Affiliation and disease risk: social networks mediate gut microbial transmission among rhesus macaques

Associations between social behaviour and proinflammatory immune activation are modulated by age in a free-ranging primate population

The effect of the social environment on the proinflammatory immune response may mediate the relationship between social environment and fitness but remains understudied outside captive animals and human populations. Age can also influence both immune function and social behaviour, and hence may modulate their relationships. This study investigates the role of social interactions in driving the concentrations of two urinary markers of proinflammatory immune activation, neopterin and soluble urokinase plasminogen activator receptor (suPAR), in a free-ranging population of rhesus macaques, Macaca mulatta. We collected 854 urine samples from 172 adult monkeys and quantified how urinary suPAR and neopterin concentrations were related to affiliative behaviour and agonistic behaviour received over 60 days. In females, but not in males, higher rates of affiliative interactions were associated with lower neopterin concentrations, while conversely, experiencing more agonistic interactions was associated with higher neopterin concentrations. The association between affiliation and neopterin concentration was modulated by age, with older females experiencing a stronger negative association between affiliative behaviour and neopterin concentration. There were no associations between suPAR concentration and social environment for either sex. This study demonstrates that proinflammatory immune activity is a potential mechanism mediating the association between social environment and fitness under naturalistic conditions and that age can be an important modulator of the effect of social environment on the immune system.

Associations between fecal glucocorticoid levels and social bonds vary with relatedness in juvenile rhesus macaques

Strong social bonds in gregarious adult animals have been associated with lower levels of glucocorticoids. However, similar research is lacking for juvenile primates. We examined relationships between social bonds and mean concentrations of fecal glucocorticoid metabolites (fGCMs) in 44 free-ranging juvenile rhesus macaques (Macaca mulatta) on Cayo Santiago, Puerto Rico. We measured frequencies of affiliative behavior (grooming, play, approaches and proximity) with other same-sex, same-aged juveniles (peers) and the total number of affiliative peer relationships. We found a positive relationship between fGCMs and grooming frequencies. Females that spent more time in proximity to peers also had higher fGCMs. In contrast, among juveniles with more closely related peers, those with more affiliative peers or more frequent play bouts had lower fGCMs. However, strong peer bonds in most juveniles did not appear to be associated with reduced glucocorticoid levels. fGCMs were higher for females than males, but were unassociated with physical activity, aggression, or peer seeking tendencies. We propose that the establishment and navigation of some peer bonds at this life stage may involve increased metabolic demand.

Social ageing can protect against infectious disease in a group-living primate

The benefits of social living are well established, but sociality also comes with costs, including infectious disease risk. This cost-benefit ratio of sociality is expected to change across individuals' lifespans, which may drive changes in social behaviour with age. To explore this idea, we combine data from a group-living primate for which social ageing has been described with epidemiological models to show that having lower social connectedness when older can protect against the costs of a hypothetical, directly transmitted endemic pathogen. Assuming no age differences in epidemiological characteristics (susceptibility to, severity and duration of infection), older individuals suffered lower infection costs, which was explained largely because they were less connected in their social networks than younger individuals. This benefit of 'social ageing' depended on epidemiological characteristics and was greatest when infection severity increased with age. When infection duration increased with age, social ageing was beneficial only when pathogen transmissibility was low. Older individuals benefited most from having a lower frequency of interactions (strength) and network embeddedness (closeness) and benefited less from having fewer social partners (degree). Our study provides a first examination of the epidemiology of social ageing, demonstrating the potential for pathogens to influence the evolutionary dynamics of social ageing in natural populations.This article is part of the discussion meeting issue 'Understanding age and society using natural populations'.

Commentary on the Adaptive Significance of Sociality Around Parturition Events, and Conspecific Support of Parturient Females in Some Social Mammals

