Zebra Stripes through the Eyes of Their Predators,Zebras, and Humans

The century-old idea that stripes make zebras cryptic to large carnivores has never been examined systematically. We evaluated this hypothesis by passing digital images of zebras through species-specific spatial and colour filters to simulate their appearance for the visual systems of zebras’ primary predators and zebras themselves. We also measured stripe widths and luminance contrast to estimate the maximum distances from which lions, spotted hyaenas, and zebras can resolve stripes. We found that beyond ca. 50 m (daylight) and 30 m (twilight) zebra stripes are difficult for the estimated visual systems of large carnivores to resolve, but not humans. On moonless nights, stripes are difficult for all species to resolve beyond ca. 9 m. In open treeless habitats where zebras spend most time, zebras are as clearly identified by the lion visual system as are similar-sized ungulates, suggesting that stripes cannot confer crypsis by disrupting the zebra’s outline. Stripes confer a minor advantage over solid pelage in masking body shape in woodlands, but the effect is stronger for humans than for predators. Zebras appear to be less able than humans to resolve stripes although they are better than their chief predators. In conclusion, compared to the uniform pelage of other sympatric herbivores it appears highly unlikely that stripes are a form of anti-predator camouflage.     

Inter-Mount Social Interactions During Heterosexual and Homosexual Consortships in Japanese Macaques

In this study, we examined whether female Japanese macaques ( Macaca fuscata ) exhibited male-typical patterns of inter-mount social behaviour during homosexual consortships. Data were collected on heterosexual and homosexual consortships from a population of free-ranging Japanese macaques in Arashiyama, Japan. Inter-mount intervals were defined as the period between two consecutive mounts. A total of 3374 heterosexual inter-mount intervals and 1412 homosexual inter-mount intervals were analysed. We examined nine different categories of inter-mount behaviour. Sex differences between heterosexually consorting males and females existed for three of the inter-mount behaviours we examined (i.e. ventral-to-dorsal orientation, aggression directed toward third party individuals, tree-shaking displays). The subordinate female partners in homosexually consorting pairs exhibited some sex-atypical inter-mount behaviours. This sex-atypicality did not appear to reflect generalized developmental canalization in the direction of a male-typical suite of behaviours. Rather, the observed behavioural sex-atypicality could be best explained in terms of the unique alliance-related dynamics that characterized homosexual consortships in Japanese macaques.     

短尾猴的社会行为与社会关系

群体生活的动物通过社会行为相联系,社会行为的类别和发生的频率决定了动物社会关系的性质,进而决定了社会结构的类型。本文根据作者在安徽黄山对短尾猴16年的观察研究,描述和分析了一些重要的社会行为,探讨了短尾猴社会中各种社会关系的特点和性质。雌性短尾猴之间的行为比较简单,缺乏多样性,主要通过近距及理毛等状态性行为建立和维持,是长久和稳固的关系;雄性短尾猴之间具有丰富的行为,事件性行为(如拥抱、爬跨等)占主要部分,易发生冲突但也易于和解;雄性和雌性关系与繁殖季节有关,交配期主要是性关系,产仔期主要是友好关系;成体和幼体的关系主要是照料与被照料的关系。     

衰老对2种猕猴血液基因表达的影响及与人类的对比

衰老是导致免疫功能和代谢活动下降的危险因素.作为最常用的非人灵长类动物模型,猕猴属Macaca被用来探索与衰老过程相关的因素.为了比较2种猕猴和人类在衰老过程基因表达变化的异同,本研究收集比较了3个物种的血液转录组.在藏酋猴M.thibetana(TM)、普通猕猴M.mulatta(CR)和人类中分别获得了2523个、...     

