Chimpanzee genital swelling and its role in the pattern of sociosexual behavior

Behavioral observations were made on thirteen female and seven male adult group-living chimpanzees (Pan troglodytes). The behavioral data were analyzed as a function of the day of the females' menstrual cycles to explore the possible interrelationship between genital swelling and sociosexual behavior of female chimpanzees. Copulatory behavior was confined almost entirely to the period of genital swelling and the occurrence of male-to-female genital inspection (both female- and male-initiated) was negatively correlated with the days from swelling onset, i.e., as the presumed day of ovulation approached, genital inspection decreased, while copulatory behavior increased. In addition, more females groomed their male cagemates during the luteal phase than in the follicular phase of their cycles, whereas male-to-female grooming was positively correlated with the progress of the cycle, with peaks during the time of swelling onset and menstruation. The profile of sociosexual behavior observed throughout the menstrual cycle suggested that, although chimpanzees exhibit an extended period of sexual receptivity and genital swelling, the presumed fertile period is not concealed. The role of genital swelling in chimpanzees is discussed in relation to the possible hormonal effect on female sexuality and the evolution of chimpanzee mating strategies. © 1992 Wiley-Liss, Inc.     

Serum levels of gonadotropins and gonadal steroids,including testosterone,during the menstrual cycle of the chimpanzee (Pan troglodytes)

The objective of this study was to expand the data on menstrual cycle serum hormone patterns in female common chimpanzees, both in terms of the number of cycles analyzed and by the addition of data on testosterone levels. Samples were obtained from 11 unanesthetized animals trained for conscious blood withdrawal. LH, FSH, 17β-estradiol (E₂), progesterone (P), and testosterone (T) were measured by radioimmunoassay, genital swelling was recorded, and menstrual blood was noted. Concurrent midcycle elevations in LH and FSH and luteal phase elevations in progesterone suggested that the cycles were ovulatory. Detumescence of genital swelling occurred about 3 days after the midcycle LH peak, 1 day after the luteal phase nadir in E₂, and 1 day after P levels exceeded 5 ng/ml. These relationships provide further support for the use of genital swelling in monitoring progress of the menstrual cycle. The hormone patterns in the chimpanzees closely resembled those of the human females, but E₂ and T levels were higher. The levels of E₂ and T were higher and the midcycle elevation in T was broader in the chimpanzee than in gorillas and orangutans. This is of interest because E₂ and T are implicated in the regulation of mating, and chimpanzees mate over a greater portion of the cycle than the other apes. These data indicate the need for further study of hormonal contributions to the different patterns of mating in the great apes. They also support the use of the female common chimpanzee as a model for the human female in endocrine studies of the menstrual cycle.     

Reproductive function in aged female chimpanzees.

Reproductive function was evaluated in ten female chimpanzees (Pan troglodytes) aged 35-48 years. Forty-eight years is the longevity record for the chimpanzee. Data on cycle frequency and duration was available for seven animals. Most were cycling regularly until death, and all had experienced at least one menstrual cycle within one year of death. After exclusion of periods when the animals were pregnant or in postpartum amenorrhea, the mean cycle frequency (+/- standard error)/year was 9.54 +/- 0.20 in seven animals aged 15-25 (432 cycles analyzed) compared to 8.6 +/- 0.76 in the same animals at age 35 + years (405 cycles analyzed); this effect approached significance (p = 0.072, Mann-Whitney U-test). Cycle length of 16 cycles in each of seven animals aged 15-25 was 32.23 +/- 0.38 days. The same animals when aged over 35 had mean cycle lengths of 35.59 +/- 0.73. This difference was not significant, although cycle lengths clearly increased with age in some individual animals. In five aged animals for which mating data was available, appropriate exposure to a male occurred in 52 cycles, but only two pregnancies occurred; one pregnancy resulted in a live birth at age 38, the other in a stillbirth at age 40. This conception rate was 3.85% compared with 20% in the same animals aged 15-25. These data suggest greatly reduced fertility after age 35, although menstrual cycle frequency remained high. The persistence of menstrual cyclicity until death, which occurred due to natural causes at latest in the fifth decade, is in striking contrast to the human female in which menopause occurs in the fifth decade and death is often postponed for several more decades.     

