Sex differences in the impact of social status on hair cortisol concentrations in rhesus monkeys (Macaca mulatta)

Social status impacts stress in primates, but the direction of the effect differs depending on species, social style, and group stability. This complicates our ability to identify broadly applicable principles for understanding how social status impacts health and fitness. One reason for this is the fact that social status is often measured as linear dominance rank, yet social status is more complex than simply high or low rank. Additionally, most research on social status and health ignores the effects of sex and sex-specific relationships, despite known differences in disease risk, coping strategies, and opposite-sex dominance interactions between males and females in many species. We examine the influence of social status, sex, and opposite-sex interactions on hair cortisol concentrations (HCC) in a well-studied species, rhesus macaques, where the literature predicts low ranking individuals would experience more chronic stress. Animals in three captive, seminaturalistic social groups (N = 252; 71 male) were observed for 6 weeks to obtain metrics of social status (rank and dominance certainty [DC]). DC is a measure of one's fit within the hierarchy. Hair samples were collected from each subject and analyzed for HCC. Generalized linear mixed models were used to examine (a) whether rank, DC, or sex predicted HCC; (b) whether same- or opposite-sex dominance relationships differentially impacted HCC; and (c) whether aggressive interactions initiated or received could explain any observed relationships. Results indicated that DC, not rank, predicted HCC in a sex-specific manner. For males, high HCC were predicted by receiving aggression from or having high DC with other males as well as having low DC with females. For females, only high DC with males predicted high HCC. These results likely relate to sex-specific life history pattern differences in inherited versus earned rank that are tied to female philopatry and male immigration.     

Influence of early stress on social abilities and serotonergic functions across generations in mice

Exposure to adverse environments during early development is a known risk factor for several psychiatric conditions including antisocial behavior and personality disorders. Here, we induced social anxiety and altered social recognition memory in adult mice using unpredictable maternal separation and maternal stress during early postnatal life. We show that these social defects are not only pronounced in the animals directly subjected to stress, but are also transmitted to their offspring across two generations. The defects are associated with impaired serotonergic signaling, in particular, reduced 5HT1A receptor expression in the dorsal raphe nucleus, and increased serotonin level in a dorsal raphe projection area. These findings underscore the susceptibility of social behaviors and serotonergic pathways to early stress, and the persistence of their perturbation across generations.     

Monkeys in the Middle: Parasite Transmission through the Social Network of a Wild Primate

In wildlife populations, group-living is thought to increase the probability of parasite transmission because contact rates increase at high host densities. Physical contact, such as social grooming, is an important component of group structure, but it can also increase the risk of exposure to infection for individuals because it provides a mechanism for transmission of potentially pathogenic organisms. Living in groups can also create variation in susceptibility to infection among individuals because circulating levels of immunosuppressive hormones like glucocorticoids often depend on an individual’s position within the group’s social structure. Yet, little is known about the relative roles of socially mediated exposure versus susceptibility in parasite transmission among free-living animal groups. To address this issue, we investigate the relationship between host dominance hierarchy and nematode parasite transmission among females in a wild group of Japanese macaques (Macaca fuscata yakui). We use social network analysis to describe each individual female’s position within the grooming network in relation to dominance rank and relative levels of infection. Our results suggest that the number of directly-transmitted parasite species infecting each female, and the relative amount of transmission stages that one of these species sheds in faeces, both increase with dominance rank. Female centrality within the network, which shows positive associations with dominance hierarchy, is also positively associated with infection by certain parasite species, suggesting that the measured rank-bias in transmission may reflect variation in exposure rather than susceptibility. This is supported by the lack of a clear relationship between rank and faecal cortisol, as an indicator of stress, in a subset of these females. Thus, socially mediated exposure appears to be important for direct transmission of nematode parasites, lending support to the idea that a classical fitness trade-off inherent to living in groups can exist.     

