Testing stable isotopes to reveal bison-plant communityiInteractions in an altered prairie landscape

Authors: TSALICKIS, ALEXANDRA - Auburn University; Campbell, Joshua; Pei, Chyna; VACHULA, RICHARD - Auburn University

Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/4/2026
Publication Date: 9/1/2026
Citation: Tsalickis, A., Campbell, J.W., Pei, C.K., Vachula, R.S. 2026. Testing stable isotopes to reveal bison-plant communityiInteractions in an altered prairie landscape. Rangeland Ecology and Management. 108:217-225. https://doi.org/10.1016/j.rama.2026.07.002.
DOI: https://doi.org/10.1016/j.rama.2026.07.002

Interpretive Summary: The American bison historically was a common large grazing mammal found throughout the Great Plains but are now only found in remnant populations located in preserves, Tribal lands, and agricultural farms. Thought to primarily consume grass species, diet preferences of unmanaged bison herds remains unknown. To determine whether unmanaged bison prefer grasses or other forbs, we used stable carbon ('¹³C) and nitrogen ('¹5N) isotopic compositions of bison dung and plant samples collected at a prairie preserve in Montana. Carbon and nitrogen isotopes can be used to determine recent diet and trophic status of organisms. We found that bison consume a significant number of forbs along with grass in their diet during the late summer. This study highlights the use of stable isotopes as an effective tool for investigating animal diets.

Technical Abstract: The shortgrass prairie of the Great Plains is one of the most endangered ecosystems in the United States, facing significant loss due to expansion of agriculture and non-native grasses. Historically, the American Bison (Bison bison) acts as a keystone species to the shortgrass prairie ecosystem, playing a crucial role in maintaining its ecological health and integrity. However, the dietary preferences of these remnant bison herds are not well understood. While research in the past few decades has primarily classified domesticated bison as grass-dominated grazers, recent studies suggest forbs comprise a larger portion of their diet. However, due to the difficulty of studying wild bison, many uncertainties persist about the applicability of domestic bison diet insights to unmanaged populations. We analyzed the stable carbon ('¹³C) and nitrogen ('¹5N) isotopic compositions of wild bison dung and plant samples and applied them to the MixSIAR stable isotope mixing model to determine the relative contributions of different plant groups to bison diet in the shortgrass prairie. Results indicate that forbs contribute the most to bison diet in late summer, challenging the traditional view of bison as strictly grass grazers. This study highlights the potential of stable isotope analysis as an effective tool for investigating wild animal diets. Additionally, our findings provide important insights for managing bison populations and restoring shortgrass prairie ecosystems, especially in the face of ongoing habitat degradation (i.e., agriculture and non-native species takeover).