Annual changes in hair length of the Japanese monkey (Macaca fuscata fuscata)

The hair length of Japanese monkeys was investigated for a period of one year and the molting phenomenon was clarified. Nine monkeys were employed in the study. The molting of the Japanese monkey was found to be of a seasonal type and occurred once during the year. The molting continued for one to four months in each monkey. The hair of the Japanese monkeys was wholly replaced during the period from April to August. The hair length was thus short in summer, and long in winter. Hair replacement in pregnant females began after parturition and was generally later than that in other individuals. During molting, both new and old hairs could be observed simultaneously in the same region of the body. The hair replacement ended around summer when the hair became the shortest. The new hairs continued to grow after molting and became the longest towards autumn or winter. Thus, the summer coat and the winter coat were essentially the same in the Japanese monkey. Such annual changes in the hair of the Japanese monkey were considered to be suitable for the climate of Japan.     

A preliminary study on hair length in the Japanese monkey (Macaca fuscata fuscata)

The hair length of Japanese monkeys was investigated. The hair of the Japanese monkey is long on the back and the lateral side of the upper arm and short on the back of the hand. There was variation in the length of hairs in the same region of the body. The distribution of hair length approximated to a normal curve and did not display any marked bias or skewness. The increase in length of hairs was remarkable from 0 to 1 year of age, and then continued at a constant rate. Sex differences in hair length were not so remarkable at any age.     

Some aspects related to conception of the Japanese monkey (Macaca fuscata)

The season of birth, age of the first parturition, gestation period, and vaginal bleeding and mating after conception were surveyed with Japanese monkeys (Macaca fuscata). The analyses of the former two items were dependent on the birth records in the Ohirayama troop collected from 1957 to 1973, and the analyses of the latter two items were dependent on data obtained by a 48-hour mating in a laboratory. Birth in the Ohirayama troop converged into the months from March to July, especially from April to June. The age of the first parturition was three years and 11 months at the earliest, and nine years and two months at the latest. The monkeys giving their first birth at the age of five or thereabouts were most frequently observed (68.6%), and most of the monkeys had their first parturition from about the age of four years to about the age of six years. The gestation period calculated from 17 cases, which was defined as the period from the first day of a 48-hour mating to the day before parturition, was 173 ± 6.9 days ranging from 161 to 188 days. In 25 out of 28 cases, the vaginal bleeding was observed after conception. It began slightly later (between 16 and 24 days after mating) than the forecasted time of the next menstrual hemorrhage, and usually lasted longer than bleeding of the usual menses. Each of three female monkeys caged together with a male monkey 30 days after conception was observed to have copulated, and the male was observed to have ejaculated.     

Amino acids in the plasma of fasting Japanese monkeys (Macaca fuscata fuscata andM. f. yakui)

The plasma levels of 26 amino acids and related compounds were determined in five male and five female adult members of each of the two subspecies of Japanese monkeys,Macaca fuscata fuscata andM. f. yakui. Activities of L-asparaginase and histaminase in plasma were also measured.Numerous differences in amino acid levels between the sexes in the subspeciesfuscata were noted, with the female consistently exhibiting lower values. Few differences were observed between the sexes of the subspeciesyakui or between the two subspecies of Japanese monkeys. These monkeys were similar to other previously studied nonhuman primates in exhibiting measurable levels of 3-methylhistidine in plasma. There were numerous quantitative differences among Japanese monkeys and stump-tailed macaques, rhesus monkeys, chimpanzees, and man, with the Japanese monkeys usually exhibiting higher plasma levels.L-asparaginase activity was not detectable in these Japanese monkeys. Histaminase activity was similar to that previously measured in pig-tailed macaques and chimpanzees, lower than that in rhesus monkeys and stump-tailed macaques, and higher than that in man.     

