Grooming Circadian Rhythmicity, Progesterone Levels and Partner Preference of the Reproductive Pair of a Captive Common Marmoset (Callithrix jacchus) Family Group during Pregnancy and after Parturition

One family group of common marmosets (Callithrix jacchus) maintained in captivity under natural environmental conditions (Natal, Brazil, 05°46'S, 35°12'W) was observed by focal sampling at two non-consecutive days per week during two non-consecutive pregnancies (pregnancy 1: the last 8 fortnights before parturition; pregnancy 2: the last 5 ones) and after parturition (4 fortnights for both). The hourly percentiles of the duration of self-grooming and allogrooming interactions of the reproductive pair were submitted to Cosinor analysis for the 24-h period (p ≤ 0.05). The reproductive female's progesterone was monitored by fecal collection twice a week between 7:00 h to 9:00 h. Levels of progesterone were determined by ELISA method. During pregnancy 1, all interactions of the reproductive pair showed a 24-h statistically significant period. However, after parturition this periodicity is not present in some behaviors of the reproductive male. This animal presents the 24-h periodicity only toward to the reproductive female, the subadult son and to the newborns. Hormonal levels of the reproductive female showed isolated increases above 100 ng/g at the second and third fortnight after parturition, but did not characterize ovulation. Between pregnancy 1 and 2, the family was increased by the birth of four animals. During pregnancy 2, a statistically significant 24-h period was find only in self-grooming of the reproductive male and female, and in the interactions between the reproductive pair. Also, in the interactions of the reproductive male with only one of the juvenile son. After parturition the reproductive female ovulated at the second fortnight and became pregnant again. At this time, those interactions still have a 24-h period, except in grooming directed to the juvenile son by the reproductive male. As in the first post-partum, grooming directed to the newborns showed statistically significant 24-h period. These results suggest that the reproductive pair performs 24-h rhythmic grooming interactions only with some animals, supposed to be the preferential grooming partners. Furthermore, the temporal grooming expression in common marmosets may be affected by the reproductive condition (progesterone levels) of the reproductive female, by the care of newborn after parturition and the group size.     

Circadian Rhythmicity of Grooming Behavior During Pregnancy in a Marmoset (Callithrix jacchus) Family Group in Captivity

One family group of common marmoset (Callithrix jacchus) was observed in captivity under natural environmental conditions to describe the circadian pattern of grooming behavior during the pregnancy of the reproductive female. The animals were observed by focal sampling, from the beginning to the end of animal's active phase, during two non-consecutive days per week, from August to November 1996. The duration of self-grooming and social grooming behavior of each animal were totalled each hour. The time series obtained were analyzed by Cluster Analysis and by Sin gle Cosinor Analysis. The daily patterns of grooming behavior during pregnancy were divided by Cluster Analysis into two stages, one corresponding to the second half of the third month of pregnancy, and the other from the last half of the third month to the last week before parturition. The confidence intervals of acrophases overlapped in all stages. The acrophases values of the first stage occurred between 10:09 h and 11:00 h, and on the second stage between 8:51 h and 11:13 h. The daily pattern of grooming behavior of adult male and female showed a trend to increase in the first hours of the active phase. This trend to advance grooming behavior during the second stage of pregnancy may be due to an effect of the coming parturition itself or to seasonal influences.     

Circadian Rhythmicity of Grooming Behavior During Pregnancy in a Marmoset (Callithrix jacchus) Family Group in Captivity

One family group of common marmoset ( Callithrix jacchus ) was observed in captivity under natural environmental conditions to describe the circadian pattern of grooming behavior during the pregnancy of the reproductive female. The animals were observed by focal sampling, from the beginning to the end of animal's active phase, during two non-consecutive days per week, from August to November 1996. The duration of self-grooming and social grooming behavior of each animal were totalled each hour. The time series obtained were analyzed by Cluster Analysis and by Sin gle Cosinor Analysis. The daily patterns of grooming behavior during pregnancy were divided by Cluster Analysis into two stages, one corresponding to the second half of the third month of pregnancy, and the other from the last half of the third month to the last week before parturition. The confidence intervals of acrophases overlapped in all stages. The acrophases values of the first stage occurred between 10:09 h and 11:00 h, and on the second stage between 8:51 h and 11:13 h. The daily pattern of grooming behavior of adult male and female showed a trend to increase in the first hours of the active phase. This trend to advance grooming behavior during the second stage of pregnancy may be due to an effect of the coming parturition itself or to seasonal influences.     