Impact of social environment on female chimpanzee reproductive cycles

The socio-sexual environment of a female is known to affect ovarian function. Increased male contact can enhance menstrual cycle regularity. Conversely, social deprivation constitutes a form of stress that often alters cyclicity and the secretion of reproductive hormones. The present study was carried out on captive female chimpanzees to examine possible interactions among housing conditions, menstrual cycle length, morphological changes in secondary sexual character expression and endocrine release patterns related to follicular and luteal function. Animals were housed over a period of 2 years either with a male conspecific or singly. Blood samples were collected over three cycles, and anogenital swelling changes registered to define menstrual cycle phases. Fecal sampling techniques were used to monitor cortisol as a measure of stress-load. Male presence seemed to affect female cyclicity. Females housed with a male had shorter and more regular cycles than singly housed females. Prolactin, gonadotropins and estradiol levels were generally higher in paired females during specific cycle phases. Group variation was not always significant. No differences were found in progesterone. Sexually cohabited females tended to have lower fecal cortisol metabolites immediately before and after maximum tumescence. We suggest that the close behavioral, physical and olfactory contact with a male conspecific can act as a sort of zeitgeber to modulate ovarian function by stabilizing the female cycle and, perhaps, enhancing folliculogenesis and ovulation.     

The effects of aging on hormone and reproductive cycles in female chimpanzees (Pan troglodytes)

In contrast to those for human females, observational cycle data available for chimpanzees suggest that menstrual cycling, and thus reproductive potential, continues until near death. This study documents age-related changes in estrous cycling and hormone profiles in 14 female chimpanzees (Pan troglodytes) ranging in age from 31 to 50 y. Estrous data were analyzed from daily cycle charts, averaging 13.3 y of cycle data per subject, after omission of gestational and postpartum amenorrhea. Concentrations of total luteinizing hormone (LH), follicle-stimulating hormone (FSH), estradiol (E2), and other hormones were assayed in serum samples taken biannually. Sample collection times were chosen to avoid the ovulatory LH and FSH peaks of the female's cycle and yielded a mean of 19.6 serum samples over an average of 14.4 y per subject. Analysis of cycle charts revealed a negative relationship between age and the percentage of cycle days at maximal tumescence. There also were positive relationships between age and the length of the estrous cycle and age and the percentage of cycle days at complete detumescence. Analysis of hormonal data revealed curvilinear relationships between age and both LH and FSH. These cycle and hormonal changes mirror those in perimenopausal and menopausal women. Our data provide evidence of perimenopause (at 30 to 35 y) and menopause (at 35 to 40 y) in the chimpanzee.     

Anogenital swelling in pregnant chimpanzees of Gombe National Park

Previous studies show that anogenital swelling patterns of pregnant chimpanzees in captivity are correlated with the female's age during pregnancy and are associated with changes in social behavior. The purpose of the present study was to investigate whether the anogenital swelling patterns of free-ranging pregnant chimpanzees resemble those reported for captive chimpanzees. We reviewed the records of 47 pregnancies experienced by 20 female chimpanzees living in Gombe National Park from 1975 to 1992. Percentage scores for swelling during each trimester and for the overall occurrence of various levels of swelling were obtained by dividing the frequency by the total number of days the subject was observed (i.e., 28 days of swelling/165 days observation = 17.2% anogenital swelling for that pregnancy). Subjects exhibited anogenital swelling an average of 25.1% of the days observed during pregnancy, yet reached maximum only 9.4% of the time. Anogenital swelling occurred less frequently as pregnancy progressed, averaging 40.8, 27.3, and 2.7% in the first, second, and third trimesters, respectively. As seen in captive chimpanzees, young pregnant females at Gombe showed anogenital swelling more often than did older ones (r = ?.65, P < .0001). These findings are consistent with reports of behavior associated with anogenital swelling (e.g., intercommunity transfer of young females exhibiting anogenital swelling). © 1993 Wiley-Liss, Inc.     

Demographic and Female Life History Parameters of Free-Ranging Chimpanzees at the Chimpanzee Rehabilitation Project, River Gambia National Park

We analyzed fertility and mortality records for 113 provisioned, free-ranging chimpanzees at the River Gambia National Park, The Gambia. The chimpanzees are rehabilitated orphans released by the Chimpanzee Rehabilitation Project (CRP), and their descendants born in a natural environment. Females experienced their 1st births at an average age of 14.3 yr, with average interbirth intervals of 68 mo. Despite limited provisioning, reproductive parameters in both released and 1st-generation females resembled those of wild chimpanzees and showed seasonal fluctuations. Mortality rates were low compared to those for wild chimpanzees, particularly for infants and juveniles; life expectancy at birth was 23.6 yr for females and 18 yr for males. The results have implications for our understanding of variation in reproductive parameters between captive and wild chimpanzees. We also discuss issues related to chimpanzee conservation and captive rearing.     