Characteristic features of the reproduction of Koshima monkeys,Macaca fuscata fuscata: A summary of thirty-four years of observation

The reproductive data for Japanese monkeys,Macaca fuscata fuscata, which had been recorded for the 34 years from 1952 to 1986 on Koshima, were analyzed in terms of the influence of changes in artificial food supplies, the differences in reproductive success between females, the timing of births, and the secondary sex ratio. Koshima monkeys increased in number until 1971 when the population density was still small and artificial provisioning was copious. As described byMori (1979b), the severe reduction in artificial food supplies, which began in 1972, had an enormous deleterious effect on reproduction: the birth ratio of adult females of 5 years of age or more fell from 57% to 25%; the rate of infant mortality within 1 year of birth rose from 19% to 45%; primiparous age rose from 6 to 9 years old on average; and there was an increased death rate among adult and juvenile females. The prolonged influence of “starvation” may be seen in the significantly delayed first births of those females that were born just before the change in food supplies. When reproductive parameters are compared between the females who belonged to six lineages in the group during these periods, they were found to be rather consistent, although some individual differences can be recognized among females and subgroups. The apparent trend was that some of the most dominant females retained superior reproductive success while that of the second-ranked females has tended to diminish over the years since 1972. Such opposing trends were seen only in the most dominant lineage group and such a difference was not recognized among the females of other lineages. The difference in reproductive success is discussed in relation to both the different situations that arise because of the artificial food supplies and differences in feeding strategies. Multiparous females, after a sterile year, gave birth somewhat earlier than those who reared infants in the preceding year and, when artificial provisioning was intense, they tended to give birth a little earlier than during other periods. There is some evidence that the mortality of later-born infants was higher than that of earlier-born infants after 1972. However, this difference may not be responsible for the differential reproductive success of females since the timing of births did not differ among lineages. Furthermore, during the time when many females gave birth continuously, prior to 1972, the infant mortality did not differ with respect to the timing of births. The differences in infant mortality were not correlated with the reproductive history, parity or age of the mother, or with the sex of the infant. The secondary sex ratio varied by only a small amount, from slightly male-biased ratio (114: 100) when correlated with reproductive history, parity, age of mother, sex and survival ratio for preceding infants, timing of birth, and lineage of the female. Furthermore, the change in artificial food supplies did not cause any modifications of the secondary sex ratios, despite its enormous deleterious effect on reproduction. The secondary sex ratio of Japanese monkeys may not be influenced by the social factors mentioned.     

Morphological characteristics of the hair of Japanese monkeys (Macaca fuscata fuscata): Length,diameter and shape in cross-section,and arrangement of the medulla

A morphological study was carried out on hairs of the Japanese monkey. The shapes in cross-section were circles or ellipses. The diameters of the hairs ranged from 13.5 to 92 μ, and the mean value in each monkey was between about 30 and 40 μ. The average value of the fibre index was approximately 90 in each monkey. The arrangement of the medulla was considered to be of the narrow medulla lattice type. Medullae were developed poorly or disappeared in hairs with a diameter of less than 30 μ. A correlation was noted between the hair thickness and presence of medulla: medullated hairs were thicker than non-medullated hairs. A tendency was found for thicker hairs to be of greater length. The hairs of the Japanese monkey could be divided broadly into two types: medullated hair and non-medullated hair. The medullated hairs could be regarded as guard hair-like hairs since they were thick and long, and the non-medullated hairs as underhair-like hairs since they were thin and short.     

Self-wrist biting in Arashiyama-B troop of Japanese monkeys (Macaca fuscata fuscata)

Self-wrist biting in the Arashiyama-B troop of Japanese monkeys was observed during a nearly 4-year study. In all, six monkeys were seen performing this behavioural pattern. Medium ranking monkeys belonging to the age class 2–7 years performed this behavioural pattern most frequently. A slight tendency for the diffusion of this behaviour along kinship lines was also observed.     

Characteristics of serial cross-sections of hairs of the Japanese monkey (Macaca fuscata fuscata)

The characteristics of serial cross-sections of hairs collected from an adult male Japanese monkey were investigated. Cross-sections were made of five to eight pieces per hair. The shapes of the cross-sections were elliptical or rounded on the whole. The fibre indices of the sections ranged from 83 to 100. In particular, those of proximal (basal) sections were close to 100. The hair diameter was 86.4 μ at maximum and 27.2 μ at minimum. A tendency was observed for the longer hairs to have thicker diameters. The changes in thickness along the fibre shaft were slightly different in relation to hair length. The thickest point was at around the middle of the fibre in the intermediate hair, somewhat towards the top of the central part in the long hair, and somewhat towards the base in the short hair. The hair of the Japanese monkey, however, was considered to be scanty in changes along the fibre shaft in comparison with many other animals. Medullae could scarcely be seen in the short hair and in the terminal and proximal sections of all hairs. Their shapes in cross-section were not uniform and rough at the margins. The fibre-medulla indices were generally less than 30 and smaller than those of many other mammals. Pigmentary granules were observed in all sections examined. The granules were black-grey in sections of the black-grey coloured part and yellow in the yellowish sections. They were dense in distal sections and scarce in sections close to the base. The cross-sectional appearance of the thickest part of the long hair was considered to be useful for hair identification, since it was good in pigmentation and medullation and relatively small fibre index.     

