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.     

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.     

Suppressed copulatory behavior and ovarian function in lactating Japanese monkeys (Macaca fuscata fuscata) during the mating season

The influence of lactation on copulatory behaviors and ovarian functions was studied in Japanese monkeys (Macaca fuscata fuscata) during the mating season. Three lactating females were housed in an outdoor group cage with their infants, and three nonlactating females were housed in an adjacent outdoor cage. They were mated by introduction of one of four rotationally chosen males into the females' cage, for two hours three times a week; the occurrence of ejaculatory copulations was recorded. Blood samples were collected on each observation day, and plasma levels of estradiol, progesterone, and luteinizing hormone (LH) were measured by specific radioimmunoassays. In nonlactating females, plasma estradiol increased during the transition into the mating season, and rose to levels over 90 pg/ml for the first time on about 50 days before the first ovulation. Shortly after plasma estradiol exceeded 90 pg/ml in the nonlactating females, the onset of ejaculatory copulations occurred. They received ejaculations continuously up to the early ovarian luteal phase. On the other hand, in lactating females, there were lower levels of plasma estradiol (below 90 pg/ml) during the transition into the mating season, and they received no ejaculation during that period. Two of the three lactating females ovulated only once, and they received ejaculations only during the periovulatory period, coinciding with the rise of their plasma estradiol levels over 90 pg/ml. The remaining lactating female remained anovulatory and received no ejaculation throughout the entire mating season. These results have demonstrated that the low sexual activity of lactating females is clearly correlated with low levels of plasma estradiol due to suppressed ovarian function.     

Cervical ripening and uterine contraction induced by prostaglandin E2-gel in pregnant Japanese monkeys (Macaca fuscata fuscata)

Effects of intracervical administration of PGE₂-gel were studied in pregnant Japanese monkeys (Macaca fuscata fuscata) near term. Administration of PGE₂-gel induced cervical ripening and an increase in maternal plasma PGE₂ but no change in PGF_2α. Ultrastructural observations of the connective tissue of the cervix after PGE₂-gel treatment revealed a decrease in the number of collagenous fibers. These results show that intracervical administration of PGE₂-gel induces cervical ripening without induction of labor in the Japanese monkey.     

Canine teeth and rank in Japanese monkeys (Macaca fuscata)

Canine teeth were extracted from seven adult male Japanese monkeys. Observations over the next four years led to the conclusion that canines are not essential for either the attainment or maintenance of high rank, but that they may play an important part in the self-defense of low-ranking males.Publication No.501 of the Oregon Regional Primate Research Center supported by NIH Grant RR 00163.     

Successful artificial insemination for indoor breeding in the Japanese monkey (Macaca fuscata) and the cynomolgus monkey (Macaca fascicularis)

Methods of artificial insemination (AI) for indoor breeding in the Japanese monkey and the Cynomolgus monkey were investigated. For the Japanese monkey AI was carried out in six females during the winter mating season and in six females during the summer non-mating season. During the mating season, semen was inseminated near ovulation time in natural menstrual cycles. In the mating season study, three females inseminated at the uterine cavity became pregnant. Three inseminated at the cervical canal failed to become pregnant. For the non-mating season study, ovulation was induced artificially by PMSG and hCG and AI was carried out near the induced ovulation time. In the non-mating season, no animals became pregnant. Of four Cynomolgus monkeys used, pregnancy occurred in two animals inseminated near ovulation time in natural menstrual cycles. AI occurred at the uterine cavity in one and cervical canal in the other. In both species ovulation was verified by laparoscopy. Semen was collected by penile electro-stimulation then diluted to 2.5 to 5.0×10⁷/ml with Whitten's medium. Diluted semen of 0.2l was inseminated at the uterine cavity or cervical canal. Our results indicate the usefulness of vaginal AI as a method of artificial indoor breeding.     

Psycholinguistic analyses of alarm calls of Japanese monkeys (Macaca fuscata fuscata)

Alarm and estrous calls emitted by Japanese macaques were recorded and analyzed in the Arashiyama West and East groups. Their responses to natural calls as well as to synthesized versions varying in the acoustic parameters that defined the vocalizations were studied. The response patterns shown by Arashiyama West group members, which were subject to a distinct change with only a slight difference of a single parameter, appeared to reflect strict underlying perceptual boundaries. This was analogous to the categorical perception that humans show with speech sounds. In contrast, continuous perception was exhibited by Arashiyama East group individuals. When several sounds were played back in combination to the former group, following stimuli were recognized by quite different cues from those by which the first sound was perceived. The groups' differences in vocal perception are discussed in terms of the ecological differences of the environments they inhabit.     

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.     

Ecological studies of reproduction in Japanese monkeys (Macaca fuscata)

Birth data of 25 troops of Japanese monkeys, which range over major areas in Japan between lat. 31°22 N. and 41°15 N., show significant differences in the timing of the birth season among different troops. The difference seems regional to some extent. Correlations between the timing of the birth season of the troop and various environmental factors—latitude, rainfall, temperature, social factors and so on, were examined, and it was suggested that the effect of environmental factors are complex and not always direct, and that the threshold value of each factor in causing the onset of the copulatory season might vary by troops. The difference in the timing of the birth season among different troops has not yet been sufficiently explained by a simple correlation with environmental conditions.While troops with large numbers of birth show annual uniform monthly distribution patterns of births, those with a smaller number of births show more fluctuations in the monthly distribution pattern of births from year to year. However, all the births in the latter come within a range of about four months, which is fixed for each troop.     

