Menstrual-cycle phase and sexual behavior in semi-free-ranging stumptail macaques (Macaca arctoides)

The sexual behavior and female reproductive cycles of a group of island-dwelling stumptail macaques (Macaca arctoides)were monitored over a 6-month period, yielding 530 observation hr and 268 copulations. Compared to nondominant males, the dominant male copulated at a relatively high rate throughout the cycle, but largely with one high-ranking female. The non-dominant males copulated most frequently at midcycle. Female presenting was highest at midcycle, but only to the dominant male. Cross-study discrepancies may be due to different observation methods and restricted environmental conditions that mask female-initiated sexual behavior. The more naturalistic setting of this study allowed for a fuller expression of proceptivity. Contrary to some previous conclusions, present findings suggest that both hormonal and socioenvironmental factors influence the patterns of sexual behavior found in stumptail macaque colonies.     

Female menstrual cyclicity and sexual behavior in stumptail Macaques (Macaca arctoides)

The sexual behavior and female reproductive cycles of a captive group of stumptail macaques (Macaca arctoides)were monitored during a 12-month period. The data, consisting of 303 ad libitummounts and copulations and 125 hr of focal-female testing, were analyzed by their frequency of occurrence during the three hormonal phases of the female menstrual cycle. Regularly cycling females exhibited statistically higher frequencies of all sexual behaviors compared to the amenorrheal controls. Contrary to previous reports which indicate no variation in sexual behavior throughout the reproductive cycle in this species, our data show marked increases in copulations during the periovulatory phase. Male dominance rank is associated with sexual behavior only at midcycle.     

Reproduction and social rank in female stumptail Macaques (Macaca arctoides)

Reproductive physiology was studied in female stumptail macaques. Initially the monkeys were housed indoors (individually and in small groups) and later as one large (92 individuals) social group in an outdoor cage. Most data were collected during the 4-year outdoor period. Plasma progesterone determination in blood samples taken at weekly intervals allowed estimation of ovulation and conception dates. The age at first ovulation (X =3.73 years) was positively correlated with body weight at 3 years of age. The average age at first birth was 4.90 years. Gestation lengths averaged 176.6 days. Following a live birth ovulations returned after a mean interval of 11 months but following an abortion or still birth this interval was 1 month. Usually a number of ovulatory cycles (X =2.37) preceded a conception. Interbirth intervals (IBIs) in the outdoor cage (X =619.4 days) were significantly longer than IBIs during the indoor period (X =523.1), because indoors the infants were weaned at the age of 7 months, while outdoors weaning occurred more naturally. IBIs following abortions or still births (X =291.9 days) were significantly shorter than IBIs following live births. Age at first ovulation, age at first birth, IBIs, and infant production rates were not correlated with dominance rank. Ovarian cycle lengths (X =30.2 days, mode = 28 days) were comparable to previously reported data from laboratory-housed stumptails. No systematic seasonal fluctuations were found in the onset of sexual maturity, in ovarian cycle lengths, in copulation frequencies, and in distribution of births.     

Heterosexual interactions of pairs of laboratory-housed stumptail macaques (Macaca arctoides) under continuous observation with closed-circuit video recording

Female-male interaction of heterosexual pairs of stumptail macaques, housed together continuously, was studied 24 hr per day using closed-circuit video recording. Two pairs were studied for approximately 2 months each. Although no generalizations can be made from such a small sample, no aspect of behavioral interaction varied significantly with the stage of the menstrual cycle of the female partner. Copulation occurred regularly but only during the daylight hours. Both pairs showed several peak ejaculation days (5–21 ejaculations/day), which were distributed throughout the entire menstrual cycle. In general, the highest number of ejaculations was observed to occur when the animals were put together either for the first time or following a separation of a few days. In one pair the female became pregnant, and from the fifth week of pregnancy onward there was a gradual increase in male aggression, coinciding with a decrease in male sexual and grooming behavior. In a second study eight different pairs were observed during the first day together and male copulatory behavior was studied. Two patterns of copulatory behavior could be discerned: pairs displaying a high number of ejaculations (19–38) and pairs displaying a low number of ejaculations (4–8). With regard to the interejaculatory interval (IEI), the male stumptail appeared to be unique. In contrast to what has been reported for other mammals, i.e., a steady increase in IEI with subsequent ejaculations, the stumptail showed increasing IEIs only during the first three to four, as well as between the last, ejaculations; in between, the IEI remained relatively constant. The maximum number of consecutive ejaculations observed was 38, displayed during a 10-hr time period (mean (± SEM)IEI, 12.9 ± 3.5 min).     

