Social network shrinking is explained by active and passive effects but not increasing selectivity with age in wild macaques.

Evidence of social disengagement, network narrowing and social selectivity with advancing age in several non-human animals challenges our understanding of the causes of social ageing. Natural animal populations are needed to test whether social ageing and selectivity occur under natural predation and extrinsic mortality pressures, and longitudinal studies are particularly valuable to disentangle the contribution of within-individual ageing from the demographic processes that shape social ageing at the population level. Data on wild Assamese macaques (Macaca assamensis) were collected between 2013 and 2020 at the Phu Khieo Wildlife Sanctuary, Thailand. We investigated the social behaviour of 61 adult females observed for 13 270 h to test several mechanistic hypotheses of social ageing and evaluated the consistency between patterns from mixed-longitudinal and within-individual analyses. With advancing age, females reduced the size of their social network, which could not be explained by an overall increase in the time spent alone, but by an age-related decline in mostly active, but also passive, behaviour, best demonstrated by within-individual analyses. A selective tendency to approach preferred partners was maintained into old age but did not increase. Our results contribute to our understanding of the driver of social ageing in natural animal populations and suggest that social disengagement and selectivity follow independent trajectories during ageing.

Modulation of cell-mediated immunity during pregnancy in wild bonobos.

During pregnancy, the mammalian immune system must simultaneously protect against pathogens while being accommodating to the foreign fetal tissues. Our current understanding of this immune modulation derives predominantly from industrialized human populations and laboratory animals. However, their environments differ considerably from the pathogen-rich, resource-scarce environments in which pregnancy and the immune system co-evolved. For a better understanding of immune modulation during pregnancy in challenging environments, we measured urinary neopterin, a biomarker of cell-mediated immune responses, in 10 wild female bonobos (Pan paniscus) before, during and after pregnancy. Bonobos, sharing evolutionary roots and pregnancy characteristics with humans, serve as an ideal model for such investigation. Despite distinct environments, we hypothesized that cell-mediated immune modulation during pregnancy is similar between bonobos and humans. As predicted, neopterin levels were higher during than outside of pregnancy, and highest in the third trimester, with a significant decline post-partum. Our findings suggest shared mechanisms of cell-mediated immune modulation during pregnancy in bonobos and humans that are robust despite distinct environmental conditions. We propose that these patterns indicate shared immunological processes during pregnancy among hominins, and possibly other primates. This finding enhances our understanding of reproductive immunology.

A central role for stressor appraisal in the social dimensions of health and aging in nonhuman primates.

Being social is by no means the default in the animal kingdom; even most mammals meet only briefly to mate and otherwise lead happy solitary lives. Because conspecifics occupy the same ecological niche, seek the same ecological conditions and resources, they can be each other's strongest competitors when resources are scarce. Yet, sociality, i.e. associating, communicating, coordinating, cooperating, and competing in structured ways, has evolved independently many times across the tree of life. The consequences of competition and conflict are often not shared equally among members of a society, resulting in status-associated health prospects. In response, affiliative strategies have evolved to navigate such structured societies and to partially compensate for certain costs of sociality. The importance of such affiliative strategies may change with age and neurodegenerative disease. Their shared longevity, physiological and anatomical similarity, including in brain areas affected by aging, and particularly the homologies in how social status, affiliation, and cooperation structure their societies, make nonhuman primates the preferred models for the social dimensions of health and aging in humans.

The long-term gut bacterial signature of a wild primate is associated with a timing effect of pre- and postnatal maternal glucocorticoid levels.

