Integrating the female masculinization and challenge hypotheses: Female dominance, male deference, and seasonal hormone fluctuations in adult blue-eyed black lemurs (Eulemur flavifrons).

In the decades since female social dominance was first described in strepsirrhine primates, researchers have sought to uncover the proximate and ultimate explanations for its development. In the females of various female-dominant species, androgens have been implicated as regulators of behavior and/or predictors of seasonal fluctuations in aggression (the 'Female Masculinization Hypothesis'). Males, more generally, respond to changing social demands via seasonal fluctuations in androgen-mediated behavior (the 'Challenge Hypothesis'), that may also entail changes in activation of the hypothalamic-pituitary-adrenal axis. Here, we explore if androgens, glucocorticoids, and intersexual behavior fluctuate seasonally in the female-dominant, blue-eyed black lemur (Eulemur flavifrons), with potential consequences for understanding female aggression and male deference. Across two studies conducted during the breeding and nonbreeding seasons, we assessed rates of mixed-sex, dyadic social behavior (aggression and affiliation) and concentrations of fecal glucocorticoid metabolites (Study 1) and serum sex hormones (androstenedione, testosterone, and estradiol; Study 2). Our results align with several predictions inspired by the Female Masculinization and Challenge Hypotheses for intersexual relations: During the breeding season, specifically, both aggression and androstenedione peaked in females, while female-initiated affiliation decreased, potentially to facilitate female resource access and reproductive control. By comparison, all target hormones (androgens, estrogen, and glucocorticoids) peaked in males, with glucocorticoid concentrations potentially increasing in response to the surge in female aggression, and unusually high estrogen concentrations year-round potentially facilitating male deference via male-initiated affiliation. These results suggest complex, seasonally and hormonally mediated behavior in Eulemur flavifrons.

Meerkat manners: Endocrine mediation of female dominance and reproductive control in a cooperative breeder.

This article is part of a Special Issue (Hormones and Hierarchies). To gain more balanced understanding of sexual selection and mammalian sexual differentiation processes, this review addresses behavioral sex differences and hormonal mediators of intrasexual competition in the meerkat (Suricata suricatta) - a cooperative breeder unusual among vertebrates in its female aggression, degree of reproductive skew, and phenotypic divergence. Focused on the evolution, function, mechanism, and development of female dominance, the male remains a key reference point throughout. Integrated review of endocrine function does not support routine physiological suppression in subordinates of either sex, but instead a ramp up of weight, reproduction, aggression, and sex steroids, particularly androgens, in dominant females. Important and timely questions about female competition are thus addressed by shifting emphasis from mediators of reproductive suppression to mediators of reproductive control, and from organizational and activational roles of androgens in males to their roles in females. Unusually, we ask not only how inequity is maintained, but how dominance is acquired within a lifetime and across generations. Antiandrogens administered in the field to males and pregnant dominant females confirm the importance of androgen-mediated food competition. Moreover, effects of maternal endocrine milieu on offspring development reveal a heritable, androgenic route to female aggression, likely promoting reproductive priority along dominant matrilines. Integrating endocrine measures with long-term behavioral, ecological, morphological, and life-history data on normative and experimental individuals, across life stages and generations, provides better appreciation of the role of naturally circulating androgens in regulating the female phenotype, and sheds new light on the evolution of female dominance, reproductive inequity, and cooperative breeding.

Genetic variation at MHC class II loci influences both olfactory signals and scent discrimination in ring-tailed lemurs.

BACKGROUND: Diversity at the Major Histocompatibility Complex (MHC) is critical to health and fitness, such that MHC genotype may predict an individual's quality or compatibility as a competitor, ally, or mate. Moreover, because MHC products can influence the components of bodily secretions, an individual's body odors may signal its MHC composition and influence partner identification or mate choice. Here, we investigated MHC-based signaling and recipient sensitivity by testing for odor-gene covariance and behavioral discrimination of MHC diversity and pairwise dissimilarity in a strepsirrhine primate, the ring-tailed lemur (Lemur catta). METHODS: First, we coupled genotyping of the MHC class II gene, DRB, with gas chromatography-mass spectrometry of genital gland secretions to investigate if functional genetic diversity is signaled by the chemical diversity of lemur scent secretions. We also assessed if the chemical similarity between individuals correlated with their MHC-DRB similarity. Next, we assessed if lemurs discriminated this chemically encoded, genetic information in opposite-sex conspecifics. RESULTS: We found that both sexes signaled overall MHC-DRB diversity and pairwise MHC-DRB similarity via genital secretions, but in a sex- and season-dependent manner. Additionally, the sexes discriminated absolute and relative MHC-DRB diversity in the genital odors of opposite-sex conspecifics, suggesting that lemur genital odors function to advertise genetic quality. CONCLUSIONS: In summary, genital odors of ring-tailed lemurs provide honest information about an individual's absolute and relative MHC quality. Complementing evidence in humans and Old World monkeys, we suggest that reliance on scent signals to communicate MHC quality may be important across the primate lineage.

