Distribution and food habits of the roof rat Rattus rattus in the recovering Sasa jotanii population 4 years after the monocarpic mass flowering in Mt. Oyama, Mikurajima Island, Izu Islands, Japan

摘要

The distribution and food habits of the roof rat Rattus rattus L.was investigated in the recovering Sasa jotanii population 4 years after the monocarpic mass flowering in April 1997 on Mt. Oyama, Mikurajima Island, Izu Islands, Japan. Three surveys using 100 trap-night samplings for rodents were performed on March 29, August 10, and November 10 in 2001 at a study site in Mt. Oyama, in which 1, 8, and 13 roof rats were captured, respectively. Results suggested that roof rats inhabited in the S. jotanii population almost throughout the year. At all survey times, the most of their stomach contents were bamboo shoots of S. jotanii, while other main plant components were Carex oshimensis flowers in March and Ilex crenata fruits in November. Bamboo shootpredation was measured as the percentage of the number of missing shoots that had been gnawed to the total number which were 52.8% and 47.8% in March and August, respectively, whereas the predation ratio of monopodial rhizome were 81.8% and 54.5% in March and August, respectively. These high predation ratios were in accordance with the dominant components in the stomach, suggesting that roof rats depended on S. jotanii as their main food supply, which suppressed the clump growth and development of the bamboo clone.