Responses to animal stimulus photographs in stumptailed macaques (Macaca arctoides)

Interest in their animate environment was studied in a captive group of 11 stumptailed macaques (Macaca arctoides). Subjects were shown projected photographic slides, most of which showed a single individual primate or non-primate. The measure of interest was the duration of viewing. Results showed that adult females exhibited more interest towards stumptailed macaques versus other macaques species, and towards adult females carrying infants versus adult females alone. Data concerning non-primates showed that subjects were especially interested by photographs of felids; this effect was partly due to the presence of two frontal and conspicuous eyes in felids.     

Social communication among captive stump-tailed macaques (Macaca arctoides)

I compared the frequency of occurrence, contextual usage, and meaning of some of the most prominent gestural signals in stump-tailed macaques. I recorded the occurrence of 15 visual and tactile behavior patterns in a multimale multifemale captive group of stump-tailed macaques with the behavior sampling method in 100 hr of observation and analyzed the data via factor analysis and analyis of variance. The hindquarter presentation was the most frequent gesture. It was displayed by subordinates to appease dominants even in the absence of impending risk of aggression. Bared-teeth, lip-smack, teeth-chatter, and present-arm are submissive signals as well, but they differ from the presentation and from one another in their contextual usage. Nonthrusting mount, hip-touch, hip-clasp, and genital manipulation are directed down the hierarchy and appear to reflect dominance, reassurance, protection, or bonding. Mock-bite is a ritualized aggressive behavior pattern, often used to resolve uncertain dominance relationships. Ventroventral embrace occurs as a female bonding pattern. Overall, most gestural signals in stump-tailed macaques relate to dominance and submission and, to a lesser extent, social bonding.     

Video-induced yawning in stumptail macaques (Macaca arctoides)

This study reports the first experimental exploration of possible contagious yawning in monkeys. Twenty-two stumptail macaques (Macaca arctoides) were presented with video clips of either yawns or control mouth movements by conspecifics. At a group level, monkeys yawned significantly more often during and just after the yawn tape than the control tape. Supplementary analysis revealed that the yawn tape also elicited significantly more self-directed scratching responses than the control tape, which suggests that yawning might have been caused by tension arising from viewing the yawn tape. Understanding to what extent the observed effect resembles contagious yawning as found in humans and chimpanzees requires more detailed experimentation.     

Non-seasonal breeding pattterns in stumptail macaques (Macaca arctoides)

This paper summarizes published reports of breeding patterns across the genusMacaca. Patterns range from strictly seasonal to non-seasonal. Data on sexual behavior and birth patterns are presented which confirm previous reports of non-seasonality forMacaca arctoides. In a captive colony, 63 births were recorded, and individuals were born during every month of the year. Heterosexual mounting activity was recorded over a two-year period and occurred during every month of that period. It is clear thatM. arctoides does not exhibit the seasonal cyclicity observed in some other macaque species.     

Environmental enrichment for captive stumptail macaques (Macaca arctoides)

Background  The behavior of animals is modified by captivity. Environmental enrichment (EE) is a program designed to enhance the welfare of confined animals by providing them with a more stimulating background. This is carried out by the implementation of a series of activities that encourages them to present behaviors typical of their species, as well as keeps them active. The aim of this study was the evaluation of the influence of the EE in the behavioral variables in a colony of 24 stumptail macaques ( Macaca arctoides ). Our hypothesis is that the application of this program will reduce aggression, stereotypes and coprophilia behaviors and, at the same time, will increase exploration and solitary play.
Methods  The behavioral frequency previous to EE was compared with that during EE implementation.
Results  Our results showed that aggression, coprophilia stereotypic behaviors and social play were significantly reduced during EE, whereas exploration was significantly enhanced. The response of the individuals according to gender was similar for both sexes.
Conclusions  Environmental enrichment programs are indispensable for captive animals' wellbeing as they reduce aggression and stress while providing animals both physical and cognitive entertainment.     

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.     