BACKGROUND: During development, elevated levels of maternal glucocorticoids (GCs) can have detrimental effects on offspring morphology, cognition, and behavior as well as physiology and metabolism. Depending on the timing of exposure, such effects may vary in strength or even reverse in direction, may alleviate with age, or may concern more stable and long-term programming of phenotypic traits. Maternal effects on gut bacterial diversity, composition, and function, and the persistence of such effects into adulthood of long-lived model species in the natural habitats remain underexplored. RESULTS: In a cross-sectional sample of infant, juvenile, and adult Assamese macaques, the timing of exposure to elevated maternal GCs during ontogeny was associated with the gut bacterial community of the offspring. Specifically, naturally varying maternal GC levels during early but not late gestation or lactation were associated with reduced bacterial richness. The overall effect of maternal GCs during early gestation on the gut bacterial composition and function exacerbated with offspring age and was 10 times stronger than the effect associated with exposure during late prenatal or postnatal periods. Instead, variation in maternal GCs during the late prenatal or postnatal period had less pronounced or less stable statistical effects and therefore a weaker effect on the entire bacterial community composition, particularly in adult individuals. Finally, higher early prenatal GCs were associated with an increase in the relative abundance of several potential pro-inflammatory bacteria and a decrease in the abundance of Bifidobacterium and other anti-inflammatory taxa, an effect that exacerbated with age. CONCLUSIONS: In primates, the gut microbiota can be shaped by developmental effects with strong timing effects on plasticity and potentially detrimental consequences for adult health. Together with results on other macaque species, this study suggests potential detrimental developmental effects similar to rapid inflammaging, suggesting that prenatal exposure to high maternal GC concentrations is a common cause underlying both phenomena. Our findings await confirmation by metagenomic functional and causal analyses and by longitudinal studies of long-lived, ecologically flexible primates in their natural habitat, including developmental effects that originate before birth. Video Abstract.

Developmental and environmental modulation of fecal thyroid hormone levels in wild Assamese macaques (Macaca assamensis).

Thyroid hormones are key modulators of development, as well as mediators of environmental conditions, by regulating developmental processes and metabolism in primates. Hormone measurement in noninvasively collected samples, that is, feces and urine, is a valuable tool for studying the endocrine function of wildlife, and recent studies have demonstrated the feasibility of measuring thyroid hormones in fecal samples of zoo-housed and wild nonhuman primates. Our study aimed to (i) validate the measurement of immunoreactive fecal total triiodothyronine (IF-T3) in wild Assamese macaques (Macaca assamensis) and (ii) to investigate its developmental changes and its response to environmental changes, including stress responses, in immature individuals. Fecal samples and environmental parameters were collected from individuals of three social groups of wild Assamese macaques living at Phu Khieo Wildlife Sanctuary, Northeastern Thailand. Our study confirmed the methodological feasibility and biological validity of measuring IF-T3 in this population. Specifically, the biological validation demonstrated higher IF-T3 levels in immatures compared to adults, and higher levels in females during late gestation compared to the preconception stage. Our analysis of IF-T3 levels in developing immature macaques revealed a significant increase with age. Furthermore, we found a positive association between IF-T3 and immunoreactive fecal glucocorticoid levels, an indicator of the physiological stress response. Neither minimum temperature nor fruit abundance predicted variation in IF-T3 levels in the immatures. Our findings indicate the possibility for differing effects of climatic factors and food availability on thyroid hormone level changes in immature versus adult animals and in wild compared to experimental conditions. Overall, our study provides the basis for further investigations into the role of thyroid hormones in shaping species-specific traits, growth, and overall primate development.

Does emotion recognition change across phases of the ovulatory cycle?

Recognizing emotions is an essential ability for successful interpersonal interaction. Prior research indicates some links between the endocrine system and emotion recognition ability, but only a few studies focused on within-subject differences across distinct ovulatory cycle phases and this ability. These studies have demonstrated mixed results that might be potentially due to heterogeneity in experimental tasks, methodologies, and lacking ecological validity. In the current study, we investigated associations between within-subject differences in ovarian hormones levels and emotion recognition from auditory, visual, and audiovisual modalities in N = 131 naturally cycling participants across the late follicular and mid-luteal phase of the ovulatory cycle. We applied a within-subject design with sessions in the late follicular and mid-luteal cycle phase, and also assessed salivary progesterone and estradiol in these sessions. Our findings did not reveal any significant difference in emotion recognition ability across two cycle phases. Thus, they emphasize the necessity of employing large-scale replication studies with well-established study designs along with proper statistical analyses. Moreover, our findings indicate that the potential link between ovulatory cycle phases (late follicular and mid-luteal) and emotion recognition ability might have been overestimated in previous studies, and may contribute to theoretical and practical implications of socio-cognitive neuroendocrinology.

Aging gut microbiota of wild macaques are equally diverse, less stable, but progressively personalized.

