Non-invasive monitoring of fecal androgens in spotted hyenas (Crocuta crocuta)

Spotted hyenas (Crocuta crocuta) exhibit an array of behavioral and morphological characteristics that set them apart from other mammals: females are heavier and more aggressive than males, and females have external genitalia that closely resemble those of the male. Because androgenic hormones might mediate the expression of these traits, androgens are of great interest in this species. Past work on circulating androgens in wild hyenas has been limited, in part because of small sample sizes. In this study we validated a non-invasive method of monitoring variation in androgens by measuring total androgen metabolites in the feces of wild and captive spotted hyenas with an enzyme immunoassay. HPLC analysis revealed multiple immunoreactive androgen metabolites in fecal extracts from both males and females. LHRH challenge in three male and two female hyenas in captivity caused an increase in fecal androgens one to three days after LHRH injection. Furthermore, presence of bone in the diet did not affect fecal androgen concentrations in captive female hyenas. In wild spotted hyenas, time of day of fecal deposition, time elapsed between deposition and freezing of the sample, and time elapsed between freezing and extraction did not systematically affect fecal androgen concentrations. Finally, in wild hyenas, fecal androgen patterns mirrored plasma testosterone patterns in that adult immigrant males had higher concentrations than adult natal males, and pregnant females had higher concentrations than lactating females. These methods can therefore be used in future studies addressing relationships among fecal androgens, social status, reproductive state, and behavior in spotted hyenas.     

Non-invasive measurement of fecal estrogens in the spotted hyena (Crocuta crocuta)

Fecal hormone analysis is a useful tool for frequent, non-invasive sampling of free-living animals. Estrogens fluctuate throughout life among reproductive states in female animals, and intensive repetitive sampling can permit accurate assessment of female reproductive condition. This type of repetitive sampling is difficult in large carnivores, including the spotted hyena (Crocuta crocuta). Patterns of estrogen secretion in captive and free-living hyenas are virtually unknown. Here we present validation of an enzyme-immunoassay to measure fecal estrogen (fE) concentrations in wild and captive spotted hyenas. Results from high-performance liquid chromatography indicate that an antibody specific for estradiol exhibits high immunoreactivity with our extracted samples. Fecal extract displacement curves paralleled our estradiol standard curve within the range of 20-80% antibody binding. Additionally, animals treated with luteinizing hormone-releasing hormone showed a measurable rise in fE concentrations. Finally, once we controlled for effects of time of day of sample collection from wild hyenas, patterns in fE concentrations resembled those in plasma estradiol, including higher levels of fE in mature than immature females, and higher levels of fE during late than early pregnancy. Together, these results suggest that fE concentrations reflect circulating estrogens in spotted hyenas.     

The anti-androgen combination, flutamide plus finasteride, paradoxically suppressed LH and androgen concentrations in pregnant spotted hyenas, but not in males

The androgen receptor blocker flutamide and the 5α-reductase inhibitor finasteride have been used in a variety of species to investigate the ontogeny of sexual dimorphisms by treating pregnant females or neonates at critical periods of sexual differentiation. Likewise, we have used these drugs to study the profound masculinization of the external genitalia in female spotted hyenas. However, a potential pitfall of administering flutamide, either alone or in combination with finasteride, is that it maintains or even raises plasma concentrations of luteinizing hormone (LH) and testosterone (T), because negative feedback of the hypothalamic-pituitary-gonadal axis is disrupted. Contrary to expectations, when pregnant spotted hyenas were treated with flutamide and finasteride (F&F), the concentrations of T during late gestation were suppressed relative to values in untreated dams. Herein, we further investigate the paradoxical effects of F&F treatment on a battery of sex hormones in spotted hyenas. Beyond the effects on T, we found plasma concentrations of LH, estradiol, progesterone and androstenedione (A4) were also significantly lower in F&F-treated pregnant hyenas than in controls. Flutamide and finasteride did not have similar effects on LH, T, and A4 concentrations in male hyenas. The paradoxical effect of F&F treatment on LH and T concentrations in the maternal circulation suggests that negative feedback control of gonadotropin and androgen secretion may be modified in spotted hyenas during pregnancy.     