In recent decades, it has become apparent that during parturition events in a number of social mammals, social support behaviours from group mates can be directed to parturient females (and their newborn neonates). Such behaviour has been documented in diverse taxa, across non-human primates, Elephantidae, Cetacea, and Chiroptera, living in a range of social group organisations, from matrilineal groups to cooperatively breeding groups and multi-male, multi-female groups. Since sociality, in association with parturition, has been demonstrated to confer several health benefits to human mothers and neonates, here, we also consider the potential adaptive significance of social support behaviours for other, non-human, social mammals. If appropriate social environments reduce a parturient female's dystocia risk and improve her responsiveness to her neonate following a successful birth, then the impacts of the peri-parturient social environment may ultimately have far-reaching impacts on the mother-neonate dyad's fitness. This seems a logical sequela since the health condition of a neonate at birth and the successful establishment of a strong maternal-neonate bond are often the most critical factors influencing mammalian offspring survival to independence. The principles of kin selection and alliance enhancement may serve to explain the fitness benefits to individuals who support group mates during their parturition and thus the selective advantage conferred to those exhibiting such behaviours. Older, multiparous females appear to hold a particularly important role in the assistance they can provide during the parturition of their group mates, given their greater level of experience of these events. Furthermore, a social birth may have an important influence on horizontal information transfer within a group. In particular, in long-lived, cognitively advanced social mammals (e.g., non-human primates, Elephantidae, Cetacea), witnessing birth events, early neonate responses, and maternal care, and engaging in allomaternal care with young neonates may be essential for nulliparous females' normal development. Such events may serve to prepare them for their own parturition and may improve their own parturition-related survivorship and that of their first-born offspring. Thus, it is vital that a better understanding is gained of the importance and salient features of social births in improving the health and survivorship outcomes for both the mother and her offspring in highly social species. The aim of this commentary is to assemble our current understanding of these highly interconnected themes. We suggest in the future, insights gained through observation of non-human social parturition in domestic and non-domestic species, by a wide and highly interdisciplinary range of stakeholders (including zookeepers, wildlife tourism guides, breeders of domestic animals, indigenous people, and ethologists), will be critical for enhancing our understanding of the influence of social environment on this rarely witnessed, yet highly important life event.

Social ageing can protect against infectious disease in a group-living primate

The benefits of social living are well established, but sociality also comes with costs, including infectious disease risk. This cost-benefit ratio of sociality is expected to change across individuals' lifespans, which may drive changes in social behaviour with age. To explore this idea, we combine data from a group-living primate for which social ageing has been described with epidemiological models to show that having lower social connectedness when older can protect against the costs of a hypothetical, directly transmitted endemic pathogen. Assuming no age differences in epidemiological characteristics (susceptibility to, severity, and duration of infection), older individuals suffered lower infection costs, which was explained largely because they were less connected in their social networks than younger individuals. This benefit of 'social ageing' depended on epidemiological characteristics and was greatest when infection severity increased with age. When infection duration increased with age, social ageing was beneficial only when pathogen transmissibility was low. Older individuals benefited most from having a lower frequency of interactions (strength) and network embeddedness (closeness) and benefited less from having fewer social partners (degree). Our study provides a first examination of the epidemiology of social ageing, demonstrating the potential for pathogens to influence evolutionary dynamics of social ageing in natural populations.

Shared Accountability Shaping the Destinies of Individual and Groups of Nonhuman Primates

At the California National Primate Research Center (CNPRC), the preferred housing for rhesus macaques involves maintaining them in complex social groups outdoors, primarily for breeding purposes. This functionally appropriate environment promotes effective coping through the expression of species-typical behaviors and important aspects of species-typical social structure, thus enabling normal animal development, higher reproductive success, and the production of high-quality biological models. Despite the benefits, social housing introduces challenges like trauma from aggressive interactions. These challenges necessitate a delicate balance between tolerating some aggression and preventing repeated targeting of individuals. Therefore, the CNPRC has established a multidisciplinary working group of behavioral management experts, veterinarians, animal care, and researchers that meets regularly to review cases of animals that may need to be removed from their social group. We discuss the criteria and decision-making processes employed to manage and mitigate aggression. We describe the systematic approach to identifying at-risk individuals and the comprehensive evaluation process that guides whether to relocate an animal from their groups or not. Considerations include the welfare of the individual and the group's social stability. This paper provides case studies demonstrating how the working group applies these criteria and processes in practical scenarios, highlighting the complexities and challenges of such decisions.

What you have, not who you know: food-enhanced social capital and changes in social behavioural relationships in a non-human primate

Social network position in non-human primates has far-reaching fitness consequences. Critically, social networks are both heterogeneous and dynamic, meaning an individual's current network position is likely to change due to both intrinsic and extrinsic factors. However, our understanding of the drivers of changes in social network position is largely confined to opportunistic studies. Experimental research on the consequences of in situ, controlled network perturbations is limited. Here we conducted a food-based experiment in rhesus macaques to assess whether allowing an individual the ability to provide high-quality food to her group changed her social behavioural relationships. We considered both her social network position across five behavioural networks, as well as her dominance and kin interactions. We found that gaining control over a preferential food resource had far-reaching social consequences. There was an increase in both submission and aggression centrality and changes in the socio-demographic characteristics of her agonistic interaction partners. Further, we found that her grooming balance shifted in her favour as she received more grooming than she gave. Together, these results provide a novel, preliminary insight into how in situ, experimental manipulations can modify social network position and point to broader network-level shifts in both social capital and social power.