Organizational and activational androgens, lemur social play, and the ontogeny of female dominance.

The role of androgens in shaping "masculine" traits in males is a core focus in behavioral endocrinology, but relatively little is known about an androgenic role in female aggression and social dominance. In mammalian models of female dominance, including the ring-tailed lemur (Lemur catta), links to androgens in adulthood are variable. We studied the development of ring-tailed lemurs to address the behavioral basis and ontogenetic mechanisms of female dominance. We measured behavior and serum androgen concentrations in 24 lemurs (8 males, 16 females) from infancy to early adulthood, and assessed their 'prenatal' androgen milieu using serum samples obtained from their mothers during gestation. Because logistical constraints limited the frequency of infant blood sampling, we accounted for asynchrony between behavioral and postnatal hormone measurements via imputation procedures. Imputation was unnecessary for prenatal hormone measurements. The typical sex difference in androgen concentrations in young lemurs was consistent with adult conspecifics and most other mammals; however, we found no significant sex differences in rough-and-tumble play. Female (but not male) aggression increased beginning at approximately 15 months, coincident with female puberty. In our analyses relating sexually differentiated behavior to androgens, we found no relationship with activational hormones, but several significant relationships with organizational hormones. Notably, associations of prenatal androstenedione and testosterone with behavior were differentiated, both by offspring sex and by type of behavior within offspring sexes. We discuss the importance of considering (1) missing data in behavioral endocrinology research, and (2) organizational androgens other than testosterone in studies of female dominance.

Local habitat, not phylogenetic relatedness, predicts gut microbiota better within folivorous than frugivorous lemur lineages.

Both host phylogenetic placement and feeding strategy influence the structure of the gut microbiome (GMB); however, parsing their relative contributions presents a challenge. To meet this challenge, we compared GMB structure in two genera of lemurs characterized by different dietary specializations, the frugivorous brown lemurs ( Eulemur spp.) and the folivorous sifakas ( Propithecus spp.). These genera sympatrically occupy similar habitats (dry forests and rainforests) and diverged over similar evolutionary timescales. We collected fresh faeces from 12 species (six per host genus), at seven sites across Madagascar, and sequenced the 16S rRNA gene to determine GMB membership, diversity and variability. The lemurs' GMBs clustered predominantly by host genus; nevertheless, within genera, host relatedness did not predict GMB distance between species. The GMBs of brown lemurs had greater evenness and diversity, but were more homogeneous across species, whereas the GMBs of sifakas were differentiated between habitats. Thus, over relatively shallow timescales, environmental factors can override the influence of host phylogenetic placement on GMB phylogenetic composition. Moreover, feeding strategy can underlie the relative strength of host-microbiome coadaptation, with Madagascar's folivores perhaps requiring locally adapted GMBs to facilitate their highly specialized diets.

The importance of scale in comparative microbiome research: New insights from the gut and glands of captive and wild lemurs.