Stress coping style predicts aggression and social dominance in rainbow trout

Social stress is frequently used as a model for studying the neuroendocrine mechanisms underlying stress-induced behavioral inhibition, depression, and fear conditioning. It has previously been shown that social subordination may result in increased glucocorticoid release and changes in brain signaling systems. However, it is still an open question which neuroendocrine and behavioral differences are causes, and which are consequences of social status. Using juvenile rainbow trout of similar size and with no apparent differences in social history, we demonstrate that the ability to win fights for social dominance can be predicted from the duration of a behavioral response to stress, in this case appetite inhibition after transfer to a new environment. Moreover, stress responsiveness in terms of confinement-induced changes in plasma cortisol was negatively correlated to aggressive behavior. Fish that exhibited lower cortisol responses to a standardized confinement test were markedly more aggressive when being placed in a dominant social position later in the study. These findings support the view that distinct behavioral-physiological stress coping styles are present in teleost fish, and these coping characteristics influence both social rank and levels of aggression.     

Three different coping styles in police dogs exposed to a short-term challenge

According to some researchers, animals show different coping styles to deal with stressful situations. In the case of social carnivores, social stress is a substantial part of the overall stress load. Previous research has established two extreme (proactive and reactive) coping styles in several animal species, but means of coping with social stress has not yet been investigated in the case of dogs. The aim of this current study was to examine whether (1) experienced working police dogs adopt different coping strategies during a short-term unexpected social challenge presented by a threatening human, (2) whether this affects post-encounter cortisol levels, and (3) whether there is an association between the cortisol response and the behavior (coping strategy) displayed during the threatening approach. Using factor analysis, we have identified three different group of dogs which were characterized by either fearfulness, aggressiveness, or ambivalence and in parallel showed specific differences in their reaction norm when threatened by an approaching stranger. This grouping also allowed to draw possible parallels between aggressiveness and the proactive behavior style and fearfulness and reactive coping style, respectively. In addition, we have revealed a third group of animals which show ambivalent behavior in a social threatening situation.     

Three different coping styles in police dogs exposed to a short-term challenge

According to some researchers, animals show different coping styles to deal with stressful situations. In the case of social carnivores, social stress is a substantial part of the overall stress load. Previous research has established two extreme (proactive and reactive) coping styles in several animal species, but means of coping with social stress has not yet been investigated in the case of dogs. The aim of this current study was to examine whether (1) experienced working police dogs adopt different coping strategies during a short-term unexpected social challenge presented by a threatening human, (2) whether this affects post-encounter cortisol levels, and (3) whether there is an association between the cortisol response and the behavior (coping strategy) displayed during the threatening approach. Using factor analysis, we have identified three different group of dogs which were characterized by either fearfulness, aggressiveness, or ambivalence and in parallel showed specific differences in their reaction norm when threatened by an approaching stranger. This grouping also allowed to draw possible parallels between aggressiveness and the proactive behavior style and fearfulness and reactive coping style, respectively. In addition, we have revealed a third group of animals which show ambivalent behavior in a social threatening situation.     

Depression,Social Support,and Coping Styles among Pregnant Women after the Lushan Earthquake in Ya’an,China

Aim

The aim of this study is to assess the depression of pregnant women in the aftermath of an earthquake, and to identify the social support that they obtained, their coping styles and socio-demographic factors associated with depression.

Methods

A total of 128 pregnant women from three hospitals in the epicenter area were recruited immediately after the Ya’an earthquake. Their depression was investigated using the Edinburgh Postnatal Depression Scale (EPDS) with a cutoff score of 14; the social support that they obtained was measured using the Social Support Questionnaire; and their coping styles were assessed using the Coping Styles Questionnaire.