Male-Infant Interactions in Baboons and Macaques: A Critique and Reevaluation

A critical reexamination of the empirical data on male-infantinteractions among baboons and macaques reveals a number ofsignificant contrasts between them. On an absolute and relativescale, the frequency of occurrence among baboons is rare. Whenmale baboons do interact with infants, only a small proportionof all available male actors do so, and even fewer still (lessthan one-quarter) account for any substantial percentage ofall interactions. In contrast, macaque males are very frequentlyand commonly involved with infants; all males of the group interactwith infants to some degree, and a greater proportion of allthe group's males can be characterized as "heavily involved"with infants. The rejection of the role of kinship in interpretingthis phenomenon, especially as it occurs among baboons, hasrested almost exclusively on the pattern of estimated paternitybetween male and infant from behavioral (consort) criteria.These behavioralbased data are incomplete at best, possiblyincorrect in some instances, and in fact, in many studies kinshipappears to be a predominant factor. Until patrilineal data arederived from independent cytogenetic studies, these evolutionaryinterpretations must be viewed with extreme skepticism.     

Coevolution of Facial Expression and Social Tolerance in Macaques

The purpose of this study is to test the hypothesis that social tolerance drives the evolution of facial expression in macaques. Macaque species exhibit a range of social styles that reflect a continuum of social tolerance. Social interactions in more tolerant taxa tend to be less constrained by rank and kinship than in less‐tolerant macaques. I predicted that macaques that are more tolerant would exhibit a wider range of facial displays than less‐tolerant species because interactions that are open to negotiation are characterized by greater uncertainty than interactions that are constrained by rank or kinship. To test this hypothesis, I conducted a phylogenetically informed regression analysis (N = 11) using previously published data on repertoire size and two quantitative measures of social tolerance (conciliatory tendency and counter‐aggression). As predicted, macaques with more tolerant social styles tended to have larger repertoires than less‐tolerant species. These results support the hypothesis that increased social tolerance favors the elaboration of communication to mitigate uncertainty.     

Mounting Interactions between Female Japanese Macaques: Testing the Influence of Dominance and Aggression

The goal of the work reported here was to determine whether female Japanese macaques (Macaca fuscata) participated in same-sex mounting interactions during homosexual consortships to communicate about asymmetries in their dominance relationships and to reduce aggression. Focal data were collected during 21 homosexual consortships involving 14 females living in a captive, mixed-sex group of 37 individuals. We identified eight types of mounts, one solicitation used specifically to request to mount (hands-on-hindquarters solicitation), two solicitations used specifically to request to be mounted (hindquarter and back presentations), and one behavior employed to facilitate mounts-in-progress (clasping). We tested whether dominant consort partners (1) mounted more and (2) requested to mount more than their subordinate partners and whether subordinate consort partners (1) requested to be mounted more and (2) facilitated mounts-in-progress more than their dominant partners. Finally, we examined whether mounting was temporally linked to the onset of aggressive interactions between consort partners and whether it functioned to defuse incipient aggression. None of these predictions was supported. All types of mounts, mount solicitations, and clasping occurred bi-directionally within consort dyads. Mutual sexual attraction and gratification provided the proximate motivation for these mounting interactions and, in turn, for the formation and maintenance of their homosexual consortships.     

Expression of DC-SIGN by Dendritic Cells of Intestinal and Genital Mucosae in Humans and Rhesus Macaques

To better understand the role of dendritic cells (DCs) in human immunodeficiency virus (HIV) transmission at mucosal surfaces, we examined the expressions of the HIV adhesion molecule, dendritic-cell-specific ICAM-3 grabbing nonintegrin (DC-SIGN), its closely related homologue DC-SIGNR, and HIV coreceptors by distinct DC populations in the intestinal and genital tracts of humans and rhesus macaques. We also developed monoclonal antibodies (MAbs) specific for DC-SIGN or DC-SIGNR. In the Peyer's patches, DC-SIGN expression was detected in the interfollicular regions and in clusters of cells in the subepithelial dome regions. DC-SIGN expression was not found on plasmacytoid DCs. DC-SIGNR expression was restricted to endothelial cells in approximately one-third of the capillaries in the terminal ileum. In the vaginal epithelium, Langerhans' cells did not express DC-SIGN, whereas subepithelial DCs in the lamina propria expressed moderate levels of DC-SIGN. Finally, the rectum contained cells that expressed high levels of DC-SIGN throughout the entire thickness of the mucosa, while solitary lymphoid nodules within the rectum showed very little staining for DC-SIGN. Triple-color analysis of rectal tissue indicated that CCR5(+) CD4(+) DC-SIGN(+) DCs were localized just beneath the luminal epithelium. These findings suggest that DC-SIGN(+) DCs could play a role in the transmission of primate lentiviruses in the ileum and the rectum whereas accessibility to DC-SIGN(+) cells is limited in an intact vaginal mucosa. Finally, we identified a MAb that blocked simian immunodeficiency virus interactions with rhesus macaque DC-SIGN. This and other specific MAbs may be used to assess the relevance of DC-SIGN in virus transmission in vivo.     

