Habitat Selection and Diet Composition of Reintroduced Native Ungulates in a Fire-Managed Tallgrass Prairie Reconstruction

Abstract

In an effort to understand native ungulate behavior in a fire-managed tallgrass prairie reconstruction effort, we conducted a two year habitat selection and diet composition study of reintroduced populations of elk (Cervus elaphus) and bison (Bison bison) in southern Iowa. Our study included intensive surveys of ungulate group locations throughout the growing season, fecal sample collections for microhistological diet analysis, and plant community surveys. Bison and elk use of the reconstructed grassland was spatially nonrandom. Available cover and farthest distance from the enclosure fence strongly influenced habitat selection by elk. Bison segregated into a small bull group consisting of older bulls and a larger mixed group that included cows, yearlings, calves, and young bulls. The bull group selected areas with high percent cover of native plants, steeper slopes, and older burn areas. The mixed group strongly selected for recently burned areas with high native plant cover and eastern aspects. Elk consumed mostly non-native forbs while over 90% of the bison diet consisted of graminoid species. Although bison did not consume significantly different proportions of native species compared to non-natives, their selection of habitat was strongly related to presence of native plants, especially in combination with burned areas. The reintroduced ungulates behaved as three functionally distinct groups. Based on behavioral and group size differences, the large mixed sex/age bison group is likely to have the greatest impact on the fire-managed reconstruction, while the effects of the bison bull groups and elk are likely to have more localized effects on the reconstructed prairie.