White-tailed deer (Odocoileus virginianus) foraging habits in Great Plains grasslands near wooded and agricultural habitat edges

Abstract

Effects of herbivores in Great Plains grasslands have fundamentally changed with the extirpation of native large grazing herbivores. Woody plant expansion into prairies also allows for new herbivore-plant interactions involving animals that were previously restricted to areas such as riparian zones, thus leading to novel edge effects near grassland ecotones. Further, grasslands are becoming increasingly fragmented, which can lead to ‘double-edge effects’, potentially increasing the magnitude of effects mediated by highly mobile organisms where multiple habitat edges converge. While few bison (Bison bison) remain, white-tailed deer (Odocoileus virginianus) have become prominent herbivores in prairies, occurring at much higher densities compared to historic abundances. To determine the potential edge effects mediated by deer, I collected observational data on browsing rates of legumes, non-leguminous forbs, and woody plants within fragmented grasslands bordered by either wooded or agricultural edges. Additionally, I implemented a double-edge experiment using transplanted forbs to evaluate magnification of edge effects by deer in corners of prairie fragments where two woodland edges converged. Deer browsing showed seasonality where in early summer they remained near the grassland edge and in late summer they browsed equally up to 100m from the edge. Further, in all surveys, deer preferentially consumed woody species, followed by legumes, and lastly non-leguminous forbs. The double-edge experiment did not reveal increased browsing intensity with a second nearby wooded edge, but the power of my experiment was compromised by high transplant mortality. Given the small amount of research that quantifies deer browsing patterns in grasslands, these findings have management implications that would allow better placement of sensitive plant species within prairie restorations and help establish new practices for deer management.