Five natural troops of Japanese monkeys on Shodoshima Island: II. A comparison of social structure

The results of a comparative study of five natural troops of Japanese monkeys living on Shodoshima Island are as follows. (1) When troops were feeding at the feeding places, various cases, such as individuals spaced out dispersively or close by in a gregarious state, were observed. (2) Differences were also observed among the troops at the feeding place; some troops always fed in a dispersive state, on the whole, while others fed in a gregarious state with small distances between individuals. (3) Differences of social structure were observed among the five troops: differences of the number of classes and sub-classes in males and females, of the relation between classes and their age distribution in males, of the proportion of individuals who intruded into the central part of the troop or who made it their core area of activity to the total male population, etc., and it was also assumed that some troops were integrated more strictly, while others were integrated loosely. (4) These differences of social structure among the troops were assumed to be closely related to the gregariousness or dispersiveness of the each troop at feeding time. From these facts several decisive factors of social structure were considered.