Bison Grazing Ecology at the Rocky Mountain Arsenal National Wildlife Refuge, Colorado

The Rocky Mountain Arsenal (RMA) National Wildlife Refuge (NWR) encompasses 6,070 hectare (ha) of shortgrass prairie approximately 16 kilometers (km) northeast of the center of Denver, Colorado. Historically, RMA was native shortgrass prairie; however, between 1880 and 1942, these lands were grazed by domestic cattle and converted to croplands and non-native grasses. The former farmland was bought in 1942 by the U.S. Army to establish the Rocky Mountain Arsenal, a chemical weapons factory. During World War II and the Cold War of the 1950s, the U.S. Army produced chemical weapons at the site and leased portions of the facility to private companies that produced agricultural pesticides. Years of chemical production left the industrial core of the site contaminated, but deer (Odocoileus virginianus), prairie dogs (Cynomys ludovicianus), coyotes (Canis latrans), eagles, and many species of hawks, owls, and other birds thrived in the surrounding fields, grasslands, and woodlots that had been protected from 40 years of urban sprawl and development. Extensive cleanup of the site began in the 1980s under an Environmental Protection Agency Superfund designation.