Invasion of the Mizorogaike Wetland by sika deer, and their effects on vegetation

A valuable source of vegetation occurs on a floating mat consisting of sphagnum peat in Mizorogaike Pond (Kyoto, Japan). To clarify the effects of sika deer on the floating mat, we used motion-sensor cameras to photograph sika deer in 2005. We obtained 33 pictures of sika deer, most taken at night. We established a 1 x 1600 m belt transect and investigated the spatial distribution of plant species and feeding scars. Fourteen herbaceous plants had feeding scars from sika deer; Menyanthes trifoliata and Iris laevigata had feeding scars in 50% or more of the sub-transects (1 x 10 m, N = 160). We suggest that sika deer use the entire floating mat for feeding because feeding scars on M. trifoliata, I. laevigata, and Isachne globosa were ubiquitous. These dominant species had feeding scars in 10% or more of the sub-transects. Sika deer are considered ecosystem engineers; severe feeding pressure by sika deer may change the vegetation in the Mizorogaike Wetland. To conserve the Mizorogaike Wetland, a deer exclosure fence must be established, and vegetation and deer effects, as well as water quality effects, in the Mizorogaike Wetland must be studied.