The effects of deer exclosures on voles and shrews in two forest habitats

- White-tailed Deer (Odocoileus virginianus) have overbrowsed much of the hemlock-mixed northern hardwood forest in northeastern Pennsylvania. I investigated the possible deleterious effect of this overbrowsing on 4 ground-cover-dependent small-mammal species through the use of deer exclosures. From May through September 19962005,4 ** 10 Sherman live-trap grids were placed in two 0.65-ha exclosures and their adjacent control sites in forest heavily browsed by deer. One exclosure was located beneath a primarily oak-maple canopy and the other exclosure under Tsuga canadensis (Eastern Hemlock). More Myodes gapperi (Southern Red-backed Vole) were captured in the oak-maple grids than in the hemlock grids and more M. gapperi were taken in the oak-maple exclosure than in the neighboring control. Microtus pinetorum (Woodland Vole) first appeared at the grids six years after the exclosure construction, and a large majority were taken in the oak-maple exclosure. Of Blarina brevicauda (Northern Short-tailed Shrew) captured at the grids, 80% were taken in the oak-maple grids and 58% in the oak-maple exclosure. Beginning in 2000, most of Sorex cinereus (Masked Shrew) captured were taken in the oakmaple habitat. Most of those trapped under the oak-maple canopy were taken in the control. These observations suggest that heavy deer browsing may depress populations of M. gapperi, M. pinetorum, and B. brevicauda, but not Sorex cinereus.