Assessment of the sexual behavior of pregnant mares

Pregnant mares (N = 12) were observed with a stallion from early gestation until parturition for sexual behavior. Observations were conducted for 20 min per day for 5 days each month from September until July. No mares exhibited full estrus and no intromissions or ejaculations occurred at any time during the study. Social interactions such as male approach and female/female mutual grooming occurred with greater mean frequency or duration in some months of spring and fall than in winter months. (P less than 0.05). None of the recorded behaviors differed by month of gestation. In a comparison of the behavior of diestrous and pregnant mares in harem groups, no estrous behavior occurred and no differences in social interactions were found. Although progesterone may be sufficient to cause the absence of sexual behavior in diestrous mares, another estrous-inhibiting substance may be present during pregnancy at times of high estrogen and low progesterone.     

The Pair-Bond Formation and Its Role in the Stimulation of Reproductive Function in Female Common Marmosets (Callithrix jacchus)

The sociosexual relationship between male and female common marmosets (Callithrix jacchus) is characterized by pair-bond formation, which includes sexual and social interactions such as contact, huddling and allogrooming. The formation of heterosexual pairs in captivity sometimes is unsuccessful in terms of reproduction. We investigated the existence of a correlation between characteristics of sociosexual interaction of marmoset pairs and its role in stimulating reproductive function in females. We studied pair-bond formation during the first 10 weeks of pairing in eight unrelated heterosexual pairs of common marmosets (Callithrix jacchus) without prior sexual experience. In three of them, pregnancy occurred during the study period (group SR), and we compared the profile of their sociosexual interactions with that of the five other couples in which pregnancy was not registered (group NS) during that period. The results show differences between the two groups, related mainly to affiliative responses between male and female, with significantly higher levels of allogrooming and simultaneous piloerection in the SR group. Although we did not find significant differences in the frequency of mounting behavior between groups, their reproductive success was different, suggesting that some behavioral patterns related to cooperative interactions between the male and female could be expressing the pair-bond. These behaviors may be influencing the females' physiology and consequently successful reproduction in the species.     

Observations of a daytime birthing event in wild titi monkeys (Callicebus oenanthe): implications of the male parental role

Behaviors displayed during birth events, including prenatal, parturition, and postpartum periods, can give insight into caretaking roles in species in which the offspring is cared for by individuals other than the mother. Titi monkeys, genus Callicebus, exhibit a pair-bonded social system along with intense male care of offspring. Here, I report the first case of a birth seen in the wild in a group of Callicebus oenanthe, a little-known species in northern Peru, and describe infant care and development during the first few months after birth. Detailed behavior during the birth sequence as well as ad libitum data postpartum were recorded on nursing and infant care behaviors, including infant carrying, infant grooming, anogenital cleaning, protection, playing, and food sharing. In the 3 h preceding and during parturition, the male remained in contact with or in close proximity to the female (<1 m). The male licked and examined the newborn 3 min after parturition, carried the infant within 24 h after birth, was the main carrier of the infant, and was the predominant manual groomer of the infant during the first 4 months after birth. I argue that the male plays an integral role during the birth in order to establish his bond with the infant as well as reinforce infant care duties to the female and in predator vigilance. In light of various explanations for the exhibition of intense paternal care, I suggest that the male titi monkey provides infant care to release the female of these duties in order that she may spend more time foraging, thus potentially increasing the pair’s overall reproductive output.     

Interactions of social,spatial and hormonal factors on the behavior of rhesus monkeys (Macaca mulatta)

In a three year study, the interactions of social, spatial and hormonal variables on the behavior of rhesus monkeys were investigated. Observations were made on (1) an oppositelysexed pair alone in a cage; (2) the pair alone in a large room; and (3) the pair together with three ovariectomized females in the same large room. Each of four males was tested with the same group of four ovariectomized females (16 pairs, 480 1-hr tests). Each female served in turn as the focal female, namely, the hormone-treated one, and received first estradiol benzoate (EB) alone and then in combination with progesterone (P). The presence of three other females (the social variable) had a marked effect on all aspects of the behavior of the focal pair, and reduced the male's ejaculations as well as other sexual and affiliative interactions with the focal female. This was due to an inhibitory influence exerted by the dominant female on the interactions of subordinate females with the male. Comparing data from two groups of females showed that female dominance rank, and not male sexual preference, was the critical factor, and that mate competition between female rhesus monkeys was operating. Decreasing the space available for the interactions of the pair appeared to imitate a bonding effect in the male, increasing male grooming and tending to increase male sexual activity. In the group setting, treating the female with EB increased sexual activity, and additional progesterone decreased it in all three test settings. The effects of progesterone were most clearly apparent when the pair was tested alone in a large area.     