Results

Immediately after the earthquake, the incidence rate of depression in pregnant women was 35.2%, higher than that of the general pregnant population (7%-14%). The EPDS scores were significantly correlated with gestation age at the time of the earthquake, objective support, subjective support, use of support, negative coping style, and positive coping style. The regression analysis indicated that risk factors of prenatal depression include the number of children, relatives wounded, subjective support, and coping styles. A further analysis of the interaction between social support and two types of coping styles with depression showed that there was interaction effect between subjective social support and positive coping styles in relation to EPDS scores. There was an inverse relationship between low EPDS scores and positive coping styles and high social support, and vice versa.

Conclusion

The timing of the occurrence of the earthquake may not necessarily affect the progress of the illness and recovery from depression, and psychological intervention could be conducted in the immediate aftermath after the earthquake. The impact of coping styles on prenatal depression appeared to be linked with social support. Helping pregnant women to adopt positive coping styles with good social support after a recent major earthquake, which is a stressor, may reduce their chances of developing prenatal depression.     

Clarifying the relationship between religiosity and psychiatric illness: the impact of covariates and the specificity of buffering effects.

Previous analyses in a large population-based sample of female twins indicated that three dimensions of religiosity--personal devotion, personal conservatism and institutional conservatism--were, in different ways, significantly related to current depressive symptoms and substance use and lifetime psychiatric and substance use disorders. Furthermore, personal devotion, but neither personal conservatism nor institutional conservatism, buffered the depressogenic effects of stressful life events (SLEs). We here explore further these results, using linear, logistic and Cox regression models. Eight personality and six demographic variables had distinct patterns of association with the three dimensions. Personal devotion was positively associated with years of education, age, and optimism and negatively correlated with neuroticism. Personal conservatism was negatively associated with education, income, age, mastery and positively correlated with neuroticism. Institutional conservatism was negatively correlated with self-esteem and parental education. Covarying for these 14 variables produced little change in their association with psychiatric and substance use outcomes. The impact of the dimensions of religiosity differed as a function of the SLE category. High levels of both personal devotion and institutional conservatism protected against the depressogenic effects of death and personal illness. High levels of personal conservatism were associated with increased sensitivity to relationship problems. These results suggest that the association between religiosity and low risk for symptoms of depression and substance use may be in part causal. The relationship between dimensions of religiosity and response to SLEs is complex but probably of importance in clarifying the nature of the coping process.     

Sex-reversed correlation between stress levels and dominance rank in a captive non-breeder flock of crows

Group living has both benefits and costs to individuals; benefits include efficient acquisition of resources, and costs include stress from social conflicts among group members. Such social challenges result in hierarchical dominance ranking among group members as a solution to avoid escalating conflict that causes different levels of basal stress between individuals at different ranks. Stress-associated glucocorticoid (corticosterone in rodents and birds; CORT) levels are known to correlate with dominance rank in diverse taxa and to covary with various social factors, such as sex and dominance maintenance styles. Although there is much evidence for sex differences in the basal levels of CORT in various species, the correlation of sex differences in basal CORT with dominance rank is poorly understood. We investigated the correlation between CORT metabolites (CM) in the droppings and social factors, including rank and sex, in a captive non-breeder group of crows. In this group, all the single males dominated all the single females, and dominance ranks were stable among single males but relatively unstable among single females. CM levels and rank were significantly correlated in a sex-reversed fashion: males at higher rank (i.e., more dominant) had higher CM, whereas females at higher rank exhibited lower CM. This is the first evidence of sex-reversed patterns of CM–rank correlation in birds. The results suggest that different mechanisms of stress–dominance relationships operate on the sexes in non-breeder crow aggregations; in males, stress is associated with the cost of aggressive displays, whereas females experience subordination stress due to males' overt aggression.     

