TROOP DESERTION BY FEMALE JAPANESE MACAQUES

Abstract

To elucidate the factors and the significance of troop desertion by females which scarcely reported in Japanese macaque Macaca fuscata, 35 adult females who disappeared from T-troop in the Hakone area between April 1972 and March 1979 were examined. Of these females, 18 were discovered alive in this area. Most deserters were the aged and the eldest daughters of their matriarchs. Deserters tended to issue from lower rank kin-groups in the troop. There were inverse correlation between food supply and number of disappeared and/or deserted females. Behaviour of females after desertion was classified into eight categories : remaining alone or only with their babies, forming a pair with an adult male, forming new troops with members of her previous troop or with strangers, and immigration into an adjacent troop. The new type of troop formation here described differs from those by troop-fission so far reported. Female desertion probably caused by unbalance between food supply and the troop size was concentrated after a change of top-ranking male in the troop or during the mating season. Troopfission and deserters of both sexes function as one of the population controlling mechanisms within the troop and the expansion of the species habitat. Troop desertion by females is one of the phenomena that necessitate reconsideration of the social structure of Japanese macaques generally accepted.