Research on animal microbiomes is increasingly aimed at determining the evolutionary and ecological factors that govern host-microbiome dynamics, which are invariably intertwined and potentially synergistic. We present three empirical studies related to this topic, each of which relies on the diversity of Malagasy lemurs (representing a total of 19 species) and the comparative approach applied across scales of analysis. In Study 1, we compare gut microbial membership across 14 species in the wild to test the relative importance of host phylogeny and feeding strategy in mediating microbiome structure. Whereas host phylogeny strongly predicted community composition, the same feeding strategies shared by distant relatives did not produce convergent microbial consortia, but rather shaped microbiomes in host lineage-specific ways, particularly in folivores. In Study 2, we compare 14 species of wild and captive folivores, frugivores, and omnivores, to highlight the importance of captive populations for advancing gut microbiome research. We show that the perturbational effect of captivity is mediated by host feeding strategy and can be mitigated, in part, by modified animal management. In Study 3, we examine various scent-gland microbiomes across three species in the wild or captivity and show them to vary by host species, sex, body site, and a proxy of social status. These rare data provide support for the bacterial fermentation hypothesis in olfactory signal production and implicate steroid hormones as mediators of microbial community structure. We conclude by discussing the role of scale in comparative microbial studies, the links between feeding strategy and host-microbiome coadaptation, the underappreciated benefits of captive populations for advancing conservation research, and the need to consider the entirety of an animal's microbiota. Ultimately, these studies will help move the field from exploratory to hypothesis-driven research.

P-Mail: The Information Highway of Nocturnal, but Not Diurnal or Cathemeral, Strepsirrhines.

Scent marking is a well-established, but highly variable, mode of communication among strepsirrhine primates. We begin by reviewing this literature, focusing on nocturnal species. Our understanding about the information content of scent signals and the factors driving species diversity remains incomplete, owing to difficulties in acquiring comparative chemical data. We therefore re-examine such a data set, representing the richness and relative abundance of volatile organic compounds (VOCs) in the urine of 12 species (from Galagidae, Lorisidae, Daubentoniidae, Cheirogaleidae, Indriidae, and Lemuridae), to explore differences between nocturnal, diurnal and cathemeral species. As predicted by the variable importance of urine marking across species, the urine of nocturnal strepsirrhines contained the most VOCs and putative semiochemicals, differed significantly in composition from that of diurnal and cathemeral species and showed the strongest species scent "signatures." Relevant to retracing the evolutionary trajectory of cathemeral strepsirrhines, nocturnal and diurnal species were most differentiated in their VOCs, with cathemeral species being intermediary, but more closely aligned with diurnal species. These data support cathemerality as an ancient expansion of diurnal animals into a nocturnal niche. Consideration of the traits and variables associated with olfactory communication offers a profitable new way for examining species diversity and patterns of evolutionary change.

Down for the count: Cryptosporidium infection depletes the gut microbiome in Coquerel's sifakas.

Background: The gut microbiome (GMB) is the first line of defense against enteric pathogens, which are a leading cause of disease and mortality worldwide. One such pathogen, the protozoan Cryptosporidium, causes a variety of digestive disorders that can be devastating and even lethal. The Coquerel's sifaka (Propithecus coquereli) - an endangered, folivorous primate endemic to Madagascar - is precariously susceptible to cryptosporidiosis under captive conditions. If left untreated, infection can rapidly advance to morbidity and death. Objective: To gain a richer understanding of the pathophysiology of this pathogen while also improving captive management of endangered species, we examine the impact of cryptosporidiosis on the GMB of a flagship species known to experience a debilitating disease state upon infection. Design: Using 16S sequencing of DNA extracted from sifaka fecal samples, we compared the microbial communities of healthy sifakas to those of infected individuals, across infection and recovery periods. Results: Over the course of infection, we found that the sifaka GMB responds with decreased microbial diversity and increased community dissimilarity. Compared to the GMB of unaffected individuals, as well as during pre-infection and recovery periods, the GMB during active infection was enriched for microbial taxa associated with dysbiosis and rapid transit time. Time to recovery was inversely related to age, with young animals being slowest to recover GMB diversity and full community membership. Antimicrobial treatment during infection caused a significant depletion in GMB diversity. Conclusions: Although individual sifakas show unique trajectories of microbial loss and recolonization in response to infection, recovering sifakas exhibit remarkably consistent patterns, similar to initial community assembly of the GMB in infants. This observation, in particular, provides biological insight into the rules by which the GMB recovers from the disease state. Fecal transfaunation may prove effective in restoring a healthy GMB in animals with specialized diets.

Next-generation genotyping of hypervariable loci in many individuals of a non-model species: technical and theoretical implications.