Parasite changes and their influence on the body weight of Japanese monkeys (Macaca fuscata fuscata) of the Koshima troop

The incidence of eggs in individual feces (percentage of infected animals) and the EPG (eggs per gram of feces) of gastrointestinal nematodes for individually discriminated Japanese monkeys of the Koshima troop were investigated monthly from October 1974 to June 1979. Eggs of four nematode species,Oesophagostomum aculeatum, Trichuris trichiura, Streptopharagus pigmentatus andStrongyloides fülleborni, were frequently found; a few cestode segments ofBertiella spp. were occasionally found.S. fülleborni had a high incidence (100%) in young monkeys, suggesting that its incidence might vary with the monkeys' age. Seasonal changes in the incidence and EPG of each parasite were observed. The monkeys were treated with the anthelmintic thiabendazole once a month from May to July, 1975. Thiabendazole exerted an excellent effect onS. pigmentatus andS. fülleborni, and a lesser effect onO. aculeatum. Decreases in parasites caused by either seasonal changes and/or the anthelmintic treatment did not produce an increase in the monkeys' body weight, indicating that body weight is more affected by food intake or some factors other than parasitic infections. It is suggested that field anthelmintic treatment on wild monkeys should be conducted with the greatest care, since reinfection can occur immediately after such treatment.     

Circulating blood volume of the Japanese monkey (Macaca fuscata) by means of the dye T-1824

The circulating blood volume has been measured in 65 healthy Japanese monkeys (Macaca fuscata) with the dye T-1824 (Evans blue). The values obtained were 83 ± 13 ml/kg in females, and 85 ± 12 ml/kg in females, almost the same as the figures reported in man.Sex difference of blood volume has been reported to be present in man, but from the data obtained here no significant difference was found in the Japanese monkey.In young monkeys aged from 1 to 5.5 years, the blood volume was 77 ± 5 ml/kg in males, and 78 ± 4 ml/kg in females. The blood volume of the monkey was found to increase with age; a significant difference was demonstrated between adult males and young males.     

Morphological studies ofMacaca fuscata: VI. Somatometry

Measurements of various parts of the head and body and weighing the body were carried out on about 170 adult Japanese monkeys (Macaca fuscata) and the results are noted with separate statistics for respective local groups. Intraspecific comparisons in the Japanese monkey and interspecific comparisons in macaques are discussed from the somatometrical point of view. Among macaques, the Japanese monkey has a comparatively large body, a very short tail, relatively wide biacromial and biiliac breadths, and markedly la ge intermembral and intercrural indices. The Japanese monkey itself shows various local variations. The most conspicuous difference is to be found between the so-called Yaku monkey living on Yaku islet (Yakushima), south of Kyushu, and the monkeys living in other parts of Japan, and, therefore, it is understandable that the Yaku monkey has been distinguished as a subspecies (M. f. yakui) of the Japanese monkey. The Yaku monkey has a somewhat small body, a relatively large head, wide hips, and slender hands and feet.     

A cytogenetic study on congenital limb malformations in the Japanese monkey (Macaca fuscata)

A cytogenetic investigation was performed on 88 Japanese monkeys (Macaca fuscata) with abnormal limbs from 11 free-ranging provisioned troops including nine individuals with abnormalities indistinguishable as to whether they were congenital or injurious. All of the monkeys with abnormal limbs including the nine questionable individuals had the same karyotypes as those of normal individuals. The chromosome number was 42, consisting of 20 bi-arm autosome pairs and a submetacentric X-chromosome and Y-chromosome. The ninth chromosome pair, which was the only chromosome pair with remarkable secondary constriction, displayed length polymorphism of the centromeric C-band and secondary constriction in both deformed and normal monkeys. These kinds of variants have also been commonly found in other monkey species, which have almost the same karyotype as the Japanese monkey and have not been reported to show frequent occurrence of limb malformation. We concluded therefore that chromosomal abnormalities could be excluded from the main causal factors for limb malformations of the Japanese monkey.     