耐多药肺结核患者心理健康状况调查及与应对方式、社会支持的相关性研究

摘要 目的：探讨耐多药肺结核患者心理健康状况的影响因素,分析其及与应对方式、社会支持的相关性。方法：选择2018年4月至2020年5月我院诊治的101例耐多药肺结核患者作为观察组,选择同期99例敏感肺结核患者作为对照组。两组均测评症状自评量表-90(SCL-90)评分、医学应对问卷(MCMQ)评分以及社会支持评定量表(SSRS)评分,分析SCL-90总评分与MCMQ各因子评分、SSRS总评分的相关性,采用Logistic回归模型分析心理健康状况的影响因素。结果：与对照组相比,观察组的躯体化、人际关系、抑郁、焦虑、敌对性、恐怖和精神病性评分以及总评分明显提高（P<0.05）。与对照组相比,观察组的面对评分、客观支持、主观支持、支持利用度评分以及总评分均降低（P<0.05）。Pearson相关性分析显示,SCL-90总评分与MCMQ评分中的回避和屈服评分呈正相关性（r=0.386、0.311,均P<0.05）,SCL-90总评分与SSRS总评分呈负相关（r=-0.332,P<0.05）。多因素Logistic回归分析显示,经济状况差、躯体健康状况差、病情严重、睡眠质量差和生活满意度低是耐多药肺结核患者心理健康不良的独立危险因素（P<0.05）。结论：耐多药肺结核患者心理健康状况差,应对方式选择面对较少,总体社会支持水平较低,患者的心理健康状况与应对方式、社会支持存在一定的相关性。在提供躯体性治疗的基础上,应结合患者的心理健康状况及相关危险因素给予适当干预。     

炎症性肠病患者希望水平与应对方式、心理韧性和社会支持的关系研究

摘要 目的：研究炎症性肠病（IBD）患者希望水平与应对方式、心理韧性和社会支持的关系。方法：选取我院于2018年10月~2020年10月期间收治的IBD患者137例。采用Herth希望量表（HHI）评价患者希望水平;采用医学应对方式问卷（MCMQ）评估患者面对疾病时所选取的应对方式;采用心理韧性量表（CD-RISC）对患者心理韧性进行评估;采用社会支持评定量表（SSRS）评价患者社会支持情况。将上述评分与国内常模进行对比,采用Pearson相关性分析IBD患者希望水平与应对方式、心理韧性和社会支持的关系。结果：IBD患者与他人保持亲密的态度关系、现实和未来的积极态度、采取积极的行动评分及总分均低于国内常模（P<0.05）。IBD患者面对评分低于国内常模,回避、屈服评分均高于国内常模（P<0.05）。IBD患者力量、乐观和坚韧评分均低于国内常模（P<0.05）。IBD患者主观支持、客观支持和对社会支持的利用度评分均低于国内常模（P<0.05）。Pearson相关性分析结果显示,HHI总分与面对、力量、乐观、坚韧、主观支持、客观支持和对社会支持的利用度呈正相关,而与回避、屈服呈负相关（P<0.05）。结论：大多数IBD患者处于中等希望水平,良好的应对方式、心理韧性和社会支持有助于患者希望水平的提高。     

Differences in basal and stress-induced HPA regulation of wild house mice selected for high and low aggression

Male wild house mice, selected for short (SAL) and long (LAL) attack latency, show distinctly different behavioral strategies in coping with environmental challenges. In this study, we tested the hypothesis that this difference in coping style is associated with a differential stress responsiveness of the hypothalamic-pituitary-adrenal (HPA) system. SAL rather than LAL mice showed a clear fluctuation in circulating corticosterone concentrations around the circadian peak with significantly higher levels in the late light phase. LAL mice showed lower basal ACTH levels and higher thymic and spleen weights compared to SAL. Under basal conditions, glucocorticoid receptor (GR) and mineralocorticoid receptor (MR) mRNA in the hippocampus and corticotropin-releasing hormone (CRH) mRNA in the paraventricular nucleus of the hypothalamus were not different between the two lines. Forced swimming for 5 min induced high immobility behavior in LAL mice which was associated with an enhanced and prolonged corticosterone response as compared to SAL, while absolute ACTH levels did not differ. In addition, LAL mice showed an increase in hippocampal MR mRNA (but not GR) and hypothalamic CRH mRNA at 24 h after forced swimming. In conclusion, a genetic trait in coping style of wild house mice is associated with an idiosyncratic pattern of HPA activity, and greater responsiveness of physiological and molecular stress markers in LAL mice. In view of the profound differences in behavioral traits and stress system reactivity, these mouse lines genetically selected for attack latency present an interesting model for studying the mechanism underlying individual variation in susceptibility to stress-related psychopathology.     

