水田地帯に同所的に生息するシマヘビElaphe quadrivirgataとヤマカガシRhabdophis tigrinusの食物重複度
1992 年 42 巻 1 号 p. 1-7
詳細
1992 年 42 巻 1 号 p. 1-7
Niche breadth and overlap of diets among two sympatric snake species, Elaphe quadrivirgata and Rhabdophis tigrinus, in the paddy fields in Yamagata were studied for four years (1983-1986). Stomach contents were taken by forced regurgitation and classified into five major categories or eight minor categories : major categories mainly consist of taxonomical groups (e.g. frogs or voles) and minor categories indicate species in a major category. In the major categories, frogs were found to be the most dominant for both E. quadrivirgata and R. tigrinus with food niche breadth, 0.331 (E. quadrivirgata) and 0.441 (R. tigrinus). Food resource overlap was 0.879 in the major categories. In the minor categories, Japanese tree frogs, Hyla japonica were most dominant among the two snake species with food niche breadth, 0.513 (E. quadrivirgata) and 0.600 (R. tigrinus). Food resource overlap was 0.875. Thus, the food breadth was slightly wider among R. tigrinus than E. quadrivirgata with high food resource overlap in both categories. No difference in food size and the distribution of the captured spots was found between the two snake species. Seasonal niche overlap was high (0.788). Abundant frogs as prey items of the snakes would permit a high overlap of food resources between the two snake species in the field studied.
