The effects of deer-proof fences and grassland management on the occurrence frequency of sika deer in artificial grasslands and the intensity of grass consumption

We aimed to clarify the effects of deer-proof fences and the differences in grassland utilization on the frequency of occurrence of sika deer and the intensity of grass consumption in artificial grasslands and adjacent forests. We evaluated the frequency of occurrence of sika deer by camera-trap surveys, and the intensity of grass consumption was evaluated by an exclosure experiment in six artificial grasslands in the Yatsugatake region, Japan. The occurrence frequency of sika deer in the artificial grasslands was higher than that in the adjacent forests, regardless of the protection offered by using deer-proof fences. In contrast, in the artificial grasslands within settlements surrounded by deer-proof fences, the occurrence frequency was much lower than in the grasslands protected individually by deer-proof fences. Sika deer intensively used grasslands unprotected by deer-proof fences, and the differences in grassland utilization did not affect their frequency of occurrence. In the artificial grasslands unprotected by the deer-proof fences, grass biomass outside the exclosures decreased significantly, up to 43%, compared to that within the exclosures. These results indicate that sika deer grazing has an intensive impact on artificial grasslands and that deer-proof fences should be established around artificial grasslands and grasslands within settlements to prevent grazing damage.