圈养条件下黑猩猩月经、排卵和妊娠周期

排卵期和妊娠期与月经周期紧密相关,监测月经周期对圈养黑猩猩（Pan troglodytes）的繁殖有着重要意义。本研究对上海动物园饲养的8只雌性黑猩猩2002年以来的月经周期记录进行统计分析,并对2只成年雌性黑猩猩共60 d尿液中促黄体生成素进行检测。黑猩猩月经周期平均为（33.5 ± 5.3）d,经期平均为（1.6 ± 1.1）d,妊娠期平均为（226.9 ± 17.3）d,产单胎和双胎有极显著差异;促黄体生成素在发情高峰期出现了峰值。     

Demography,female life history,and reproductive profiles among the chimpanzees of Mahale

Demography provides critical data to increase our understanding of the evolution, ecology, and conservation of primate populations. The chimpanzees of the Mahale Mountains National Park, Tanzania, have been studied for more than 34 yr on the basis of individual identification and standardized attendance records. From this long-term study, we derived the following demographic data: The major cause of death was disease (48%), followed by senescence (24%) and within-species aggression (16%). Fifty percent of Mahale chimpanzees died before weaning. The median ages of female life history variables were: first maximal swelling, 10.0 yr (n = 5); emigration, 11.0 yr (n = 11); and first birth, 13.1 yr (n = 5). The median period of adolescent infertility was 2.8 yr (n = 4) when calculated from the age at immigration to that at first birth. Female fecundity was highest between 20 and 35 yr of age, with an annual birth rate of 0.2. Twenty-six females that were observed from a young age (10-13 yr) to death at various ages (15-40 yr) gave birth to an average of 3.9 and weaned an average of 1.4 offspring. Twenty-five females that were observed from middle age (18-33 yr) to death in older age (31-48) gave birth to an average of 2.7 and weaned an average of 2.0 offspring. The post-reproductive lifespan for female chimpanzees was defined as the number of years that passed from the year when the last offspring was born to the year when the female died, minus 5. Twenty-five percent of old females had a post-reproductive lifespan. The interbirth interval after the birth of a son (x = 72 mo) tended to be longer than that after the birth of a daughter (x = 66 mo). The extent of female transfer, which is a rule in chimpanzees, is influenced by the size and composition of the unit group and size of the overall local community.     

Neuroendocrine changes in the aging reproductive axis of female rhesus macaques (Macaca mulatta)

Femalerhesus macaques show monthly menstrual cycles and eventually enter menopause at approximately 25 yr of age. To help identify early biomarkers of menopause in this nonhuman primate, we monitored reproductive hormones longitudinally from aged female macaques during the transitions from premenopause to perimenopause and postmenopause and found that, indeed, elevated plasma FSH was a better predictive factor of menopause onset than age. In a second experiment, we compared reproductive hormone profiles of young adult macaques (8-10 yr old) with those of regularly cycling old macaques (approximately 24 yr old). Indwelling vascular catheters were used for remote blood collection for at least 100 consecutive days, thereby covering three complete menstrual cycles in each macaque. Plasma levels of estradiol, progesterone, LH, FSH, follicular phase inhibin B, and anti-müllerian hormone (AMH) were determined during each menstrual cycle and were averaged for each animal; group mean differences were analyzed using one-way ANOVA. Old premenopausal macaques showed regular menstrual cycles that were qualitatively indistinguishable from those of young macaques; peak plasma levels of estradiol, progesterone, and LH were not significantly different. In marked contrast, peak plasma FSH concentrations were significantly higher, while inhibin B and AMH levels were generally lower, in the old premenopausal macaques compared with those in the young macaques. These data provide further evidence that rhesus macaques serve as an excellent model to study underlying mechanisms of human menopause. Furthermore, the data suggest that an age-related change in FSH, inhibin B, and AMH secretion may be the first endocrine manifestation of the transition into perimenopause, potentially having value in predicting the onset of the perimenopausal transition.     

