Alpha-male sooty mangabeys differentiate between females’ fertile and their postconception maximal swellings

Exaggerated Sexual Swellings and the Probability of Conception in Wild Sanje Mangabeys (Cercocebus sanjei)

Females of several catarrhine primate species exhibit exaggerated sexual swellings that change in size and coloration during the menstrual cycle and, in some species, gestation. Although their function remains under debate, studies indicate that swellings may contain information males could use to discern ovulation and the probability that a cycle will be conceptive. Here we combine visual ratings of swellings with hormonal data for a group of Sanje mangabeys (18 adult, 3 adolescent females) to determine if their swellings provide reliable information on female fertility. In all cases where ovulation was detected (N = 7), it occurred during maximum tumescence, and in 83.3% during the first two days of the "shiny phase," a period during maximum tumescence when the swelling was brightest. There were no significant differences in maximum tumescence and shiny phase duration among cycles of different probability of conception, although there was a trend toward conceptive cycles exhibiting shorter shiny phases than nonconceptive ones. Only 25% (N = 4) of postconceptive swellings developed the shiny phase, and adolescents displayed the longest maximum tumescence and shiny phases. The conspicuous nature of the shiny phase and the frequent overlap between its onset and ovulation suggest that its presence serves as a general signal of ovulation and that the cycle has a high probability of being conceptive. It also suggests that swellings in some Sanje mangabeys are more accurate signals of fertility than in other primates.

Multimodal Advertisement of Pregnancy in Free-Ranging Female Japanese Macaques (Macaca fuscata)

The role of multiple sexual signals in indicating the timing of female ovulation, and discrimination of this timing by males, has been particularly well studied among primates. However the exhibition of pregnancy signals, and how such signals might modulate male post-conception mating decisions, is still poorly understood. Here we aimed to determine if Japanese macaque males use changes in female sexual signals (behavioral, visual and auditory) to discriminate pregnancy and adjust their socio-sexual behaviors. We combined behavioral observations, digital photography and endocrinological (progestogen and estrogen) data, collected systematically during three one-month periods: the pre-conceptive period, the 1st month of pregnancy and the 2nd month of pregnancy. We analyzed variation in the probability of detecting male and female socio-sexual behaviors and estrus calls, as well as changes in female face color parameters, in relation to female reproductive state. Based on our focal observations, we found that males did not copulate during the pregnancy period, and that female socio-sexual behaviors generally decreased from the pre-conceptive to post-conceptive periods. Female face luminance decreased from the pre-conceptive month to the pregnancy period whereas face color only varied between the 1st and 2nd month of gestation. Our results suggest that Japanese macaque females display sexual cues of pregnancy that males might use to reduce energy wasted on non-reproductive copulations with pregnant females. We hypothesize that females advertize their pregnancy through changes in behavioral, visual and potential auditory signals that males can use to adjust their mating behaviors. We finish by discussing implications for male and female post-conception strategies.

Reproductive characteristics of wild Sanje mangabeys (Cercocebus sanjei)

An accurate description of reproductive characteristics and ovarian endocrinology is necessary to address questions about the reproductive strategies and life history of a species and for meaningful, cross species analyses. Here we used analysis of fecal estradiol (fE) and behavioral observations to determine for the first time the reproductive characteristics and endocrinology of a wild group (N = 18 adult and 3 adolescent females) of Sanje mangabeys (Cercocebus sanjei). The study was conducted in the Udzungwa Mountains National Park, Tanzania, from October 2008 through September 2010. Average cycle length (±SD) was 29.3 ± 3.2 days in adults and 51.4 ± 5.5 days in adolescents. Menses appeared within 5.1 ± 2.1 days in adults and 4.8 ± 0.3 days in adolescents after the end of maximum tumescence, and lasted 6.7 ± 3.1 and 10.3 ± 5.0 days, respectively. Infant death tended to reduce the number of cycles to conception (4.3 ± 1.5 cycles after a surviving infant vs. 2.6 ± 1.0 cycles after infant death). Adolescents cycled for at least 16 months without conceiving. Implantation bleeding began 17.5 ± 0.7 days from the onset of detumescence, and lasted 10.0 ± 1.4 days. Gestation length averaged 171.8 ± 3.4 days. Postpartum amenorrhea lasted 6.7 ± 2.3 months while females whose infants had died resumed cycling within 14.3 ± 5.9 days. The interbirth interval after a surviving infant averaged 20.0 ± 4.3 months. These reproductive characteristics of the Sanje mangabey resembled those of other mangabeys and related cercopithecines, with the exception of an earlier onset and longer duration of menstruation and implantation bleeding. Further information on the physiology of the Sanje mangabey is needed to clarify what factors may cause the unusual characteristics of both, their menses and implantation bleeding.

