White-tailed deer use of clearings relative to forage availability

Use of woodland clearings by white-tailed deer (Odocoileus virginianus) may be in response to increased availability of forage within open patches or increased ability of deer to locate predators. We tested predictions, based upon the forage-maturation hypothesis, that white-tailed deer used areas with the greatest availability of high-quality forage, and that habitat use changed seasonally depending upon availability and quality of major types of forage in their diet. We tested those predictions in subtropical thorn woodland in South Texas, United States. Treatments included (1) areas with continuous woody cover as controls, (2) clearings with high availability of forbs and shrub sprouts, (3) clearings with low availability of shrub sprouts, (4) clearings with low availability of forbs, and (5) clearings with low availability of forbs and shrub sprouts. Intensity of use by deer during summer and autumn increased with increasing biomass of shrub sprouts and then declined with increasing shrub biomass as areas became dominated by mature shrubs with less accessible, usable forage. During spring, intensity of deer use increased in clearings with increases in forage availability and quality, indicated by an index to carrying capacity, then declined as vegetation matured. Responses of white-tailed deer to clearings supported the forage-maturation hypothesis in which herbivore responses to clearings resulted, in part, from the presence of shrub sprouts of high nutritional quality, particularly during summer and autumn when forage availability was low. Maintenance of clearings that are interspersed in a woodland matrix and maintaining high levels of immature shrub sprouts may alter the spatial distribution of white-tailed deer on the landscape.