The impact of housing on birth outcomes in breeding macaque groups across multiple research centers

Demand for nonhuman primates in research has increased over the past several years, while nonhuman primate supply remains a challenge in the United States. Global nonhuman primate supply issues make it increasingly important to maximize domestic colony production. To explore how housing conditions across primate breeding colonies impact infant survival and animal production more broadly, we collected medical records from 7959 rhesus macaques (Macaca mulatta) and 492 pigtail macaques (Macaca nemestrina) across seven breeding facilities and used generalized mixed-effect modeling to determine prenatal and infant survival odds by housing type and group size. Infant survival odds for each housing type and group size varied for prenatal, neonatal, early infant, and late infant age groups. Odds of prenatal survival were lowest in paired indoor housing and small and medium outdoor groups. No housing type performed better than large outdoor groups for neonatal survival. Odds of early infant survival was greatest in indoor and mixed indoor/outdoor housing compared to large outdoor enclosures. Large outdoor housing was associated with higher survival odds for late infant survival compared to small and medium outdoor housing. These results may influence housing choices at macaque breeding facilities hoping to maximize infant success, although there are relative care costs, the promotion of species-typical behaviors, and infrastructure factors to also consider. Our study used an interinstitutional collaboration that allowed for the analysis of more infant macaque medical records than ever before and used the broad variations across the seven national primate research centers to make the results applicable to many other facilities housing macaques.

Yearly variation coupled with social interactions shape the skin microbiome in free-ranging rhesus macaques

While skin microbes are known to mediate human health and disease, there has been minimal research on the interactions between skin microbiota, social behavior, and year-to-year effects in non-human primates-important animal models for translational biomedical research. To examine these relationships, we analyzed skin microbes from 78 rhesus macaques living on Cayo Santiago Island, Puerto Rico. We considered age, sex, and social group membership, and characterized social behavior by assessing dominance rank and patterns of grooming as compared to nonsocial behaviors. To measure the effects of a shifting environment, we sampled skin microbiota (based on sequence analysis of the 16S rRNA V4 region) and assessed weather across sampling periods between 2013 and 2015. We hypothesized that, first, monkeys with similar social behavior and/or in the same social group would possess similar skin microbial composition due, in part, to physical contact, and, second, microbial diversity would differ across sampling periods. We found significant phylum-level differences between social groups in the core microbiome as well as an association between total grooming rates and alpha diversity in the complete microbiome, but no association between microbial diversity and measures of rank or other nonsocial behaviors. We also identified alpha and beta diversity differences in microbiota and differential taxa abundance across two sampling periods. Our findings indicate that social dynamics interact with yearly environmental changes to shape the skin microbiota in rhesus macaques, with potential implications for understanding the factors affecting the microbiome in humans, which share many biological and social characteristics with these animals. IMPORTANCE Primate studies are valuable for translational and evolutionary insights into the human microbiome. The majority of primate microbiome studies focus on the gut, so less is known about the factors impacting the microbes on skin and how their links affect health and behavior. Here, we probe the impact of social interactions and the yearly environmental changes on food-provisioned, free-ranging monkeys living on a small island. We expected animals that lived together and groomed each other would have more similar microbes on their skin, but surprisingly found that the external environment was a stronger influence on skin microbiome composition. These findings have implications for our understanding of the human skin microbiome, including potential manipulations to improve health and treat disease.

Social complexity as a driving force of gut microbiota exchange among conspecific hosts in non-human primates

The emergent concept of the social microbiome implies a view of a highly connected biological world, in which microbial interchange across organisms may be influenced by social and ecological connections occurring at different levels of biological organization. We explore this idea reviewing evidence of whether increasing social complexity in primate societies is associated with both higher diversity and greater similarity in the composition of the gut microbiota. By proposing a series of predictions regarding such relationship, we evaluate the existence of a link between gut microbiota and primate social behavior. Overall, we find that enough empirical evidence already supports these predictions. Nonetheless, we conclude that studies with the necessary, sufficient, explicit, and available evidence are still scarce. Therefore, we reflect on the benefit of founding future analyses on the utility of social complexity as a theoretical framework.

