Reproductive Behavior in the Rhesus Monkey: Social and Endocrine Variables

SYNOPSIS. Social groups of rhesus monkeys (Macaca mulatto) livingin outdoor environments exhibit a distinct seasonal mating patternand female rhesus are observed to be sexually receptive fordiscrete periods averaging about 9 days duration. In the laboratoryenvironment mating occurs throughout the year and, in the pairtest, female rhesus are observedto be sexually receptive throughall phases of a menstrual cycle, with a periovulatory peak incopulatorybehavior. The apparent conflict between results from field andlaboratory studies has been difficult to resolve because ofmethodological limitations inherent in each study environment.Studies conducted on social groups of rhesus monkeys housedin outdoor compounds, an environment in which the species typicalseasonal mating pattern is preserved and which allowsfor concomitantmeasurement of behavioral and hormonal variables, provided informationabout the covariance between female sexual behavior and ovariancycles. Female copulations were observed only in associationwith ovulatory cycles, and were limited to the follicular andperi-ovulatory phases of such cycles, demonstrating that copulatorybehavior in female rhesus monkeys is strongly influenced bycyclic hormonal variables. The studies also revealed that femalestend to conceive on the first ovulatory cycle of the season,that there was no synchrony of cycles among the females, andthat the best predictor of the timing of ovulation in a particularfemale is reproductive outcome in the previous year.     

Sneaky Monkeys: An Audience Effect of Male Rhesus Macaques (Macaca mulatta) on Sexual Behavior

Males and females have different sexual interests and subsequently may show conflicting sexual strategies. While dominant males try to monopolize females, promiscuity benefits females and subordinate males. One way to escape monopolization by dominant males is to copulate in their absence. We tested this inhibitory effect of males on the sexual behavior of their group members in captive group‐living Rhesus macaques. Copulations between females and nonalpha males almost exclusively took place when the alpha male was out of sight. Furthermore, the inhibiting effect was not unique for the alpha male. An upcoming nonalpha male also inhibited copulations of its group members, and three other nonalpha males inhibited female copulation solicitations. Females adjusted their behavior to the presence of bystander males, as they initiated and accepted initiations more often in absence than in presence of bystander males. Although not significant, in males, a similar pattern was found. The observed reduction in mating behavior in presence of bystander males is in accordance with an “audience effect,” in which the behavior is modulated in relation to the presence or absence of third parties. This audience effect may serve as an important mechanism to reduce (aggressive) interruptions of subordinate male copulations.     

Nature Needs Nurture: The Interaction of Hormonal and Social Influences on the Development of Behavioral Sex Differences in Rhesus Monkeys

Thirty years of research on early social and hormonal environments and their relationship to the expression of behavioral sex differences in rhesus monkeys are reviewed. These studies demonstrate that whether aggressive and submissive behaviors are sexually dimorphic depends primarily on the social and not the hormonal environment. Early rearing environments without mothers or allowing brief periods of peer interaction produced higher levels of male aggression and female submission. Presenting behavior was expressed more by females than males in environments with high male aggressivity and female submissiveness. No sex differences in presenting occurred in low aggressivity environments, unless monkeys were reared isosexually, when males presented more than females. Rough and tumble play and foot-clasp mounting were consistently exhibited more by males than females across all rearing environments studied, but rearing environment affected the degree of the sex difference. When reared isosexually males displayed less, and females more, foot-clasp mounting than when heterosexually reared. No social environment increased the low frequency of female rough and tumble play. Suppressing neonatal androgen in males did not effect any sexually dimorphic behavior. Prenatal androgen administration to genetic females masculinized many aspects of their juvenile behavior, consistently increasing rough and tumble play and foot-clasp mounting across different social environments. Thus the sexually dimorphic behaviors which showed the smallest variability across social contexts were the most profoundly affected by the prenatal hormonal environment. These studies demonstrate that the expression of consistent juvenile behavioral sex differences results from hormonally induced predispositions to engage in specific patterns of juvenile behavior whose expression is shaped by the specific social environment experienced by the developing monkey.     

Olfaction, Sexual Behavior, and the Pheromone Hypothesis in Rhesus Monkeys: A Critique

SYNOPSIS. Evidence in support of and contrary to the hypothesisthat rhesus monkeys possess a sexual pheromonal system is presentedand discussed. New evidence demonstrates that solicitationsof females given estradiol are more attractive to males in partbecause the females allow males to mount much more frequentlyonly when the females have initiated the sexual interaction.In addition, evidence is presented which demonstrates that anodorous control substance stimulates sexual activity just aswell as the purported "active component" of vaginal secretionsunder restricted conditions of evaluation. Finally, preliminaryevidence suggests the possibility that odorous products fromthe vagina, unrelated to short-chain aliphatic acids, presentqualitatively distinct cues to the male during the periovulatoryphase of the menstrual cycle. However, only sexually experiencedmales, and not young adult "virginal" males nor adult isosexually-rearedmales, selectively attended to midcycle vaginal products whenthese were placed on environmental surfaces. It is concludedthat male rhesus monkeys may utilize odorous cues from the femaleduring sexual interactions, but these cues are neither necessarynor sufficient for the coordination of fertile matings. Furthermore,olfactory communication in this species does not fit the accepteddefinition of pheromone: the odors are not specific for onespecies; the behavior elicited is not specific to sexual arousal;and volatile materials other than vaginal products can stimulatesexual activity.     

Intraspecific Variability in Parenting Styles of Rhesus Macaques (Macaca mulatta): The Role of the Social Environment

This study tested the hypothesis that differences in parenting styles between two captive populations of rhesus macaques, one living in the UK (Madingley) and the other in the USA (Yerkes), are associated with differences in the degree to which social interactions with other group members pose a risk to infants. Twenty-eight mother–infant dyads, 17 living at Madingley and 11 at Yerkes, were observed for 24 h during the first 12 wks of infant life. Mother–infant dyads living at Madingley spent a higher percentage of time in contact than those living at Yerkes. The Madingley mothers also restrained and retrieved their infants more often, and rejected them less often than the Yerkes mothers. Consistent with the prediction, the protective parenting style of the Madingley mothers was associated with higher frequency of infant kidnapping and higher risk of infant harassment from other group members. Interpopulation differences in risks to infants and parenting styles are likely to be the result of differences in social density in the two environments rather than differences in the matrilineal structure of the two populations.     

太行山猕猴的死婴携带行为初报

于2012年5月2日至5月28日,采用焦点动物取样法和全事件记录法对河南省济源市五龙口风景区的一个太行山猕猴群(WLK-5)内一例成年雌性的死婴携带行为进行了观察和记录。结果表明:死婴携带持续26d,属长期携带;母亲对死婴的照料行为主要包括携带行为、理毛行为和亲吻行为等;在此期间,母亲行为表现异常:情绪低落、胆小怕人、很少与其他个体接触。本文对猕猴的死婴携带行为进行了初步探讨。     

The Role of Landscape Structure in Primate Crop Feeding: Insights from Rhesus Macaques (Macaca mulatta) in Northern India

International Journal of Primatology - Human-modified landscapes play an important role in supporting the survival of primate populations, but they may also facilitate human–primate...