Phylogenetic comparisons implicate sex hormone-binding globulin in "masculinization" of the female spotted hyena (Crocuta crocuta)

Exposures to sex steroids during fetal development are thought to contribute to the unique urogenital anatomy and social dominance of the female spotted hyena: overt phenotypes not shared by other hyenids (i.e. striped hyena, brown hyena, and aardwolf). Because both androgens and estrogens influence development of genitalia and behavior, and because plasma SHBG regulates their access to tissues, we compared the Shbg gene sequences, structures, and steroid-binding properties in the four extant hyenids. We found the hyenid Shbg genes (>95% identical) and mature protein sequences (98% identical) are highly conserved. As in other mammals, the hyenid SHBG all bind 5α-dihydrotestosterone with high affinity (K(d) = 0.62-1.47 nm), but they also bind estrone and dehydroepiandrosterone with similarly high affinity, and this unusual property was attributed to specific amino acids within their SHBG steroid-binding sites. Phylogenetic comparisons also indicated that the spotted hyena SHBG precursor uniquely lacks two leucine residues and has a L15W substitution within its secretion signal polypeptide, the reduced size and hydrophobicity of which markedly decreases the production of SHBG and may therefore explain why serum SHBG concentrations in male and female spotted hyenas are approximately five times lower than in other hyenids. This is important because low plasma SHBG concentrations in spotted hyenas will increase exposure to biologically active androgens and estrogen as well as to their precursors (dehydroepiandrosterone and estrone), which may contribute to the masculinized external genitalia of female spotted hyenas and to female social dominance over males.     

Noninvasive fecal monitoring of glucocorticoids in spotted hyenas, Crocuta crocuta.

The aim of this study was to validate a method for measuring glucocorticoids noninvasively in feces of spotted hyenas (Crocuta crocuta). Three established enzyme immunoassays (EIA) for cortisol, corticosterone, and 11-oxoetiocholanolone were tested, but proved unsatisfactory. A new EIA using another corticosterone antibody was established and was used for all subsequent analyses; this EIA was validated by demonstrating parallelism between serial dilutions of spotted hyena fecal extracts and dilutions of standard corticosterone and by the recovery of corticosterone added to fecal extracts. High-performance liquid chromatography (HPLC) fractions analyzed by EIA showed various immunoreactive substances with polarities of unconjugated steroids. The physiological relevance of fecal glucocorticoid metabolites was further validated by demonstrating that (1) injection of exogenous ACTH to four males and two females led to a significant increase in fecal glucocorticoid metabolites within 24-50 h, (2) the translocation of a male spotted hyena to a new enclosure resulted in a fivefold increase compared to baseline concentrations, and (3) agonistic social interactions and physical conflict resulted in large increases of fecal glucocorticoid metabolites in both protagonists. Fecal steroid assessment is therefore of use in monitoring adrenal activity in spotted hyenas.     

