Free-ranging Group Of Japanese Monkeys Research Articles

Old grandmothers provide essential care to their young granddaughters in a free-ranging group of Japanese monkeys (Macaca fuscata)

This study reports 2 cases in which old grandmothers without dependent offspring provided essential care to their young granddaughters in a free-ranging group of Japanese monkeys (Macaca fuscata). In the first case, a 24-year-old grandmother provided essential care for the survival of her 2-month-old granddaughter for at least 6 days during which the mother had temporarily disappeared from the group for reasons unknown. In the second case, a 14-month-old granddaughter began sucking from her 23-year-old grandmother within 6 weeks after her mother gave birth to a younger sibling. For at least 6 months, the grandmother exhibited various patterns of maternal behavior toward her granddaughter. The behavioral data obtained in this study indicated that old yet healthy females without dependent offspring could contribute to the survival of their young grandchildren.

Long‐term grooming partnerships between unrelated adult females in a free‐ranging group of Japanese monkeys (Macaca fuscata)

In order to examine the presence of long-term grooming relationships among unrelated females, grooming interactions of 18 adult females (range: 16-32 years) in a free-ranging group of Japanese monkeys (Macaca fuscata) were recorded in 2003 and compared with those recorded 10 years earlier, i.e., in 1993. In 2003, on average, each female who had survived the 10 years had grooming interactions with 2.2 surviving old partners with whom she was recorded to have grooming interactions in 1993, 3.5 females related to the surviving old partners, and 4.5 unrelated females who were other than the surviving old partners or their related females. By calculating the ratio of actual grooming partners to available females in 2003, we concluded that females had a greater possibility of selecting surviving old partners as their grooming partners than other unrelated partners, and that they also had a greater possibility of selecting females related to surviving old partners than females other than surviving old partners and their related females. These findings indicate that with regard to grooming relationships, female Japanese monkeys are basically conservative, showing a tendency to concentrate their grooming interactions on closely related females and certain familiar unrelated females such as surviving old partners and some females closely related to these partners. At the same time, however, female Japanese monkeys also showed a progressive trait for grooming since they formed grooming relationships with new partners. The necessity of long-term psychological bonding for long-term grooming relationships between unrelated females is discussed in this work.

Case Reports on Parturition and Maternal Behavior in a Free-Ranging Group of Japanese Monkeys at Katsuyama.

We reported one case of parturition behavior and five other cases of maternal behaviors which were rarely observed in a free-ranging group of Japanese monkeys (Macaca fuscata). An eight-year-old female spent more than 3 hours alone before delivery and almost 2 hours afterwards, without being approached by any other group members. The frequency and duration of constractions gradually increased, and the female frequently touched her vulva and perineal region with the fingers of her hand, as the time for delivery grew near. She started to approach other group members about 2 hours after the delivery.A nine-year-old female did not hold her first newborn to her ventrum after parturition, but walked bipedally, grasping the newborn with both hands. These inappropriate maternal behaviors disappeared the following day. An 11-year-old female carried her newborn ventrally and her yearling dorsally at the same time. This simultaneous carrying of two offspring was recorded for only the first five days after the birth of the newborn. Two other females allowed their one-year-old offspring to nurse after their newborn infant died within two weeks of the infant's life. Moreover, a 13-year-old multiparous female with a four-week-old newborn adopted a week-old newborn and took care of both in the same manner.

Age-related differences in social grooming among adult female Japanese monkeys ( Macaca fuscata).

The present study investigated the influence of dominance rank in combination with kinship on age-related differences in social grooming among adult females in a free-ranging group of Japanese monkeys ( Macaca fuscata). Eighty-three adult females were divided into six sub-groups according to age-class (younger: 5-9 years old; middle: 10-14 years old; older: 15-22 years old) and dominance rank (high and low rank). The ratio of the number of unrelated females that each female groomed to the total number of available unrelated females and grooming bouts which she gave to unrelated females decreased with increasing age for both high- and low-ranking females, whereas age did not appear to affect corresponding values for related females. On the other hand, compared with low-ranking females, high-ranking females of all age-classes received grooming more often from a larger number of unrelated females. Moreover, older females of low rank received grooming less often from a smaller number of unrelated females than younger females of low rank. These results indicate that with increasing age females are more likely to concentrate on related females when they have grooming interactions with other females. This tendency seems to be more apparent for low-ranking females. Moreover, the present findings also indicate that older high-ranking females could maintain their social attractiveness as high as younger high-ranking females.

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 (Macaca 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.

Influences of older sibling on social relationships of juvenile Japanese monkeys (Macaca fuscata) in a free-ranging group

Effects of the presence of older sibling on the social relationships of juveniles with other monkeys were assessed in a free-ranging group of Japanese monkeys at Katsuyama, Okayama Prefecture, by comparison between fifteen 2-year-old juveniles with older siblings (3-6year old) and nine 2-year-old juveniles without older siblings. The juveniles' proximity and playmate relationships with other monkeys in the group were analyzed in a situation where the juveniles were apart more than 2m from their mothers. The juveniles without older siblings tended to maintain more frequent proximity relationships with same-aged monkeys than did the juveniles with older siblings, while the juveniles with older siblings were in more frequent proximity with adults than did the juveniles without older siblings. These results suggest that the juveniles with older siblings had more opportunities to interact with elder monkeys through agent of their older siblings than did the juveniles without older siblings. The juveniles without older siblings tended to interact more frequently with same-aged monkeys than did the juveniles with older siblings, due to the lack of such opportunities. The male juveniles with older brothers and the female juveniles with older sisters were in more frequent proximity with each other than were those who had the older siblings of the opposite sex. The male juveniles had opportunities to interact with elder males, when they were in proximity with their older brothers.