BACKGROUND: Pronounced heterogeneity of age trajectories has been identified as a hallmark of the gut microbiota in humans and has been explained by marked changes in lifestyle and health condition. Comparatively, age-related personalization of microbiota is understudied in natural systems limiting our comprehension of patterns observed in humans from ecological and evolutionary perspectives. RESULTS: Here, we tested age-related changes in the diversity, stability, and composition of the gut bacterial community using 16S rRNA gene sequencing with dense repeated sampling over three seasons in a cross-sectional age sample of adult female Assamese macaques (Macaca assamensis) living in their natural forest habitat. Gut bacterial composition exhibited a personal signature which became less stable as individuals aged. This lack of stability was not explained by differences in microbiota diversity but rather linked to an increase in the relative abundance of rare bacterial taxa. The lack of age-related changes in core taxa or convergence with age to a common state of the community hampered predicting gut bacterial composition of aged individuals. On the contrary, we found increasing personalization of the gut bacterial composition with age, indicating that composition in older individuals was increasingly divergent from the rest of the population. Reduced direct transmission of bacteria resulting from decreasing social activity may contribute to, but not be sufficient to explain, increasing personalization with age. CONCLUSIONS: Together, our results challenge the assumption of a constant microbiota through adult life in a wild primate. Within the limits of this study, the fact that increasing personalization of the aging microbiota is not restricted to humans suggests the underlying process to be evolved instead of provoked only by modern lifestyle of and health care for the elderly. Video abstract.

Responsiveness of fecal immunoglobulin A to HPA-axis activation limits its use for mucosal immunity assessment.

The assessment of mucosal immunity as a component of animal health is an important aspect for the understanding of variation in host immunity, and its tradeoff against other life-history traits. We investigated immunoglobulin A (IgA), the major type of antibody associated with mucosal immunity, in relation to changes in parasitic burden following anthelminthic treatment in noninvasively collected fecal samples in a semi-free ranging group of Barbary macaques (Macaca sylvanus). We measured IgA in 340 fecal samples of fourteen females and nine males. As IgA has been found to be responsive to stressors, we also related fecal IgA (fIgA) levels to fecal glucocorticoid metabolites (fGCM) measured in the same samples as part of a previous study. We found a high variability within and between individual fIgA levels over time. Running generalized additive mixed models, we found that fIgA levels were higher in males than in females, but did not change in response to the anthelmintic treatment and the resulting reduction in worm burden. Instead, fIgA level changes were significantly correlated to changes in fGCM levels. Our findings indicate that due to the strong responsiveness of fIgA to HPA-axis activity, the measurement of fIgA may have certain limitations with respect to reflecting gastrointestinal parasitic burden. Moreover, the responsiveness of fIgA to stressors interferes with the interpretation of IgA levels in fecal samples as a measure of mucosal immunity, at least in our study population of the Barbary macaques.

Dominance style is a key predictor of vocal use and evolution across nonhuman primates.

Animal communication has long been thought to be subject to pressures and constraints associated with social relationships. However, our understanding of how the nature and quality of social relationships relates to the use and evolution of communication is limited by a lack of directly comparable methods across multiple levels of analysis. Here, we analysed observational data from 111 wild groups belonging to 26 non-human primate species, to test how vocal communication relates to dominance style (the strictness with which a dominance hierarchy is enforced, ranging from 'despotic' to 'tolerant'). At the individual-level, we found that dominant individuals who were more tolerant vocalized at a higher rate than their despotic counterparts. This indicates that tolerance within a relationship may place pressure on the dominant partner to communicate more during social interactions. At the species-level, however, despotic species exhibited a larger repertoire of hierarchy-related vocalizations than their tolerant counterparts. Findings suggest primate signals are used and evolve in tandem with the nature of interactions that characterize individuals' social relationships.

Triiodothyronine and cortisol levels in the face of energetic challenges from reproduction, thermoregulation and food intake in female macaques.

Energy availability drives an individual's fitness and can be affected by diverse energetic challenges. The assessment of hormones involved in metabolic activity and energy mobilization provides a gateway to the study of physiological adaptations in response to changes in energy availability. Here, we investigated immunoreactive urinary total triiodothyronine (uTT3, thyroid hormone secreted through the hypothalamus-pituitary-thyroid axis and regulating the basal metabolic rate) alongside glucocorticoids (i.e. urinary cortisol, uCort, secreted through the hypothalamus-pituitary-adrenal axis and mediating energy mobilization) in wild female Assamese macaques (Macaca assamensis). Combining more than 2900; of behavioral data from 42 adult females with physiological data from 382 urine samples, we evaluated both uTT3 and uCort in relation to potential energetic challenges encountered by a female, namely fluctuations in energy intake, travel distance, reproductive state and minimum ambient temperature. As predicted, levels of both hormones changed in response to variation in energy intake with a tendency toward a positive effect on uTT3 and a significant negative effect on uCort levels. Unexpectedly, neither hormone was influenced by variation in travel distance. Reproductive state affected both hormones with higher levels of uTT3 and uCort in the second half of gestation. Finally, a decrease of minimum temperature triggered an increase in uCort but unexpectedly not in uTT3. Collectively, our results highlight the respective contribution of two endocrine axes when facing energetic challenges and the underlying metabolic strategies to cope with them. Overall, assessing thyroid hormones together with glucocorticoids provides an integrative picture in the evaluation of an individual's energy status.