Symbiotic bacteria appear to mediate hyena social odors

All animals harbor beneficial microbes. One way these microbes can benefit their animal hosts is by increasing the diversity and efficacy of communication signals available to the hosts. The fermentation hypothesis for mammalian chemical communication posits that bacteria in the scent glands of mammals generate odorous metabolites used by their hosts for communication and that variation in host chemical signals is a product of underlying variation in the bacterial communities inhabiting the scent glands. An effective test of this hypothesis would require accurate surveys of the bacterial communities in mammals’ scent glands and complementary data on the odorant profiles of scent secretions—both of which have been historically lacking. Here we use next-generation sequencing to survey deeply the bacterial communities in the scent glands of wild spotted and striped hyenas. We show that these communities are dominated by fermentative bacteria and that the structures of these communities covary with the volatile fatty acid profiles of scent secretions in both hyena species. The bacterial and volatile fatty acid profiles of secretions differ between spotted and striped hyenas, and both profiles vary with sex and reproductive state among spotted hyenas within a single social group. Our results strongly support the fermentation hypothesis for chemical communication, suggesting that symbiotic bacteria underlie species-specific odors in both spotted and striped hyenas and further underlie sex and reproductive state-specific odors among spotted hyenas. We anticipate that the fermentation hypothesis for chemical communication will prove broadly applicable among scent-marking mammals as others use the technical and analytical approaches used here.Every animal is populated by communities of microbes that can profoundly affect its biology, often in beneficial ways (1, 2). Indeed, symbiotic microbes are critical contributors to animal nutrition and immune health, and they serve as important catalysts for the effective development and functioning of animal tissues and neural circuitry (2–5). It also is becoming apparent that symbiotic microbes can extend host behavioral phenotypes in beneficial ways, including facilitating their feeding, antipredator, reproductive, and communicative behaviors (6, 7).An effective communication system is a critical component of an animal’s behavioral repertoire, and one way in which symbiotic microbes might contribute to their hosts’ behavioral phenotypes is by increasing the diversity and/or efficacy of the signals available to them (6, 8). Most animals communicate to some extent via chemical means, and mammals in particular often rely on odorous secretions from integumental scent glands to signal conspecifics (8–10). These glands occupy myriad locations on mammals’ bodies and are typically warm, moist, nutrient-rich, and largely anaerobic. As such, they are conducive to the proliferation of symbiotic, particularly fermentative, bacteria (10). The fermentation hypothesis for mammalian chemical communication posits that as bacteria ferment or otherwise metabolize the nutrient-rich substrates in these glands, they generate odorous metabolites that subsequently are used by their hosts to communicate with conspecifics (6, 10–12). The hypothesis further suggests that variation in chemical signals among mammals with specialized scent glands results largely from an underlying variation in the odor-producing bacterial communities within these glands. If this hypothesis is true, then (i) mammalian scent gland secretions should contain fermentative, odor-producing bacteria, (ii) the bacterial and odor profiles of secretions should covary, and (iii) these profiles should vary with the host characteristics being signaled, such as species identity, group membership, sex, or reproductive state (6).Effective testing of these predictions of the fermentation hypothesis requires accurate surveys of the bacterial communities in the scent gland secretions of mammals as well as complementary data on the odorant profiles of these secretions. Historically, technical limitations of cultivation-based surveys and, to a lesser extent, molecular fingerprinting surveys, of symbiotic bacteria have impeded our ability to test these predictions effectively because these approaches often underestimate the actual diversity in bacterial communities (6, 13). As a consequence, evaluations of the hypothesis typically have concluded that the bacterial diversity in integumental scent gland secretions is insufficient to underlie the observed diversity of chemical signals (6, 14). In a recent study, we used next-generation sequencing to thoroughly survey the bacterial communities in the scent gland secretions of adult female spotted hyenas, Crocuta crocuta (15). That study revealed more types of bacteria than the 15 previous surveys of specialized mammalian scent glands combined and demonstrated that most of these bacteria were members of fermentative, odor-producing clades. It also revealed that the bacterial communities in scent secretions varied among hyena social groups, suggesting that their diversity was sufficient to explain social group-specific odors in spotted hyenas (16). Although that study afforded support for the fermentation hypothesis, it did not include complementary data on the odor profiles of hyena scent gland secretions—data needed to evaluate the hypothesis effectively—and the scope of host traits considered was limited. Here we concurrently analyze the bacterial and odor profiles of scent gland secretions collected from wild spotted and striped hyenas, Hyaena hyaena, in Kenya (Fig. S1) to determine whether the two profiles covary in each species and to ascertain the extent to which the two profiles vary with hyena species, sex, and, in the spotted hyena, female reproductive state.The lifestyles of spotted and striped hyenas differ greatly. Spotted hyenas—found throughout sub-Saharan Africa—live in large, hierarchically structured groups, called clans, that typically contain 40–80 individuals (17). Clans include multiple breeding males and multiple overlapping generations of females, and adult members cooperatively maintain and defend their group’s territory against neighboring clans (18). To mediate the complex social relationships within and among clans, spotted hyenas use a rich repertoire of tactile, visual, vocal, and chemical signaling behaviors (19, 20). In contrast, striped hyenas—found in North, West, and East Africa—live in small groups containing one or two reproductively mature females and one or more adult males (21). Although the home ranges of group members overlap considerably, striped hyenas usually rest, travel, and forage alone; therefore they seldom interact directly with groupmates (21). Little is known of striped hyena communicative behavior, especially in natural populations, but striped hyenas appear to have a very modest vocal signaling repertoire, with no long-distance vocalizations (22). Therefore, among striped hyenas, chemical signaling likely serves a prominent role in territorial behavior and potentially in reproduction as well.Despite their very different lifestyles, spotted and striped hyenas both commonly exhibit a conspicuous chemical signaling behavior called “pasting,” a form of scent marking in which a hyena deposits an odorous secretion, called “paste,” from its subcaudal scent pouch on a grass stalk (20, 22). The major volatile constituents in paste are volatile fatty acids (VFAs), esters, hydrocarbons, alcohols, and aldehydes (23, 24). Previous investigations have shown that the odors of spotted hyena pastes vary with individual identity, group membership, sex, and, potentially, female reproductive state (16, 24, 25). Effects of striped hyena traits on paste odors have not yet been investigated.This study of mammalian scent marking marries data from in-depth, next-generation bacterial surveys with targeted odor analyses of scent secretions from natural populations. We show that the bacterial communities in hyena pastes are dominated by fermentative bacteria and that the structures of these communities covary with the VFA profiles of pastes. Furthermore, we show that the bacterial and VFA profiles of paste differ between spotted and striped hyenas and that, among spotted hyenas in the same social group, both profiles vary with hyena sex and reproductive state. As such, this study illustrates that the diversity of symbiotic bacterial communities in paste appears sufficient to underlie chemical signaling of host traits in hyenas and affords strong empirical support for the fermentation hypothesis for chemical communication.     

