Analysis of Social Structure Based on Spatial Disribution of Animals in a Free-Ranging Group of Japanese Monkeys (Macaca fuscata)

Abstract

This study was conducted on a free-ranging group of Japanese monkeys at Katsuyama Prefecture during the period from June 1980 through September 1981.The subjects were a total of 100 monkey of four years of age or more.The spatial distribution of each monkey was recorded totally in 71 times in normative situations and 91 times in feeding situations.The results indicate that the dominant animals were found more frequently in the observation area than the subordinate ones in both situations throughout the year (Table 2).Monkeys were found more crowded in the feeding situations than in the normative ones, some showing preference for particular positions in the feeding area (Table 3).The central adult males were distributed distantly in the feeding situations.In general, positional preference of adult females reflects their dependency on the central adult males.The results of cluster analysis of inter-individual spatial proximity indicated that clusters were found more in the feeding situations than in the normative ones because of crowding by feeding (Fig.1).The results of inter-individual spatial distribution revealed structure of close linkage between individuals of same genealogies in the normative situation and of different genealogies in the feeding situation (Table 4).The central part of Katsuyama group consists of the core of central adult males and individuals of higher ranking genealogies (Fig.2).The individuals of higher ranking genealogies evidently showed strong proximity to the central adult males, which enabled them to maintain their status and priority to get desirable resorces such as food.