Effect of cattle grazing on the rooting by wild boars in abandoned cultivated land

The number of wild boars (Sus scrofa) causing serious agricultural damage is increasing in Chugoku district, Japan. In this district, many plots of abandoned cultivated land are scattered. Therefore, it is guessed that the wild boar has expanded its habitat by venturing onto the abandoned cultivated land. However, little information is available on the use of abandoned cultivated land by wild boar. In this research, we investigated the use of such lands by the wild boar. In addition, the influence that the grazing of cattle on the abandoned cultivated land exerted on the main flora and on rooting by the wild boar was examined. Experiments were carried out in an area of abandoned cultivated land located in the middle of the Shimane Prefecture in southwestern Japan (35 deg 12min North latitude and 13 deg 34min East longitude). The mean annual temperature and precipitation were 16 deg C and 1,770 mm, respectively. The area of the investigation field was 1ha, and the cattle grazing was started in 1999. The number of grazing cattle was 200-300 head/ ha/year. The results obtained were as follows: 1 The predominant plants in the surveyed field were Japanese plume-grass {Miscanthus sinensis) and kudzu vine (Pueraria lobata). The former was present at 45.3 stocks/100 square m, and the latter at 28.6 stocks/ 100 ma. Though 16 kinds of plants appeared in addition to these two species, the presence of the other plants was relatively slight. Therefore, the ground surface of 82% of the interrow space of Japanese plume-grass was bare land. 2 The wild boars were actively rooting in the investigation field. Indications of their rooting activity were evident in 29.1 places/100 square m, over a total of 12.02 square m/100 square m. The predominant plant species (94.4%) adjacent to the sites of rooting activity was kudzu vines. 3 Rooting activity by the wild boar was observed chiefly in winter. The target of rooting was a starch conserved in the root of kudzu vine. 4 When the grazing of cattle introduced in the investigation field, Japanese plume-grass and kudzu vine declined rapidly. Thereafter, no new rooting activity by the wild boar was observed. 5 From these results, it was thought that the grazing of cattle on abandoned cultivated land had the effect of controlling the rooting activity of the wild boar by impinging on the wild boar's refuge (Japanese plume-grass) and removing its food source (kudzu vine).