Mammalian sexual differentiation: lessons from the spotted hyena.

Female spotted hyenas (Crocuta crocuta) are the only female mammals that lack an external vaginal opening. Mating and birth take place through a urogenital canal that exits at the tip of a hypertrophied clitoris. This 'masculine' phenotype spurred a search for an alternate source of fetal androgens. Although androstenedione from the maternal ovary is readily metabolized to testosterone by the hyena placenta, formation of the penile clitoris and scrotum appear to be largely androgen independent. However, secretions from the fetal testes underlie sex differences in the genitalia and central nervous system that are essential for male reproduction. Naturally circulating androgens, acting prenatally, reduce reproductive success in adult female spotted hyenas. Effects on aggression and dominance might offset these reproductive 'costs' of female androgenization in utero.     

Prenatal Ethanol Exposure Differentially Alters Behavior in Males and Females on the Elevated Plus Maze

Rodents prenatally exposed to ethanol demonstrate hypothalamic-pituitary-adrenal and behavioral hyperactivity to a variety of stressful situations. The present study examined both behavioral and corticosterone (CORT) responses to the elevated plus maze (+-maze), an anxiety- or fear-provoking task. Sprague-Dawley male and female offspring from fetal ethanol-exposed (E), pair-fed (PF), and ad libitum-fed control (C) groups were tested at 60 to 90 days of age. In experiment 1, behavior was measured in animals exposed to the +-maze for 5 min on two consecutive days; 2 weeks later, both behavioral and CORT responses were measured in animals confined to the open and closed arms of the maze for 20 min. In experiment 2, animals were placed in an open field (OF) for 5 min before a single 5-min exposure to the +-maze. Factor analysis of the scored behaviors from the two experiments indicated two main factors, designated "exploration" and "fear." E males and females both exhibited higher levels of exploratory behaviors when placed directly on the +-maze from their homecages without prior exposure to the OF, compared with C males and females. In addition, when confined to the closed arms of the +-maze, E males and females demonstrated higher levels of activity, compared with C males and females. After OF exposure, however, both E males and females demonstrated lower levels of exploratory behaviors than C males and females, and E females also had increased CORT levels, compared with PF and C females. Interestingly, E females, but not E males, showed an increase in fear-related behaviors on the +-maze, compared with controls, regardless of prior OF exposure. These data demonstrate that prenatal ethanol exposure may differentially affect both behavioral and hormonal responses of males and females in an aversive behavioral task and suggest that there may be a sex difference in the sensitivity of the mechanism(s) underlying these responses.     

Validation of an enzyme immunoassay for the measurement of faecal glucocorticoid metabolites in spotted hyenas (Crocuta crocuta)

The use of enzyme immunoassays (EIAs) to measure faecal glucocorticoid metabolites (fGCM) is a useful non-invasive technique to monitor adrenocortical activity in vertebrates. The first objective of this study was to validate an 'in-house' EIA (cortisol-3-CMO) for the measurement of fGCM concentrations in spotted hyenas. High-performance liquid chromatography (HPLC) was used to characterise fGCM in samples from a captive hyena that received an i.v. injection of [(3)H] cortisol. All HPLC fractions were analysed with the EIA for the presence and quantities of radiolabelled fGCM. Radiolabelled fGCM consisted of substances with a higher polarity than cortisol and substances of lower polarity that eluted between cortisol and corticosterone. Authentic radiolabelled cortisol was not detected. The EIA measured substantial amounts of immunoreactivity corresponding to the radioactive peaks. It also detected a significant increase in fGCMs after an adrenocorticotropic hormone (ACTH) challenge in two other captive animals and a significant increase in fGCMs in a fourth captive animal after anaesthesia. The second objective was to investigate an age effect on fGCM: we conducted pairwise comparisons of fGCM concentrations in individual free-ranging juvenile spotted hyenas when less than 6months of age and when between 6 and 24months of age. We expected juveniles to experience a more unpredictable and therefore more stressful environment when younger than when older. When younger, juveniles had significantly higher fGCM concentrations than when they were older. Our results demonstrate that our assay can be used to assess adrenocortical activity in spotted hyenas.     