Quantifying within-group variation in sociality—covariation among metrics and patterns across primate groups and species

Abstract

It has long been recognized that the patterning of social interactions within a group can give rise to a social structure that holds very different places for different individuals. Such within-group variation in sociality correlates with fitness proxies in fish, birds, and mammals. Broader integration of this research has been hampered by the lack of agreement on how to integrate information from a plethora of dyadic interactions into individual-level metrics. As a step towards standardization, we collected comparative data on affinitive and affiliative interactions from multiple groups each of five species of primates to assess whether the same aspects of sociality are measured by different metrics and indices. We calculated 16 different sociality metrics used in previous research and thought to represent three different sociality concepts. We assessed covariation of metrics within groups and then summarized covariation patterns across all 15 study groups, which varied in size from 5 to 41 adults. With some methodological and conceptual caveats, we found that the number of weak ties individuals formed within their groups represented a dimension of sociality that was largely independent from the overall number of ties as well as from the number and strength of the strong ties they formed. Metrics quantifying indirect connectedness exhibited strong covariation with strong tie metrics and thus failed to capture a third aspect of sociality. Future research linking affiliation and affinity to fitness or other individual level outcomes should quantify inter-individual variation in three aspects: the overall number of ties, the number of weak ties, and the number or strength of strong ties individuals form, after taking into account effects of social network density.

Significance statement

In recent years, long-term studies of individually known animals have revealed strong correlations between individual social bonds and social integration, on the one hand, and reproductive success and survival on the other hand, suggesting strong natural selection on affiliative and affinitive behavior within groups. It proved difficult to generalize from these studies because they all measured sociality in slightly different ways. Analyzing covariation between 16 previously used metrics identified only three rather independent dimensions of variation. Thus, different studies have tapped into the same biological phenomenon. How individuals are weakly connected within their group needs further attention.

Respiratory Disease Risk of Zoo-Housed Bonobos Is Associated with Sex and Betweenness Centrality in the Proximity Network

Infectious diseases can be considered a threat to animal welfare and are commonly spread through both direct and indirect social interactions with conspecifics. This is especially true for species with complex social lives, like primates. While several studies have investigated the impact of sociality on disease risk in primates, only a handful have focused on respiratory disease, despite it being a major cause of morbidity and mortality in both wild and captive populations and thus an important threat to primate welfare. Therefore, we examined the role of social-network position on the occurrence of respiratory disease symptoms during one winter season in a relatively large group of 20 zoo-housed bonobos with managed fission-fusion dynamics. We found that within the proximity network, symptoms were more likely to occur in individuals with higher betweenness centrality, which are individuals that form bridges between different parts of the network. Symptoms were also more likely to occur in males than in females, independent of their social-network position. Taken together, these results highlight a combined role of close proximity and sex in increased risk of attracting respiratory disease, two factors that can be taken into account for further welfare management of the species.

Association of Primate Veterinarians' Guidelines for the Judicious Use of Antimicrobials

The Association of Primate Veterinarians (APV) recognizes that antimicrobials are commonly prescribed for prophylactic, therapeutic, and experimental management of nonhuman primates (NHP). While clinicians should use antimicrobials to treat documented cases of illness, the decision to prescribe antimicrobials must take into account the increasing resistance of bacterial populations, leading to decreasing efficacy of critical pharmaceuticals in both human and veterinary medicine. The intent of this document is to provide guidance to veterinarians, research staff, and institutional animal care and use committees (IACUCs) on the use of antimicrobials in NHP.

Sociality predicts individual variation in the immunity of free-ranging rhesus macaques

Social integration and social status can substantially affect an individual’s health and survival. One route through which this occurs is by altering immune function, which can be highly sensitive to changes in the social environment. However, we currently have limited understanding of how sociality influences markers of immunity in naturalistic populations where social dynamics can be fully realized. To address this gap, we asked if social integration and social status in free-ranging rhesus macaques (Macaca mulatta) predict anatomical and physiological markers of immunity. We used data on agonistic interactions to determine social status, and social network analysis of grooming interactions to generate measures of individual variation in social integration. As measures of immunity, we included the size of two of the major organs involved in the immune response, the spleen and liver, and counts of three types of blood cells (red blood cells, platelets, and white blood cells). Controlling for body mass and age, we found that neither social status nor social integration predicted the size of anatomical markers of immunity. However, individuals that were more socially connected, i.e., with more grooming partners, had lower numbers of white blood cells than their socially isolated counterparts, indicating lower levels of inflammation with increasing levels of integration. These results build upon and extend our knowledge of the relationship between sociality and the immune system in humans and captive animals to free-ranging primates, demonstrating generalizability of the beneficial role of social integration on health.

