Yasuo Kojima

Carrying and Washing of Grass Roots by Free-Ranging Japanese Macaques at Katsuyama

The acquisition and transmission of new feeding behaviours in Japanese macaques (Macaca fuscata) such as sweet potato washing [1, 2], wheat washing [2] and caramel eating [3, 4] have been well documented. These behaviours are all related to provisioned food. Here we report carrying and washing of grass roots by Japanese macaques in a free-ranging group. This would appear to be the first report of washing of dirt from natural food, such as grass roots, among macaques. Furthermore, some monkeys in the present study rubbed dirt from roots by rolling them along the surface of a flat rock at the edge of a river. This may be considered a tool-using behaviour.

Interactions among adult males and females before and after the death of the alpha male in a free-ranging troop of Japanese macaques

This report documents the social interactions among adult Japanese macaques in a free-ranging troop before and after the death of the alpha male, who died at 28 years of age after occupying his rank position for 17 years. The alpha male’s physical condition had deteriorated due to his extreme age for several months before his death. However, he maintained his alpha position. When he was attacked by the second-ranking adult male, he was rescued by the alpha female. Thereafter, whenever the second-ranking male approached him, the alpha male screamed for the alpha female’s support. The number of adult females to whom the alpha male maintained proximity during his last four months was similar to that during the same period of the previous year. Prior to his death, the alpha male was observed in close proximity to the alpha female much more frequently than was the second-ranking male. These results indicate that the alpha male maintained his position by depending on female support and particularly that of the alpha female.

Parturition in a free-ranging Japanese monkey (Macaca fuscata)

Parturition behavior of a multiparous female and her interactions with group members throughout the birth process were recorded for a free-ranging Japanese monkey (Macaca fuscata). The female showed evidence of 18 contractions during the 35 min prior to delivery, with a mean duration and a mean intercontraction interval of 30 sec and 96 sec, respectively. These values were similar to those in individually caged Japanese monkeys. Some adult females remained in proximity to the female who was giving birth during the prepartum phase, and her 2-year-old daughter watched the delivery of the infant. Even during the prepartum phase the female moved in order to keep up with the group which traveled from the feeding site to a sleeping site in the forest.

Maternal Regulation of Sibling Interactions in the Preschool Years: Observational Study in Japanese Families

Characteristics of three maternal regulating behaviors--(1) reference to one siblings actions or emotional states toward the other sibling, (2) encouragement of sibling interactions, (3) distraction of one siblings attention away from the other sibling-and their associations with childrens positive and negative behaviors toward their siblings were investigated through semistructured home observations for 40 sibling pairs (1-4 years, 2-8 years) and their mothers in Japanese families. Maternal regulating behaviors were observed more frequently when the younger sibling was still in an early developmental stage in the preschool years, although the findings were modest. The older siblings negative behaviors toward the younger sibling positively correlated with maternal distraction toward the younger; alternatively, the younger siblings negative behaviors do not correlate with maternal distraction but do correlate with maternal encouragement directed toward the older sibling. Reliable associations were found between maternal regulating behaviors and prosocial exchanges between siblings; maternal reference to the younger siblings actions or emotional states directed toward the older sibling was associated with the older siblings positive behavior toward the younger sibling. Maternal regulating behaviors during mother-sibling triadic interactions were associated with the quality of sibling relationships.

Continuity of affiliative relationships among infants and juveniles in a free-ranging group of Japanese monkeys (Macaca fuscata).

5 infants were observed during the first 13 mo. after birth in a free-ranging group of Japanese monkeys (Macaco fuscata) to examine whether they maintained relatively frequent affiliative relationships with particular immature individuals. The number of immature affiliative partners rapidly increased from the first 3-mo. period after birth to the second 4-mo. period after birth, and the infants thereafter maintained affiliative relationships with particular individuals, mostly same-aged infants, at least in the second half of their first year. These findings show that infants were likely to interact with a larger number of different animals in the early stage of development, and thereafter selected particular individuals with whom they maintained affiliative relationships. The effects of sex on the selection of these long-term partners are also discussed.