BACKGROUND: Across species, diversity at the Major Histocompatibility Complex (MHC) is critical to disease resistance and population health; however, use of MHC diversity to quantify the genetic health of populations has been hampered by the extreme variation found in MHC genes. Next generation sequencing (NGS) technology generates sufficient data to genotype even the most diverse species, but workflows for distinguishing artifacts from alleles are still under development. We used NGS to evaluate the MHC diversity of over 300 captive and wild ring-tailed lemurs (Lemur catta: Primates: Mammalia). We modified a published workflow to address errors that arise from deep sequencing individuals and tested for evidence of selection at the most diverse MHC genes. RESULTS: In addition to evaluating the accuracy of 454 Titanium and Ion Torrent PGM for genotyping large populations at hypervariable genes, we suggested modifications to improve current methods of allele calling. Using these modifications, we genotyped 302 out of 319 individuals, obtaining an average sequencing depth of over 1000 reads per amplicon. We identified 55 MHC-DRB alleles, 51 of which were previously undescribed, and provide the first sequences of five additional MHC genes: DOA, DOB, DPA, DQA, and DRA. The additional five MHC genes had one or two alleles each with little sequence variation; however, the 55 MHC-DRB alleles showed a high dN/dS ratio and trans-species polymorphism, indicating a history of positive selection. Because each individual possessed 1-7 MHC-DRB alleles, we suggest that ring-tailed lemurs have four, putatively functional, MHC-DRB copies. CONCLUSIONS: In the future, accurate genotyping methods for NGS data will be critical to assessing genetic variation in non-model species. We recommend that future NGS studies increase the proportion of replicated samples, both within and across platforms, particularly for hypervariable genes like the MHC. Quantifying MHC diversity within non-model species is the first step to assessing the relationship of genetic diversity at functional loci to individual fitness and population viability. Owing to MHC-DRB diversity and copy number, ring-tailed lemurs may serve as an ideal model for estimating the interaction between genetic diversity, fitness, and environment, especially regarding endangered species.

Beyond aggression: Androgen-receptor blockade modulates social interaction in wild meerkats.

In male vertebrates, androgens are inextricably linked to reproduction, social dominance, and aggression, often at the cost of paternal investment or prosociality. Testosterone is invoked to explain rank-related reproductive differences, but its role within a status class, particularly among subordinates, is underappreciated. Recent evidence, especially for monogamous and cooperatively breeding species, suggests broader androgenic mediation of adult social interaction. We explored the actions of androgens in subordinate, male members of a cooperatively breeding species, the meerkat (Suricata suricatta). Although male meerkats show no rank-related testosterone differences, subordinate helpers rarely reproduce. We blocked androgen receptors, in the field, by treating subordinate males with the antiandrogen, flutamide. We monitored androgen concentrations (via baseline serum and time-sequential fecal sampling) and recorded behavior within their groups (via focal observation). Relative to controls, flutamide-treated animals initiated less and received more high-intensity aggression (biting, threatening, feeding competition), engaged in more prosocial behavior (social sniffing, grooming, huddling), and less frequently initiated play or assumed a 'dominant' role during play, revealing significant androgenic effects across a broad range of social behavior. By contrast, guarding or vigilance and measures of olfactory and vocal communication in subordinate males appeared unaffected by flutamide treatment. Thus, androgens in male meerkat helpers are aligned with the traditional trade-off between promoting reproductive and aggressive behavior at a cost to affiliation. Our findings, based on rare endocrine manipulation in wild mammals, show a more pervasive role for androgens in adult social behavior than is often recognized, with possible relevance for understanding tradeoffs in cooperative systems.

Androgens predict parasitism in female meerkats: a new perspective on a classic trade-off.

The immunocompetence handicap hypothesis posits that androgens in males can be a 'double-edged sword', actively promoting reproductive success, while also negatively impacting health. Because there can be both substantial androgen concentrations in females and significant androgenic variation among them, particularly in species portraying female social dominance over males or intense female-female competition, androgens might also play a role in mediating female health and fitness. We examined this hypothesis in the meerkat (Suricata suricatta), a cooperatively breeding, social carnivoran characterized by aggressively mediated female social dominance and extreme rank-related reproductive skew. Dominant females also have greater androgen concentrations and harbour greater parasite loads than their subordinate counterparts, but the relationship between concurrent androgen concentrations and parasite burdens is unknown. We found that a female's faecal androgen concentrations reliably predicted her concurrent state of endoparasitism irrespective of her social status: parasite species richness and infection by Spirurida nematodes, Oxynema suricattae, Pseudandrya suricattae and coccidia were greater with greater androgen concentrations. Based on gastrointestinal parasite burdens, females appear to experience the same trade-off in the costs and benefits of raised androgens as do the males of many species. This trade-off presumably represents a health cost of sexual selection operating in females.

