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.     

Male Masturbation in Free-Ranging Japanese Macaques

We studied masturbatory behavior of males over a 14-mo period in free-ranging Japanese macaques (Macaca fuscata yakui) on Yakushima island, Japan. We distinguished 2 types: (1) masturbation only and (2) masturbation with final ejaculation. Both types occurred in all 15 adult troop males. We calculated masturbation only as an index (M/h). It occurred over the whole year; however, it was more frequent during the mating than during the non-mating periods. Masturbation with ejaculation was restricted to the mating period. Male mating success correlated positively with social status. Both rate of masturbation only and masturbatory ejaculations increased as male social status and male mating success declined. Lower-ranking males had higher rates of masturbation only, i.e., they spent more time masturbating than higher-ranking males did. Lower-ranking males also had higher proportions of ejaculates for masturbation, while higher-ranking males used most of their ejaculates for mating.     

The calming effect of stimuli presentation on infant Japanese Macaques (Macaca fuscata) under stress situation: a preliminary study

In human newborns, presentation of sounds and odors under stress situations had a calming effect on behavioral and cortisol responses (Kawakami et al., 1996, 1997). These calming effects were examined with 10-day- and 15-day-old Japanese macaques. In Study 1, white noise presentation (Experimental conditions) at the blood sampling was compared with no sound presentation (Control conditions) at the blood sampling. White noise presentation has a calming effect on coded behavioral responses. In Study 2, lavender scent presentation (Experimental conditions) at the blood sampling was compared with no odor presentation (Control conditions) at the blood sampling. Lavender presentation has a calming effect on cortisol responses in the marginal level. From the data of these studies, the salivary cortisol levels were related to the cortisol levels in plasma. Our results may suggest the different effects of sound and odor on infant Japanese macaques.     

Distribution of Grooming Among Adult Females in a Large,Free-Ranging Group of Japanese Macaques

We analyzed grooming episodes recorded among adult females in a large, provisioned, free-ranging group of Japanese macaques (Macaca fuscata) at an individual level. Each female groomed on average 10 of the other 84 females, and 54% of them devoted 50% of their grooming to a single female grooming partner, which indicates that most females had grooming interactions with a relatively small subset of available females. Although 65% of the total grooming bouts were between related females, 25% of females disproportionately groomed unrelated females, 22% groomed related and unrelated females equally, and grooming was kin-biased for the remaining 53%. Moreover, 11 of 16 kin-groups included at least one female that groomed unrelated females significantly more often than related females. In 18% of unrelated dyads, grooming was directed down the hierarchy, in 58%, grooming was well-balanced between the two females, and in the remaining 25%, grooming was directed up the hierarchy. The results indicate that although Japanese macaques are considered a despotic species based on their dominance style, this group included some females that showed egalitarian tendencies, i.e., grooming was directed down the hierarchy or was well-balanced, and was directed toward unrelated females as often as or more often than toward related females. The presence of egalitarian individuals might be important to maintain a well-organized, female-bonded group.     

Parity-related differences in suckling behavior and nipple preference among free-ranging Japanese macaques

Suckling behavior of primiparae in free-ranging Japanese macaques (Macaca fuscata) was compared with that of multiparae at Jigokudani Monkey Park, the Shiga Heights, Nagano Prefecture, Japan, from April 1984 to June 1994. The estimated rates of milk secretion in a single preferred nipple among primiparae were lower than those among multiparae from birth to 5 months of age. Milk secretion capabilities of primiparous mothers, hence, appear to be inferior to those of multiparous mothers. In nutritive sucking, although Japanese macaque infants preferred one single nipple, nipple preferences in primiparae were weaker than those in multiparae. With supplementary two-nipple use during sucking, however, the infants of primiparae appear to overcome a suckling flaw of their primiparous mothers. After infants were 5 months of age and after a drop (from approximately 10% to approximately 5%) in the rates of milk secretion, however, milk secretion rates in a single preferred nipple among primiparae were similar to those in multiparae and the supplementary two-nipple use in primiparous mother-infant dyads disappeared. Am. J. Primatol. 42:331–339, 1997. © 1997 Wiley-Liss, Inc.     

Skewed sex ratios and female homosexual activity in Japanese macaques: An experimental analysis

In this paper we present the results of a behavioral experiment conducted to test whether homosexual consortships and sexual solicitations among female Japanese macaques (Macaca fuscata) increase in the context of operational sex ratios that are heavily skewed towards females. The study involved a baseline period of observation on an intact social group which had a female-biased sex ratio typical of this species. During the experimental period which followed, we created a sub-group with an operational sex ratio that was heavily skewed towards females. Compared to the baseline period, females solicited significantly more same-sex individuals for sex and formed significantly more homosexual consortships during the experimental period of the study. Females did not appear to engage in homosexual activity during the study's experimental period simply because they lacked heterosexual alternatives. Instead, we suggest that an abundance of certain types of preferred, same-sex sexual partners and/or a scarcity of opposite-sex sexual competitors best account for the increased levels of female homosexual behavior observed at this time.     