Measuring male-female relationships during the mating season in wild Japanese macaques (Macaca fuscata yakui)

Heterosexual relationships during one mating season were examined in a wild troop of Japanese macaques (Macaca fuscata yakui) on Yakushima Island, Japan. Validation tests of putative mate choice behaviors demonstrated that female initiation and maintenance of proximity, female lookback at the male, and sexual presents to the male, were associated with increased mating. Male grooming the female was also associated with increased mating. Ten dyadic social behaviors were subject to principal components analysis to empirically define behavioral dimensions of male-female relationships. The analysis yielded four relationship dimensions: ‘Mutual Choice and Male Coercion,’ ‘Female Choice’ (two types), and ‘Mutual Choice’ Dyads tended to be characterized by more than one dimension. The results suggested that females sought matings with multiple males of various dominance ranks. Female relationships with high ranking males contained elements of male coercion and mate guarding, however, because these males attempted to inhibit females from mating with lower ranking males. The correlation between each relationship dimension and mating success depended, in part, on the dominance rank of males. Relationships involving high ranking males, which were most likely to contain elements of male coercion and mate guarding, were associated with mating success. Relationships involving low ranking males, which usually lacked such coercive elements. were less strongly correlated with mating success. These results, obtained from a wild troop, are compared to those previously obtained in captive and provisioned groups of Japanese macaques.     

Gestation length in rhesus macaques (Macaca mulatta)

We describe some of the sources of variation in gestation length among rhesus macaques. the data were obtained from the timed-mating breeding program at the California Regional Primate Research Center (CRPRC). Information about approximately 700 pregnancies that resulted in spontaneous vaginal deliveries of liveborn young is presented. The average length of these pregnancies was 166.5 days. In this population, older females with higher parities had significantly longer pregnancies and significantly heavier infants than other females did. Other factors, including infant sex, month of conception, maternal reproductive history, and paternal identity, had no consistent effect upon gestation length.     

A comparison of the mating behavior of adolescent and adult female rhesus macaques (Macaca mulatta)

This study compares adult and adolescent female rhesus macaques with regard to (1) characteristics of their copulatory partners, (2) their proceptive behaviors, and (3) adult male behaviors toward them during estrus. We conducted focal follows of 24 adolescent and 65 adult free-ranging estrous female rhesus macaques on Cayo Santiago during two mating seasons. Compared to adult females, adolescents presented sexually to males at higher rates; copulated more frequently with rankless young male, and extra-group males; and, in one of two mating seasons, were ignored more frequently by males to whom they presented sexually. Adolescents tended to copulate with ranked, resident males at higher frequencies on days when the operational sex ratio (adult males:estrous adult females) was high. Males directed “muzzle-up” signals to adolescents at lower rates than to adults in one of two mating seasons, although this effect vanished when males who might have fathered adolescent females were excluded from analysis. Adolescents did not differ consistently from adults in strength of the correlation between proximity maintenance (dyadic Hinde's Index) and copulation rate, or in approach rate to males. Adolescent females, relative to adult females, presented sexually more to rankless young males, but did not present more to ranked, resident males. Both proximate (e.g. endocrine) and ultimate (e.g. differential fecundity; female-female mate competition) explanations may account for the reported differences between adult and adolescent female rhesus macaque sexuality.     

Group fission in a semifree-ranging population of Barbary macaques (Macaca sylvanus)

During a 16-month study of semifree-ranging Barbary macaques (Macaca sylvanus) the group under observation divided into two groups. Observations were carried out in 1987–1988, at «La Montagne des Singes,” Kintzheim, France. A subgroup of monkeys, which was already cohesive at the beginning of the study, became progressively autonomous in relation to the rest of the main group, during the mating season. Overt aggression between the males of the two groups during this period brought about the fission. Only low-ranking genealogies left their group of origin. Dominance relations between females remained identical in both groups except for one lineage. The alpha male and the alpha female of the subgroup had a close relationship before the fission occurred. The sequence of agonistic intergroup relations is described and analyzed in relation to male sexual competition and female alliance power. The results suggest that: (1) the males of the subgroup instigated the fission because it was the best strategy for them to counter sexual competition; and (2) the females followed the males in order to maintain their alliance network, necessary to insure their dominance status over subordinate females.     

