Date on Master's Thesis/Doctoral Dissertation

5-2024

Document Type

Doctoral Dissertation

Degree Name

Ph. D.

Department

Biology

Degree Program

Biology, PhD

Committee Chair

Eason, Perri

Committee Member

Emery, Sarah

Committee Member

Yanoviak, Stephen

Committee Member

Pigg, Rachel

Committee Member

Mitchell, Robert

Author's Keywords

animal behavior; group consensus; american bison; bison bison

Abstract

The American bison is an iconic mammal that lives in large social herds and is considered a threatened species. Little is known about how bison make decisions as a group, whether through despotic individuals or group consensus. In this dissertation, I researched the mechanisms bison use to make herd movement decisions in 3 herds in the United States. In chapter one I examined the number of bison that participated in voting events for herd movement decisions and whether the final movement decision matched the direction with the most votes. Bison herd movements did match the direction with the most adult votes in 72-80% of events, and a logistic regression revealed a strong correlation between the winning margin and the final outcome being democratic. In chapter two, I studied the influence of bison’s sex on voting behaviors and the greater influence females potentially wielded. Studying a herd in Kentucky, I recorded the sex of each voting bison and its vote, i.e. the direction it faced while standing. The most significant effect on bison voting patterns came from the total winning margin of votes, with sex having no significant effect on the outcomes. Bison consensus decisions likely stem from the margins of voting, with nondemocratic decisions more likely with narrow voting margins, a pattern exhibited both in this and the previous study. v In Chapter three I studied the independence of calves from their mothers as measured by the average distance they ranged from her, and I also recorded when calves began to exhibit voting behaviors. I observed a cohort of 14 newborn calves for one year beginning in May, 2022. Calves’ average distance from their mothers increased over time, occurring in a nonlinear fashion. Calves generally remaining near their mothers for two months, ranging further away in their third month, staying closer to their mothers in their fourth month, and moving greater distances from their mothers again in their 5th and 6th months. Calves began to vote at 9.5 months of age, but did not vote regularly until after they were a year old.

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