Social control is associated with increased reproductive skew in a wild mammal.

In group-living species, reproductive variation among individuals of the same sex is widespread. By identifying the mechanisms underlying this reproductive skew, we gain fundamental insights into the evolution and maintenance of sociality. A common mechanism, social control, is typically studied by quantifying dominance, which is one of many attributes of sociality that describes how individuals exert influence on others and is an incomprehensive measure of social control as it accounts only for direct relationships. Here, we use the global reaching centrality (GRC), which quantifies the degree of hierarchy in a social network by accounting for both direct and indirect social relationships. Using a wild, free-living population of adult female yellow-bellied marmots (Marmota flaviventris), we found a positive relationship between the reproductive skew index and GRC: more despotic social groups have higher reproductive skew. The GRC was stronger predictor for skew than traditional measures of social control (i.e. dominance). This allows deeper insights into the diverse ways individuals control other group members' reproduction, a core component in the evolution of sociality. Future studies of skew across taxa may profit by using more comprehensive, network-based measures of social control.

Cultural sips: Exploring sociodemographic and dominance factors in French wine appraisal.

This study investigates the intricate relationship between sociodemographic factors, social dominance orientation (SDO), and perceptions of wine in France. Emphasizing the symbolic role of wine in French culture, and employing a survey-based approach, the research explores how societal hierarchies and individual positioning within these structures influence the appraisal of rosé wine. The findings revealed that sociodemographic factors, particularly education level, significantly influence wine appraisal, while social dominance orientation serves as a mediating factor. This research contributes to the understanding of the cultural and social dynamics shaping wine consumption in France, highlighting the fact that wine appraisal is deeply embedded in societal structures.

Environmental enrichment enhances ethanol preference over social reward in male swiss mice: Involvement of oxytocin-dopamine interactions.

The impact of environmental enrichment (EE) on natural rewards, including social and appetitive rewards, was investigated in male Swiss mice. EE, known for providing animals with various stimuli, was assessed for its effects on conditioned place preference (CPP) associated with ethanol and social stimuli. We previously demonstrated that EE increased the levels of the prosocial neuropeptide oxytocin (OT) in the hypothalamus and enhanced ethanol rewarding effects via an oxytocinergic mechanism. This study also investigated the impact of EE on social dominance and motivation for rewards, measured OT-mediated phospholipase C (PLC) activity in striatal membranes, and assessed OT expression in the hypothalamus. The role of dopamine in motivating rewards was considered, along with the interaction between OT and D1 receptors (DR) in the nucleus accumbens (NAc). Results showed that EE mice exhibited a preference for ethanol reward over social reward, a pattern replicated by the OT analogue Carbetocin. EE mice demonstrated increased social dominance and reduced motivation for appetitive taste stimuli. Higher OT mRNA levels in the hypothalamus were followed by diminished OT receptor (OTR) signaling activity in the striatum of EE mice. Additionally, EE mice displayed elevated D1R expression, which was attenuated by the OTR antagonist (L-368-889). The findings underscore the reinforcing effect of EE on ethanol and social rewards through an oxytocinergic mechanism. Nonetheless, they suggest that mechanisms other than the prosocial effect of EE may contribute to the ethanol pro-rewarding effect of EE and Carbetocin. They also point towards an OT-dopamine interaction potentially underlying some of these effects.

The dissection of a despotic society: exploration, dominance and hormonal traits.

Naked mole-rats (Heterocephalus glaber) live in large colonies with one breeding female (queen), one to three breeding males (BMs) and the remainder are non-reproductive subordinates. The animals have a linear dominance rank with the breeders at the top of the hierarchy. We investigated how dominance rank in naked mole-rats differs with exploration (the propensity to explore a novel environment) and related endocrine markers. Exploration behaviour, faecal progestagen metabolite (fPM), faecal glucocorticoid metabolite (fGCM), faecal androgen metabolite (fAM) and plasma prolactin concentrations were quantified in breeding, high-, middle- and low-ranked females and males from five naked mole-rat colonies. There were no significant differences between the dominance rank and exploration behaviour. Interestingly, the queens and high-ranking females had higher fGCM and fAM concentrations compared with middle- and low-ranked females. The queens had significantly higher fPM concentrations than all other ranked females, since they are responsible for procreation. In the males, the BMs had higher fGCM concentrations compared with high- and low-ranked males. In addition, BMs and middle-ranking males had overall higher prolactin levels than all other ranked males, which could be linked to cooperative care. Overall, the results suggest that physiological reproductive suppression is linked to high dominance rank.

Benefits but not the dual functions of submissive signals differ between two Malagasy primates.