Social convergence of gut microbiomes in vampire bats

The 'social microbiome' can fundamentally shape the costs and benefits of group-living, but understanding social transmission of microbes in free-living animals is challenging due to confounding effects of kinship and shared environments (e.g. highly associated individuals often share the same spaces, food and water). Here, we report evidence for convergence towards a social microbiome among introduced common vampire bats, Desmodus rotundus, a highly social species in which adults feed only on blood, and engage in both mouth-to-body allogrooming and mouth-to-mouth regurgitated food sharing. Shotgun sequencing of samples from six zoos in the USA, 15 wild-caught bats from a colony in Belize and 31 bats from three colonies in Panama showed that faecal microbiomes were more similar within colonies than between colonies. To assess microbial transmission, we created an experimentally merged group of the Panama bats from the three distant sites by housing these bats together for four months. In this merged colony, we found evidence that dyadic gut microbiome similarity increased with both clustering and oral contact, leading to microbiome convergence among introduced bats. Our findings demonstrate that social interactions shape microbiome similarity even when controlling for past social history, kinship, environment and diet.

Combining epidemiological and ecological methods to quantify social effects on Escherichia coli transmission

Enteric microparasites like Escherichia coli use multiple transmission pathways to propagate within and between host populations. Characterizing the relative transmission risk attributable to host social relationships and direct physical contact between individuals is paramount for understanding how microparasites like E. coli spread within affected communities and estimating colonization rates. To measure these effects, we carried out commensal E. coli transmission experiments in two cattle (Bos taurus) herds, wherein all individuals were equipped with real-time location tracking devices. Following transmission experiments in this model system, we derived temporally dynamic social and contact networks from location data. Estimated social affiliations and dyadic contact frequencies during transmission experiments informed pairwise accelerated failure time models that we used to quantify effects of these sociobehavioural variables on weekly E. coli colonization risk in these populations. We found that sociobehavioural variables alone were ultimately poor predictors of E. coli colonization in feedlot cattle, but can have significant effects on colonization hazard rates (p ≤ 0.05). We show, however, that observed effects were not consistent between similar populations. This work demonstrates that transmission experiments can be combined with real-time location data collection and processing procedures to create an effective framework for quantifying sociobehavioural effects on microparasite transmission.

The relationship between personality, season, and wounding receipt in zoo-housed Japanese macaques (Macaca fuscata): A multi-institutional study

It is important to those managing Japanese macaques (Macaca fuscata) in captive settings to understand predictors of wounding. While studies have demonstrated that season (breeding or nonbreeding) and sex predict rates of wounding received by zoo-housed Japanese macaques, we investigated whether individual differences in personality ratings also might explain some of the observed interindividual variance in wounding. Such patterns were previously observed in rhesus macaques (M. mulatta), such that individuals rated higher on Anxiety and Confidence received greater wounding. Here, we collected wounding data over 24 months on 48 Japanese macaques from eight AZA-accredited zoos. Each macaque was also rated by keepers using a 26-item personality questionnaire. Principle components analysis of these ratings revealed four personality components: Openness, Friendliness, Dominance, and Anxiety/Reactivity. The model with the best fit revealed an interaction effect between season (breeding vs. nonbreeding) and the personality component Friendliness, such that individuals rated higher on Friendliness incurred fewer wounds in the nonbreeding season. The second-best model revealed both a main effect of the season as well as an interaction effect between season and Openness, such that macaques rated higher in Openness received more wounds in the nonbreeding season than those rated lower in Openness. Thus, as with rhesus macaques, personality mediated wounding receipt rate in Japanese macaques, although different personality components explained interindividual variance in wounding for these two species. These differences likely reflect species differences in behavior and personality structure, as well as the influence of differing management practices, highlighting the importance of species-specific approaches for captive primate care and welfare. This study provides further support for understanding primate personality to create individualized strategies for their care.

