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.     

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.     

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.     

Differences in hair density of Japanese monkeys (Macaca fuscata fuscata) with locality and age

The hair density of free-ranging Japanese monkeys (Macaca fuscata fuscata) living in three different areas was investigated. The Japanese monkeys had thicker hair than other macaques. The hair density in the Japanese monkeys varied with locality: the northern monkeys had thicker hair than the southern ones. The density did not vary markedly with age up to 3 years of age, but then decreased gradually up to adult age (≧7 years old). The remarkable growth of the trunk suggested that the total number of hairs increased with age, especially during the period as a juvenile.     

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.     

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.     

Seasonal changes in the spermatogenic epithelium of adult Japanese macaques (Macaca fuscata fuscata)

A histological study was undertaken to clarify seasonal changes in the spermatogenic epithelium of Japanese macaques. Testicular tissue samples were excised by biopsies from five adult laboratory-maintained males in mating and non-mating seasons. The samples were fixed with Bouin's solution, embedded in paraffin, and stained with PAS and hematoxylin. Microscopic observations on cross-sections of seminiferous tubules revealed that the seminiferous epithelium in the mating season was thicker than in the non-mating season. PAS-stained granules were found in some of the dark A-type spermatogonia, which significantly increased in the non-mating season. Spermatids of the steps preceding the appearance of the acrosomic cap in stages I to III were observed significantly more often than those in the step coinciding with the formation of the acrosomic cap in stage IV. In stage I, the ratio of mature spermatids or spermatozoa to immature spermatids in the mating season was higher than that in the non-mating season. These findings suggest that spermiogenesis, as well as spermatocytogenesis, is inhibited in the non-mating season.     

Development of co-feeding relationships in immature free-ranging Japanese monkeys (Macaca fuscata fuscata)

The co-feeding relationships of immature Japanese monkeys in the provisioned situation were studied. The most frequent co-feeders for immature females were diversified as compared to those for immature males. The number of immature females who showed strong co-feeding relationships with their mothers gradually decreased with age in both high- and middle/low-ranking matrilines, but the percent decrease was greater for middle/low-ranking immatures. Almost all immature females who displayed strong co-feeding relationships with adult males were from middle/low-ranking matrilines. Strong co-feeding relationships with mothers among immature males from high-ranking matrilines remained until 4 years of age. In contrast, strong co-feeding relationships with mothers among middle/low-ranking immature males decreased rapidly in the first year of life, and most 1- to 4-year-olds showed no strong co-feeding relationships with other group members. It is considered that middle/low-ranking mothers may not provide their immatures with a secure base for obtaining food in the provisioned situation.     

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.     

Longitudinal studies on annual changes in plasma testosterone,body weight and spermatogenesis in adult Japanese mankeys (Macaca fuscata fuscata) under laboratory conditions

The present study was undertaken to clarify the annual changes in testicular function of Japanese monkeys under laboratory conditions. Five adult males were kept in an air-conditioned room with artificial 12/12 hr lighting. Measurements of body weight and blood sampling were conducted monthly for 13 months. The concentrations of plasma testosterone were determined by radio-immunoassay. The testicular size was measured and testicular tissues taken by biopsy were examined histologically at the four seasons. The body weight and plasma testosterone levels showed coincidental annual changes with a peak in September and a nadir in March or May. The percentage of seminiferous tubules including pachytene spermatocytes and the number of pachytene spermatocytes in tubular cross-sections were significantly increased in both the autumn and winter and decreased in the spring. Electron microscopically, the seasonal change was reflected in an increased size of fat granules in Sertoli cells in the breeding season.     

Mirror guided behavior in Japanese monkeys (Macaca fuscata fuscata)

Two male Japanese monkeys were trained to use a mirror to reach an object that could not be seen directly. Training to use a mirror in this way proceeded, step-by-step, from reaching a piece of apple to key-tracking. In Experiment 1 the monkeys were trained to use the mirror to locate a desired object, a piece of apple in a box facing the mirror, which could be seen only by looking into the mirror. The apple, once located, however, could be grasped without further reference to the mirror. This behavior is referred to as mirror mediated object discrimination. In subsequent experiments the monkeys could not reach the goal object except by observing it and his hand movement in the mirror. In Experiment 2 the target was a piece of apple visible in the mirror, in Experiment 3 an illuminated key and in Experiment 4 a series of keys which were illuminated sequentially. Mirror guided behavior such as shown in Experiment 2, 3, and 4 has not previously been demonstrated in monkeys.     

Hematological analyses of the Japanese monkey (Macaca fuscata)

Various hematological examinations were performed on a total of 208 Japanese monkeys (Macaca fuscata). One hundred and fifty-eight of the monkeys were originally from different habitats in the western part of Japan, where they existed as free-ranging animals. The remaining 50 monkeys were kept in an open-enclosure for about one year. Laboratory examinations on blood specimens included the following; the erythrocyte and leukocyte counts, hemoglobin concentration, hematocrit, the specific gravity of the blood and plasma, protein concentration of the plasma, SGO-T, SGP-T, A/G ratio and the erythrocyte sedimentation rate. Results were similar to those reported for otherMacaca species. When the data reported here was compared with the known values for man, the Japanese monkey showed lower values for the erythrocyte count, hemoglobin concentration, hematocrit, and the specific gravity of the blood. Higher values were shown for the leukocyte count and SGO-T activity, with a wider overall range of variation.     

