Seasonal changes in food resource distribution and feeding sites selected by Japanese macaques on Koshima Islet, Japan

Moe Go

多くの霊長類にとって食物資源の分布は、行動域の利用に大きく影響を与えることが知られている。ニホンザルは年間を通して多くの品目を採食しているため、サルの行動域内の食物資源量とサルの採食量を対応させ、サルの遊動はどのような食物品目の分布に影響を受けるのかを明らかにした。宮崎県幸島主群のニホンザルにとって、どの季節も複数の食物品目の資源量がサルの遊動（特に採食場所の選択）に影響を与えていると考えられ、サルの遊動に影響を与える食物の特徴は、限られた季節の限られた場所にしかない果実だった。また、サルの行動域内に広く分布している常緑広葉樹の葉は、冬や春には最も長い時間食べられている主要な食物であったが、それらの食物資源量の多少がサルの採食場所の選択に有意な影響を与えていることは少なかった。群れで生活するニホンザルは、限られた季節の限られた場所にしかない食物資源が多くある場所で採食することにより、多くの個体の要求を満たし、さまざまな品目をより効率よく採食していると考えられた。

Primates, 51:149-158

Feeding sites of Japanese macaques (Macaca fuscata) change according to seasonal fluctuations in food resource distribution. To examine what characteristics of food items affect feeding site selection, I describe herein the seasonal changes in food items, feeding sites, and food resource distributions of this species. Feeding behavior of monkeys and their food resource distributions were investigated on Koshima Islet, southern Japan, for four study periods (i.e., seasons) in 2002. Monkeys showed large variations in their diet between seasons. To weigh the relative influence of the distribution and abundance of food items on feeding site selection in each season, multiple regression analyses were performed by 100 m 9 100 m grid. In the analyses, feeding time was a dependent variable and the abundance of staple food items, for which feeding time was over 5% in each season, in each grid square was an independent variable. There was no correlation between the resource distribution of most food items and the distribution of feeding time by monkeys in each season. Monkeys spent more feeding time where multiple staple food items were available. Food items that affected feeding site selection by monkeys had the following three characteristics: (1) clumped distribution, (2) seasonal availability, and (3) fruit. This suggests that monkeys are likely to select feeding sites to consume food items whose availability is limited temporally and spatially, which may enable them to simultaneously use other widely distributed, abundant food items efficiently.

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