On the handedness of Japanese monkeys

Forty-one monkeys living on the Koshima Island were tested for handedness by throwing a peanut 10 or 20 times toward each subject and recording which hand was used to pick it up. Handedness was judged at the 5% level of confidence. Animals showing no preference for the left or right hand after 20 trials were considered to be ambidextrous. The following distribution of handedness was found: left-handed, 17 (41%); right-handed, 8 (20%); ambidextrous, 16 (39%). These findings were compared with other studies on the handedness of Japanese monkeys. Handed monkeys outnumber the ambidextrous ones and the left-handed monkeys outnumber the right-handed ones. The characteristic distribution of handedness was shown to be irrespective of troop. By looking over the data from these different sources, the proportions of the left-handed, the ambidextrous, and the right-handed in Japanese monkeys were estimated at 39%, 33%, and 28% respectively. The method used in this study was compared withKawai's catching behavior and reasons for disagreement between judgments of handedness were discussed.     

Preferred hand use in the japanese macaque troop,arashiyama-R,during visually guided reaching for food pellets

A troop of Japanese macaques, which consisted of about 45 monkeys and was raised at the Primate Research Institute, Kyoto University, was observed during the period from April to June 1988, to evaluate the preferred choice of hand when reaching for food pellets. Nineteen monkeys showed a consistent left-hand preference, 5 monkeys showed a consistent right-hand preference, and the remaining 20 monkeys did not reveal a preference for either hand. Monkeys of more than 8 years of age tended to exhibit a greater left-hand preference with a lower incidence of absence of preference. A tendency to use either left or right hand increased with increasing age: the correlation ratio between age in years and the index to use either hand, designated as the laterality index, was significant (t-test,p<0.001,N=42). Children of mothers with a left-hand preference tended to show a left-hand preference.     

Hand preference during unimanual and bimanual reaching actions in Sichuan snub-nosed monkeys (Rhinopithecus roxellana)

Hand preferences were investigated during one unimanual action (food-reaching) and one bimanual action (mount-reaching) in a semi-free-ranging group of Sichuan snub-nosed monkeys (Rhinopithecus roxellana) in Zhouzhi National Nature Reserve, Qinling Mountains of China. Nine of 14 individuals tested on the unimanual food-reaching action and all six individuals tested on the bimanual mount-reaching action exhibited a manual preference. Both significant right- and left-handed preferences were observed in the two actions. Sex did not affect either direction or strength of hand preference in the unimanual action. Hand preference for the bimanual action was stable over time, and the strength of hand preference was significantly stronger in the bimanual action than in the unimanual action.     

Play behavior in immature moor macaques (Macaca maura) and Japanese macaques (Macaca fuscata)

Play is widespread across mammalian taxa, but species strongly vary in the ways they play. In less despotic primate species (i.e., with less steep dominance hierarchies, less severe conflicts, and more reconciliation), play has been described as being more frequent, cooperative, and freely expressed. To study the link between social play and dominance style, we compared play behavior in free-ranging infants, juveniles and subadults of more despotic Japanese macaques (Macaca fuscata, N = 24) and less despotic moor macaques (Macaca maura, N = 17). We found interspecific differences in play behavior that corresponded with the contrasting dominance styles of the study species, largely confirming our predictions. In particular, moor macaques spent a larger proportion of time in solitary and social play than Japanese macaques, while Japanese macaques spent a larger proportion of time in grooming interactions. In moor macaques, play sessions included more players, a larger variety of play behaviors, greater play face rates, a greater proportion of time in contact play, and a higher rate of reciprocal play-biting than in Japanese macaques. Aggressive escalations were not common, but more frequent in Japanese macaques. Finally, a higher frequency of play faces during play sessions predicted the occurrence of more reciprocal play-bites, but not the proportion of time spent in contact play behaviors. Additional studies on other groups and species will allow a better understanding of the link between dominance style and social play.     

How laboratory-raised Japanese monkeys (Macaca fuscata) perceive rotated photographs of monkeys: Evidence for an inversion effect in face perception

Five laboratory-raised Japanese monkeys (Macaca fuscata) were presented various types of photographs of Japanese and rhesus monkeys (Macaca mulatta) in upright, horizontal, and inverted orientations in a sensory-reinforcement experiment. The ratio of the duration of potential viewing time for the photographs which the subjects controlled to the interval between subject-controlled presentations of them (the D/I score) was used as a measure of preference for the photographs. When inverted photographs were presented, the D/I scores were lower than for upright photographs. The difference in D/I scores between photographs of the two species, which indicated discriminability between them, also diminished when the photographs were inverted. The results obtained suggest an inversion effect in face perception in macaque monkeys.     