Stress sensitivity and the development of affective disorders

Depressive disorders are the most common form of mental illness in America, affecting females twice as often as males. The great variability of symptoms and responses to therapeutic treatment emphasize the complex underlying neurobiology of disease onset and progression. Evidence from human and animal studies reveals a vital link between individual stress sensitivity and the predisposition toward mood disorders. While the stress response is essential for maintenance of homeostasis and survival, chronic stress and maladaptive responses to stress insults can lead to depression or other affective disorders. A key factor in the mediation of stress responsivity is the neuropeptide corticotropin-releasing factor (CRF). Studies in animal models of heightened stress sensitivity have illustrated the involvement of CRF downstream neurotransmitter targets, including serotonin and norepinephrine, in the profound neurocircuitry failure that may underlie maladaptive coping strategies. Stress sensitivity may also be a risk factor in affective disorder development susceptibility. As females show an increased stress response and recovery time compared to males, they may be at an increased vulnerability for disease. Therefore, examination of sex differences in CRF and downstream targets may aid in the elucidation of the underlying causes of the increased disease presentation in females. While we continue to make progress in our understanding of mood disorder etiology, we still have miles to go before we sleep. As an encouraging number of new animal models of altered stress sensitivity and negative stress coping strategies have been developed, the future looks extremely promising for the possibility of a new generation of drug targets to be developed.     

Associations Between Perceived Weight Discrimination and the Prevalence of Psychiatric Disorders in the General Population

Despite the increased prevalence of weight discrimination, few studies have examined the association between perceived weight discrimination and the prevalence of current psychiatric disorders in the general population. This study utilized a subsample of overweight and obese individuals (N = 22,231) from Wave 2 of the National Epidemiologic Survey on Alcohol and Related Conditions (NESARC), a cross‐sectional nationally representative study of noninstitutionalized US adults. Perceived weight discrimination is associated with substantial psychiatric morbidity and comorbidity. These results remained significant after adjusting for a potential confound, perceived stress. Moreover, social support did not buffer against the adverse effects of perceived weight discrimination on mental health. Controlling for BMI did not diminish the associations, indicating that perceived weight discrimination is potentially harmful to mental health regardless of weight. These results highlight the urgent need for a multifaceted approach to address this important public health issue, including interventions to assist overweight individuals in coping with the mental health sequelae of perceived weight discrimination.     

Mitochondrial Dysfunction and Psychiatric Disorders

Mitochondrial oxidative phosphorylation is the major ATP-producing pathway, which supplies more than 95% of the total energy requirement in the cells. Damage to the mitochondrial electron transport chain has been suggested to be an important factor in the pathogenesis of a range of psychiatric disorders. Tissues with high energy demands, such as the brain, contain a large number of mitochondria, being therefore more susceptible to reduction of the aerobic metabolism. Mitochondrial dysfunction results from alterations in biochemical cascade and the damage to the mitochondrial electron transport chain has been suggested to be an important factor in the pathogenesis of a range of neuropsychiatric disorders, such as bipolar disorder, depression and schizophrenia. Bipolar disorder is a prevalent psychiatric disorder characterized by alternating episodes of mania and depression. Recent studies have demonstrated that important enzymes involved in brain energy are altered in bipolar disorder patients and after amphetamine administration, an animal model of mania. Depressive disorders, including major depression, are serious and disabling. However, the exact pathophysiology of depression is not clearly understood. Several works have demonstrated that metabolism is impaired in some animal models of depression, induced by chronic stress, especially the activities of the complexes of mitochondrial respiratory chain. Schizophrenia is a devastating mental disorder characterized by disturbed thoughts and perception, alongside cognitive and emotional decline associated with a severe reduction in occupational and social functioning, and in coping abilities. Alterations of mitochondrial oxidative phosphorylation in schizophrenia have been reported in several brain regions and also in platelets. Abnormal mitochondrial morphology, size and density have all been reported in the brains of schizophrenic individuals. Considering that several studies link energy impairment to neuronal death, neurodegeneration and disease, this review article discusses energy impairment as a mechanism underlying the pathophysiology of some psychiatric disorders, like bipolar disorder, depression and schizophrenia.     