Many animals use formalized signals to communicate dominance relationships. In some primates, such as macaques, the function of such signals varies with dominance style. Despotic species produce unidirectional submission signals that have a dual function: in conflict contexts, they signal a willingness to withdraw, whereas in peaceful contexts, they indicate the agreement to subordination. More despotic species produce these calls to a lesser extent than less despotic species. Here, we investigated whether the use of unidirectional submission signals is also related to dominance style in two lemur species and whether signalling subordination stabilizes social relationships at the group level. Ring-tailed lemurs (Lemur catta) exhibit a more despotic dominance hierarchy than Verreaux's sifakas (Propithecus verreauxi). We observed social interactions in 75 dyads of Verreaux's sifakas and 118 dyads of ring-tailed lemurs. Both species used unidirectional submissive calls that have a dual function, potentially suggesting convergent evolution of the function of these signals in independent primate lineages. However, signalling subordination did not stabilize social relationships at the group level in both species. Additionally, subordination occurred more frequently in dyads of the more despotic ring-tailed lemurs than in Verreaux's sifakas, indicating opposite patterns to macaques in the coevolution of social traits with dominance style. This article is part of the theme issue 'The power of sound: unravelling how acoustic communication shapes group dynamics'.

Executive functions and brain morphology of male and female dominant and subordinate cichlid fish.

BACKGROUND: Living in a social dominance hierarchy presents different benefits and challenges for dominant and subordinate males and females, which might in turn affect their cognitive needs. Despite the extensive research on social dominance in group-living species, there is still a knowledge gap regarding how social status impacts brain morphology and cognitive abilities. METHODS: Here, we tested male and female dominants and subordinates of Neolamprologus pulcher, a social cichlid fish species with size-based hierarchy. We ran three executive cognitive function tests for cognitive flexibility (reversal learning test), self-control (detour test), and working memory (object permanence test), followed by brain and brain region size measurements. RESULTS: Performance was not influenced by social status or sex. However, dominants exhibited a brain-body slope that was relatively steeper than that of subordinates. Furthermore, individual performance in reversal learning and detour tests correlated with brain morphology, with some trade-offs among major brain regions like telencephalon, cerebellum, and optic tectum. CONCLUSION: As individuals' brain growth strategies varied depending on social status without affecting executive functions, the different associated challenges might yield a potential effect on social cognition instead. Overall, the findings highlight the importance of studying the individual and not just species to understand better how the individual's ecology might shape its brain and cognition.

Association between social dominance hierarchy and PACAP expression in the extended amygdala, corticosterone, and behavior in C57BL/6 male mice.

The natural alignment of animals into social dominance hierarchies produces adaptive, and potentially maladaptive, changes in the brain that influence health and behavior. Aggressive and submissive behaviors assumed by animals through dominance interactions engage stress-dependent neural and hormonal systems that have been shown to correspond with social rank. Here, we examined the association between social dominance hierarchy status established within cages of group-housed mice and the expression of the stress peptide PACAP in the bed nucleus of the stria terminalis (BNST) and central nucleus of the amygdala (CeA). We also examined the relationship between social dominance rank and blood corticosterone (CORT) levels, body weight, motor coordination (rotorod) and acoustic startle. Male C57BL/6 mice were ranked as either Dominant, Submissive, or Intermediate based on counts of aggressive/submissive encounters assessed at 12 weeks-old following a change in homecage conditions. PACAP expression was significantly higher in the BNST, but not the CeA, of Submissive mice compared to the other groups. CORT levels were lowest in Submissive mice and appeared to reflect a blunted response following events where dominance status is recapitulated. Together, these data reveal changes in specific neural/neuroendocrine systems that are predominant in animals of lowest social dominance rank, and implicate PACAP in brain adaptations that occur through the development of social dominance hierarchies.

Social niche shapes social behavior and cortisol concentrations during adolescence in female guinea pigs.

Individualized social niches arise in social groups, resulting in divergent social behavior profiles among group members. During sensitive life phases, the individualized social niche can profoundly impact the development of social behavior and associated phenotypes such as hormone (e.g. cortisol) concentrations. Focusing on adolescence, we investigated the relationship between the individualized social niche, social behavior, and cortisol concentrations (baseline and responsiveness) in female guinea pigs. Females were pair-housed in early adolescence (initial social pair formation), and a social niche transition was induced after six weeks by replacing the partner with either a larger or smaller female. Regarding social behavior, dominance status was associated with aggression in both the initial social pairs and after the social niche transition, and the results suggest that aggression was rapidly and completely reshaped after the social niche transition. Meanwhile, submissive behavior was rapidly reshaped after the social niche transition, but this was incomplete. The dominance status attained in the initial social pair affected the extent of submissive behavior after the social niche transition, and this effect was still detected three weeks after the social niche transition. Regarding cortisol concentrations, higher baseline cortisol concentrations were measured in dominant females in the initial social pairs. After the social niche transition, cortisol responsiveness significantly increased for the females paired with a larger, older female relative to those paired with a smaller, younger female. These findings demonstrate that the social niche during adolescence plays a significant role in shaping behavior and hormone concentrations in females.

