Abstract
Using long-term behavioral data recorded between1950 and 2010, we studied cases of change in the alpha individual and its social background in a captive troop of Japanese macaques (Macaca fuscata) housed in Ueno Zoological Gardens, Tokyo, Japan. During this period, nine alpha males and four alpha females were recorded. Among the alpha males, three were juveniles. All alpha males except for one continued to keep their position until they died or were removed from the group. Alpha females, on the other hand, lost their position when they were in estrus/pregnant/nursing, after which time they continued to stay in the group. Unlike cases in free-ranging populations, captive male Japanese macaques are included in the social hierarchy of their natal group, and dominance relationship between males and females were unclear. Under such conditions, dominant females and their juveniles can become alpha individual when the former alpha disappears and/or there are no dominant male(s) present. Appearance of female/juvenile alpha individuals in the Ueno Zoo troop seems to be one of the bi-products of a captive environment and in order to keep social relationships of captive animals similar to those of free-ranging populations, artificial transfer (removal/introduction) of adult males should be considered.