Focused grooming networks and stress alleviation in wild female baboons

We examine the relationship between glucocorticoid (GC) levels and grooming behavior in wild female baboons during a period of instability in the alpha male rank position. All females' GC levels rose significantly at the onset of the unstable period, though levels in females who were at lower risk of infanticide began to decrease sooner in the following weeks. Three factors suggest that females relied on a focused grooming network as a coping mechanism to alleviate stress. First, all females' grooming networks became less diverse in the weeks following the initial upheaval. Second, females whose grooming had already focused on a few predictable partners showed a less dramatic rise in GC levels than females whose grooming network had been more diverse. Third, females who contracted their grooming network the most experienced a greater decrease in GC levels in the following week. We conclude that close bonds with a few preferred partners allow female baboons to alleviate the stress associated with social instability.     

Grooming Between Male Chimpanzees at Ngogo,Kibale National Park. II. Influence of Male Rank and Possible Competition for Partners

Allogrooming contributes to the development and maintenance of social relationships, including those that involve alliances, in many primate species. Variation in relatedness, dominance rank, and other factors can produce variation in the value of others as grooming partners. Several models have been developed to account for variation in the distribution of grooming in relation to dominance ranks. These start from the premise that individuals are attracted to high-ranking partners, but time limits, direct competition, and prior grooming engagement between high-ranking individuals can constrain access to them. Sambrook et al. (1995) formalized some of these models and showed the importance of taking group size variation into account when assessing them. Chimpanzees form multimale communities in which males are the philopatric sex. Males commonly associate and groom with each other; they also form dominance hierarchies and form alliances that influence dominance ranks and mating success. Both male rank and the rank distance between partners are significantly correlated with the distribution of grooming between males in an extremely large chimpanzee community at Ngogo, Kibale National Park, Uganda, that has more males than any other known community. High-ranking males had more grooming partners than mid- or low-ranking males. Grooming predominantly went up the dominance hierarchy, but was also concentrated among males that were close in rank. Rank and rank distance apparently both affected grooming independently of reciprocity in grooming and independently of the frequency with which males associated in temporary parties. However, the data do not clearly indicate how constraints on access to partners might have operated. Published data from a smaller chimpanzee community at Mahale show no rank or rank distance effect on male grooming. These results and earlier, conflicting findings on the association between dominance rank and grooming in male chimpanzees indicate that variation in group size, i.e., the number of males per community, probably influences the strength of any such effects, as happens for grooming between females in several cercopithecine species. Data on coalitions at Ngogo support the argument that high-ranking males are valuable social partners, and similarity in strategies of alliance formation may influence the distribution of grooming.     

Delays in GABAergic interneuron development and behavioral inhibition after prenatal stress