Evaluating the Effects of Noise Pollution on the Levels of Blood Cortisol, Testosterone, and Thyroid in Male Wistar Rats

Background: Noise pollution is a global problem causing changes in the secretion of various hormones and consequently affecting social well-being and quality of life in cities. Objectives: This study aimed to investigate the effect of noise pollution on the levels of testosterone, thyroid, and cortisol hormones in male rats. Methods: In this experimental study, a total of 70 male Wistar rats (200 - 250 g) were randomly assigned into one control and six experimental groups, with 10 rats in each group. Experimental groups were exposed to noise with different intensity (dB) and time (min) as follows: (I) 60 dB, 30 min; (II) 60 dB, 60 min; (III) 85 dB, 30 min; (IV) 85 dB, 60 min; (V) 110 dB, 30 min; (VI) 110 dB, 60 min; (VII) controls. Animals in the experimental groups were exposed to noise in an acoustic chamber designed for this purpose for 50 days. The Noise.exe software was used to generate noise, and the sound level meter (model TES 1358) was used to determine the accuracy of the intensity and frequency of sound. To determine plasma levels of the hormones, appropriate research and commercial kits were used, which were based on the ELISA method. To determine the concentration of hormones other than TSH, human assay kits were used. All statistical tests were performed in SPSS software version 21. Results: Serum levels of cortisol in the 110-dB (30 and 60 min), 65-dB (60 min), and 85-dB (60 min) groups were significantly higher than the control group (P ≤ 0.05). Also, cortisol levels in the 65-dB and 85-dB (30 minutes) groups were higher than the control group; however, the increase was not significant (P > 0.05). The levels of T4, T3, and TSH in the 60-dB and 85-dB groups were significantly lower than in the control group (P ≤ 0.05). The serum levels of T4, T3, and TSH hormones in the 110-dB group were insignificantly lower than the control group (P > 0.05). The serum level of testosterone in the 110-dB group was significantly lower than the control group (P ≤ 0.05). The mean serum levels of testosterone in the 65-dB and 85-dB groups were insignificantly lower than the control group (P > 0.05). Conclusions: Based on this study, exposure to noise pollution increased cortisol secretion and decreased T4, T3, TSH, and testosterone levels in rats. As this hormonal imbalance may create direct and indirect effects, studies and strategies are recommended to control the imbalance of hormones in the polluted environments.

Social networks research in ex situ populations: Patterns, trends, and future directions for conservation-focused behavioral research

Social networks research using non-human animals has grown over the past decade, utilizing a wide range of species to answer an array of pure and applied questions. Network approaches have relevance to conservation, evaluating social influences on fecundity, health, fitness and longevity. While the application of network approaches to in situ populations with conservation concern appears in published literature, the degree to which ex situ and zoo-housed populations are the focus of "social networks for conservation research" is limited. Captive environments provide scientists with an ability to understand the social behavior of species that may be hard to observe consistently in the wild. This paper evaluates the scope of network research involving ex situ populations, analyzing output from 2010 to 2019 to determine trends in questions and subjects using ex situ populations. We show that only 8.2% of ex situ social network analysis (SNA) implications are of conservation-focus, apparent in papers relating to birds, carnivores, bats, primates, reptiles, and ungulates. Husbandry and welfare questions predominate in ex situ network research, but over half of these papers have nonpractical application (basic science). The chance of a citation for a basic science paper was 95.4% more than for a conservation-based paper. For taxonomic groups, primate-focused papers had the most citations. The focus of ex situ conservation-based networks research may be driven by the needs of conservation programs (e.g., population recovery outcomes) or by a need to evaluate the efficacy of ex situ conservation goals. We evaluate our findings considering the IUCN's One Plan Approach to conservation to show how in situ and ex situ network research is applicable to global conservation efforts. We have identified that there is a lack of application and evaluation of SNA to wildlife conservation. We highlight future areas of research in zoos and hope to stimulate discussion and collaboration between relevant parties.

Multilayer network analyses as a toolkit for measuring social structure

The formalization of multilayer networks allows for new ways to measure sociality in complex social systems, including groups of animals. The same mathematical representation and methods are widely applicable across fields and study systems, and a network can represent drastically different types of data. As such, in order to apply analyses and interpret the results in a meaningful way the researcher must have a deep understanding of what their network is representing and what parts of it are being measured by a given analysis. Multilayer social networks can represent social structure with more detail than is often present in single layer networks, including multiple "types" of individuals, interactions, or relationships, and the extent to which these types are interdependent. Multilayer networks can also encompass a wider range of social scales, which can help overcome complications that are inherent to measuring sociality. In this paper, I dissect multilayer networks into the parts that correspond to different components of social structures. I then discuss common pitfalls to avoid across different stages of multilayer network analyses-some novel and some that always exist in social network analysis but are magnified in multi-layer representations. This paper serves as a primer for building a customized toolkit of multilayer network analyses, to probe components of social structure in animal social systems.

