In many areas of Ohio, population densities of white-tailed deer (Odocoileus virginianus) are extremely high due to their generalist foraging capabilities and limited predation. At high densities, browsing by white-tailed deer damages forest ecosystems through inhibition of tree regeneration and decreasing tree species diversity. This may result in a trophic cascade in forested habitats. Furthermore, forest fragmentation is occurring throughout much of the range of white-tailed deer, creating new grasslands and open field habitats which present alternate foraging opportunities to deer.
We conducted a giving-up density (GUD) study in northeast Ohio to discern how white-tailed deer forage in fragmented habitats, and if they prefer to forage in grasslands or forests. The GUD indicates the amount of food that an animal is prepared to consume in a given habitat before it forages elsewhere. A low GUD indicates high habitat preference. Data were collected from three sites; at each site we examined GUDs at the forest-grassland ecotone and then 20 m and 60 m from the ecotone in both the forest and grassland. GUD data were collected during winter, spring and summer to analyze if seasonality altered habitat preference.
Results/Conclusions
Deer habitat preference varied depending on both seasonality and sites. During the winter, when available forage was lowest, deer at two sites showed the lowest GUDs (i.e., most preferred) near the ecotone or in the grassland habitats. At the third site, GUDs were greatest 60 m in the forest and foraging near the ecotone or in the fields was minimal. However, as plant primary production increased in spring and summer, GUDs at all sites became more evenly distributed across both habitats and distances from the ecotone. Variability in GUDs are usually attributed to either predator avoidance or differences in forage quality. Because adult white-tailed deer encounter almost no predation in our study areas, we believe that the difference in GUDs between sites can be attributed to disparities in plant species compositions. Future research will analyze the vegetative community of each site, which will serve to inform what plants deer prefer during winter months. This information can then be used to manage deer populations by limiting available winter forage that sustains deer populations when primary production is at a minimum.