Behavioral and Hormonal Analysis of Social Relationships Between Oldest Females in a Wild Monogamous Group of Common Marmosets (Callithrix jacchus)

Social organization in common marmosets (Callithrix jacchus) appears to be based on a hierarchy of dominance, in which dominant females limit the reproductive functioning of subordinates. Reduced fertility was documented for captive but not for wild females. We investigated social dynamics and hormonal profiles of females living in a wild group. We collected behavioral and hormonal data during 7 mo from the reproductive and two nonreproductive adult females (probably daughters), and their interactions with the reproductive male. The subjects lived in a monogamous group at Nísia Floresta field station in northeastern Brazil. We collected behavioral data as all day follows, once a week and fecal material twice a week. We analyzed fecal samples for cortisol and progesterone using enzyme immuno assay (EIA) techniques. During the first three months we monitored the reproductive female (GRE) and the oldest nonreproductive female, (GIO). After the disappearence of GIO, we monitored the next oldest subordinate adult female, (GRA). GRE had just given birth at the beginning of the study, and she gave birth 6 mo later. During the last 2 weeks of GRE's gestation, GRA showed elevated progesterone levels, indicating ovarian cycling. Cortisol levels from GRE and GRA reached very high levels then. During GRA's cycling period, her interactions with the reproductive male (GT) were lower than when she was not cycling. We saw sexual interactions only between GT and GRE. The results provide evidence that ovarian function in mature subordinate females might be affected by the reproductive condition of the dominant female.     

Changes in Social Behavior and Their Hormonal Correlates during Pregnancy in Pig-tailed Macaques

I conducted a longitudinal study of hormones and social behavior during pregnancy in 8 female pig-tailed macaques (Macaca nemestrina) living in a captive social group. Females exhibited reduced grooming activity after the first month of pregnancy and reduced aggressiveness in the last month. Female-male hindquarter presentations and male-female foot-clasp mounts decreased steadily during pregnancy. The week before parturition was associated with lower involvement in all social activities. Monthly changes in plasma concentrations of estradiol and progesterone are correlated with some changes in sexual behavior and grooming performed by pregnant females. Altogether, the findings suggest that pregnancy does not bring about a major disruption of female social relationships with other group members and that the influence of pregnancy hormones on female affiliative and agonistic behavior is less marked than that previously observed for infant-directed behavior.     

Circadian and Ultradian Periodicities of Grooming Behavior in Family Groups of Common Marmosets (Callithrix jacchus) in Captivity

Three families' groups of common marmosets were observed to describe the characteristics of their grooming rhythmicity, as the duration of the episodes of self- and social grooming made and received by the animals, in captivity under natural environmental conditions. Data were collected by focal animal sampling, at 20 min hourly intervals during 16 non-consecutive days, from January to March in 1994 (sunrise: 05:24 h ± 2 min; sunset: 17:34 h ± 1 min). Time series were obtained for each individual and for each family through hourly duration of grooming. Family time serie was obtained through the mean of its individuals time series. Spectral analysis revealed statistically significant circadian rhythms for all families and individuals. Ultradian components were detected in 50% of the families and in 46.7% of the animals. Acrophases of self- and social grooming calculated by Single Cosinor took place between 9:21 h and 10:39 h, for the families. For individuals self- and social grooming made and received, acrophases occurred from 8:35 h to 12:43 h. The confidence limits of acrophases did not show differences between the families and the individuals within the families, irrespective of their sex, age and reproductive condition, suggesting that this behavior has a stronger temporal marking. Grooming has circadian and ultradian components of rhythmicity in captive families' groups of common marmosets, under natural environmental conditions. Since only some animals showed the ultradian component, it may be consequence of social or environmental masking, or yet phenotypic plasticity of temporal genotype. Further studies are needed to test these possibilities.     