Seasonal changes in prolactin and luteinizing hormone in the polyandrous spotted sandpiper, Actitis macularia

The polyandrous spotted sandpiper (Actitis macularia) is a species characterized by female dominance over males and predominant male parental care. Prolactin (Prl) and luteinizing hormone (LH) were analyzed in plasma samples obtained serially from individuals across different stages of the breeding season. The reproductive status of each sampled individual was known in detail. Similar Prl values were obtained independently by two different assays. Males tended to have higher plasma Prl levels than females throughout the breeding season. Prl was significantly elevated in both sexes by the first few days of incubation. This rapid rise in Prl may indicate its role in brood patch development and the onset of incubation behavior. In males Prl continued to rise during incubation, whereas it remained constant in females. Higher levels of Prl in males than females, especially late in incubation, reflects the greater contribution of males to incubation. LH declined markedly in males and females from prelaying to early incubation. There was a significant negative correlation between Prl and LH among males, especially from the prelaying to early incubation phases of the season. There was no such correlation among females.     

Sex differences in male-typical copulatory behaviors in response to androgen and estrogen treatment in rats

The present experiment was performed to test the hypothesis that gender differences in the capacity for brain estrogen synthesis could constitute a sexually dimorphic mechanism that limits the activational effects of testosterone (T) in females, and enhances them in males. We determined the effects of treatments with equivalent levels of either T or estradiol (E2) on olfactory behavior and mounting in age-matched heterosexually naive gonadectomized male and female rats that were genitally ansthetized with lidocaine paste in order to minimize the contribution of sexually dimorphic somatosensory inputs to the expression of copulatory behavior. We found that T stimulated mounting to a greater extent in males than in females, but had equivalent effects on mount latency and genital investigation in the two sexes. On the other hand, E2 stimulated equivalent levels of mounting in males and females and reduced mount latency to a similar extent in males and females. However, E2 had a pronounced effect on the levels of genital investigation in males but not in females. Serum steroid levels and the levels of nuclear steroid receptor occupation in the brain were not different between males and females, suggesting that the behavioral differences between males and females cannot be attributed to differences in peripheral steroid metabolism or brain uptake. The results obtained corroborate previous studies suggesting that female rats normally undergo considerable male-typical behavioral masculinization during fetal development. However, such male-typical features of normal development in female rats do not extend to the regulation of preoptic aromatase activity or to the capacity of females to display olfactory behaviors in response to adult E2 exposure, functions which are sexually dimorphic even in the rat. The present results support the view that gender differences in the capacity for brain estrogen synthesis contribute to the sexually dimorphic display of T-stimulated male-typical sexual motivation and copulatory behavior in rats.     

Effects of age, gender, and gonadectomy on neurochemistry and behavior in animal models of Parkinson's disease

The effects of aging and gender on the neurochemistry of the dopaminergic system have been studied extensively; however, data on comparative behavioral consequences of lesions of the dopaminergic system in aging and in female animals are limited. This study presents experimental results on the behavioral and morphological outcome in young, aging, and gonadectomized male and female rats in the 6-OHDA model of Parkinson's disease. Both young and aging male animals were more susceptible to 6-OHDA than females: female rats had significantly less dopaminergic cell loss and showed a higher degree of behavioral recovery. Although the dopaminergic cell loss was only slightly more in the aging rats of the same sex, they showed more severe behavioral deficits in both gender groups. Ovariectomy did not significantly influence the dopaminergic cell loss, but behavioral recovery was worse when compared to non-ovariectomized females. In contrast, castrated males had significantly less dopaminergic cell loss than non-castrated males, but the behavioral recovery was not significantly better. The obtained results are discussed in light of the available literature on the age and gender differences in animals models of Parkinson's disease.     