Reproductive aging in captive and wild common chimpanzees: factors influencing the rate of follicular depletion

We examine and discuss evidence of contrasting differences in fertility patterns between captive and wild female chimpanzees, Pan troglodytes, as they age; in the wild females reproduce in their 40s, but captive studies suggest that menopause occurs around that time. Thus, despite the increased longevity generally observed in captive populations reproductive life span is shortened. We outline a hypothesis to explain the apparent differential pace of reproductive decline observed between wild and captive populations. The breeding schedules of captive primates may contribute to accelerated reproductive senescence because continuous cycling in captive animals results in early depletion of the ovarian stock and premature senescence. Available evidence supports the hypothesis that women with patterns of high oocyte loss experience earlier menopause. Chimpanzees in captivity live longer, and thus, similar to humans, they may experience follicular depletion that precedes death by many years. In captivity, chimpanzees typically have an early age at menarche and first birth, shorter interbirth intervals associated with short lactational periods as young mature faster, and nursery rearing, which allows mothers to begin cycling earlier. Variables typical of wild chimpanzee populations, including late age at menarche and first birth, long interbirth intervals associated with prolonged lactational periods, and a long period of female infertility after immigration, spare ovulations and may be responsible for the later age at reproductive termination. Finally, we describe and discuss the timing of specific reproductive landmarks that occur as female chimpanzees age, distinguishing between functional menopause (age at last birth) and operational menopause (end of cycling). Am. J. Primatol. 71:271–282, 2009. © 2008 Wiley‐Liss, Inc.     

Seasonal influence on reproduction in chimpanzees of gombe national park

Although wild chimpanzees are not seasonal breeders, there are seasonal effects on several aspects of chimpanzee reproduction. I examined the seasonal incidence of anogenital swelling in cyclic, pregnant, and acyclic female chimpanzees in Gombe National Park, May 1975–April 1992, and surveyed important reproductive events to determine whether there is a seasonal effect. I analyzed data by season (wet vs. dry) and seasonal quarter;early dry season = May–July;late dry = August–October;early wet = November–January;late wet = February–April. When data for the 17 years are combined, the percentage of females in each reproductive state remains consistent throughout the year. In a given month, 30–35% of subjects were in the cyclic category, 11–15% were pregnant, and 54–61% were acyclic. Cyclic females showed full swelling more often during the late dry season. Pregnant females exhibited anogenital swelling more often during the late dry and early wet seasons. Acyclic females also exhibited a seasonal effect with more anogenital swelling during the late dry season. There is no seasonal difference in frequency of live births (dry, 20;wet, 23). However, the timing of conception showed a seasonal effect (dry, 32;wet, 16). Consistent with earlier reports, the onset of postpartum cycles is highly seasonal;30 occurred during dry season, 9 during wet season. The occurrence of first full swellings for young females is also concentrated in the late dry season. It appears that the dry season is a time of great change for Gombe chimpanzee reproductive physiology. Previous studies indicated that seasonal changes in food availability play a role in increasing group size during the dry season and social contact between females can enhance cyclicity. Accordingly, I suggest that seasonal changes in diet may play a role, either directly (food content) or indirectly (social contact), to alter reproductive physiology.     

Skeletal and dental growth and development in chimpanzees of the Taï National Park, Côte D'Ivoire

An extraordinary collection of 22 immature skeletons from Taï National Park, Côte d'Ivoire, has provided a rare opportunity to establish the timing of dental eruption and its correlation with skeletal fusion and morphometrics in wild chimpanzees of known chronological ages. Comparison of the immature Taï chimpanzees Pan troglodytes verus with adults from the same population show that sex differences in skeletal maturation apparently appear during the Juvenile II stage, about age 8. A few skeletons from other chimpanzee field sites conform to the dental and skeletal growth in Taï chimpanzees. The tempo of wild chimpanzee growth contrasts sharply with the rate demonstrated for captive individuals. Captive chimpanzees may mature as much as 3 years earlier. The ability to link physical development with field observations of immature chimpanzees increases our understanding of their life-history stages. These data provide an improved dataset for comparing the rates of growth among chimpanzees, Homo sapiens and fossil hominids.     

