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.     

A description of genealogical rank changes in a troop of Japanese monkeys (Macaca fuscata)

Rank changes among females of a troop of 154 Japanese monkeys (Macaca fuscata) are described. A medium ranking female, with support from the alpha male, successfully challenged the alpha female. Following this dominance shift, almost all members of the two genealogical groups underwent rank changes. The observations provide some evidence that the role of alpha female may be competed for, just as the alpha male position is, in macaque social groups.     

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.     

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.     

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.     

Female rank and reproductive success among arashiyama B Japanese macaques (Macaca fuscata)

Five hypotheses that related female rank and reproductive success were tested in an intact troop of free-ranging, provisioned, Japanese macaques. The hypotheses stated that high-ranking females (1) begin parturition earlier in life than low-ranking females; (2) produce more offspring than low-ranking females; (3) give birth during some optimal time during the birth season to a greater extent than low-ranking females; (4) experience less infant mortality than low-ranking females;and (5) more frequently produce male offspring, while low-ranking females more frequently produce female offspring. A statistical analysis of the data which included three birth seasons and 55 adult females and 34 pubescent females, all of known age, rank, and matrifocal membership in the Arashiyama B troop, revealed few significant results. An association was found between the rank of the matrifocal unit and the age of first birth. However, the relationship was the reverse of hypothesis 1, i.e., females of the lower-ranking matrifocal units began parturition earlier than females of higher-ranking matrifocal units. Therefore, in this troop of Japanese monkeys— where alternative feeding strategies existed— there was little association between female rank and reproductive success.     

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.     

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.     

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.     

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.     

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.     

An experimental analysis of a mother-daughter rank reversal in Japanese macaques (Macaca fuscata)

This paper describes in detail how a 2.5-year-old female belonging to the second-ranking family in a captive group of three families managed to outrank her healthy, three-times heavier mother with the aid of the two immature daughters of the alpha female who was not herself directly involved. After the outranking was completed, the two active allies were removed. This had no effect on the rank relation between the female and her daughter. It is only after the mother of the two allies was removed (in addition to her daughters) that the mother recovered her rank above her daughter. This case study and the few other reported cases of changes in rank among females are discussed in relation to the issue of the stability of rank relations in hierarchical systems where rank is socially inherited rather than based solely on dyadic power contests. On the basis of this combined evidence, it appears that when attempting to rise in rank, females do not challenge dominants by allying with subordinates, but that they rather ally with an individual ranking above the target. This phenomenon, together with the fact that support is given to other females downwards the hierarchy, might explain the stability of female dominance relations and be the manifestation of an Evolutionarily Stable Strategy.