Date of Graduation

5-2026

Document Type

Thesis

Degree Name

Bachelor of Science in Anthropology

Degree Level

Undergraduate

Department

Anthropology

Advisor/Mentor

Amelia Villaseñor

Committee Member

Lucas Delezene

Second Committee Member

Jeffrey Lewis

Third Committee Member

Jared Phillips

Abstract

In North America, grasslands are a cornerstone of the environment. Historically, the tallgrass prairie was expansive and reached from Manitoba in Canada to Texas. Today this unique ecosystem is highly fragmented and reduced, but it remains an important ecosystem for biodiversity and cattle management. While there are many complex ecological interactions in the prairie, recent research shows that large herbivores are vital in maintaining grasslands through grazing and other behaviors that reduce woody encroachment and support nutrient cycling. Here, we examine cow and bison dietary behaviors and connect these to the ecosystem services provided by these large herbivores. In the Joseph H. Williams Tallgrass Prairie, Oklahoma, we take advantage of a natural experiment separating bison and cows on fire-maintained grasslands and examine stable carbon and nitrogen isotopes from large herbivore feces. These data show what types of plants (carbon isotopes differentiate grasses or forbs) these grazers are eating as well as how the vegetation they consume differs in protein (nitrogen isotopes). Data collected in 2025 show that bison have higher carbon values, indicating a focus on grass. In contrast, cows prefer a wider range of vegetation that may include forbs (such as wildflowers). Nitrogen values vary from year to year, but there are more extreme differences in cow nitrogen isotope values. Bison’s preference for native grasses allows for growth of diverse forbs, increasing overall species richness and promoting biodiversity in grasslands. This and previous studies suggest that large herbivores, both bison and cows, are important for promoting plant diversity and resilience. However, bison may promote greater biodiversity than cows. Our research identifies keystone behaviors isotopically; these behaviors can be examined in the hominin fossil record and set the stage for future research on grassland diversity.

Keywords

Tallgrass Prairie, Ecosystem, Bison, Isotopes, Biodiversity

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