Fermented food consumption in wild nonhuman primates and its ecological drivers.

OBJECTIVES: Although fermented food use is ubiquitous in humans, the ecological and evolutionary factors contributing to its emergence are unclear. Here we investigated the ecological contexts surrounding the consumption of fruits in the late stages of fermentation by wild primates to provide insight into its adaptive function. We hypothesized that climate, socioecological traits, and habitat patch size would influence the occurrence of this behavior due to effects on the environmental prevalence of late-stage fermented foods, the ability of primates to detect them, and potential nutritional benefits. MATERIALS AND METHODS: We compiled data from field studies lasting at least 9 months to describe the contexts in which primates were observed consuming fruits in the late stages of fermentation. Using generalized linear mixed-effects models, we assessed the effects of 18 predictor variables on the occurrence of fermented food use in primates. RESULTS: Late-stage fermented foods were consumed by a wide taxonomic breadth of primates. However, they generally made up 0.01%-3% of the annual diet and were limited to a subset of fruit species, many of which are reported to have mechanical and chemical defenses against herbivores when not fermented. Additionally, late-stage fermented food consumption was best predicted by climate and habitat patch size. It was more likely to occur in larger habitat patches with lower annual mean rainfall and higher annual mean maximum temperatures. DISCUSSION: We posit that primates capitalize on the natural fermentation of some fruits as part of a nutritional strategy to maximize periods of fruit exploitation and/or access a wider range of plant species. We speculate that these factors contributed to the evolutionary emergence of the human propensity for fermented foods.

Social contagion of affiliation in female macaques.

Social contagion of non-interactive behaviour is widespread among animals including humans. It is thought to facilitate behavioural synchronization and consequently group cohesion, coordination and opportunities for social learning. Contagion of interactive behaviour-particularly affiliation-has received much less attention. Here, we investigated in female rhesus macaques (Macaca mulatta) the effect of observing group members groom on a subject's subsequent grooming behaviour and the potential modulation of contagion by relationship quality and social status. We recorded behaviour after subjects witnessed a grooming event and compared it to behaviour in a control condition with the same individuals in proximity but in the absence of a stimulus grooming event. Compared to the control condition, after observing others groom, females engaged in a grooming interaction sooner, and were more likely to be the initiator and to take on the active groomer role. Dominance rank of the focal individual and more weakly also of the stimulus individuals affected the latency to the next grooming interaction of the focal subject. Latency to the next grooming interaction decreased with increasing rank of the subject potentially reflecting lower social constraints faced by high ranking individuals in this highly despotic species. Relationship quality between the subject and the stimulus individuals had no effect on latency to grooming. Collectively, our findings provide evidence for visual contagion of affiliation in rhesus macaques. Future studies should explore the systematic variation in contagion of interactive behaviour in relation to a gradient of social tolerance.

Non-invasive assessment of metabolic responses to food restriction using urinary triiodothyronine and cortisol measurement in macaques.