Reproductive endocrine patterns and volatile urinary compounds of Arctictis binturong: discovering why bearcats smell like popcorn.

Members of the order Carnivora rely on urinary scent signaling, particularly for communicating about reproductive parameters. Here, we describe reproductive endocrine patterns in relation to urinary olfactory cues in a vulnerable and relatively unknown viverrid--the binturong (Arctictis binturong). Female binturongs are larger than and dominate males, and both sexes engage in glandular and urinary scent marking. Using a large (n = 33), captive population, we collected serum samples to measure circulating sex steroids via enzyme immunoassay and urine samples to assay volatile chemicals via gas chromatography-mass spectrometry. Male binturongs had expectedly greater androgen concentrations than did females but, more unusually, had equal estrogen concentrations, which may be linked to male deference. Males also expressed a significantly richer array of volatile chemical compounds than did females. A subset of these volatile chemicals resisted decay at ambient temperatures, potentially indicating their importance as long-lasting semiochemicals. Among these compounds was 2-acetyl-1-pyrroline (2-AP), which is typically produced at high temperatures by the Maillard reaction and is likely to be responsible for the binturong's characteristic popcorn aroma. 2-AP, the only compound expressed by all of the subjects, was found in greater abundance in males than females and was significantly and positively related to circulating androstenedione concentrations in both sexes. This unusual compound may have a more significant role in mammalian semiochemistry than previously appreciated. Based on these novel data, we suggest that hormonal action and potentially complex chemical reactions mediate communication of the binturong's signature scent and convey information about sex and reproductive state.

D'scent of man: a comparative survey of primate chemosignaling in relation to sex.

This article is part of a Special Issue (Chemosignals and Reproduction). As highly visual animals, primates, in general, and Old World species (including humans), in particular, are not immediately recognized for reliance in their daily interactions on olfactory communication. Nevertheless, views on primate olfactory acuity and the pervasiveness of their scent signaling are changing, with increased appreciation for the important role of body odors in primate social and sexual behavior. All major taxonomic groups, from lemurs to humans, are endowed with scent-producing organs, and either deposit or exude a wealth of volatile compounds, many of which are known semiochemicals. This review takes a comparative perspective to illustrate the reproductive context of primate signaling, the relevant information content of their signals, the sexually differentiated investigative responses generated, and the behavioral or physiological consequences of message transmission to both signaler and receiver. Throughout, humans are placed alongside their relatives to illustrate the evolutionary continuum in the sexual selection of primate chemosignals. This ever-growing body of evidence points to a critical role of scent in guiding the social behavior and reproductive function throughout the primate order.

Baby on board: olfactory cues indicate pregnancy and fetal sex in a non-human primate.

Olfactory cues play an integral, albeit underappreciated, role in mediating vertebrate social and reproductive behaviour. These cues fluctuate with the signaller's hormonal condition, coincident with and informative about relevant aspects of its reproductive state, such as pubertal onset, change in season and, in females, timing of ovulation. Although pregnancy dramatically alters a female's endocrine profiles, which can be further influenced by fetal sex, the relationship between gestation and olfactory cues is poorly understood. We therefore examined the effects of pregnancy and fetal sex on volatile genital secretions in the ring-tailed lemur (Lemur catta), a strepsirrhine primate possessing complex olfactory mechanisms of reproductive signalling. While pregnant, dams altered and dampened their expression of volatile chemicals, with compound richness being particularly reduced in dams bearing sons. These changes were comparable in magnitude with other, published chemical differences among lemurs that are salient to conspecifics. Such olfactory 'signatures' of pregnancy may help guide social interactions, potentially promoting mother-infant recognition, reducing intragroup conflict or counteracting behavioural mechanisms of paternity confusion; cues that also advertise fetal sex may additionally facilitate differential sex allocation.

Individual recognition through olfactory-auditory matching in lemurs.