Sex differences in social development during the first 4 years in a free-ranging group of Japanese monkeys, Macaca fuscata

The behavioural development of a birth cohort (14 males, six females) during the first 4 years of life in the Awajishima free-ranging group of Japanese monkeys is described. The study focused on maturational changes in the relationships of immature males and females with their mothers and with other group members. Males tended to interact with their mothers less frequently than did females. Certain individuals interacted with their mothers more frequently than others during the first 4 years of life. Individuals were also consistent in their social interactions with group members other than their mothers. Males maintained close relationships with males of similar age, primarily through social play, from approximately the second year onward. This indicates that the males' preference for association with males of similar age precedes peripheralization and that peripheralization does not bring about essential changes in their social relationships with group members. Females preferred relationships with female group members of various ages, and also relationships with infants and fully adult males. This may explain why females remain in the central part of the group throughout their lives. The results of the study suggest that the preparation for adult male/female social roles starts as early as the second year of age.

Behavior of infant Japanese monkeys (Macaca fuscata) with congenital limb malformations during their first three months.

Locomotion and mother-infant interactions of a severely malformed, a slightly malformed, and a normal infant were observed in a free-ranging group of Japanese monkeys (Macaca fuscata). The severely malformed infant had no feet and had hands consisting of 2 digits. The slightly malformed infant had normal feet and hands consisting of 2 digits. The severely malformed infant was more retarded in development of posture and locomotion than the other infants; however, it developed locomotor patterns appropriate to its defects. All infants spent approximately the same amount of time in contact with their mothers. High mother-infant contact of malformed infants was maintained because their mothers were very attentive and carried and held them. Mothers reared their handicapped infants even though the infants lacked the movement necessary for clinging.

Analysis of Social Structure Based on Spatial Disribution of Animals in a Free-Ranging Group of Japanese Monkeys (Macaca fuscata)

This study was conducted on a free-ranging group of Japanese monkeys at Katsuyama Prefecture during the period from June 1980 through September 1981.The subjects were a total of 100 monkey of four years of age or more.The spatial distribution of each monkey was recorded totally in 71 times in normative situations and 91 times in feeding situations.The results indicate that the dominant animals were found more frequently in the observation area than the subordinate ones in both situations throughout the year (Table 2).Monkeys were found more crowded in the feeding situations than in the normative ones, some showing preference for particular positions in the feeding area (Table 3).The central adult males were distributed distantly in the feeding situations.In general, positional preference of adult females reflects their dependency on the central adult males.The results of cluster analysis of inter-individual spatial proximity indicated that clusters were found more in the feeding situations than in the normative ones because of crowding by feeding (Fig.1).The results of inter-individual spatial distribution revealed structure of close linkage between individuals of same genealogies in the normative situation and of different genealogies in the feeding situation (Table 4).The central part of Katsuyama group consists of the core of central adult males and individuals of higher ranking genealogies (Fig.2).The individuals of higher ranking genealogies evidently showed strong proximity to the central adult males, which enabled them to maintain their status and priority to get desirable resorces such as food.

Behavioral development of a malformed infant in a free-ranging group of Japanese monkeys

The behavioral development of a malformed male infant in a free-ranging Japanese monkey group, whose hands were completely missing and whose hind feet were distorted, was investigated during the first one year of life, by comparison with normal infants. In the first few weeks of life, the malformed infant was not able to move by himself and was almost completely dependent on his mother's help. He gradually became able to creep with his forelimb elbows and distorted hind feet at about the first month of life, and was able to walk bipedally on his hind feet, though unstably, after the sixth month of life. His locomotor ability, however, was essentially inferior to that of normal infants throughout the first one year of life. His social interactions with the group members were different from those of normal infants. Normal infants increased their interactions with sameaged infants or older juveniles through active behavior-like play, whereas the malformed infant developed relations particularly with adults through behavior such as passive body contact. The conditions for survival of the observed malformed infant are discussed.

The Behavioral Development of Mother-Infant Relations in the First Six Months of the Infant's Life in the Japanese Monkey (Macaca fuscata fuscata) (1)

Many studies have been reported on the development of mother-infant relations in nonhuman primates which indicate the importance of early mother-infant relations on the development of the infant. The present study was designed to clarify the development of filial cling and maternal embrace and grooming in the first six months of the infant's life. In the past, we have mainly studied relations between the infant's age of maternal isolation and the patterns of stereotyped behavior induced by the isolation. But this should be based on the study of the development of the mother-infant relations under the normative condition. This is the major reason why the present study was conducted.The subjects used in the present investigation were three multiparous adult females and their male infants. The adult females were trapped in a freeranging group of Japanese Monkeys at Katsuyama, Okayama Prefecture and were raised at Osaka University Laboratory where they were fertilized (Table 1). Each of the pregnant females was housed in a 60×93×125 cm cage. The observation started at their parturition. All infants were males. Mother-infant interaction was observed for 15 minutes, once or twice a week.Results were as follows.1) The infant's locomotion tended to increase and filial cling was inclined to decrease in the first three months of the infant's life (Fig. 1 and Fig. 2).2) Maternal embrace tended to decrease as same as filial cling did in the first three months (Fig. 3). Maternal grooming, however, did not show this tendency (Fig. 4).3) The infant's locomotion and filial cling was affected by maternal embrace in the first three months of the infant's life, and by both maternal embrace and grooming after that time.4) This suggests that the behavioral development of the infant is affected by maternal behavior even in the early months of the infant's life.