Effectiveness of a Combined Electric and Wire-netting Fence in Preventing Sika Deer (<i>Cervus nippon</i>) Invasions in Grasslands

<p>The present study explored the effectiveness of a physical protective fence in combination with an electric fence in preventing sika deer (Cervus nippon) invasions in grasslands. Specifically, we implemented a combined wire-netting and electric fence to prevent the invasion of sika deer in meadows and comprehensively evaluated the effectiveness of this strategy from the viewpoints of effort and cost for fence setup and maintenance. Further, we compared the frequency of emergence of sika deer as well as the yield of Japanese barnyard millet (Echinochloa utilis Ohwi et Yabuno) during summer cultivation and Italian ryegrass (Lolium multiflorum Lam.) during winter cultivation. The following three treatments were assigned: (1) a control group (May 2017-May 2018), in which no measures to prevent deer invasion were implemented; (2) an electric fence group (June 2018-May 2019), in which electric fences (5-polywires, height: 20, 40, 70, 100, and 140cm) were set to prevent deer invasion; and (3) a combination group (June 2019-May 2020), in which a combined electric and wire-netting fence (height, 120cm; set 30cm beyond the electric fence) was set to prevent deer invasion. The average number of sika deer photographed per day with a sensor camera during the cultivation periods of Japanese barnyard millet and Italian ryegrass was respectively 7.4 and 11.1 heads in the control group, 1.6 and 6.1 heads in the electric fence group, and 0 heads in the combination group. Observation of the behavioral responses of sika deer to the fences revealed that the deer repeatedly passed through the electric fence without touching it with the tip of their nose in the electric fence group during the cultivation period of Italian ryegrass, however, the majority of the individuals in the combination group evaded the fences after looking at them merely without trying to pass through them during the cultivation period of both grasses. The reduction in the yield of both grasses was extensive in the control and electric fence groups (89-99% and 32-92%, respectively), while there was no yield reduction in the combination group.</p><p>In conclusion, a combined electric (5-polywires) and wire-netting (height, 120cm) fence effectively prevented sika deer invasions visually in grasslands without causing any harm to the animals.</p>