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.     

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.     

Age gradations in vocalization and body weight in Japanese monkeys (Macaca fuscata)

449 syllables in 174 food calls of Japanese monkeys of various ages were analyzed spectrographically. The fundamental frequency bands were divided into 55 frequency modulation patterns. The percentage of harsh syllables changed with age class among adults. Although the duration of syllables did not change with age, the maximum fundamental frequency and the minimum fundamental frequency showed age-related changes. Both were distinctly decreased by 6-8 years of age and thereafter the decline was far more gradual. Body weight also increased up to 6 years of age for females and 8 years for males, thereafter stabilizing for both sexes. The matching in age-related changes between fundamental frequency and body weight indicates that it is increase in size of the vocal folds with physical growth that lowers the fundamental frequency.     

Sequential analysis of the social behavior of infants in groups of Japanese monkeys (Macaca fuscata fuscata)

We employed techniques of behavioral entropy to carry out a quantitative analysis of sequences of behavioral patterns evident in the interaction between infants and other members of a group of Japanese monkeys (Macaca fuscata fuscata). The group concerned included examples both of monkeys in captivity and in the wild state. The results were examined as a function of the animal age and environmental differences (cage-field). An example is given to illustrate the use of information theory. Findings partially confirmed that the variability of social behavior decreases as the age of the animals increases.     

An ecological study of troop fissions of Japanese monkeys (Macaca fuscata yakui) on Yakushima Island,Japan

Wild, habituated, Japanese monkeys were observed from 1975 to 1979 on Yakushima Island, Southern Japan. The monkey troops had a continuous distribution in a warm temperate forest. Demographic data on local populations was collected. The population density was 33 animals/km². The growth rate of the studied troop was 3.0% per year. A significant correlation between home range areas (R) and troop size (P) was found (r=0.955,p<0.005), using anR-P equation,R=1.84P. One troop split into three troops through two successive fissions. Twenty-one intertroop encounters were observed. Five types of encounters were distinguished. The encounters were apparently territorial defence. Increases in birth rate and socionomic sex ratio after the fissions were prominent. The following four factors had a direct effect upon the dispersion of the troops after fission: (1) dominance relation between the fission troops; (2) social pressure of the neighbors; (3) troop's attachment to its home range; and (4) structure of the environment. The home range of Japanese monkeys is a territory, and territoriality is a population regulating mechanism which serves to reduce competition for food.     

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.     

Proximity relationships within a birth cohort of immature Japanese monkeys (Macaca fuscata) in a free-ranging group during the first four years of life

This study was designed to characterize the proximity relationships among 20 immature Japanese monkeys (Macaca fuscata) of the same age in a free-ranging group during the first 4 years of life. Most male and female immature monkeys showed a consistent preference for proximity within their cohort to certain same-sex individuals whose dominance ranks were immediately adjacent to their own throughout the first 4 years. Such prolonged proximity relationships between peers of the same sex were largely a reflection of those between their mothers. Therefore, the proximity relationships between peers seem to be formed under the influence of social relationships between the mothers. © 1996 Wiley-Liss, Inc.     

Menstrual cycle and some other related aspects of Japanese monkeys (Macaca fuscata)

The menstrual cycle and some other related aspects of Japanese monkeys (Macaca fuscata) were dealt with in this paper. Almost all the monkeys had regular menstrual cycles only in the mating season, and had no menstrual cycles, or only irregular ones, in the non-mating season. The average length of the menstrual cycle in the mating season was 26.3 ±5.4 days. Many monkeys had a tendency to have their own individual and relatively regular cycles. Ninety out of 108 monkeys kept in the air-conditioned quarters for five years showed “periodical changes” essentially coincident with the changes of outdoor season, and this fact suggests that the rhythm of the seasonal change of Japanese monkeys remains for a relatively long period even if the monkeys are kept in air-conditioned quarters where room temperature and lighting are kept constant throughout the year. Vaginal smear, cervical mucus, sexual skin, etc. were observed in relation to ovulation. These characters showed cyclic changes with menstrual cycles in about half of all cases observed, but ovulation occurred even in the cases in which no cyclic change was observed. Therefore, it was not necessarily easy to estimate the ovulation by observing these characters.