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.     

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.     

Activity patterns of a troop of Japanese monkeys (Macaca fuscata yakui) on Yakushima Island,Japan

Activity patterns of Japanese monkeys (Macaca fuscata) were observed for 240 hr from August to December 1976 on the western slope of Mt. Kuniwari, Yakushima Island, Japan. Activity patterns and the time budget of a habituated wild troop which consisted of 47 animals in August 1976, were studied quantitatively by using the scan-sampling method at 15-min intervals. Six thousand seven hundred and six animals were recorded in 959 scans during the study period and the mean number of animals seen per scan was 7.0. The time budget established for different categories of activity was as follows: inactive—20.9%; moving—22.8%; feeding—23.5%; social grooming—27.9%; self-grooming—1.2%; and other activities—3.7%. Adult males spent less time in feeding and more time in resting or being inactive than females or juveniles. The daily activity patterns were highly variable with respect to time. Intraspecific variations were examined between troops in several regions of Japan and it was noted that the percentages of time devoted to feeding were similar in all areas. Inter-species variations in the activity budgets of several species of primates were also examined. The percentage of time spent in social grooming by Japanese monkeys is exceptionally high compared to that recorded in other species.     

Object manipulation in a captive troop of Japanese monkeys (Macaca fuscata): A developmental analysis

A captive troop of Japanese monkeys (Macaca fuscata) was presented with a nylon rope, a wooden cube, and an iron tube, and their subsequent manipulations were observed in detail. In total, 202 manipulation patterns were distinguished on the basis of three components: the actions performed, body-parts used, and relations to other objects. The developmental changes in these modes of manipulation were analyzed cross-sectionally, revealing four characteristics: (1) the most manipulative members of the troop were those aged 2–3 and 4–6 years old; (2) most of the manipulatory repertoire appeared by 4–6 years old; (3) actions such as Roll, Rub, and Slide and the use of bodyparts continued to increase in variety until 4–6 years old, while the variety of other actions showed plateaus after 2–3 years old or an earlier age; and (4) secondary manipulations appeared at 1 year old and continued to increase in variety even after 4–6 years old.     

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.     

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.     

Socio-sexual factors of troop fission in wild Japanese monkeys (Macaca fuscata yakui) on Yakushima Island,Japan

The troop fissions which occurred in a wild population of Japanese monkeys (Macaca fuscata yakui) were observed from 1977 to 1979 on Yakushima Island. The fissions were initiated in the breeding season by non-troop males who established a consort relation with estrous females. In order to analyze the socio-sexual factors which accelerated the fissions, the male emigrations and immigrations before and after two successive fissions, and the copulation frequencies, competition among males and preferences of mating partners in both sexes in the 1977–78 breeding season after the first fission were examined. The results indicated that three factors (a large number of non-troop males, a shortage of troop males and the females' choice of mating partners) effectively influenced on the establishment of consort relationships between non-troop males and estrous females. It is suggested that these factors may exert different effects on the troop disorganization in relation to troop size. In small-sized troops, a large number of non-troop males and a shortage of troop males may lead to stronger competition between them, and the females' choice affected by prolonged intimate relations with the dominant TMs may reduce their priority of access to estrous females. This situation possibly stimulates fission or male emigration in small-sized troops under the natural conditions on Yakushima Island. In contrast, in large-sized troops under isolated conditions, a surplus rather than a shortage of troop males may contribute to troop disorganization, as most former studies have suggested. A higher socionomic sex ratio may decrease the mating activities of subordinate troop males and increase the competition among them. This situation possibly accelerates the fission of large-sized troops through prolonged interactions between females and subordinate or peripheral troop males. A lower ratio and the females' choice, however, raise the mating chances of subordinate troop males and may not promote the fission of large-sized troops under isolated conditions. This study was financed in part by a Grant-in-Aid for Special Project Research on Biological Aspects of Optimal Strategy and Social Structure from the Japan Ministry of Education, Science and Culture, and by the Cooperative Research Fund of the Primate Research Institute, Kyoto University.     

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.     

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.     

How social relationships influence a monkey's choice of feeding sites in the troop of Japanese macaques (Macaca fuscata fuscata) on Koshima islet

When the individual Japanese macaques of the Koshima troop feed on natural food, they usually feed alone. In situations where animals usually feed without other animals, there is a possibility that subordinate animals may avoid feeding sites at which dominant animals are feeding. This paper examines whether social relationships such as kinship or dominance exert any influence on an animal's choice of feeding sites, by analyzing episodes in which an animal approached and climbed into a tree where other animals were. As a result, it was found that social relationships did not influence whether an animal climbed into a tree where other animals were feeding, and that no particular age-sex pair co-fed. Agonistic interactions frequently occurred when the inter-individual distance was less than 1 m. From these findings, the feeding sites were divided into two spaces: (1) a tolerance feeding space, and (2) an intolerance feeding space. It is presumed that animals can feed without entering others' intolerance feeding spaces when food is abundant, as it was in the present study period. Thus social relationships do not influence an animal's choice of feeding sites in such a situation.     

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.     

Sexual maturation among members of a transported troop of Japanese macaques (Macaca fuscata)

Data on the sexual maturation of a transported natural troop of Japanese macaques were collected during the 1973–74 and 1974–75 breeding seasons. Analysis of the data revealed that the sexual maturation of many monkeys was delayed one to two years. It is suggested that the delay of sexual maturation is related to a failure of the pubescent-aged monkeys to attain appropriate weight levels after transportation. This study was partially supported by a University of Oregon, Department of Anthropology PHS Biomedical Science Grant 50-262-1112.     

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.     

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.     

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.     

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.     

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.