川金丝猴摄食过程中“手”的选择使用

本文对20只川金丝猴(Rhinopithecus roxellana) 摄食过程中左右“手”的使用频次进行了观察和分析。在样本较小的条件下, 尽管被研究动物中有一半个体明显地倾向于使用右手, 但没有发现统计学上明显的种群水平的单手利现象。虽然本研究中成体金丝猴使用右手的比例在数量上高于幼体, 但在统计学上, 单手利行为不存在明显的年龄差别; 同样, 单手利用行为也不存在统计学上明显的性别差异。建议在未来的研究中采用大样本在解决复杂问题过程中对单手利行为做进一步的探讨。     

叶猴(Presbytis)、金丝猴(Rhinopithecus)、长臂猿(Hylobates)自由取食时的利手现象

本文报道叶猴、金丝猴、长臂猿自由取食时的利手现象。本研究共用金丝猴12只(雄性8只,雌性4只),叶猴25只(雄性16只、雌性9只),长臂猿5只(雄性3只,雌性2只)。对每个动物而言,总观察次数不少于30次,其结果显示:在雄性金丝猴中,62.5％的动物显示右利,25％显示主利,12.5％无利手现象。在雄性叶猴中,62.5％的动物显示右利,18.7％显示左利,18.7％无利手现象。在3只雄性长臂猿中,2只显示右利,一只无利手现象。 统计结果表明:雄性金丝猴有明显的右利手现象(P<0.05),雄性叶猴右利手现象接近显著(P=0.06),长臂猿因观察数量太少,未进行统计。 在上述三种动物中,雌性个体无利手现象。 木工作结果提示:(1)雄性金丝猴,叶猴在自由取食时具有右利手现象,长臂猿也可能有右利手现象,(2)大脑两半球的不对称性与性别有关。     

Somatometrical features of Japanese monkeys in the Koshima islet: In viewpoint of somatometry,growth, and sexual maturation

The Japanese monkeys inhabiting Koshima islet were investigated morphologically, and compared with those living in other areas of Japan. The morphological features of the Koshima monkeys are thought to reflect many interrelated factors. Their body size is the smallest inMacaca fuscata fuscata. The lower latitude and the warmer winter of the islet represent the major factors in this small body size. Another physical characteristic is their longer limbs, which may be related to the same environmental factors. The adult males of the Koshima troop show the widest variation, while the variation in the adult females is the narrowest, among the troops ofMacaca fuscata examined. This may be explained either by sexually differentiated growth, that is, males continue to grow considerably after 8 years of age, whereas females do not; or by isolation, that is, males sometimes immigrate into or emigrate from the islet, whereas almost of all the females remain there. It was found that the influence of food limitations on body weight depends on sex and age; babies and juveniles, and adult males did not lose their body weight, but monkeys aged from 3 to 7 years and adult females had lost much weight compared to those of the same ages and sexes measured in 1963 (feeding was not limited). This fact may support the idea of “sex-age-class selection” proposed byMori (1979), but the weight loss pattern could be explained by changes of body composition with growth. The growth of the anterior trunk length, too, was restrained. Sexual maturation in males was delayed by at least one year.     

Lipofuscin in the corpus luteum of macaque ovaries

The present study examined the histochemistry of pigments in the corpus luteum of the ovaries of cynomolgus monkeys (Macaca fascicularis), Japanese monkeys (Macaca fuscata), and rhesus monkeys (Macaca mulatta). Yellowish brown pigments were found in the regressing corpus luteum cells. Histochemical studies revealed that these pigments consisted of lipofuscin, the so-called age pigment. The findings obtained suggest that accumulation of lipofuscin might be related to cellular aging of the corpus luteum.     

Species preference by infant macaques with controlled social experience

In Experiment 1, infant Japanese monkeys and rhesus monkeys were artificially reared in pairs with conspecific or heterospecific monkeys. Preferences of these monkeys for a variety of pictures of Japanese monkeys and rhesus monkeys were repeatedly tested during the first 1 or 2 years of life. The duration of lever-pressing responses to see those pictures was a measure of the preference. All monkeys, Japanese or rhesus, preferred pictures of rhesus monkeys to pictures of Japanese monkeys, without regard to their social experiences. Experiment 2, with an adult Japanese monkey as the subject, and Experiment 3, with different pictures as stimuli, suggested that this preference was not a consequence of any bias in the pictures used. In Experiment 4, a Japanese monkey reared by a rhesus foster mother and rhesus monkeys reared by Japanese monkey mothers received the same preference test. The Japanese monkey infant preferred to see pictures of rhesus monkeys. However, rhesus infants did not show clear species preferences. These results suggest that infants of both Japanese and rhesus monkeys have a native tendency to prefer to see physical characteristics of rhesus monkeys over Japanese monkeys.     

