Effects of Horning and Rubbing Behavior by Bison (Bison bison) on Woody Vegetation in a Tallgrass Prairie Landscape

Abstract

-Horning and rubbing behaviors of American bison (Bison bison) and their effects on woody vegetation were investigated for 2 yr on a herd of 300+ animals reintroduced to a 1973-ha tallgrass prairie site in Oklahoma. Horning and rubbing activity was significantly higher in summer than in other seasons. Whether this increase was associated with rut, shedding of winter pelage, insect harassment, or a combination of these factors was unclear; however, these behaviors did have measurable impacts on the woody vegetation of the area. Bison injury to trees was minimal, although one willow (Salix nigra) was uprooted and killed during the study, and several other trees were seriously damaged. Bison horning had the greatest effect on saplings and shrubs, killing or severely damaging 4% of the woody plants documented within the study area and causing moderate injury to 13% and light injury to 12%. Bison showed a strong preference for small willows, killing or severely damaging 17% of the saplings and shrubs of this species during the study. Bison also used artificial, man-made objects present on the landscape such as utility poles and fenceposts. Results suggest that horning and rubbing by bison, along with fire and drought, may have influenced the historical distribution of woody vegetation in prairie environments.