Regulation of energy allocation and metabolic rate plays an important role in determining behavior and fitness in wild animals, calling for the validation of non-invasive markers of energetic condition. Recently, the thyroid hormone triiodothyronine (T3) has emerged as a promising marker as concentrations decrease to lower the metabolic rate during energetically challenging periods. However, it remains largely unclear whether T3 merely represents an alternative or provides additional information compared to other compounds involved in the regulation of energy acquisition and allocation, like cortisol and C-peptide, as few joint measurements have been conducted to date in non-invasively collected samples. We aimed to validate the non-invasive measurement of immunoreactive urinary total T3 (uTT3), in comparison to urinary cortisol (uCort) and urinary C-peptide (uCP), as a marker of metabolic response to variation in food intake in macaques, and to address a number of issues regarding the collection, storage and processing of samples which are important for application of uTT3 measurements under field conditions. We used daily samples and body mass measures from a prior food restriction-refeeding experiment over 4 weeks with six captive macaques and analyzed concentrations of uTT3 and uCort in samples collected prior to (fasting) and after morning feeding (non-fasting). Concentrations of uTT3 decreased in response to restriction in food supply and were also lower during weeks of food restriction compared to weeks of refeeding. Variation in uTT3 also correlated positively with variation in body mass and concentrations of uCP. As expected, uCort showed the reverse pattern, increasing during food restriction and decreasing following refeeding, but was not associated with variation in body mass. Generally, compared to fasting samples, concentrations were higher in post-morning feeding, i.e. non-fasting, samples for uTT3 but not uCort. Contamination of urine samples with fecal matter, but not soil, and exposure to UV light led to a decrease in uTT3. uTT3 was largely unaffected by repeated freeze-thaw cycles and by refrigeration for medium-term storage (2 days) but degraded substantially when stored at ambient temperature for the same period. In conclusion, uTT3 measurements inform on the effect of food intake and its associated metabolic response to variation in energetic status. Since uTT3 is reasonably robust to many issues associated with collection and storage of urine samples under field conditions, it is a promising biomarker for studies of energetic condition and basal metabolic rate in wild macaques.

A refined panel of 42 microsatellite loci to universally genotype catarrhine primates.

Microsatellite genotyping is an important genetic method for a number of research questions in biology. Given that the traditional fragment length analysis using polyacrylamide gel or capillary electrophoresis has several drawbacks, microsatellite genotyping-by-sequencing (GBS) has arisen as a promising alternative. Although GBS mitigates many of the problems of fragment length analysis, issues with allelic dropout and null alleles often remain due to mismatches in primer binding sites and unnecessarily long PCR products. This is also true for GBS in catarrhine primates where cross-species amplification of loci (often human derived) is common.We therefore redesigned primers for 45 microsatellite loci based on 17 available catarrhine reference genomes. Next, we tested them in singleplex and different multiplex settings in a panel of species representing all major lineages of Catarrhini and further validated them in wild Guinea baboons (Papio papio) using fecal samples.The final panel of 42 microsatellite loci can efficiently be amplified with primers distributed into three amplification pools.With our microsatellite panel, we provide a tool to universally genotype catarrhine primates via GBS from different sample sources in a cost- and time-efficient way, with higher resolution, and comparability among laboratories and species.

The evolution of social philopatry in female primates.

The transition from solitary life to sociality is considered one of the major transitions in evolution. In primates, this transition is currently not well understood. Traditional verbal models appear insufficient to unravel the complex interplay of environmental and demographic factors involved in the evolution of primate sociality, and recent phylogenetic reconstructions have produced conflicting results. We therefore analyze a theoretical model for the evolution of female social philopatry that sheds new light on the question why most primates live in groups. In individual-based simulations, we study the evolution of dispersal strategies of both resident females and their offspring. The model reveals that social philopatry can evolve through kin selection, even if retention of offspring is costly in terms of within-group resource competition and provides no direct benefits. Our model supports the role of predator avoidance as a selective pressure for group-living in primates, but it also suggests that a second benefit of group-living, communal resource defense, might be required to trigger the evolution of sizable groups. Lastly, our model reveals that seemingly small differences in demographic parameters can have profound effects on primate social evolution.

Bonds of bros and brothers: Kinship and social bonding in postdispersal male macaques.

Group-living animals often maintain a few very close affiliative relationships-social bonds-that can buffer them against many of the inevitable costs of gregariousness. Kinship plays a central role in the development of such social bonds. The bulk of research on kin biases in sociality has focused on philopatric females, who typically live in deeply kin-structured systems, with matrilineal dominance rank inheritance and life-long familiarity between kin. Closely related males, in contrast, are usually not close in rank or familiar, which offers the opportunity to test the importance of kinship per se in the formation of social bonds. So far, however, kin biases in male social bonding have only been tested in philopatric males, where familiarity remains a confounding factor. Here, we studied bonds between male Assamese macaques, a species in which males disperse from their natal groups and in which male bonds are known to affect fitness. Combining extensive behavioural data on 43 adult males over a 10-year period with DNA microsatellite relatedness analyses, we find that postdispersal males form stronger relationships with the few close kin available in the group than with the average nonkin. However, males form the majority of their bonds with nonkin and may choose nonkin over available close kin to bond with. Our results show that kinship facilitates bond formation, but is not a prerequisite for it, which suggests that strong bonds are not restricted to kin in male mammals and that animals cooperate for both direct and indirect fitness benefits.