A hormonal basis for sex differences in the self-grooming of rats

The self-grooming behavior of prepubescent male and female rats is described. Sex differences were observed in components of grooming addressed to the genitals, but not in other aspects of grooming. A hormonal basis for the sex difference was examined in two experiments. When females were injected with testosterone propionate (TP) on the day of birth, their subsequent grooming was found to be no different from that of control-treated females. However, males and females gonadectomized at weaning and treated daily with TP each performed significantly more genital self-grooming than oil-treated controls. There were no sex differences in gonadectomized, oil-treated rats, and sex differences in response to TP were limited to greater responsiveness of females to a 50-micrograms, but not 200-micrograms, TP dose. These results lead to the conclusion that sex differences in self-grooming can be accounted for primarily by differences in testosterone availability during the peripubertal period.     

Re-evaluation of reproductive cycle and fecundity of finetooth sharks Carcharhinus isodon (Valenciennes 1839) from the Northwest Atlantic Ocean,with new observations on ovarian cycle and reproductive endocrinology of biennially reproducing sharks

To provide updated information on life history for improved fishery management, the reproductive cycle of the finetooth shark Carcharhinus isodon from Northwest Atlantic (NWA) populations was investigated by examining temporal changes in morphology and histology of reproductive organs. Changes in plasma concentrations of gonadal sex hormones in relation to reproductive stage were also examined. Increases in testis width, epididymis head width, plasma testosterone concentrations and occurrence of mature spermatozoa were observed in male sharks between December and April, suggesting a seasonal pattern in reproduction that culminates with copulatory activity in May. Increases in maximum follicular diameter, oviducal gland width, plasma 17β-estradiol concentrations and occurrence of vitellogenic follicles were observed in non-pregnant female sharks during the same time period along with the occurrence of newly pregnant females in May, demonstrating strong synchronicity between male and female reproductive cycles. Pregnant females bearing full-term embryos were also observed in May, indicating that parturition occurs between mid-May and early June and gestation requires 12 months. Only transient temporal changes in follicle size and oviducal gland width were observed in pregnant females, indicating that reproductive periodicity is biennial; nonetheless, a single female exhibiting signs of concurrent vitellogenesis and pregnancy was observed. Mean brood size ± S.D. was 3.9 ± 0.9 offspring/female. Fecundity was not significantly correlated with female size, in part due to an unexpectedly high rate of early embryo mortality, which occurred in 11% of pregnant females, and was more common in larger individuals. Changes in ovarian activity during mid-pregnancy were observed, suggesting possible roles for the ovary in regulating some aspects of early to mid-gestation. This study confirms that earlier characterizations of the reproductive cycle and fecundity in NWA finetooth sharks remain valid for use in fishery management. This study also highlights unusual features of finetooth shark pregnancy (e.g., early embryo death, mid-pregnancy changes in ovarian function) that may have broader relevance to understanding elasmobranch reproduction.     

The amount of time that a meadow vole, Microtus pennsylvanicus, self-grooms is affected by its reproductive state and that of the odor donor

Many hypotheses have been put forth to account for differences in the amount of time that animals engage self-grooming when exposed to conspecifics or their odors, but most ignore the possibility that self-grooming may be associated with olfactory communication between groomers and conspecifics. As yet, we do not know the function of self-grooming and why animals do so when they encounter the odors of conspecifics. The present experiment tests the hypothesis that the amount of time that a meadow vole, Microtus pennsylvanicus, self-grooms is affected by the reproductive state of the odor donor and its own reproductive state. The findings support the hypothesis. Male voles spent more time self-grooming when they were exposed to bedding scented by female voles in postpartum estrus (PPE) compared to that of female voles in other reproductive states and female mice. PPE female voles spent more time self-grooming when they were exposed to bedding scented by testosterone-treated male voles than either to that of gonadectomized male voles and male mice. PPE female voles spent more time than OVX+E and more time than OVX females self-grooming when they were exposed to bedding scented by testosterone-treated male voles. GX+T male voles spent more time than GX male voles self-grooming when they were exposed to bedding scented by PPE female voles. The results suggest that individuals self-groom more in the presence of an odor of a highly receptive potential mate than that of a less receptive mate.     

