Distribution and Diet of Bison and Pocket Gophers in a Sandhills Prairie

Abstract

Native herbivores are generally preferred over introduced species for managing prairie preserves. However, contemporary prairies are fragments of the original ecosystem, and their size and management may not match the foraging and/or social behavior of native herbivores. We conducted field studies from May 1988 through April 1991 within a 3000‐ha sandhills prairie to describe bison (Bos bison) and pocket gopher (Geomys bursarius) use of native Great Plains grassland at a size relevant to current land ownership and management units. The distribution and diet of bison and pocket gophers were compared to vegetation patterns at several scales. The study area is characterized by a matrix of warm‐season grasses occurring on four range sites (topo‐edaphic units). Patches characterized by forbs, shrubs, and trees occur within the matrix communities associated with the four range sites. Bison distribution appears to be influenced by a complex interaction between seasonal forage availability, herd size, and habitat openness. Bison diets during the growing season are strongly linked to the warm‐season grasses of the prairie matrix. Pocket gopher activity is ubiquitous throughout the study area, but is particularly high in forb patches and appears to be responsive to bison impacts. Pocket gopher diets are strongly linked to forbs, both in the forb patches and in the prairie matrix. Field data indicate that bison and pocket gophers use herbage resources that have distinctly different distributions within the sandhills prairie. It appears that bison remain well adapted to prairie remnants of the size we studied, and through interactions with other herbivores and vegetation patterns, will support a diverse landscape.