淡路島ニホンザル集団における報酬と負荷が意思決定に及ぼす影響

抄録

We examined sensitivity to efficiency of foraging in Japanese monkeys (Macaca fuscata) by using an experimental method at the feeding site of the Awajishima Group. Three feeding drawers which contained identical food reward, with different number of weights (condition1 and condition2) or in different food distance (condition3), were presented. Monkeys were allowed to pull each drawer to get each reward in any order. Twenty-five of 399 individuals have participated. The number of trials totaled 4079 during 14 days. We found that monkeys tended to choose the lightest or the nearest food first. These results show that monkeys adjusted their foraging strategies according to the cost of food reward. Sex and age contributed to the high selectivity of the first choice of the lowest load, which could be highly related with body weight. Interestingly, monkeys selected the remaining two choices with the same frequency in both condition1 and condition2. These results indicate that their adjustment of foraging strategies was also affected by the other factors such as social condition, since other individuals around them change constantly during the test sessions. In addition to the social factors, current results can be also discussed on the basis of “contrafreeloading”.