Female reproductive cycles and the sexual behavior of moor macaques (Macaca maurus) in their natural habitat,South Sulawesi,Indonesia

The female reproductive cycles and sexual behavior of moor macaques (Macaca maurus) were studied in their natural habitat. Female moor macaques showed repeated perineal swelling. The average cycle length was 36.2 days and the mean duration of swelling was 11.9 days. The estimated duration of gestation in two observed cases was 175 and 176 days, respectively. Females did not exhibit post-conception sexual swelling. Males appeared to ejaculate in multi-mounts. Serial mounting by the alpha male was concentrated on swelling females, while second- and third-ranking males sometimes mounted non-swelling females in series.     

Anatomical brain asymmetry in monkeys: frontal, temporoparietal, and limbic cortex in Macaca

Measurements evaluating possible cerebral hemispheric asymmetries were taken by hand on frontal, parietal, and temporal cortex on 60 formalin-fixed Macaca mulatta and Macaca fascicularis brain specimens. No statistically significant (P less than 0.05) right/left side differences in the mean length of four sulci in visual-processing areas of the cortex were found. The sulcus adjacent to the region cytoarchitecturally homologous to the motor speech area in the human brain did not show pronounced asymmetry. In both species, however, a small parietal lobe sulcus showed greater development on the left hemisphere than in the right. In measurements made using digital planimetry, right/left side differences in the area of the dorsal cingulate gyrus were not found. Behavioral evidence suggests that monkeys do not exhibit a consistent pattern of cerebral dominance for functions associated with most of these regions of the brain.     

A study of correlates of hand preferences in squirrel monkeys (Saimiri sciureus)

The purpose of this study was to test the influence of sex, age, social rank, matriline membership, posture, and visual and tactual motor control on manual preferences inSaimiri sciureus. A well-established social group of 12 squirrel monkeys, aged 2 to 14 yrs and consisting of two matrilines with social rank known for each animal, was presented with four different food-reaching tasks and assessed for hand preferences with a minimum of 100 reaches per animal. Frequency of occurrence of hand preferences at the group level and degree of hand preferences at the individual level depended on posture and on whether the reaching act took place under visual or tactual guidance. Sex, age, social rank, and matriline membership were not found to determine frequency of occurrence, direction or degree of hand preferences with the exception of one task in which a significant negative correlation between the degree of hand preference and age was found. Nine out of 12 monkeys showed task-dependent changes in the hand they used preferentially while only three animals preferred the same hand in all four tasks. Significant preferences for the use of right or left hand on a given task were distributed almost equally between individuals. Thus, the results of this study suggest task-specific demands like posture and/or whether reaching was visually or tactually guided to be the major correlates of hand preferences in food-reaching tasks in squirrel monkeys.     

The influence of snowfall,temperature and social relationships on sleeping clusters of Japanese monkeys during winter in Shiga Heights

We studied Japanese monkeys (Macaca fuscata) of the Shiga A₁ troop at their sleeping sites in Shiga Heights, Japan, for 41 nights during 3 winters. Monkeys chose their sleeping sites in Japanese cedars and in deciduous broad-leaved forests on non-snowing nights and in Japanese cedar forests on snowing nights. We counted 399 sleeping clusters in which 2 or more monkeys remained in physical contact through the night and 43 solitary sleeping monkeys, though monkeys did not maintain physical contact with others in the daytime. We found 397 clusters on tree branches and 2 clusters on rocks. The mean size of huddling clusters was 3.06±1.22 SD. The cluster size (3.17±1.26 SD) at lower ambient temperatures between −7 and −4°C was larger than that at higher temperatures between −2 and 4°C (cluster size 2.88±1.13 SD). Most clusters were composed of kin. Females kept close to related females in the daytime and huddled with them at night. The highest-ranking male mainly huddled with his kin and his familiar females. Other males kept farther apart from each other in the daytime, probably to avoid social conflicts. Through cold winter nights, however, such males reduced inter-individual distances and huddled with other males. Japanese monkeys appear to recognize three types of inter-individual distances: an intimate distance less than 1 m, a personal distance of 1–3 m and a social distance of 3–20 m; they change their inter-individual distances according to social and ecological circumstances.     

