野生ニホンザル社会における, 個体分布テスト

幸島の群れについて

抄録

A series of field studies has been carried on about the spatial distribution of individuals of several natural groups of the Japanese macaque. One of these studies was the test on the beach rocks named “Ikada-no-iwa” (photo) in “Kosima”, a small island near the southeast coast of Kyusyu. The test was made as follows. The rocks were fictionally divided into 6 sections as Fig. 2, and the sections 1-5 had wheat grains scattered on their upper surfaces, while the remainder section 6 had no grain. One group of 20 monkeys (Table 1) came and fed on these grains. Every 5 minutes, locations of all individuals were recorded or determined by the numbers of the sections occupied by them. Fig. 3 shows the individual records of 2 test series executed in Feb. and Nov. 1954, either of them involving 50 observation times. Fig. 4 shows the differences between the means of the 2 test series. Based on these calculated figures, it was concluded that the position of every individual in the group space, was characteristic of his own status in the group organization, and that every change in the individual position between the 2 test series was regular and reasonable in accordance with the change in the status. As a whole, the picture of distribution of individuals in this test, is in good correlation with the scheme, Fig. 1, which is the simplified conclusion from the several years' field experiences.