Impact of individual demographic and social factors on human-wildlife interactions: a comparative study of three macaque species

Despite increasing conflict at human-wildlife interfaces, there exists little research on how the attributes and behavior of individual wild animals may influence human-wildlife interactions. Adopting a comparative approach, we examined the impact of animals' life-history and social attributes on interactions between humans and (peri)urban macaques in Asia. For 10 groups of rhesus, long-tailed, and bonnet macaques, we collected social behavior, spatial data, and human-interaction data for 11-20 months on pre-identified individuals. Mixed-model analysis revealed that, across all species, males and spatially peripheral individuals interacted with humans the most, and that high-ranking individuals initiated more interactions with humans than low-rankers. Among bonnet macaques, but not rhesus or long-tailed macaques, individuals who were more well-connected in their grooming network interacted more frequently with humans than less well-connected individuals. From an evolutionary perspective, our results suggest that individuals incurring lower costs related to their life-history (males) and resource-access (high rank; strong social connections within a socially tolerant macaque species), but also higher costs on account of compromising the advantages of being in the core of their group (spatial periphery), are the most likely to take risks by interacting with humans in anthropogenic environments. From a conservation perspective, evaluating individual behavior will better inform efforts to minimize conflict-related costs and zoonotic-risk.

Social Network Predicts Exposure to Respiratory Infection in a Wild Chimpanzee Group

Respiratory pathogens are expected to spread through social contacts, but outbreaks often occur quickly and unpredictably, making it challenging to simultaneously record social contact and disease incidence data, especially in wildlife. Thus, the role of social contacts in the spread of infectious disease is often treated as an assumption in disease simulation studies, and few studies have empirically demonstrated how pathogens spread through social networks. In July-August 2015, an outbreak of respiratory disease was observed in a wild chimpanzee community in Kibale National Park, Uganda, during an ongoing behavioral study of male chimpanzees, offering a rare opportunity to evaluate how social behavior affects individual exposure to socially transmissible diseases. From May to August 2015, we identified adult and adolescent male chimpanzees displaying coughs and rhinorrhea and recorded 5-m proximity data on males (N = 40). Using the network k-test, we found significant relationships between male network connectivity and the distribution of cases within the network, supporting the importance of short-distance contacts for the spread of the respiratory outbreak. Additionally, chimpanzees central to the network were more likely to display clinical signs than those with fewer connections. Although our analyses were limited to male chimpanzees, these findings underscore the value of social connectivity data in predicting disease outcomes and elucidate a potential evolutionary cost of being social.

Social and affective touch in primates and its role in the evolution of social cohesion

Primates are long-lived, highly social mammals who maintain long-term social bonds and cohesive social groups through many affiliative mechanisms, foremost among them social touch. From birth through adulthood, social touch - primarily mutual grooming - creates and maintains relationships of trust and reliance, which are the basis for individual physical and emotional well-being and reproductive success. Because social touch helps to establish, maintain, and repair social alliances in primates, it contributes to the emotional stability of individuals and the cohesion of social groups. In these fundamental ways, thus, social touch supports the slow life histories of primates. The reinforcing neurochemistry of social touch insures that it is a pleasurable activity and this, in turn, makes it a behavioral commodity that can be traded between primates for desirable rewards such as protection against future aggression or opportunities to handle infants. Social touch is essential to normal primate development, and individuals deprived of social touch exhibit high levels of anxiety and lower fertility compared to those receiving regular social touch. Understanding the centrality of social touch to primate health and well-being throughout the lifespan provides the foundation for appreciating the importance of social touch in human life.

Early Life Experience Shapes Male Behavior and Social Networks in Drosophila

Living in a group creates a complex and dynamic environment in which behavior of individuals is influenced by and affects the behavior of others. Although social interaction and group living are fundamental adaptations exhibited by many organisms, little is known about how prior social experience, internal states, and group composition shape behavior in groups. Here, we present an analytical framework for studying the interplay between social experience and group interaction in Drosophila melanogaster. We simplified the complexity of interactions in a group using a series of experiments in which we controlled the social experience and motivational states of individuals to compare behavioral patterns and social networks of groups under different conditions. We show that social enrichment promotes the formation of distinct group structure that is characterized by high network modularity, high inter-individual and inter-group variance, high inter-individual coordination, and stable social clusters. Using environmental and genetic manipulations, we show that visual cues and cVA-sensing neurons are necessary for the expression of social interaction and network structure in groups. Finally, we explored the formation of group behavior and structure in heterogenous groups composed of flies with distinct internal states and documented emergent structures that are beyond the sum of the individuals that constitute it. Our results demonstrate that fruit flies exhibit complex and dynamic social structures that are modulated by the experience and composition of different individuals within the group. This paves the path for using simple model organisms to dissect the neurobiology of behavior in complex social environments.