Neonatal estrogen decreases neural density of the septum-midbrain central gray connection underlying the lordosis-inhibiting system in female rats

Neurons in the lateral septum (LS) with projecting axons to the midbrain central gray (MCG) exert an inhibitory influence on lordosis. The number of such neurons is greater in female than in male rats. In this experiment, effects of neonatal estrogen on the density of the LS-MCG connections and on lordosis behavior were examined in female rats. On postnatal day 4 (day 0 = day of birth), females were injected subcutaneously with 50 or 100 mug estradiol benzoate (EB) or oil. On postnatal day 60, females and control males were gonadectomized. Behavioral tests were carried out after the implantation of silicone tubes containing estradiol. Lordotic activities in both males and EB-treated females were lower than in oil-treated females. After completing the behavioral tests, the animals were injected with Fluoro-Gold (FG), a retrograde tracer, into the right-side MCG and the number of FG-labeled neurons in the LS was measured. In all groups, the right-side LS ipsilateral to the FG injection had more FG-labeled neurons than the left-side LS. The number of FG-labeled neurons in the LS of oil-treated females was larger than that of males on both right and left sides. In the females treated with 100 mug EB (EB100), the number of FG-labeled neurons was comparable with that of males and lower than that of oil-treated females. The number of FG-labeled neurons in the EB50 females was also lower than that in oil-treated females, but tended to be larger than that observed in the EB100 group. These results indicate that neonatal estrogen decreases both lordotic activity and the density of the LS-MCG neural connections in female rats.     

Sexual differences in the Japanese quail: behavior, morphology, and intracellular metabolism of testosterone

Three experiments were carried out to study whether differences in the intracellular metabolism of testosterone (T) can explain sexually differential responses to T in Japanese quail. In the first experiment, a series of dose-response curves in which length of Silastic testosterone implants was related to effects on several behavioral and physiological variables was established. In Experiment 2, adult males and females were assigned to six experimental groups: intact males and females (I-males and I-females), castrated males and females implanted subcutaneously with 40-mm Silastic implants of T (T-males and T-females), and castrated males and females without hormone treatment (CX-males and CX-females). No CX-bird (male or female) and no I-female exhibited male sexual behavior. However, I-males and T-males regularly copulated during the behavioral tests. No crowing was ever heard in CX-animals and I-females. T-females crowed less than T-males and their crowing sounded weaker than those of males. The cloacal glands of T-females were less developed than those of males. Radioimmunoassay of T and 5 alpha-DHT showed that T-males and T-females have similar plasma levels of androgens. No striking differences were observed in the way testosterone is metabolized by the pituitary gland and central nervous tissues of males and females. By contrast, the production of 5 alpha-dihydrotestosterone (5 alpha-DHT) and 5 alpha-androstane-3 alpha, 17 beta-diol (5 alpha, 3 alpha-diol) was higher in the cloacal glands of males than in those of females. These sex differences were not detected between T-males and T-females. In experiment 3, the cloacal gland of males produced more 5 alpha-reduced metabolites than those of females. The pituitary gland of females also produced more 5 beta-androstane-3 alpha, 17 beta-diol (5 beta, 3 alpha-diol). In syringeal muscles, the production of 5 beta-dihydrotestosterone (5 beta-DHT) and 5 beta, 3 alpha-diol was higher in females compared to males.     

Psychosocial influences on female 'protection' among cynomolgus macaques

We evaluated atherosclerosis (coronary artery, aortic and carotid bifurcation), plasma lipids, and blood pressure in 15 male and 23 female cynomolgus macaques (Macaca fascicularis). In addition, female social behavior and ovarian function were monitored. The females lived in stable (unmanipulated) or unstable (periodically altered composition) social groups while males lived in stable groupings. All animals were fed for 30 months an atherogenic diet which resulted in moderate hyperlipoproteinemia (median total plasma cholesterol congruent to 275 mg/dl). Socially dominant females had less extensive and severe coronary artery atherosclerosis than males or socially subordinate females; atherosclerosis extent and severity were similar in these latter two groups. Importantly, dominant females also had regular ovarian function and relatively small adrenal glands while subordinate females had impaired ovarian function (increased frequency of anovulatory cycles and luteal phase deficiencies) and relatively large adrenal glands. The dominant and subordinate females did not differ in plasma lipids. These results suggest that female 'protection' from coronary artery atherosclerosis may be influenced as much by behavioral and hormonal characteristics as by plasma lipids. Among other findings, males had more extensive atherosclerotic lesions at the carotid bifurcations than females. In addition, males had lower high density lipoprotein cholesterol concentrations and higher blood pressures than females. The gender difference in extent of atherosclerosis at the carotid bifurcation was unrelated to social factors or plasma lipids; it may have been due, in part, to the higher blood pressures of the males.     