Individual recognition can be facilitated by creating representations of familiar individuals, whereby information from signals in multiple sensory modalities become linked. Many vertebrate species use auditory-visual matching to recognize familiar conspecifics and heterospecifics, but we currently do not know whether representations of familiar individuals incorporate information from other modalities. Ring-tailed lemurs (Lemur catta) are highly visual, but also communicate via scents and vocalizations. To investigate the role of olfactory signals in multisensory recognition, we tested whether lemurs can recognize familiar individuals through matching scents and vocalizations. We presented lemurs with female scents that were paired with the contact call either of the female whose scent was presented or of another familiar female from the same social group. When the scent and the vocalization came from the same individual versus from different individuals, females showed greater interest in the scents, and males showed greater interest in both the scents and the vocalizations, suggesting that lemurs can recognize familiar females via olfactory-auditory matching. Because identity signals in lemur scents and vocalizations are produced by different effectors and often encountered at different times (uncoupled in space and time), this matching suggests lemurs form multisensory representations through a newly recognized sensory integration underlying individual recognition.

Integrating microbiome science and evolutionary medicine into animal health and conservation.

Microbiome science has provided groundbreaking insights into human and animal health. Similarly, evolutionary medicine - the incorporation of eco-evolutionary concepts into primarily human medical theory and practice - is increasingly recognised for its novel perspectives on modern diseases. Studies of host-microbe relationships have been expanded beyond humans to include a wide range of animal taxa, adding new facets to our understanding of animal ecology, evolution, behaviour, and health. In this review, we propose that a broader application of evolutionary medicine, combined with microbiome science, can provide valuable and innovative perspectives on animal care and conservation. First, we draw on classic ecological principles, such as alternative stable states, to propose an eco-evolutionary framework for understanding variation in animal microbiomes and their role in animal health and wellbeing. With a focus on mammalian gut microbiomes, we apply this framework to populations of animals under human care, with particular relevance to the many animal species that suffer diseases linked to gut microbial dysfunction (e.g. gut distress and infection, autoimmune disorders, obesity). We discuss diet and microbial landscapes (i.e. the microbes in the animal's external environment), as two factors that are (i) proposed to represent evolutionary mismatches for captive animals, (ii) linked to gut microbiome structure and function, and (iii) potentially best understood from an evolutionary medicine perspective. Keeping within our evolutionary framework, we highlight the potential benefits - and pitfalls - of modern microbial therapies, such as pre- and probiotics, faecal microbiota transplants, and microbial rewilding. We discuss the limited, yet growing, empirical evidence for the use of microbial therapies to modulate animal gut microbiomes beneficially. Interspersed throughout, we propose 12 actionable steps, grounded in evolutionary medicine, that can be applied to practical animal care and management. We encourage that these actionable steps be paired with integration of eco-evolutionary perspectives into our definitions of appropriate animal care standards. The evolutionary perspectives proposed herein may be best appreciated when applied to the broad diversity of species under human care, rather than when solely focused on humans. We urge animal care professionals, veterinarians, nutritionists, scientists, and others to collaborate on these efforts, allowing for simultaneous care of animal patients and the generation of valuable empirical data.

Nasopalatine ducts and flehmen behavior in the mandrill: reevaluating olfactory communication in Old World primates.

Compared to other modes of communication, chemical signaling between conspecifics generally has been overlooked in Old World primates, despite the presence in this group of secretory glands and scent-marking behavior, as well as the confirmed production and perception of olfactory signals. In other mammalian species, flehmen is a behavior thought to transport primarily nonvolatile, aqueous-soluble odorants via specialized ducts to the vomeronasal organ (VNO). By contrast, Old World primates are traditionally thought to lack a functional VNO, relying instead on the main olfactory system to process volatile odorants from their environment. Here, in the mandrill (Mandrillus sphinx), we document unusual morphological and behavioral traits that typically are associated with the uptake of conspecific chemical cues for processing by an accessory olfactory system. Notably, we confirmed that both sexes possess open nasopalatine ducts and, in response to the presentation of conspecific odorants, we found that both sexes showed stereotyped behavior consistent with the flehmen response. If, as in other species, flehmen in the mandrill serves to mediate social or reproductive information, we expected its occurrence to vary with characteristics of either the signaler or receiver. Flehmen, particularly in a given male, occurred most often in response to odorants derived from male, as opposed to female, conspecifics. Moreover, odorants derived during the breeding season elicited more flehmen responses than did odorants collected during the birthing season. Lastly, odorants from reproductively cycling females also elicited more responses than did odorants from contracepted females. Although confirming a link between the nasopalatine ducts, flehmen behavior, and olfactory processing in mandrills would require further study, our observations provide new information to suggest anatomical variability within Old World primates, calling further attention to the underappreciated role of chemical communication in this lineage.