Male mating behaviour in relation to female sexual swellings, socio-sexual behaviour and hormonal changes in wild Barbary macaques

In many cercopithecine primates females display probabilistic cues of fertility to indicate the periovulatory period to males. These cues may include female behaviour, acoustic signals, and morphological signs such as the anogenital swelling. However, the extent to which males can utilise this information varies between species. We describe male sexual behaviour in relation to changes in anogenital swelling size, timing of ovulation and female socio-sexual behaviour in wild Barbary macaques (Macaca sylvanus). We further compare male sexual behaviour during conception and post-conception cycles to evaluate if males differentiate between these qualitatively different cycle types. Our results show that during conception cycles male mating behaviour was concentrated around the fertile phase implying that males inferred information from more than swelling size alone. Male mating frequency increased in line with female socio-sexual behaviour, namely female presenting and the frequency of copulations with copulation calls. Most strikingly our results show that males invested equally in mating during fertile and non-fertile, i.e. post-conception, maximum swelling phases. Whether post-conception swellings were merely a result of changes in hormone concentrations during pregnancy or part of a female reproductive strategy remains elusive. In sum, this study adds to the body of research on the evolution of female sexual signals and how males may infer information from these cues.

Female sexual behavior and sexual swelling size as potential cues for males to discern the female fertile phase in free-ranging Barbary macaques (Macaca sylvanus) of Gibraltar

Although female catarrhine primates show cyclic changes in sexual behavior and sexual swellings, the value of these sexual signals in providing information to males about timing of the fertile phase is largely unclear. Recently, we have shown that in Barbary macaques, males receive information from females which enables them to discern the fertile phase and to focus their reproductive effort accordingly. Here, we investigate the nature of the cues being used by examining female sexual behavior and the size of sexual swelling as potential indicators of the fertile phase. We collected behavioral data and quantified swelling size using digital images of 11 females of the Gibraltar Barbary macaque population and related the data to the time of ovulation and the fertile phase as determined from fecal hormone analysis. We found that rates of female sexual behaviors were not correlated with female estrogen levels and did not significantly differ between the fertile and non-fertile phases of the cycle. In contrast, swelling size was significantly correlated with female estrogen levels and increased predictably towards ovulation with size being maximal during the fertile phase. Moreover, frequencies of male ejaculatory copulations showed a strong positive correlation with swelling size and highest rates were found during maximum swelling. Our data provide strong evidence that female Barbary macaques honestly signal the probability of fertility through sexual swelling and that males apparently use this information to time their mating activities. Honest advertising of the fertile phase might be part of a female strategy to manipulate male mating behavior for their own advantage, such as ensure fertilization with high quality sperm or influence paternity outcome.

Post-conception mating in wild long-tailed macaques (Macaca fascicularis): characterization, endocrine correlates and functional significance

In many anthropoid primates, mating activity is not restricted to the ovarian cycle but also occurs during pregnancy. Although it has been suggested that the main function of this post-conception mating is to confuse paternity, studies showing whether or not male primates can distinguish between the fertile phase of the conception cycle (FPCC) and the period of peak post-conception mating (peak PCM) are almost non-existent. Here, we examine whether the pattern of female sexual traits (specific sexual behaviors, sexual swelling) and female attractiveness to males differ between FPCC and peak PCM in 6 wild female long-tailed macaques. We also use fecal hormone analysis to investigate whether female traits during peak PCM are related to changes in female sex hormones. All females exhibited a distinct period of heightened mating activity around days 45-60 of gestation. During peak PCM, swelling size and frequency of female solicitations (but not reaching back) were significantly correlated with changes in the estrogen to progestogen ratio. Swelling size, frequency of female sexual behaviors and copulations and proportion of male-initiated copulations and ejaculations were not significantly different between FPCC and peak PCM. Although males spent significantly less time consorting females during peak PCM, all (particularly low-ranking and non-resident males) invested heavily in terms of reproductive costs associated with mate-guarding and mating during pregnancy. We conclude that post-conception mating in wild long-tailed macaques is not merely a by-product of endocrine changes and devoid of adaptive function. Our results more strongly support the hypothesis that it may form part of a female reproductive strategy to confuse paternity, which appears to apply particularly to low-ranking and extra-group males.

Reproductive parameters and life-history variables in captive golden-bellied mangabeys (Cercocebus agilis chrysogaster)

An understanding of the reproductive physiology of captive primates is vital for their successful management. We report on reproductive parameters and life-history variables collected at the Sacramento Zoo for five female golden-bellied mangabeys (Cercocebus agilis chrysogaster) over a 7-year period. For each female, we collected data on their sexual skins, menses, gestation, and other pregnancy-related factors, such as postconception bleeding and swelling. We used these data to estimate life-history variables, such as age at onset of estrus, menses, and conception, as well as the duration of intervals between births, and between parturition and the resumption of cycling. Cercocebus agilis chrysogaster is comparable to other Cercocebus species in terms of reproductive parameters, although variability is exhibited within and among female subjects. In some cases, it appears that stressful incidents altered cycle length or halted cycling altogether. We suggest the use of husbandry practices that include consistent data collection to enhance regularity in reproductive cycles, and maximize captive breeding success for this rare species.