The menstrual cycle and its effect on behaviour in the Talapoin monkey (Miopithecus talapoin)

The menstrual cycles of 14 captive Talapoin monkeys ( Miopithecus talapoin ) were studied by making serial observations on the vaginal smears and sexual skin swellings for up to 15 months. Twelve of these females menstruated and the mean duration of their cycle was32–9 days (95% confidence limits 28.0-37.7). The corresponding value for the seven most regular females was 33.0 days (29.1-36.8). There were rhythmic changes in the vaginal smears and sexual skin during the menstrual cycle. Maximum cornification of the smears and maximum sexual skin swelling were observed at midcycle; the sexual skin deflated and the smear became less cornified during the luteal phase. The follicular phase—i.e. from menstruation to maximum skin swelling lasted 20.4 days with a wide distribution, in contrast to the mean duration of the luteal phase (13.7 days) which showed a pronounced peak at 14 days. The menstrual cycle of the talapoin thus resembles those of certain other Old World monkeys that exhibit perineal sexual skin swelling.
Sexual behaviour of the male and female was maximal near the female's midcycle and minimal during the luteal phase, with intermediate values in the follicular phase. The males were most aggressive towards other females of the group when one female was at midcycle; there were no consistent changes in aggression between the male and the female herself. The number of times one animal looks at another (a characteristic behaviour pattern in talapoins) was measured and occurred most often at midcycle, but other preliminary observations indicated a more pronounced correlation between this behaviour pattern and an animal's position in the hierarchy.     

Female sexual swelling size, timing of ovulation, and male behavior in wild West African chimpanzees

Conspicuous swellings of the perineal skin can be observed in females of many catharrine primate species particularly during the middle stages of the ovarian cycle. The functional significance of this trait remains poorly understood. Recently, two hypotheses, the "reliable indicator" hypothesis and the "graded signal" hypothesis that take into account not only the pattern but also the exaggerated size of sexual swellings, have gained attention. Here we test several predictions made by these hypotheses by combining (i) direct size measures (from video captures) of female sexual swellings with (ii) urinary hormone data to indicate timing of ovulation through enzyme immunoassay measurements of estrone conjugates and pregnanediol glucuronide (PdG) and (iii) behavioral observations of male mating efforts throughout 36 ovulatory cycles in 12 wild chimpanzees. We are able to show that (i) even within the traditionally defined maximum swelling period, further slight increases in swelling size indicate approaching ovulation, and (ii) that male mating interest changes according to the changes in swelling size. Furthermore, absolute swelling size during the periovulatory period increases and the alpha male associates more with females as the number of cycles to conception decreases. Finally, when having the choice between several "maximally" tumescent females, the alpha male prefers the female that is in the fertile phase of her cycle rather than that with the biggest swelling at that time. Thus, most of our findings are in line with the predictions of the graded signal hypothesis while none of them would support the reliable indicator hypothesis.     

Method of endoscopy in the chimpanzee: relations of ovarian anatomy, endometrial histology and sexual swelling

Endoscopy was performed on adult female chimpanzees at various intervals before and after detumescence of the sexual swelling. The method required inhalation anesthesia, Trendelenberg positioning, abdominal insufflation with CO₂ and a 10 mm photo-endoscope inserted infra-umbilically. Accessory instruments were introduced into each of the lower quadrants. Mechanical ventilation and careful physiologic monitoring were necessary to control cardiac arrhythmias. Before detumescence of the swelling, unovulated follicles were observed. Immediately after detumescence of the swelling began, ovulated follicles or early corpora lutea were present. Secretory endometria and plasma progesterone values in excess of 4.0 mg/ml did not occur until three days after detumescence of the sexual swelling commenced. Endoscopic ovarian visualization offers a means of establishing accurate correlations between ovarian morphology and other parameter in chimpanzee menstrual cycles. The data presented support the interpretation that in this species, ovulation and sexual swelling detumescence are closely related in time.     

Chimpanzees share forbidden fruit

The sharing of wild plant foods is infrequent in chimpanzees, but in chimpanzee communities that engage in hunting, meat is frequently used as a 'social tool' for nurturing alliances and social bonds. Here we report the only recorded example of regular sharing of plant foods by unrelated, non-provisioned wild chimpanzees, and the contexts in which these sharing behaviours occur. From direct observations, adult chimpanzees at Bossou (Republic of Guinea, West Africa) very rarely transferred wild plant foods. In contrast, they shared cultivated plant foods much more frequently (58 out of 59 food sharing events). Sharing primarily consists of adult males allowing reproductively cycling females to take food that they possess. We propose that hypotheses focussing on 'food-for-sex and -grooming' and 'showing-off' strategies plausibly account for observed sharing behaviours. A changing human-dominated landscape presents chimpanzees with fresh challenges, and our observations suggest that crop-raiding provides adult male chimpanzees at Bossou with highly desirable food commodities that may be traded for other currencies.     