Ontogenetic Patterning of Skeletal Fluctuating Asymmetry in Rhesus Macaques and Humans: Evolutionary and Developmental Implications

I address the question of how fluctuating asymmetry (FA)—the distribution of random deviations from bilateral symmetry—varies ontogenetically in the mammalian skeleton. This question is significant because of the light that such patterns can shed on the causes of variation in developmental stability in bone as well as other structures. Based on large ontogenetic skeletal series of Macaca mulatta and Homo sapiens, I report that the FA variances of skeletal metric traits increase ontogenetically. Coupled with the finding that FA variances also accumulate to greater magnitudes in slower growing mammals, this result is consistent with the hypotheses that FA in bone is primarily caused by (a) cumulative effects of asymmetrical mechanical factors, (b) accumulation of variation in the (local) regulation of growth, or (c) a tendency for bone morphology to drift through undirected remodeling. I discuss the implications of these optional explanations for primate evolution and bone development.     

Speaking and Listening with the Eyes: Gaze Signaling during Dyadic Interactions

Cognitive scientists have long been interested in the role that eye gaze plays in social interactions. Previous research suggests that gaze acts as a signaling mechanism and can be used to control turn-taking behaviour. However, early research on this topic employed methods of analysis that aggregated gaze information across an entire trial (or trials), which masks any temporal dynamics that may exist in social interactions. More recently, attempts have been made to understand the temporal characteristics of social gaze but little research has been conducted in a natural setting with two interacting participants. The present study combines a temporally sensitive analysis technique with modern eye tracking technology to 1) validate the overall results from earlier aggregated analyses and 2) provide insight into the specific moment-to-moment temporal characteristics of turn-taking behaviour in a natural setting. Dyads played two social guessing games (20 Questions and Heads Up) while their eyes were tracked. Our general results are in line with past aggregated data, and using cross-correlational analysis on the specific gaze and speech signals of both participants we found that 1) speakers end their turn with direct gaze at the listener and 2) the listener in turn begins to speak with averted gaze. Convergent with theoretical models of social interaction, our data suggest that eye gaze can be used to signal both the end and the beginning of a speaking turn during a social interaction. The present study offers insight into the temporal dynamics of live dyadic interactions and also provides a new method of analysis for eye gaze data when temporal relationships are of interest.     

Social and Demographic Influences on Mothering Style in Pigtail Macaques

This study represents the first investigation of variability in mothering styles in pigtail macaques, Macaca nemestrina nemestrina. Fifteen group-living mother-infant pairs were focally observed during the first 12 wk of infant life and several measures of maternal and infant behavior were recorded. Variability in mothering styles occurred along the three dimensions of maternal protectivencss, rejection, and warmth. Maternal parity and aggression received by mothers were the best predictors of variability in protectiveness and warmth, whereas variability in rejection was not predicted by any of the variables considered. This study provides clear evidence that aggression towards mothers and previous maternal experience have an important influence on mothering styles in pigtail macaques.     

