White-tailed deer (Odocoileus virginianus) browse damage in Ann Arbor, Michigan; Bird Hills Nature Area, Winter 2015

White-tailed deer (Odocoileus virginianus) browse damage in Ann Arbor, Michigan;
Bird Hills Nature Area, Winter 2015

Jacqueline Courteau, Ecologist, Moriah Young, University of Michigan, Independent Study Research This survey of 142 tree saplings (less than 2 meters tall) and shrubs in Bird Hills Nature Area shows that 80% have been browsed by deer, and 51% have half or more branches browsed. This level of browsing could interfere with forest regeneration and diminish the flowers and fruit available for birds, butterflies, and bees. Further monitoring would be necessary to track mortality, to reveal whether particular tree and shrub species of concern are browsed in future years, and to assess whether wildflower species are also being heavily browsed.

The deer browse figures compiled in this survey may underestimate actual browse damage in several ways. First, the survey excluded plants that were already dead or lacked live buds for identification. Many of the excluded plants showed clear signs of deer browse, which suggests that browse damage could be contributing to mortality, but estimating browse-related mortality was beyond the scope of this study. Numerous other studies suggest that browse damage over several decades may already have eliminated or greatly reduced populations of deer-preferred species (Côté et al. 2004, Rooney and Waller 2003, Ferker et al. 2014). Second, it is not possible to count how many buds are missing from a plant, so we focused on the number of branches browsed. However, some unbrowsed branches were counted even if they were quite small, while the portions of branches browsed off may have been larger than those that remained. Third, we assessed browse damage on all species, rather than on a set of species known to be preferred by deer; damage on preferred species could be even higher.