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.     

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.     

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.     

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.     

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.     

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.     

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.     

Discrimination of mother by infant among Japanese Macaques (Macaca fuscata)

Experiments on five mother-infant pairs of Japanese monkeys (Macaca fuscata)living together in a captive group were conducted during the first 12 weeks after birth in order to assess the time at which infants begin to discriminate their own mothers from other adult females. After removal from their social group, infants exposed to their mothers and three unfamiliar adult females at a distance of 150 cm failed to orient visually toward their mothers. However, when the infants were allowed to approach the four females, they responded preferentially to their mothers during the third month of life. We concluded that by 8–12 weeks of age, infant Japanese macaques are able to discriminate between their mothers and other adult females.     

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.     

Bioenergetics of Japanese monkeys (Macaca fuscata) on Kinkazan Island during winter

An adult female Japanese monkey was chosen as a focal animal in order to assess the nutritional condition of the species during winter on Kinkazan Island, which is covered by deciduous forest of the cool temperate zone. Five whole-day-long observations were performed at the end of November (late autumn) and also at the end of February (late winter). In November, the daily energy intake and protein intake were estimated to be 1,449 kcal and 36 g, respectively: both satisfied the intake requirement even in view of a digestibility of 55%. These findings suggest that the focal animal could accumulate body fat in November. In contrast, in February, the daily energy intake and protein intake were estimated to be 556 kcal and 12 g, respectively: both did not satisfy the intake requirement in view of a digestibility of 55%. These findings suggest that the focal animal consumed accumulated body fat in February. Various data for food intake, nutritional content, etc. on Kinkazan were compared with those on Koshima, which is covered by evergreen forest of the warm temperate zone. The nutritional intake in February on Kinkazan was much smaller than that in November on Kinkazan as well as those in November and February on Koshima. The small intake of the former appeared to be strongly influenced by the sign ficantly lower speed of dry weight intake, which derived partly from the significantly lighter unit weight of the food items (e.g., buds ofZanthoxylum piperitum, Castanea crenata, andCornus macrophylla; leaves and stems ofOplismenus uadulatifolius andZoysia japonica). The monkeys on Kinkazan Island increased their food diversity, shortened their daily travel distance, and avoided repeated use of sites within their home range to offset the deterioration of the food quality in February.     

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.     

Female sexual behavior in the absence of male-male competition in captive Japanese macaques (Macaca fuscata)

A captive group of Japanese macaques (Macaca fuscata). consisting of one adult male and three adult females, was observed for 88 hr during the 1988 mating season. We focused on the group's sexual activities because understanding how social dynamics affect reproductive behavior may enhance our ability to establish self-sustaining captive populations. The adult male exhibited distinct preferences in copulation partners, although all females were receptive and cycled during the study period. The dominant female participated in the most copulations and successfully harassed and disrupted copulations between the male and the other females. The alpha female, therefore, actively constrained the formation of mating pairs. Further, the male did not consort with his year-round female grooming partner. This female, the least dominant member of the group, engaged in the most autosexual and homosexual behavior. Birth season data show that only the dominant female bore offspring. This study emphasizes the influence of social dynamics on a group's reproductive potential and suggests an alternative means by which females can influence consort formation.     

Puberty in male Japanese macaques (Macaca fuscata): Social and sexual behavior in a confined troop

The social and sexual behaviors of four groups of males (4, 5, 9, and 10 years old) were compared throughout one complete mating season in a confined troop of Japanese macaques (Macaca fuscata). The aim of this research was to document social behavior changes that occurred during adolescence and to relate them to changes in sexual behavior that occurred at puberty. The 4-year-old males all mounted females and ejaculated but they had significantly fewer ejaculations and female partners than did the older males. The 4-year-old males also showed a pattern of delayed development in tail carriage and courtship, and they played more frequently than the older males. There were no significant differences in the frequency of aggression among the groups, but both 4-year-old and 5-year-old males were displaced by adult males and females more frequently than were the older males. We concluded that the development of adult patterns of social behavior in this genus is not climactic, but occurs slowly one to two years after physiological puberty has been reached.     

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.     

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.