A Neural Circuit Covarying with Social Hierarchy in Macaques

Despite widespread interest in social dominance, little is known of its neural correlates in primates. We hypothesized that social status in primates might be related to individual variation in subcortical brain regions implicated in other aspects of social and emotional behavior in other mammals. To examine this possibility we used magnetic resonance imaging (MRI), which affords the taking of quantitative measurements noninvasively, both of brain structure and of brain function, across many regions simultaneously. We carried out a series of tests of structural and functional MRI (fMRI) data in 25 group-living macaques. First, a deformation-based morphometric (DBM) approach was used to show that gray matter in the amygdala, brainstem in the vicinity of the raphe nucleus, and reticular formation, hypothalamus, and septum/striatum of the left hemisphere was correlated with social status. Second, similar correlations were found in the same areas in the other hemisphere. Third, similar correlations were found in a second data set acquired several months later from a subset of the same animals. Fourth, the strength of coupling between fMRI-measured activity in the same areas was correlated with social status. The network of subcortical areas, however, had no relationship with the sizes of individuals'' social networks, suggesting the areas had a simple and direct relationship with social status. By contrast a second circuit in cortex, comprising the midsuperior temporal sulcus and anterior and dorsal prefrontal cortex, covaried with both individuals'' social statuses and the social network sizes they experienced. This cortical circuit may be linked to the social cognitive processes that are taxed by life in more complex social networks and that must also be used if an animal is to achieve a high social status.     

Paternal Relatedness Predicts the Strength of Social Bonds among Female Rhesus Macaques

Forming strong, equitable, and enduring social bonds with a few individuals in a group carries adaptive benefits in terms of increased longevity, offspring survival and paternity success in birds and mammals, including humans. These recent insights generated a new interest in the factors creating variation in the strength of social relationships. Whether and how animals discriminate paternal kin from non-kin and bias their social behavior accordingly is being debated. This study explores the relative importance of dominance rank, age, maternal and paternal relatedness in shaping dyadic affiliative relationships in a group of 30 captive rhesus macaque females. The strength of social relationships, measured by the composite sociality index from observational data, was independently predicted in GLMMs by both maternal and paternal relatedness as well as rank similarity. In addition, social bonds between paternal half-sisters were stronger than between distantly related kin suggesting that females biased their affiliative effort towards paternal relatives. Despite identical relatedness coefficients bonds between mothers and their daughters were three times as strong as those between full sisters. Together these results add to the growing body of evidence for paternal kin biases in affiliative behavior and highlight that females prefer descendent over lateral kin.     

Serotonin Transporter Genotype Modulates Social Reward and Punishment in Rhesus Macaques

Background

Serotonin signaling influences social behavior in both human and nonhuman primates. In humans, variation upstream of the promoter region of the serotonin transporter gene (5-HTTLPR) has recently been shown to influence both behavioral measures of social anxiety and amygdala response to social threats. Here we show that length polymorphisms in 5-HTTLPR predict social reward and punishment in rhesus macaques, a species in which 5-HTTLPR variation is analogous to that of humans.

Methodology/Principal Findings

In contrast to monkeys with two copies of the long allele (L/L), monkeys with one copy of the short allele of this gene (S/L) spent less time gazing at face than non-face images, less time looking in the eye region of faces, and had larger pupil diameters when gazing at photos of a high versus low status male macaques. Moreover, in a novel primed gambling task, presentation of photos of high status male macaques promoted risk-aversion in S/L monkeys but promoted risk-seeking in L/L monkeys. Finally, as measured by a “pay-per-view” task, S/L monkeys required juice payment to view photos of high status males, whereas L/L monkeys sacrificed fluid to see the same photos.

Conclusions/Significance

These data indicate that genetic variation in serotonin function contributes to social reward and punishment in rhesus macaques, and thus shapes social behavior in humans and rhesus macaques alike.     

Indirect Genetic Effects and the Dynamics of Social Interactions

BackgroundIndirect genetic effects (IGEs) occur when genes expressed in one individual alter the expression of traits in social partners. Previous studies focused on the evolutionary consequences and evolutionary dynamics of IGEs, using equilibrium solutions to predict phenotypes in subsequent generations. However, whether or not such steady states may be reached may depend on the dynamics of interactions themselves.ResultsIn our study, we focus on the dynamics of social interactions and indirect genetic effects and investigate how they modify phenotypes over time. Unlike previous IGE studies, we do not analyse evolutionary dynamics; rather we consider within-individual phenotypic changes, also referred to as phenotypic plasticity. We analyse iterative interactions, when individuals interact in a series of discontinuous events, and investigate the stability of steady state solutions and the dependence on model parameters, such as population size, strength, and the nature of interactions. We show that for interactions where a feedback loop occurs, the possible parameter space of interaction strength is fairly limited, affecting the evolutionary consequences of IGEs. We discuss the implications of our results for current IGE model predictions and their limitations.