Retardation of sexual maturation of free-ranging Japanese macaques induced by controlled provisioning

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Provisioning support the high density of the Koshima population of Japanese macaques. The amount of provisioned food was severely restricted from the autumn of 1972 until June, 1977. This caused a population declining phase. Soy beans were provisioned for 1 and half months in the summer after 1977, which caused a stable phase of population growth. Male sexual maturation has been studied under these conditions, and we studied two topics under the framework, "Male maturation and desertion from the natal troop", "Transformation of a small bisexual group into a group having the characteristics of a male group".The body weight growth curve against age is depicted using cross sectional data of 1972 when provisioning food was not restricted. Body weight growth of each monkey in the 1970's was slowed down, and growth continued until age 15. Two groups were found, one which was around 10kg and the other 8kg body weight after age 15. Large variation in growth curves was observed after 8 years ol … More d, which may be related to sexual maturation. Attendance of each male at the provisioning area revealed that males deserted the main group at adolescence, and joined the small branch group, or the all male gatherings. Then they came back to the main group after reaching 15 years of age, participating in reproductive activity. The low body weight males deserted the main group at around 8 years, and came back to the main group later than the heavier males. The age of desertion varied much, having a peak at 6-8 years, and a body weight of around 5kg. Later desertors were heavier, indicating social factors for these males.The small branch group accepted young deserter males, which influenced the characteristics of this bisexual group becoming more like a male group. The group members showed loose association as compared to the main group. Unlike the normal situation, group movement was rarely coordinated by "coo" sound, and even females showed frequent tree-shaking which is common in a male group. As the moving range of the group was small, individuals visited only a small number of feeding trees, and visited the same trees repeatedly. Members joined at the trees, and adult males tolerated females feeding with them. Senior adolescent males visited the feeding trees while other members were moving in a different area. When they met females at the trees, they chased them away or retreated from the trees because of the cries of females. The junior adolescent males waited for the occupying adult females to leave the feeding trees before. Just prior to the mating season, outside males and adolescent males waited for females at their small number of feeding trees, which had a strong affect on the feeding activities of females Less