Cheek-pouch dispersal of seeds by Japanese monkeys (Macaca fuscata yakui) on Yakushima Island, Japan

Seed dispersal by Japanese monkeys (Macaca fuscata yakui) via cheek-pouch was studied in a warm temperate evergreen forest on Yakushima Island. Plant list was compiled based on a study during 1986–1995, of which troops of monkeys have been habituated without artificial feeding. We followed the well-habituated monkeys in 1993 and 1994 to observe the feeding behavior and their treatments of fruits and seeds, and collected seeds dispersed by monkeys to record the distance carried from the mother trees. We checked the difference of germination ratio between seeds dispersed via cheek-pouch and seeds taken from mother trees by sowing experiments. Seeds and acorns of 22 species were observed to be dispersed via cheek-pouch of monkeys. Among them, three species with acorns were never dispersed via feces, and 15 species with drupes were seldom dispersed via feces. Plant species of which seeds are dispersed only via cheek-pouch had larger seeds than those of dispersed both via cheek-pouch and via feces, and typically had only one or two seeds in a fruit. As for one of cheek-pouch dispersal species,Persea thunbergii, the mean distance when seeds were carried from the mother trees via cheek-pouch was 19.7 m, and the maximum distance was as long as 105 m although more than 80% of seeds were dispersed within 30 m from mother trees. And 82% of seeds dispersed via cheek-pouch germinated. The easy separation of seeds from other parts of the fruit seems to facilitate cheek-pouch dispersal more than dispersal via feces. Cheek-pouch dispersal by monkeys has possibly enhanced the natural selection for larger seeds which bring forth larger seedlings with high shade-tolerance. In conclusion, cheek-pouch dispersal by monkeys is quite an important mode for trees in the mature stand in a warm temperate evergreen forest on Yakushima Island.     

An analysis of dyadic interactions of male Japanese monkeys (Macaca fuscata fuscata) in a cage-room observation

This is a laboratory observation (Home-cage and observation room) for individual and social behavior of four male Japanese monkeys. The monkeys were placed in a dyadic and trio situation with the purpose to investigate the relationships between aggressive and affinitive factors which regulated their social behaviour. Total amounts of attacks and receiving groom showed a consistent order for four monkeys through the pairwise conditions, which was presumed to indicate a dominance order. Grooming and mounting behavior, however, were influenced by the particular dyadic interactions, probably social attraction, rather than dominance order itself. The presence of the third animal facilitated such a social preference between animals positioned closely in the rank order as well as elicited aggression from the dominant animals.     

Dermal melanocytosis in Japanese monkeys (Macaca fuscata)

The skin of Japanese monkeys (Macaca fuscata) shows diffuse discolorations resembling human dermal melanocytosis. Very few laboratory animals have melanocytes in the dermis. The purpose of this study was to clarify the dermatologic characteristics of Japanese monkeys in terms of gross appearance, skin color, and histopathologic findings. A colorimeter was used to record the skin colors of pigmented and nonpigmented sites. Tissue specimens obtained from both types of sites were examined histopathologically. All animals examined had pigmented sites on their bodies, and the discolorations extended over 25% to 33% of the body surface. The colorimeter could detect differences in skin color due to dermal melanocytosis. All parameters of the colorimetric systems used (Yxy, L*a*b*, and L*C*h* systems) demonstrated significant differences between pigmented and nonpigmented sites. In pigmented sites, the epidermis lacked melanocytes, but the dermis had numerous melanocytes with abundant melanin. Activated melanocytes with well-developed dendrites were distributed throughout the upper part of the dermal layer. Melanocytes were not arranged in clusters, and elastic and collagen fibers in the dermis showed no histological abnormalities. Nonpigmented sites lacked melanin granules in both the epidermis and dermis. This study revealed that gross dermal melanocytosis correlated well with colorimetric results and histopathologic findings. These findings suggest that the pigmentation of Japanese monkeys is equivalent to dermal melanocytosis in humans, to the end that Japanese monkeys may be a useful animal model for investigating dermal melanogenesis.     

Use of a mirror to direct their responses in Japanese monkeys (Macaca fuscata fuscata)

Two male Japanese monkeys used a mirror to inspect an object attached to their bodies but not directly visible. These monkeys had been trained previously to use a mirror to guide their hand to a target. In Experiment 1 their behavior in the presence of a mirror was observed. In Experiment 2 the monkeys used the mirror to locate a picture projected on a screen to the left or right rear side of the cage. In Experiment 3 the monkeys used a mirror to observe and finally grasp an object attached behind their heads. Two monkeys who were not trained to use a mirror to obtain an otherwise hidden object did not show such behavior.     

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.     

Monitoring the reproductive status of Japanese monkeys (Macaca fuscata) by measurement of the steroid hormones in fecal samples

The menstrual cycles as well as the pregnancy in female Japanese monkeys (Macaca fuscata) were monitored by measuring the fecal estradiol concentrations and relative amounts of fecal progesterone. Steroids from fecal samples were extracted by using a previously developed simplified two-step method and then measured by radioimmunoassay. We successfully demonstrated that the two-step method is effective and convenient for monitoring the reproductive status of Japanese monkeys.     

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.