Testosterone and cortisol are negatively associated with ritualized bonding behavior in male macaques.

Neuroendocrine research on the formation of social bonds has primarily focused on the role of nonapeptides. However, steroid hormones often act simultaneously to either inhibit or facilitate bonding. Testosterone is proposed to mediate a trade-off between male mating effort and nurturing behavior; therefore, low levels are predicted during periods of nurturing infant care and social bonding. In species where social bonding and support regulates hypothalamic-pituitary-adrenal axis activity, we also expect glucocorticoid levels to be low during bonding periods. We investigated how immunoreactive urinary testosterone (iuT) and cortisol (iuC) were related to triadic male-infant-male interactions - a ritualized male bonding behavior - as well as infant care in male Barbary macaques (Macaca sylvanus). We collected >3000 h of behavioral observation data during full-day focal animal follows from 14 adult males and quantified iuT and iuC from 650 urine samples. iuT was negatively correlated with rates of triadic interactions within subjects, but positively correlated between subjects. iuC was negatively correlated with triadic interactions both within and between subjects. Time spent caring for infants was positively correlated to both iuT and iuC within subjects, but not between subjects. The observed negative relationship between iuT and triadic interactions within subjects may be beneficial to lower competitive tendencies between adult males and to not inhibit bond formation. However, the positive correlation of iuT with triadic interactions between subjects was unexpected. We speculate that it could be due to a link between triadic interactions and coalition formation. A negative relationship between triadic interactions and iuC could reflect increased bonding and perceived social support as triadic interactions predict future coalition formation in this species, or reflect buffered tensions between males. The positive relationship of iuT and iuC with infant care suggests that the handling of infants may be less nurturing but rather protective or competitive in this species. Measuring steroid hormones in relation to bonding and nurturing can help us interpret behaviors within the ecological contexts that they occur.

Selective attention for affiliative and agonistic interactions of dominants and close affiliates in macaques.

Monitoring conspecifics is a crucial process in social learning and a building block of social cognition. Selective attention to social stimuli results from interactions of subject and stimulus characteristics with dominance rank often emerging as an important predictor. We extend previous research by providing as stimuli naturally occurring affiliative interactions between group members instead of pictorial or auditory representations of conflicts, and by extending to the affiliative relationship, i.e. social bond, between subject and stimulus instead of just their dominance relations. Our observational data on adult female rhesus macaques support the prediction that subjects pay more attention to affiliative interactions of others than to solitary controls. Exceedingly more attention was paid to conflicts unfolding in the group which can have more prompt and direct consequences than others' friendly interactions. The valence of the stimulus (affiliative vs. agonistic) affected biases towards individuals dominant over the subject, but not the ubiquitous bias towards close affiliates of the subject. Keeping track of the whereabouts and interactions of key social partners has been proposed as a prerequisite for behavioral coordination among bonded partners. In groups of socially very active monkeys, social attention is gated by both social dominance and social bonding.

Integrative personality assessment in wild Assamese macaques (Macaca assamensis).

In nonhuman animals, individuals of the same sex and age differ in their behavior patterns consistently across time, comparable with human personality differences. To draw conclusions about the adaptive value of behavior traits, it is essential to study them in the wild where animals are subject to the ecological pressures that promoted the evolution of behavior strategies. This study was conducted in the Phu Khieo Wildlife Sanctuary, Thailand, on 4 groups of habituated wild Assamese macaques by observers who had familiarized themselves with the subjects over the course of an ongoing long-term study. We used a multimethod approach enabling the most comprehensive understanding of variation in stable interindividual differences in a species-typical ecological setting. We combined trait ratings (TRs), assessed with observer-report questionnaires (54-item Hominoid Personality Questionnaire) of 107 individuals of diverse age-sex classes, with behavior codings (BCs) of 24 adult males. We found male and female personality constructs to be congruent and examined reliability and construct validity. Combining trait rating and behavioral coding, we found two solutions with five factors to best describe the personality structure of the males: one structure comprised the dimensions GregariousnessBC, AggressivenessBC, SociabilityBC and VigilanceBC, complemented by a ConfidenceTR domain and the other structure OpportunismTR, ConfidenceTR, FriendlinessTR, ActivityTR complemented with VigianceBC. We discuss our findings with regard to the importance of construct validity and reproducibility in the context of method development and standardization in nonhuman animal personality research. (PsycINFO Database Record (c) 2020 APA, all rights reserved).