Relation between circulating sex steroid concentrations and sexual behaviour during pregnancy and post partum in the domestic rabbit

Sexual behaviour of 16 female and 12 male rabbits was studied during pregnancy and early post partum. The main behavioural events of the male (nuzzling and mounting) did not differ in the presence of receptive or non-receptive females. When introduced into the cage of the male, receptive and non-receptive females flattened to the floor or circled around. Sexual receptivity to males decreased in early pregnancy and increased to a maximum a few days around parturition; on Days 1 and 6 post partum, all experimental rabbits submitted to mating. Two groups of females were distinguished: one group submitting to mating whatever the stage of pregnancy, the second being receptive only during the few days before parturition or post partum. During pregnancy and early post partum there was no relation between the colour of the vulva and the female sexual behaviour. Does remained sexually receptive even when progesterone concentrations were high. Nevertheless, the number of receptive females was higher when progesterone concentrations decreased around parturition and the mean daily progesterone values were consistently higher in non-receptive than in receptive females. Oestrogen concentrations during pregnancy were very low and were not related to receptive behaviour.     

In‐house monitoring of steroid hormone metabolites in urine informs breeding management of a giant anteater (Myrmechophaga tridactyla)

Although numbers of giant anteaters within North American facilities have been steadily increasing for the last 15 years, the population now exhibits an unstable age distribution with genetically valuable individuals nearing reproductive senescence. Contributing to this issue is the Association of Zoos and Aquariums (AZA) described lack of standardization of breeding introduction practices and high risk of female injury occurring during such pairings. This report describes the development of a successful breeding protocol at Cleveland Metroparks Zoo based on hormone monitoring and efficient communication between science and animal management teams that minimizes risk of female injury. By training a female giant anteater for urine sample and body weight data collection, staff members accurately predicted estrus, and timed breeding introductions to facilitate positive interactions between the male and female. Such training also allowed for careful monitoring of two pregnancies through parturition (169–184 days from breeding) and post‐partum return to estrus (114–129 days from parturition). Urinary hormone monitoring revealed a sharp progestogen increase averaging >five‐fold over basal levels (0.52 ± 0.05 ng/mg creatinine) which was sustained throughout the second half of pregnancy. Mean regular estrous cycle length (n = 14 cycles), was calculated as 46.17 ± 1.39 days, measured as days between estrogen peaks of mean concentration 2.27 ± 0.19 ng/mg creatinine. This report summarizes impressive collaborative efforts among multiple zoological departments to achieve extensive hormonal and body weight monitoring from a female giant anteater, adding valuable information on reproductive parameters, and specifics for novel hormone assay techniques.     

Hormonal and Behavioral Variation in Pied Tamarins Housed in Different Management Conditions

Pied tamarins are an endangered Amazonian primate that has limited breeding success in zoos. Unfortunately, little is known about their reproductive biology and adrenocortical activity. Objectives were: (1) determine if fecal hormones could be utilized to monitor gonadal and adrenocortical activity; (2) characterize male and female gonadal and adrenocortical hormones; and (3) determine if there were differences between adrenocortical activity and behavior in a nonbreeding, on‐exhibit (NB‐ON) pair compared to a breeding, off‐exhibit (B‐OFF) pair. Fecal samples were collected from four (two males; two females) individuals. Hormones were analyzed for fecal progesterone (FPM), androgen (FAM), and glucocorticoid (FGM) metabolites by enzyme immunoassay. Behavioral observations were conducted for 6 months. Data were collected on instantaneous behavior, location, and all occurrences of intraspecific behaviors. Fecal progesterone metabolites were validated by pregnancy (mean ± SE, pregnant: 28.47 ± 1.60 μg/g; nonpregnant: 8.63 ± 0.89 μg/g). Fecal androgen metabolites were higher (T = 31,971, P < 0.05) in the B‐OFF male (863.66 ± 46.30 μg/g) than the NB‐ON male (838.63 ± 60.70 μg/g). Fecal glucocorticoid metabolites were validated by response to veterinary procedure with elevated values (7.31 ± 1.48 μg/g) seven times the baseline (0.37 ± 0.04 μg/g) at 24‐hr postphysical. Females had higher baseline FGM than the males (P < 0.05). Baseline FGM were higher (P < 0.05) in the NB‐ON female (0.93 ± 0.03 μg/g) compared to the B‐OFF female (0.38 ± 0.02 μg/g). Similarly, the NB‐ON male's FGM baseline (0.71 ± 0.03 μg/g) were higher (P < 0.05) than the B‐OFF male (0.21 ± 0.01 μg/g). Behavioral data revealed stereotypical behaviors in the NB‐ON pair but no stereotypical behaviors in the B‐OFF pair. Fecal hormone monitoring and behavioral analysis may provide insight on the limited breeding success of pied tamarins in zoos. Zoo Biol. 32:299–306, 2013. © 2012 Wiley Periodicals, Inc.     

