BOTANICAL COMPOSITION OF BISON DIETS ON TALLGRASS PRAIRIE IN OKLAHOMA

Diets of bison (Bison bison L.) were examined using microhistological fecal analysis in a 2-yr study on a tallgrass prairie site in northcen tral Oklahoma. Graminoids comprised at least 98% of the diet across al l seasons. Bison showed strong feeding selectivity; grasses and sedges formed a significantly higher proportion of diets than was generally available in herbage on the landscape, Bison avoided forbs, which were less than or equal to 2% of the diet, Sedges were a large (17-44 %) d iet component in winter and spring but decreased substaintially during summer and fall (11-16%), These changes in sedge use corresponded to seasonal variation in sedge availability. Our results confirm that bis on are primarily grazers in prairie habitats, potentially having a sig nificant role in shaping structure and function of tallgrass prairie.