Population genetical study of Japanese macaques,Macaca fuscata,in the shimokita A1 troop,with special reference to genetic variability and relationships to Japanese macaques in other troops

The genetic variations of 35 individuals of the Shimokita A1 troop of mainland Japanese macaques,Macaca fuscata fuscata, which live at the northern end of the habitat of the species, were investigated using 33 electrophoretically detectable blood protein loci. Among the loci examined, six were polymorphic. The average heterozygosity per individual was calculated as 0.0442. This was the highest value among all troops of Japanese macaques so far investigated. The mainland macaques of the Shimokita A1 troop were more differentiated genetically from other mainland macaque troops than were Yaku macaques, the subspeciesM. f. yakui.     

Mirrors,monkeys, and group dynamics

When presented with his/her own reflection in a mirror (within an environment that is natural for that particular group of primates) the position that animal holds within the group affects his/her interpretation of that image. Each individual perceives the animal in the mirror to be another animal of equal circumstances as him/herself. An alpha animal sees a potential alpha animal attempting to take over the troop. A beta or lesser animal sees another non-alpha animal attempting to enter the troop through affiliation. In this study a group of zoo raised Japanese macaques were challenged with their own reflection in a mirror. Incidents of aggressive behavior rose in the alpha animals while all affiliative behavior ceased between members of the group. The lesser animals vied for time with the mirror, each attempting to be near the perceived con-specific.     

Grooming-at-a-distance by exchanging calls in non-human primates

The ‘social bonding hypothesis'' predicts that, in large social groups, functions of gestural grooming should be partially transferred to vocal interactions. Hence, vocal exchanges would have evolved in primates to play the role of grooming-at-a-distance in order to facilitate the maintenance of social cohesion. However, there are few empirical studies testing this hypothesis. To address this point, we compared the rate of contact call exchanges between females in two captive groups of Japanese macaques as a function of female age, dominance rank, genetic relatedness and social affinity measured by spatial proximity and grooming interactions. We found a significant positive relationship between the time spent on grooming by two females and the frequency with which they exchanged calls. Our results conform to the predictions of the social bonding hypothesis, i.e. vocal exchanges can be interpreted as grooming-at-a-distance.     

Influence of Female Copulation Calls on Male Sexual Behavior in Captive Macaca fascicularis

We investigated the function of copulation calls—vocalizations by females during mating—in captive groups of long-tailed macaques. We tested predictions of the contest-competition, sperm competition, synchronized orgasms, mate again, alpha-male notification and graded-signal hypotheses. We observed 371 copulations of 36 females wherein the presence or absence of a copulation call was clear. Females call equally often with different males and shortly after ejaculation. Copulation calls occurred equally with copulations with and without ejaculation. Calls did not incite disruptions of the mating. Following calls females mated again, more often than expected, with their mating partner. Both pregnant and fertile females uttered copulation calls. Two females conceived and mated mainly with the alpha male then. We conclude that copulation calls do not incite male contest competition for sexual access to females and that it is unlikely that calls synchronize male and female orgasms. Several hypotheses remain plausible, but not all predictions are borne out unequivocably. This alerts us to the possibility that the calls could have multiple beneficial effects; natural selection might strike a compromise among functions. Investigation of the mate again, sperm competition and alpha-male notification hypotheses, and of hypotheses not tested in our study concerning female breeding overlap and female-female agonism, is required.     

Grooming relationships of adolescent orphans in a free-ranging group of Japanese macaques (Macaca fuscata) at Katsuyama: a comparison among orphans with sisters, orphans without sisters, and females with a surviving mother

The present study examined grooming relationships of adolescent females in a free-ranging group of Japanese macaques (Macaca fuscata) at Katsuyama. To assess whether the loss of the mother influenced the grooming relationships of adolescent females (5–7 years old), we compared the time spent in grooming interactions and the number of grooming partners among the following three groups: 6 adolescent orphans with sisters, 9 adolescent orphans without sisters, and 11 adolescent non-orphans with surviving mothers. In Japanese macaques, grooming most frequently occurs between mothers and their daughters. Therefore, it is expected that if the mother is lost, orphans will devote less time to grooming interactions than non-orphans. However, the time spent in overall grooming interactions did not differ among the three groups. While non-orphans maintained grooming relationships with their mothers, orphans acquired alternative grooming relationships with other group members. Orphans adopted two kinds of tactics to compensate for the loss of the mother. First, adolescent orphans with sisters developed more affiliative grooming relationships with their sisters than non-orphans with sisters. Secondly, adolescent orphans without sisters spent more time in grooming interactions with same-aged females and non-related adult females. Moreover, regarding grooming interactions with same-aged females and non-related adult females, orphans without sisters had a larger number of grooming partners than non-orphans. These results indicate that adolescent females have enough flexibility to develop their grooming network after the loss of their mothers, and that the lack of mother and sisters might accelerate socialization of adolescent females and enable them to be integrated in reciprocal adult grooming relationships.     