Sociality in Callithrix penicillata: II. Individual Strategies During Intergroup Encounters

In social animals, intergroup interactions, whether through agonistic and competitive behaviors or affiliative ones, can influence important parameters such as home range, territory sizes, and access to resources, which may directly affect both female and male fitness. We studied the intergroup interaction patterns of a wild group of black-tufted-ear marmosets (Callithrix penicillata) in central Brazil. Agonistic interactions occurred at low frequencies during intergroup encounters. The marmosets directed agonistic interactions without physical aggression primarily against same-sex individuals, suggesting that male and female aggression patterns are shaped by their sexual interests. However, females of the focal group also directed agonistic behavior toward extragroup males that attempted copulation. The marmosets appeared to use intergroup encounters to gather information about possible partners and extragroup reproductive opportunities. Intergroup sexual interactions occurred mainly in the form of copulations or attempted copulations by all adults, with the exception of the dominant female. Our results suggest that a possible reproductive strategy used by males is to attempt fertilization of extragroup females. Adult males copulated with the same extragroup female during several opportunities, which suggests sperm competition or the establishment of social bonds with neighboring females.     

The effect of breed, time spent with dam and late pregnancy induction of parturition on behavioural development in dairy calves

Three experiments examined the impact of breed, time spent with dam (TWD), gender, and late pregnancy induction of parturition and caesarean on the behavioural and heart rate responses of dairy calves at 2 and 6 weeks of age to Open field, Novel object and Startle tests and a Learning task. In Experiment 1 with male Jersey, Friesian and Friesian × Angus calves, there were some significant breed effects on responses to the Open field and the Novel object tests; Jersey calves appeared more curious and less fearful than Friesian × Angus calves. In Experiment 2, in which male and female Friesian calves were removed from their dams either between 0 and 12 h or 12 and 24 h after birth, there were no significant effects of gender or TWD. In Experiment 3, which studied the effect of induction of parturition using a long-acting glucocorticoid combined with short-acting progesterone 10 days prior to due calving date, there were no significant effects of late pregnancy induction of parturition. Across all three experiments, age at testing was the main factor influencing the responses of the calves. However, a number of interactions suggest that gender, time spent with dam and late pregnancy induction of parturition modified some of the responses to the tests as the calves developed.     

Social relationships among adult female baboons

Adult female baboons were studied over a 15-month period which included sexual cycling, pregnancy, and lactation. Females could be ranked in a linear dominance hierarchy which accurately predicted the direction, but not the frequency, of agonistic interactions. Females were most attractive to others during lactation, receiving less aggression, more friendly gestures, more grooming, and grooming by more different individuals than females in other reproductive states. In all three reproductive states high-ranking females were more attractive than others. When differences in behaviour related to changes in reproductive state were factored out, individual females groomed animals next to themselves in the dominance hierarchy more than others. A model is presented showing how rank-relaed access and attractiveness may interact to perpetuate this distribution of grooming over time.     

Social and developmental influences on urinary androgen levels in young male white-faced marmosets (Callithrix geoffroyi)

Callitrichine primates (marmosets and tamarins) often remain in their natal groups beyond the time of sexual maturity. Although studies have characterized the development of female reproductive function in callitrichine offspring, less is known about the male reproductive development. To document reproductive development in male marmosets, we monitored urinary androgen (uA) excretion in males housed in a captive colony of white-faced marmosets (Callithrix geoffroyi). Young male marmosets showed relatively low and stable rates of uA excretion early in life, with elevated production at the end of the juvenile period (9-10 months) and again at the onset of adulthood (16 months). uA levels of adult breeding males were also measured to compare to adult-aged sons. Although breeding males did have higher uA levels than their adult-aged sons, these differences did not reach conventional levels of significance. Evidence from some other reports has suggested that androgen levels of males in other species are influenced by social factors, such as the presence of a sexually receptive female or of dependent offspring. In this study, however, uA levels did not vary, based on their mothers' pregnancy status or the presence of younger siblings in the natal group. Patterns of androgen excretion in the white-faced marmoset roughly reflect those of other callitrichine species. Furthermore, unlike callitrichine daughters, gonadal activity in sons does not seem to be sensitive to within-group social cues.