Alexandra Tsalickis, Joshua W. Campbell, Chengkui Pei, Richard S. Vachula
The shortgrass prairie of the Great Plains is one of the most endangered ecosystems in the United States, having faced significant losses and alterations due to anthropogenic land conversion and species introductions. Historically, the American bison ( Bison bison ) acted as a keystone species to the shortgrass prairie ecosystem, providing grazing and wallowing disturbances important to promoting grassland ecological diversity. However, the dietary preferences of these reintroduced bison herds are not well understood in today’s novel landscapes but methods such as stable isotope analysis may be advantageous in understanding the diets of bison in open environments. We analyzed the stable carbon (ẟ¹³C) and nitrogen (ẟ¹⁵N) isotopic compositions of open-ranging bison dung and plant samples and applied them to the MixSIAR stable isotope mixing model to test the relative contributions of different plant groups to bison diet in shortgrass prairie with an assemblage of native and nonnative plant species. Our results indicate that forbs may contribute the most to bison diet in early summer, and that native species made up a greater composition of consumed plants. This study highlights the potential of stable isotope analysis as an effective tool for investigating wild and/or open-ranging animal diets. Additionally, our findings lay a foundation for providing important insights for managing bison interactions with plant communities in altered shortgrass prairie ecosystems within the Northwestern Great Plains/Northwestern Glaciated Plains ecoregion with invasive cool-season grasses and other nonnative plant species.