EFFECTS OF HORNING AND RUBBING BEHAVIOR BY BISON (BISON-BISON) ON WOODY VEGETATION IN A TALLGRASS PRAIRIE LANDSCAPE

Horning and rubbing behaviors of American bison (Bison bison) and thei r effects on woody vegetation were investigated for 2 yr on a herd of 300+ animals reintroduced to a 1973-ha tallgrass prairie site in Oklah oma. Horning and rubbing activity was significantly higher in summer t han in other seasons. Whether this increase was associated with rut, s hedding of winter pelage, insect harassment, or a combination of these factors was unclear; however, these behaviors did have measurable imp acts on the woody vegetation of the area. Bison injury to trees was mi nimal, although one willow (Salix nigra) was uprooted and killed durin g the Study, and several other trees were seriously damaged. Bison hor ning had the greatest effect on saplings and shrubs, killing or severe ly damaging 4% of the woody plants documented within the study area an d causing moderate injury to 13% and light injury to 12%. Bison showed a strong preference for small willows, killing or severely damaging 1 7% of the saplings and shrubs of this species during the study. Bison also used artificial, man-made objects present on the landscape such a s utility poles and fenceposts. Results suggest that horning and rubbi ng by bison, along with fire and drought, may have influenced the hist orical distribution of woody vegetation in prairie environments.