Genetic benefits enhance the reproductive success of polyandrous females

Although it is generally accepted that females can gain material benefits by mating with more than one male, the proposal that polyandry provides genetic benefits remains controversial, largely because direct experimental support is lacking. Here, we report the results of a study testing for genetic benefits to polyandry in the pseudoscorpion Cordylochernes scorpioides. In an experiment that controlled for male mating experience and the number of spermatophores accepted by a female, twice-mated females received either one sperm-packet from each of two different males (the "DM" treatment) or two sperm-packets from a single male (the same male or "SM" treatment). Over their lifetime, DM females gave birth to 32% more offspring than did SM females, primarily because of a significantly reduced rate of spontaneous abortion. This result could not be attributed to male infertility nor to lack of sexual receptivity in males paired with previous mates. Spermatophore and sperm numbers did not differ between males presented with a previous mate and males paired with a new female. Because SM and DM females received the same quantity of ejaculate, it was possible to eliminate material benefits as a contributor to the enhanced reproductive success of DM females. The reduction in embryo failure rate achieved by DM females is most consistent with the genetic incompatibility avoidance hypothesis, i.e., that polyandry enables females to exploit postcopulatory mechanisms for reducing the risk and/or cost of fertilization by genetically incompatible sperm. This study, which rigorously controlled for material benefits and excluded inbreeding effects, demonstrates that polyandry provides genetic benefits that significantly enhance female lifetime reproductive success.     

The effects of stress on social preferences are sexually dimorphic in prairie voles.

Prairie voles (Microtus ochrogaster) are monogamous rodents that form pair bonds characterized by a preference for a familiar social partner. In male prairie voles, exposure to either the stress of swimming or exogenous injections of corticosterone facilitate the development of a social preference for a female with which the male was paired after injection or swimming. Conversely, adrenalectomy inhibits partner preference formation in males and the behavioral effects of adrenalectomy are reversed by corticosterone replacement. In female prairie voles, swim stress interferes with the development of social preferences and corticosterone treatments inhibit the formation of partner preferences, while adrenalectomized females form preferences more quickly than adrenally intact controls. Because sex differences in both behavior and physiology are typically reduced in monogamous species, we initially predicted that male and female prairie voles would exhibit similar behavioral responses to corticosterone. However, our findings suggest an unanticipated sexual dimorphism in the physiological processes modulating social preferences. This dimorphic involvement of stress hormones in pair bonding provides a proximate mechanism for regulating social organization, while permitting males and females to adapt their reproductive strategies in response to environmental challenges.     

Multivariate analysis of Drosophila courtship

Courtship records of 15 pairs of Drosophila melanogaster were analyzed for temporal stationarity of courtship behaviors, behavioral diversity, behavioral intercorrelations, sequential properties, and information transmission for both sexes. Durations of one male behavior, “orient-back,” and two female behaviors, “preen” and “stand still,” were found to change from the first to the second half of courtship. Male diversity was greater than female diversity, and both were stationary over time. Correlation analyses failed to single out any particular male or female behaviors as being influential in controlling courtship duration. Male behavior sequences formed several multibehavior loops; female behavior consisted of only a few terminal two-tuple transitions. Transmission analysis carried out on the joint male/female transition matrix showed a higher transmission rate from males to females (12%) than from females to males (7%). Potential applications of this multivariate analysis to investigations of neurobiological and evolutionary aspects of Drosophila courtship behavior are proposed.     

Smoking cessation in women: effects of the menstrual cycle.

Ten females in the midcycle phase of the menstrual cycle, 10 females in the premenstrual phase of the menstrual cycle, and 10 males agreed to try and stop smoking for two consecutive days. The Smoking Motivation Questionnaire and Profile of Mood States Questionnaire (POMS) were completed by all subjects beforehand. On each "no smoking" day, the POMS and a Smoking Withdrawal Questionnaire were completed. Males and midcycle females achieved significantly greater smoking reduction than premenstrual females during the "no smoking" days. Premenstrual females reported becoming significantly more tired, confused, depressed, anxious, and irritable than midcycle females. Midcycle females reported only slight changes in feeling state during cigarette withdrawal. The position of the males was broadly intermediate between the two female groups.