habitat patches affects habitat occupancy by this herbivore, and cotto n rats balanced risk against reward.