A multiplex centrality metric for complex social networks: sex, social status, and family structure predict multiplex centrality in rhesus macaques

Members of a society interact using a variety of social behaviors, giving rise to a multi-faceted and complex social life. For the study of animal behavior, quantifying this complexity is critical for understanding the impact of social life on animals' health and fitness. Multilayer network approaches, where each interaction type represents a different layer of the social network, have the potential to better capture this complexity than single layer approaches. Calculating individuals' centrality within a multilayer social network can reveal keystone individuals and more fully characterize social roles. However, existing measures of multilayer centrality do not account for differences in the dynamics and functionality across interaction layers. Here we validate a new method for quantifying multiplex centrality called consensus ranking by applying this method to multiple social groups of a well-studied nonhuman primate, the rhesus macaque. Consensus ranking can suitably handle the complexities of animal social life, such as networks with different properties (sparse vs. dense) and biological meanings (competitive vs. affiliative interactions). We examined whether individuals' attributes or socio-demographic factors (sex, age, dominance rank and certainty, matriline size, rearing history) were associated with multiplex centrality. Social networks were constructed for five interaction layers (i.e., aggression, status signaling, conflict policing, grooming and huddling) for seven social groups. Consensus ranks were calculated across these five layers and analyzed with respect to individual attributes and socio-demographic factors. Generalized linear mixed models showed that consensus ranking detected known social patterns in rhesus macaques, showing that multiplex centrality was greater in high-ranking males with high certainty of rank and females from the largest families. In addition, consensus ranks also showed that females from very small families and mother-reared (compared to nursery-reared) individuals were more central, showing that consideration of multiple social domains revealed individuals whose social centrality and importance might otherwise have been missed.

PC software-based portable cyclic voltammetry system with PB-MCNT-GNPs-modified electrodes for E. coli detection

PC software-based portable cyclic voltammetry (PCV) systems have the advantages of portability, high performance, and real-time detection. In this paper, the PCV system used cyclic voltammetry (CV) as the main detection and analysis method and contained the following components: a three-electrode unit, a portable potentiostat, and PC software. The PC software was used as the system control and display, and a dynamic peak position adjustment (DPPA) algorithm for E. coli measurements based on thick biofilm modification on electrodes was designed especially for this system to realize the real-time correspondence between the measured results and the modified electrodes. The performance test results obtained by setting different detection parameters in the PCV system were compared with those of commercial electrochemical workstations. The difference was less than 4.99%, with a relative standard deviation less than 0.20%. An electrochemical biosensor based on a Prussian blue-multiwalled carbon nanotube-gold nanoparticle composite was developed for E. coli detection. After constructing an antibody-BSA-E. coli electrode modification on the sensor, experimental data processed by the DPPA algorithm showed that the logarithm (lg Df_E.coli) of the E. coli dilution factor and the peak current response had a linear relationship. The PCV system could quickly and accurately detect E. coli concentrations with dynamic adjustment algorithms for biofilm-modified electrodes. Furthermore, the system could detect the electrochemical activities of various high-sensitivity biomolecules, showing great detection potential for on-site monitoring and meeting the requirements of real-time and portable detection in various food safety fields.

Deconstructing sociality: the types of social connections that predict longevity in a group-living primate

Many species use social interactions to cope with challenges in their environment and a growing number of studies show that individuals which are well-connected to their group have higher fitness than socially isolated individuals. However, there are many ways to be 'well-connected' and it is unclear which aspects of sociality drive fitness benefits. Being well-connected can be conceptualized in four main ways: individuals can be socially integrated by engaging in a high rate of social behaviour or having many partners; they can have strong and stable connections to favoured partners; they can indirectly connect to the broader group structure; or directly engage in a high rate of beneficial behaviours, such as grooming. In this study, we use survival models and long-term data in adult female rhesus macaques (Macaca mulatta) to compare the fitness outcomes of multiple measures of social connectedness. Females that maintained strong connections to favoured partners had the highest relative survival probability, as did females well-integrated owing to forming many weak connections. We found no survival benefits to being structurally well-connected or engaging in high rates of grooming. Being well-connected to favoured partners could provide fitness benefits by, for example, increasing the efficacy of coordinated or mutualistic behaviours.