The present study examines the concept of peripheralization and spatial structure in the Arashiyama West troop of Japanese macaques (Macaca fuscata) , and employs an objective method to assess the existence of a central-peripheral tendency in the spatial organization of this Japanese macaque troop. By calculating each adult male's mean distance in meters from the 'alpha' male of the troop, it was possible to rank males according to their distances from the alpha male. The resultant linear gradation of males illustrates the troop's spatial organization. This study did not find evidence supporting the notion that a rigid central-peripheral structure exists in the Arashiyama West troop. Indeed, there appears to be no objective criterion whereby some males can be labelled "central" and others "peripheral", for the linear gradation of distances that defines the spatial organization of adult males can be bisected arbitrarily at any point along its continuum. In this thesis "spatial status" is defined as a gradation of the distance between each male and the alpha male, where the shortest mean distance corresponds to the highest spatial status. The predictors age, dominance rank and maternal lineage are examined for their influence in determining a male's spatial status within the troop. The isolated and cumulative effects of the aforementioned variables are also examined to explain variations in male sexual behavior. Results from this study indicate that a male's spatial status is directly influenced by the combined effects of age, rank and lineage, as well as by the isolated effects of any one of the previously mentioned variables. Furthermore, the results indicate that a male's age and spatial status explain the most variability in male mating behavior. Whether the process of peripheralization and the existence of adult male spatial status are "exaptations", that is, traits which probably were NOT selected for during the course of evolution of Macaca fuscata, cannot be proved by the data in this thesis. However, the available evidence does suggest that spatial status in particular is more likely to be an "exaptation" rather than an "adaptation", and accordingly it probably does not contribute to male fitness. / Thesis / Master of Arts (MA)