Aspects of fight interference in free-ranging and compound-dwelling rhesus macaques (Macaca mulatta)

Patterns of fight interference (agonistic aiding) were compared among three groups of rhesus monkeys (Macaca mulatta) living in two settings: (1) two groups at Cayo Santiago (Caribbean Primate Center); and (2) one group at the Yerkes Regional Primate Research Center (YRPRC). A total of 1,227 interference episodes were recorded in 1,650 hours of observation. The only significant intergroup difference was the increased tendency of males at YRPRC to aid aggressors rather than victims. Among other findings, females aided relatives, interfered against target animals dominant to themselves, aided juveniles, and aided victims more consistently and frequently than did males. Importantly, female interference became more male-like in pattern when aid was given to nonrelatives. Neither the dominant males nor males in general displayed a unique or consistent tendency to interfere in fights in a manner which could be interpreted as controlling aggression. The males' interference patterns also did not suggest they were forming coalitions to either attain or defend status rankings. It is concluded that, overall, observations of compound-dwelling and free-ranging rhesus monkeys reveal similar relationships. Further, while female rhesus monkeys interfered in fights in a manner consistent with the control of aggression and protection of kin, the motives of male interferers remain unknown; however, their behavior is consistent with the hypothesis that they were reducing intermale tensions while, at the same time, minimizing physical risk.     

Changes in the social structure of two groups of stumptail macaques (Macaca arctoides)

Two previously studied groups of stumptail macaques were restudied to investigate stabilities and instabilities within group structures. Frequency data for nonsocial and dyad behaviors were collected. While there was considerable group stability, several important changes occurred. The most noteworthy group changes were in grooming and playing. Individual changes centered upon females. The first and fourth ranking females of one group switched dominance positions. The roots of this reversal were minimally reflected by aggressive and submissive interactions, and more fully exposed by quiet association patterns such as grooming, huddling, and sitting together. Increased frequencies of huddling, touching, and approaching indicated that the lowest ranking female of each group moved closer to other group members. There was no hint of this change in agonistic interactions.     

Alternative seed-handling strategies in primates: seed-spitting by long-tailed macaques (Macaca fascicularis)

Summary The seeds in fruits consumed by primates may be chewed and digested, swallowed and defecated intact, or separated from the flesh and spat out. We show by a combination of close field observations and experiments with caged animals, that long-tailed macaques (Macaca fascicularis) have a remarkably low threshold of 3–4 mm for swallowing seeds and also that wild macaques rarely break them. The seeds of 69% of the ripe fruit species eaten are spat out intact or cleaned outside the mouth and dropped. Seed-spitting significantly reduces the swallowed food bulk and may lessen the risk of releasing seed toxins during mastication. However, it requires that even small fruits are processed in the mouth one or a few at a time. We suggest that fruit storage in the cheek pouches of cercopithecine monkeys allows them to spit seeds individually without excessively slowing fruit intake while feeding on patchily distributed fruit. In contrast, Apes and New World monkeys apparently swallow and defecate most ripe seeds in their diet and colobine monkeys break and digest them, detoxifying seed defenses by bacterial fermentation.     

Vocal communication of wild bonnet macaques (Macaca radiata)

Field observations and spectrographic analyses of sound recordings of South Indian bonnet macaques revealed a vocal repertoire of at least 25 basic patterns. The repertoire consists of well separated sound classes and acoustic categories connected by structural intergradation. Besides structural variations within and between different elements of the repertoire, the vocal system ofMacaca radiata is characterized by regular combinations of particular basic patterns. These combinations occurred not only between calls of similar structure and function but also between calls usually emitted in entirely different social contexts. According to the qualitative analysis, sex-specific asymmetries of the vocal behaviour were less pronounced than age-dependent characteristics. The comparison of clear call vocalizations ofMacaca radiata andM. fuscata revealed significant species-specific differences on the structural and the behavioural level. Evaluations of the structural features of alarm calls of various macaque species imply marked differences between members of thefascicularis group andsinica group on one hand and thesilenus group andarctoides group on the other.     

Perception of stimuli presented as photographic slides in cynomolgus macaques (Macaca fascicularis)

The present study was designed to assess a monkey's perception of specific visual stimuli by measuring both the behavioral responses and duration of attention to the presentation of photographic slides. Five adult male cynomolgus macaques (Macaca fascicularis) were placed individually in an open field apparatus and presented a series of slides consisting of apples, a gorilla mask, a collage of colors, a human being, and a plain field. The slide of the gorilla mask followed by that of the human being received the most attention while the plain field received the least. In addition, the gorilla mask and human being elicited a range of behavioral responses with the higher ranking animals displaying a greater number of aggressive responses and the lower ranking animals displaying a greater number of submissive gestures. Taken together, these data would suggest that the slides of the gorilla mask and the human being were perceived by the monkeys as threatening. These results are consistent with a continuing theme observed among a number of studies of primate social perception — namely, that potentially threatening stimuli are a significant determinant of visual observing.