Naosuke Itoigawa

Demography and reproductive parameters of a free-ranging group of Japanese macaques (Macaca fuscata) at Katsuyama

Demographic and reproductive data were analyzed for a period of 28 years in the females of a free-ranging group of Japanese macaques at Katsuyama, Okayama Prefecture, Japan. The overall mean, age-specific fecundity rates were 5.43% for 4-year-olds and 41.86% for 5-year-olds, increasing to a peak of 66.67% for 13-year-olds. Fecundity remained relatively high (52.31–54.24%) in 16–19-year-olds, but decreased sharply (45.45–17.86%) in 20–23-year-olds, and became very low in 24–26-year-olds. Females aged 27 years or more did not produce infants. The average age at first birth was 5.41 years. Births peaked in mid-May. The timing of the first births each year remained essentially unchanged during the study period, whereas the timing of the median and last births shifted towards the later part of the season. The mean interbirth interval for all females was 1.56 years. The value was 1.54 years for multiparous females and 1.29 years for females following infant loss. These intervals were significantly shorter than those for primiparous females, and females with surviving infants. The overall mean infant mortality within the first year of life was 10.2%. The value was 8.6% for 10–14-year-olds, and 7.5% for 15–19-year-olds. The timing of birth differed among the four female matrilineal dominance rank-classes. The female fecundity rates increased as a function of matrilineal dominance rank. It is suggested that all demographic and reproductive data should be analyzed in detail with respect to the groups history.

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.

Experimental study on sexual behavior between mother and son in Japanese monkeys (Macaca fuscata)

A mother, her adult son, four adult males and six adult females from a free-ranging group at Katsuyama were paired in a cage in the sexual seasons from 1976 to 1980. The paired subjects were classified into the following three types: mother and son, familiar pairs and unfamiliar pairs. The familiar pairs consisted of monkeys who had been in the Katsuyama group until about six months before the experiment. The unfamiliar pairs consisted of monkeys who had not met each other at all or who had not met each other for more than eight years before the experiment. Serial mounts which terminated with ejaculation occurred in nine of ten unfamiliar pairs, four of five familiar pairs, but there were none between the son and mother. The son and mother did not appear to be sexually aroused between themselves, although they were sexually active to other partners. However, on rare occasions, the son mounted singly on the mother, and on one occasion he ejaculated. Their interaction did not change essentially during the three years. The son rarely mounted serially on a female who had a close relationship with his mother.

Intelligence and Learning Disabilities in 6- to 8-year-old Children Weighing under 1000 Grams at Birth

Intellectual ability and learning disabilities (LD) were assessed in a cohort of 33 extremely low-birthweight (1000 grams) children at 6-8 years of age with a psychometric test battery. The children were classified into the following three groups: a LD-suspected group of 9 boys (27.3%), a mentally delayed group of 3 boys and 3 girls (18.2%), and a typically developing group of 6 boys and 11 girls (51.5%). No correlation was found between birthweight and intelligence quotient (IQ) at 6-8 years of age. A negative correlation was found between IQ and gestational age (GA) at a nearly significant level. The mean verbal IQ for the 11 small for gestational age (SGA) children was significantly lower than that of the appropriate for gestational age (AGA) children. The LD-suspected group was characterised by lower scores on spatial relationships and rapid but inaccurate solving of the visuo-motor integration tasks on the Frostig test.

Behavioral Differences Between Feral Group-Reared and Mother-Reared Young Japanese Monkeys

We have studied effects of isolation on behaviors of Japanese monkeys such as distortions of social behaviors, restrictions in contact with physical environment, and development of stereotyped behaviors (Itoigawa 1967), and have found that these effects depend on the development of monkeys (Minami 1974). The stereotyped behaviors, especially locomotive stereotyped behaviors, increase in encountering situations where some degree of “tension” appears to be present (Yamaguchi 1977). We consider that the stereotyped behaviors reflect emotional disturbance in monkeys.

Cardiac and Behavioral Responses to Humans in an Adult Female Japanese Monkey (Macaca Fuscata)

ABSTRACTThe effects of the appearance of a human on the mean arterial blood pressure (BP) and behavior of an adult female Japanese monkey were examined to clarify whether or not the monkey discriminated between men and women, and between caretakers and strangers. Each human (5 male and 6 female caretakers; 5 male and 6 female strangers) sat facing the monkey whose BP was recorded with an unrestrained telemetry system. Behavior of the monkey was recorded on videotape and BP was measured for 10 minutes prior to the appearance of the human (pre-appearance stage) and for 10 minutes during which the human appeared and faced the monkey (appearance stage). The BP and the frequency of alert behavior increased immediately after the appearance of a human. The increase in the BP and the duration during which the BP was high were significantly greater with men than with women. The duration of alert behavior in the beginning of the appearance stage was longer with men than with women and its duration at the beginning ...

Parenting and Family Support in Japan for 6- to 8-year-old Children Weighing under 1000 Grams at Birth

The purpose of this study was to explore the variables related to paternal involvement in the caregiving of 6- to 8-year-old extremely low-birthweight (ELBW) children, specifically, sociodemographic factors related to the family or individual biological factors related to ELBW. Thirty-three children with a mean birthweight of 845.5 grams and a mean gestational age of 27.4 weeks participated in this research. Approximately 29% of their fathers were classified by the mothers as nonco-operative in overall child care. The paternal involvement in caregiving was related to the sociodemographic variables of the family; the co-operative fathers were proportionally more often from families where the child had no older female sibling(s) and/or grandparent(s), whereas the nonco-operative fathers were proportionally more often from families where the child had older female sibling(s) and/or grandparent(s). The individual perinatal risk variables and IQ, and the paternal variables (age, socioeconomic status) were not related to the paternal co-operativeness. Our sample mothers seemed to have raised their children in more difficult parenting and economic situations, and to have received proportionally more support from grandparent(s) than did typical Japanese mothers. The childrens relationships with peers differed between the paternal co-operative and nonco-operative groups; there were proportionally more children from the nonco-operative group who preferred to play alone than to play with peer(s) at the ages of 3-5 years. Thus, scarce paternal involvement in the process of caregiving appeared to influence the childrens sociability.