Find Me Gallery Medicine Bow Mountains This mountain range is to the southeast in this scene. Bison once lived there, too, even at high elevations. Black-Tailed Prairie Dog Bison kept the grass low enough for prairie dogs (Cynomys ludovicianus) to colonize: short grass is more nutritious and exposes predators. Bison Wallow Bison make wallows, or depressions in the soil or mud, and roll around in them in part to escape heat and insects. These shallow dishes of dirt store precious rainwater during dry periods. Blue Grama Like buffalograss, blue grama (Bouteloua gracilis) is a drought-resistant native grass favored by bison. It has distinctive curved flowerheads. Buffalograss Bison thrived on short-grass prairies, where this short, native grass was abundant. Brown-Headed Cowbird Grazing bison rustle insects in the grass and cowbirds (Molothrus ater) follow closely to eat them.