A fatal attack on an unweaned infant by a non-resident male in a free-ranging group of Japanese macaques (Macaca fuscata) at Katsuyama

A non-resident male attacked a 4-month-old unweaned infant in a free-ranging group of Japanese macaques (Macaca fuscata) and it died 2 days later from a severe wound. When the infant was alone at the feeding site, the non-resident male rushed at it. The infant ran away as soon as it became aware of the male, but was captured. The male bit the infant on its hand, foot, and arm, while continuously scanning his surroundings. He did not kill the infant immediately and, after the infant escaped, he did not chase or attack it at all. Although the infants right arm was bleeding heavily, it survived until the following day. The infanticide occurred a few weeks before the mating season began, so the victims mother soon resumed estrus and the subsequent inter-birth interval was shortened. The first-, second-, and fourth-ranking adult males had died or disappeared a few months before this infanticide, and there were no other group members near the infant when the infanticidal male appeared. The infanticidal male had not been observed before this incident. Compared to one-male groups, the occurrence of infanticide in multi-male groups of Japanese macaques is extremely infrequent. However, in other reports of infanticide in Japanese macaques as well as in this case, it has been noted that infanticide is likely to occur in the pre- or early-mating season, when there are no resident males to defend the infant against attacks, and when a threatening male is least likely to be the infants father.Electronic Supplementary Material Supplementary material is available for this article at     

Demography and reproductive parameters of a free-ranging group of Japanese macaques (Macaca fuscata) at Katsuyama

Demographic and reproductive data were analyzed for a period of 28 years in the females of a free-ranging group of Japanese macaques at Katsuyama, Okayama Prefecture, Japan. The overall mean, age-specific fecundity rates were 5.43% for 4-year-olds and 41.86% for 5-year-olds, increasing to a peak of 66.67% for 13-year-olds. Fecundity remained relatively high (52.31–54.24%) in 16–19-year-olds, but decreased sharply (45.45–17.86%) in 20–23-year-olds, and became very low in 24–26-year-olds. Females aged 27 years or more did not produce infants. The average age at first birth was 5.41 years. Births peaked in mid-May. The timing of the first births each year remained essentially unchanged during the study period, whereas the timing of the median and last births shifted towards the later part of the season. The mean interbirth interval for all females was 1.56 years. The value was 1.54 years for multiparous females and 1.29 years for females following infant loss. These intervals were significantly shorter than those for primiparous females, and females with surviving infants. The overall mean infant mortality within the first year of life was 10.2%. The value was 8.6% for 10–14-year-olds, and 7.5% for 15–19-year-olds. The timing of birth differed among the four female matrilineal dominance rank-classes. The female fecundity rates increased as a function of matrilineal dominance rank. It is suggested that all demographic and reproductive data should be analyzed in detail with respect to the group's history.     

Courtship behaviour in Japanese macaques during heterosexual and homosexual consortships

Female Japanese macaques (Macaca fuscata) in the Arashiyama population near Kyoto, Japan, are unusual, in that they exhibit what many would consider to be male-typical sexual characteristics. Specifically, they mount other females within the context of temporary, but exclusive, sexual relationships (i.e., homosexual consortships) and they sometimes exhibit a preference for female sexual partners, even when given the choice of a sexually motivated male alternative. In this study, we examined whether female Japanese macaques also exhibited male-typical patterns of courtship behaviour during homosexual consortships. Data were collected on courtship behaviour during heterosexual and homosexual consortships in free-ranging Japanese macaques from the Arashiyama (Japan) population. We analyzed the occurrence of 12 different courtship behaviours during 3374 heterosexual inter-mount intervals and 1412 homosexual inter-mount intervals. Sex differences between heterosexually consorting males and females existed for only two of the 12 courtship behaviours we investigated: inclined-back presentations and sexual vocalizations. Dominant and subordinate homosexually consorting females were sex-typical in their expression of inclined-back presentations and sexual vocalizations. Consequently, facultative same-sex sexual partner preference, mounting and consortships do not co-occur with male-typical patterns of courtship behaviour in female Japanese macaques.