The northern Great Plains ecosystem of North America was once inhabited by free ranging herds of bison ranging in the millions. In the 1800s, human settlement in the area led to large scale slaughter of bison and conversion of much of the grass prairie to agriculture. Only relatively recently have restoration and conservation efforts led to protected tracts of mixed-grass prairie and bison herds. Since reestablishing this relationship, scientists have documented the many beneficial roles that bison play as a keystone species in their ecosystems. Through their unique grazing behavior, bison contribute to changes in plant and animal species composition, alterations of the physical and chemical environment, increased spatial and temporal heterogeneity in vegetation structure, soil resource availability and a variety of ecosystem processes (Knapp et al. 1999).