Chemical differences between voided and bladder urine in the aye-aye (Daubentonia madagascariensis): implications for olfactory communication studies.

Urine serves a communicative function in many mammalian species. In some species, the signaling function of urine can be enhanced by the addition of chemical compounds from glands along the distal portion of the urogenital tract. Although urine marking is the main mode of chemical communication in many primate species, there has been no study of the contribution of urogenital secretions to the chemical complexity of primate urine. Here, we compared the chemical composition of bladder urine versus voided urine in the aye-aye, Daubentonia madagascariensis, a strepsirrhine primate that relies on urine in intraspecific communication. Both types of urine, collected from each of 11 aye-ayes representing both sexes of varying adult ages, underwent headspace analysis via gas chromatography and mass spectrometry. Although the average number of compounds was similar in bladder and voided urine, 17% of the compounds detected occurred exclusively in voided urine (but only in a subset of individuals). An overall measure of chemical complexity (using a nonmetric multidimensional scaling analysis) showed that both types of urine were chemically different at the individual level. There was no apparent sex or age differences in the chemical components found in aye-aye urine. Nonetheless, the individual dissimilarities between bladder urine and voided urine indicate chemical contributions from structures along the urogenital tract and offer further support for the relevance of urinary communication in the aye-aye.

The "secret" in secretions: methodological considerations in deciphering primate olfactory communication.

Olfactory communication in primates is gaining recognition; however, studies on the production and perception of primate scent signals are still scant. In general, there are five tasks to be accomplished when deciphering the chemical signals contained in excretions and secretions: (1) obtaining the appropriate samples; (2) extracting the target organic compounds from the biological matrix; (3) separating the extracted compounds from one another (by gas chromatography, GC or liquid chromatography, LC); (4) identifying the compounds (by mass spectrometry, MS and associated procedures); and (5) revealing biologically meaningful patterns in the data. Ultimately, because some of the compounds identified in odorants may not be relevant, associated steps in understanding signal function involve verifying the perception or biological activity of putative semiochemicals via (6) behavioral bioassays or (7) receptor response studies. This review will focus on the chemical analyses and behavioral bioassays of volatile, primate scent signals. Throughout, we highlight the potential pitfalls of working with highly complex, chemical matrices and suggest ways for minimizing problems. A recurring theme in this review is that multiple approaches and instrumentation are required to characterize the full range of information contained in the complex mixtures that typify primate or, indeed, many vertebrate olfactory cues. Only by integrating studies of signal production with those verifying signal perception will we better understand the function of olfactory communication.

Effects of oxytocin receptor blockade on dyadic social behavior in monogamous and non-monogamous Eulemur.

A prominent body of research spanning disciplines has been focused on the potential underlying role for oxytocin in the social signatures of monogamous mating bonds. Behavioral differences between monogamous and non-monogamous vole species, putatively mediated by oxytocinergic function, constitute a key source of support for this mechanism, but it is unclear to what extent this hormone-behavior linkage extends to the primate order. In a preregistered experiment, we test if oxytocin receptor blockade affects affiliative behavior in mixed-sex pairs of Eulemur, a genus of strepsirrhine primate containing both monogamous and non-monogamous species. Inconsistent with past studies in monogamous voles or monkeys, we do not find confirmatory evidence in Eulemur that monogamous pairs affiliate more than non-monogamous pairs, nor that oxytocin receptor blockade of one pair member selectively corresponds to reduced affiliative or scent-marking behavior in monogamous species. We do, however, find exploratory evidence of a pattern not previously investigated: simultaneously blocking oxytocin receptors in both members of a monogamous pair predicts lower rates of affiliative behavior relative to controls. Our study demonstrates the value of non-traditional animal models in challenging generalizations based on model organisms, and of methodological reform in providing a potential path forward for behavioral oxytocin research.