Consistency of hand preference across low-level and high-level tasks in capuchin monkeys (Cebus apella)

Numerous studies investigating behavioral lateralization in capuchins have been published. Although some research groups have reported a population-level hand preference, other researchers have argued that capuchins do not show hand preference at the population level. As task complexity influences the expression of handedness in other primate species, the purpose of this study was to collect hand preference data across a variety of high- and low-level tasks to evaluate how task complexity influences the expression of hand preference in capuchins. We tested eleven captive brown capuchin monkeys (Cebus apella) to determine if they show consistent hand preferences across multiple high- and low-level tasks. Capuchins were expected to display high intertask consistency across the high-level tasks but not the low-level tasks. Although most individuals showed significant hand preferences for each task, only two of the high-level tasks that involved similar hand motions were significantly positively correlated, indicating consistency of hand preference across these tasks only. None of the tasks elicited a group-level hand preference. High-level tasks elicited a greater strength of hand preference than did low-level tasks. No sex differences were found for the direction or strength of hand preference for any task. These results contribute to the growing database of primate laterality and provide additional evidence that capuchins do not display group-level hand preferences.     

Laterality in spontaneous motor activity of chimpanzees and squirrel monkeys

Varieties of nonmanipulative motor responses were observed in chimpanzees and squirrel monkeys. Chimpanzees displayed a right hand preference for touching their inanimate environments but used their right and left hands equally for touching their faces and their bodies. The latter result was not consistent with previous reports of a left hand preference for face touching in apes. The right hand preference for environmental touching was stronger in male than in female chimpanzees. Squirrel monkeys had a right preference for combined hand and foot responses directed to their bodies, but expressed no handedness for environmentally directed touching. These limb preferences in chimpanzees and squirrel monkeys indicate that neither precise, complex manipulation nor postural instability are necessary conditions for population level hand preferences. Factor analysis of the chimpanzee manual responses showed distinct self and environmentally directed factors. Analysis of the squirrel monkey data also showed self and environmental factors, except that body scratching had a negative loading on the environmental factor. This latter result suggests that self-scratching by squirrel monkeys is a displacement activity that suppresses manual exploration of the environment. © 1992 Wiley-Liss, Inc.     

Factors Affecting Proximity Among Members of a Wild Group of Moor Macaques During Feeding,Moving, and Resting

We studied the effects of kinship, age, sex, and other factors on patterns of spatial proximity among group members in a wild group of moor macaques (Macaca maurus) in Sulawesi, Indonesia. We assessed the importance of each factor via multiple linear regression analyses. Moor macaques stay close to their matrilineal relatives more frequently when the group moves or rests than when they feed. Subjects of similar age, sex, or rank tended to stay close to each other. Females were in the proximity of females with newborn infants regardless of the phase of activity of the group. Kinship may have less effect on proximity during feeding in moor macaques than in Japanese macaques. Weak effects of kinship during feeding may result from weak contest competition for food within the group.     

Postnatal changes in the blood of Japanese monkeys (Macaca fuscata): I. Immunoglobulins Ig G,Ig M and Ig A

The levels of immunoglobulin Ig G, Ig M and Ig A in the plasma of Japanese monkeys (Macaca fuscata) from birth to 180 days of age were examined. The level of Ig G reached a minimum at 50 to 80 days of age, when the neonates weighed 600–800 g. Anti streptolysin O antibody decreased from birth with age and was not detected from day 80 to 150. The level of Ig M showed a temporary peak at 20–30 days of age and increased again from 60–80 days. The concentration of Ig A increased gradually to reach 20% of the adult level at day 180.     

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.     

Clinical examinations of the Japanese monkey (Macaca fuscata)

Since 1962 clinical examinations have been performed on all 466 Japanese monkeys from the troops of the western part of Japan.During the external inspection we found a few cases of malformation of the hand and foot in some troops, but except for these they were in good physical condition, negative in tuberculin test and in Shigella and Salmonella infection.In all troops a high rate of helminthic infection was detected and there was a difference in the rate of occurrence of certain helminths betweenMacaca fuscata fuscata andM. fuscata yakui. No single case with the antibody to the B Virus was encountered, and it seems that no infection of the B Virus is present among the Japanese monkey.The free-ranging condition under which the Japanese monkey inhabits in troops seems to be satisfactory and they seem to have no serious problem of any kind at present.