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.     

Digging and eating of underground plant-parts by wild Japanese monkeys (Macaca fuscata)

It has been reported that Japanese monkeys pull out and eat underground parts of plants, but they do so only a little and occasionally. The authors observed that wild Japanese monkeys in the mountains area near Hinohara Village ate underground plant-parts as one of the main components of their diet and they spent a lot of time digging for them. From information obtained from local old people, it appears that they have exhibited this behavior for many years as part of their feeding repertoire.     

Expression and identification of HERV-W family in Japanese monkeys (Macaca fuscata)

We investigated structural genes (gag, pol, env) of HERV-W family in the Macaca fuscata (Japanese monkey). Those genes are expressed in various tissues (testis, prostate, kidney, cerebellum, thymus, pancreas, intestine, stomach, ovary) of the Japanese monkey in RT-PCR and sequencing analyses. Nine clones for gag, thirty-one clones for pol and thirty-four clones for env fragments of the HERV-W family in monkey tissues were identified and analyzed. These clones showed a high degree of sequence similarity, 82.2-84.7% for gag, 88.4-91.7% for pol, and 90.8-95.4% for env, to those of HERV-W family. Translation to amino acids in all clones derived from the monkey indicated that they showed multiple interruptions of frameshifts and termination codons by deletion/insertion or point mutation. Identical sequences from different tissues of the monkey were found in env and pol clones of the HERV-W family.     

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.     

Display behavior of three troops of Japanese monkeys (Macaca fuscata)

In this paper the display (i.e., “branch-shaking”) behavior of three troops of Japanese monkeys—the confined Oregon troop as reported byModahl andEaton (1977), the semi-free-ranging Arashiyama West troop and the free-ranging Arashiyama B troop—are compared. The comparison reveals several similarities and dissimilarities between the Oregon troop and the two genetically related Arashiyama troops. The similarities include three display postures (shaking, kicking and leaping) and an increased frequency of male but not female displaying during the breeding season. The dissimilarities include the absence of two Oregon display postures (tossing and swinging) and collective displaying among Arashiyama monkeys. The hypothesis ofModahl andEaton (1977) that male displaying influences the females' choice of male mating partners is discussed. The evidence suggests the Oregon monkeys have incorporated male displaying into their socio-sexual behavior to a greater extent than Arashiyama monkeys. However, field observations indicate that males who migrate to the Arashiyama B site during the breeding season can influence female choice by “advertizing” their location with displays.     

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.     

Hierarchy,kinship and social interaction among Japanese monkeys (Macaca fuscata)

The study reports the relationship between hierarchy, genetic relatedness and social interaction in captive Japanese macaques. Grooming and proximity were found to be positively related to both dominance rank and degrees of relatedness. Ranks also positively correlated with threats while no relationship was observed between genetic relationships and agonistic interactions. The removal of a-male tightened the male hierarchy while the female hierarchy became relatively loose. Affiliative behaviour became more correlated with ranks than degrees of genetic relatedness. In the absence of α-male, the next dominant male avoided involvement in either agonistic or afliliative interactions with reintroduced animals and group females.     

Characterization of obesity in Japanese monkeys (Macaca fuscata) in a pedigreed colony

BACKGROUND: Japanese monkey, Macaca fuscata, is recognized as the monkey species inhabiting the northernmost area in the world, and thus likely to possess unique fat-depositing mechanisms to resist cold weather in winter. We report that obese females are present in the Wakasa group of Japanese monkey reared in an open enclosure of the Primate Research Institute, Kyoto University. METHODS AND RESULTS: Eight of 12 females were categorized as obese, showing percentage body fat of over 22%. The levels of serum leptin (mean +/- SD, 4.9 +/- 2.3 ng/ml) measured in these obese monkeys were significantly higher than those of non-obese peers of the same group (n = 4; 1.2 +/- 0.5 ng/ml) and another Japanese monkey group (Takahama, n = 14; 0.8 +/- 0.25 ng/ml); however, serum levels of adiponectin, insulin, glucose, hemoglobin A1c, and fructosamine did not differ between obese and non-obese monkeys. Few serum lipid parameters such as triglyceride and cholesterol showed lower levels in obese monkeys than their non-obese peers. CONCLUSIONS: These results show that these obese monkeys in the Wakasa group have not developed obesity-related diseases/disorders such as diabetes. In the Wakasa group, the frequency of obese individuals was high in some maternal lineages, suggesting that genetic factors responsible for obesity may have been inherited in these lineages.     

Decisions on time allocation to different food patches by Japanese monkeys (Macaca fuscata)

From the standpoint of the possible development of an optimal foraging strategy, the time allocation to different food patches and the decision as to when to leave any given patch were examined in wild Japanese monkeys (Macaca fuscata). The investigations yielded the following results: (1) There was no tendency for feeding bouts to be of longer duration in higher-quality patches, i.e. the monkeys did not employ an energy-maximizing strategy during their feeding bouts. (2) The speed of feeding barely decreased with passage of time during a bout. In most cases, therefore, a decrease in feeding speed was not considered relevant to the decision to leave a patch. These findings are evaluated in terms of social factors, and it appears that following a monkey's own family group or the troop usually contributes to the timing of leaving a food patch.