Case study of a chimpanzee recovered from poachers and temporarily released with wild conspecifics

This case study describes the behavior ofBahati (BA), a captive, wild-born, 4 – 6 yr old, female chimpanzee (Pan troglodytes schweinfurthii), before and after her temporary release into Kibale National Park, Uganda. Post-release interactions with habituated, wild chimpanzees were recorded.BA was not attacked by the wild chimpanzees at the time of introduction and observations during her period of travel with conspecifics indicate that she received significantly more affiliative contact than aggressive.BA foraged further from humans, glanced less at observers and climbed ever higher in the canopy as the project proceeded.BA associated closely with two wild chimpanzees: a fully adult male and a young juvenile female. In the latter stages of the project, she spent progressively less time in proximity to conspecifics. After six weeks,BA no longer followed wild chimpanzees and repeatedly returned to human settlements. The attempt was terminated after two months andBA returned to captivity. On the basis of this case study, we suggest possible adjustments to re-introduction criteria, and discuss the outcomes of pre-release training, public involvement, and health screening under field conditions.     

Effects of 12-hour rotating shifts on menstrual cycles of photoelectronic workers in Taiwan

12 h rotating shifts are common in high-tech industries in Taiwan. The aim of this longitudinal study was to evaluate the effect of the disruption of circadian rhythms by the shift schedule on menstrual cycle length (MCL) and regularity of female workers at an optoelectronic company in Taiwan. We recruited females who worked rotating shifts in a clean room environment as the shift-work group and female office workers who worked normal business hours as the comparison group. Every participant recorded their MCL for each menstruation cycle up to eight consecutive months prospectively and provided demographic characteristics, reproductive history, and menstrual characteristics. We collected data on 1,135 and 117 menstruation cycles in the shift-work (n = 280) and comparison groups (n = 49). Whereas the two groups had similar group means for MCL and number of menstrual bleeding days, the prevalence of menstrual cycle irregularity (cycles <25 or >35 days) was higher in the shift-work group ( p = 0.04). Univariate and multivariate logistic regression analyses demonstrated that rotating shift work was an independent predictor of menstrual cycle irregularity (odds ratio = 1.71, 95% confidence interval: 1.03-2.88) after adjusting for shift-work history, employment duration, coffee consumption,and pre-employment menstrual cycle irregularity. Although further study is required to confirm our findings plus to explore prevention and control measures, our data indicate rotating shift work can increase the risk of MCL irregularity.     

Female reproductive parameters in the Javan gibbon (Hylobates moloch)

Javan gibbons (Hylobates moloch) are one of the most endangered gibbon species in the world. Data on the reproductive biology of the species are almost nonexistent, and a general understanding of the female reproductive biology of this species is important for both ex situ and in situ conservation. Using 18 years of data from 11 captive individuals, we provide new information on the reproductive biology of Javan gibbons based on sexual swelling and menstrual bleeding, including reproductive development, interbirth intervals, and ovarian cycle lengths. Menarche and the onset of sexual swelling occurred at 6.2 and 6.5 years respectively, followed by a period of adolescent sterility of about 1.5 years. Average age at first birth was 8.8 years, and interbirth intervals were about 2.3 years, decreasing to 1.0 year during cases of infant mortality at or shortly after birth. Ovarian cyclicity was measured through periods between menstrual bleeding and sexual swelling. Menstrual bleeding indicates the start of a new ovarian cycle, while sexual swelling normally occurs near the time of ovulation. Menstrual bleeding intervals gave a cycle length of 25.6 days, while sexual swelling intervals gave a cycle length of 27.3 days. These both correspond closely to cycle lengths in other gibbon species, as well as hormonal studies in Javan gibbons. In particular, observing the presence/absence of swellings was found to be a useful and easy method to monitor female ovarian cycles, and could be a practical noninvasive technique for caretakers and researchers. Zoo Biol 29:449–456, 2010. © 2009 Wiley‐Liss, Inc.