Prenatal stress is associated with altered behavioral, cognitive, and psychiatric outcomes in offspring. Due to the importance of GABAergic systems in normal development and in psychiatric disorders, prenatal stress effects on these neurons have been investigated in animal models. Prenatal stress delays GABAergic progenitor migration, but the significance of these early developmental disruptions for the continued development of GABAergic cells in the juvenile brain is unclear. Here, we examined effects of prenatal stress on populations of GABAergic neurons in juvenile and adult medial frontal cortex (mFC) and hippocampus through stereological counting, gene expression, and relevant anxiety‐like and social behaviors. Postnatally, the total GABAergic cell number that peaks in adolescence showed altered trajectories in mFC and hippocampus. Parvalbumin neuron proportion in juvenile brain was altered by prenatal stress, but parvalbumin gene expression showed no differences. In adult brain, parvalbumin neuron proportions were altered by prenatal stress with opposite gene expression changes. Adult prenatally stressed offspring showed a lack of social preference on a three‐chambered task, increased anxiety‐like behavior on the elevated plus maze, and reduced center time in an open field. Despite a lack of significant group differences in adult total GABAergic cell populations, performance of these tasks was correlated with GABAergic populations in mFC and hippocampus. In conclusion, prenatal stress resulted in a delay in GABAergic cell number and maturation of the parvalbumin subtype. Influences of prenatal stress on GABAergic populations during developmentally dynamic periods and during adulthood may be relevant to the anxiety‐like behaviors that occur after prenatal stress. © 2015 Wiley Periodicals, Inc. Develop Neurobiol 76: 1078–1091, 2016     

Social correlates of variation in urinary cortisol in wild male bonobos (Pan paniscus)

Cortisol excretion in males of group living species is often associated with social rank and competition for oestrous females. Rank-related patterns of cortisol levels can be used to study mechanisms of rank maintenance and costs associated with mate competition. Bonobos (Pan paniscus) are interesting because males form a linear dominance hierarchy but are not dominant over females and therefore aggressive male-male competition over access to females alone is not considered to be a successful reproductive strategy. In this study on social correlates of urinary cortisol in wild male bonobos, we investigated the relationship between cortisol levels and several aspects of mate competition, including male rank, aggression rates, and association time with oestrous females. We found that cortisol levels correlated positively with dominance rank when oestrous females were present, but not when they were absent. This result is consistent with the idea that aggressive behaviour plays a minor role in maintenance of high rank. While aggression received from males and females explained within-individual variation in cortisol levels, it was the time spent in association with oestrous females that best explained between-individual variation in male cortisol levels. The observed increase in male cortisol may be associated with spatial proximity to oestrous females and could result from anticipated aggression from other group members, reduced feeding time in the males, or a combination of both.     

Social behavior, foraging strategies, and fecal glucocorticoids in female blue monkeys (Cercopithecus mitis): potential fitness benefits of high rank in a forest guenon

Socioecological theory predicts that aggressive feeding competition is associated with linear dominance hierarchies and reproductive advantages for high-ranking females. Female blue monkeys contest fruits and have a linear dominance hierarchy, yet previous research has shown no evidence that high-ranking females benefit from greater feeding success or fertility. Here, we assess whether individuals differ in fecal glucocorticoid (fGC) excretion and examine proximate determinants of such differences to infer potential fitness correlates of rank, using data collected from two study groups in the Kakamega Forest, Kenya. We found that higher ranking females had preferential access to fruits in both groups, although the behavioral mechanisms leading to this effect varied between groups. Despite a consistent rank difference in feeding on fruits, an overall rank effect on fGCs emerged in only one group; females of this group spent comparatively more time feeding on fruits, fruits accounted for a greater proportion of the diet, and females engaged in more frequent food-related agonism. In addition, more females in this group were lactating during a period of low fruit availability, when rank effects on fGCs were particularly strong. Regardless of fruit availability, among lactating females of both groups higher rank was associated with lower fGC levels, indicating lower energetic stress in higher ranking females when energy demands were particularly high. Individual rates of agonism, a potential psychological stressor, were unrelated to fGCs at all times. After we accounted for rates of agonism and feeding on fruits, females of one group who groomed others more had lower fGCs, suggesting that variable social coping behavior can contribute to fGC variation in some groups. This study provides the first empirical evidence that high-ranking female blue monkeys may obtain fitness benefits from their social status, by gaining priority of access to fruits during critical times in the reproductive cycle.