Differences in physiology and behavior between male winner and loser mice in the tube test.

Social hierarchy is a crucial element for survival, reproduction, fitness, and the maintenance of a stable social group in social animals. This study aimed to investigate the physiological indicators, nociception, unfamiliar female mice preference, spatial learning memory, and contextual fear memory of male mice with different social status in the same cage. Our findings revealed significant differences in the trunk temperature and contextual fear memory between winner and loser mice. However, there were no major discrepancies in body weight, random and fasting blood glucose levels, whisker number, frontal and perianal temperature, spleen size, mechanical and thermal pain thresholds, preference for unfamiliar female mice, and spatial memory. In conclusion, social status can affect mice in multiple ways, and, therefore, its influence should be considered when conducting studies using these animals.

Epigenetic signatures of social status in wild female spotted hyenas (Crocuta crocuta).

In mammalian societies, dominance hierarchies translate into inequalities in health, reproductive performance and survival. DNA methylation is thought to mediate the effects of social status on gene expression and phenotypic outcomes, yet a study of social status-specific DNA methylation profiles in different age classes in a wild social mammal is missing. We tested for social status signatures in DNA methylation profiles in wild female spotted hyenas (Crocuta crocuta), cubs and adults, using non-invasively collected gut epithelium samples. In spotted hyena clans, female social status influences access to resources, foraging behavior, health, reproductive performance and survival. We identified 149 differentially methylated regions between 42 high- and low-ranking female spotted hyenas (cubs and adults). Differentially methylated genes were associated with energy conversion, immune function, glutamate receptor signalling and ion transport. Our results provide evidence that socio-environmental inequalities are reflected at the molecular level in cubs and adults in a wild social mammal.

Capuchin monkeys' (Sapajus [Cebus] apella) categorization of photos of unknown male conspecifics suggests attention to fWHR and a dominance bias.

The ability to quickly perceive others' rank minimizes costs by helping individuals behave appropriately when interacting with strangers. Indeed, humans and at least some other species can quickly determine strangers' rank or dominance based only on physical features without observing others' interactions or behavior. Nonhuman primates can determine strangers' ranks by observing their interactions, and some evidence suggests that at least some cues to dominance, such as facial width-to-height ratio (fWHR), are also present in other primates. However, it is unknown whether they can determine strangers' rank simply by looking at their faces, rather than observing their interactions. If so, this would suggest selective pressure across the primates on both cues to dominance and the ability to detect those cues accurately. To address this, we examined the ability of male and female tufted capuchin monkeys (Sapajus [Cebus] apella) to categorize images of the faces of unknown conspecifics (Sapajus from different colonies) and humans (computer-generated and real) as dominant or nondominant based only on still images. Capuchins' categorization of unknown conspecific faces was consistent with fWHR, a cue to dominance, although there was a strong tendency to categorize strangers as dominant, particularly for males. This was true despite the continued correct categorization of known individuals. In addition, capuchins did not categorize human strangers in accordance with external pre-ratings of dominance by independent human raters, despite the availability of the same cue, fWHR. We consider these results in the context of capuchin socio-ecology and what they mean for the evolution of rapid decision-making in social contexts.

The role of exogenous testosterone and social environment on the expression of sociosexuality and status-seeking behaviors in young Chilean men.

Testosterone plays an important role as a social hormone. Current evidence suggests that testosterone is positively related to sociosexuality increasing the psychological attitudes toward investing in short-term versus long-term mating and promotes status-seeking behaviors both by dominance and prestige. In addition, the social environment may play an important role in the expression of mating effort through changes in sociosexuality and status-seeking behaviors. However, the causal relationships among the mentioned variables are still debated. We employed a double-blind, placebo-controlled within-individual design, in order to test and integrate the proposed causal relationships between testosterone and social environment over short-term and long-term mating orientation and dominant and prestigious status-seeking behaviors in a sample of 95 young Chilean men. We did not find evidence that the administration of exogenous testosterone increased short-term or decreased long-term mating orientation as expected. Moreover, exogenous testosterone did not affect either aggressive or cooperative behavior failing to support the social status hypothesis. We also did not find any relationship between short or long-term mating orientation with status-seeking behaviors. Finally, we found support for the effect of social environment on sociosexual attitudes but not over status-seeking behaviors. Thus, men reported higher levels of short-term mating orientation in the presence of a woman compared to a man and no differences were found for long-term mating orientation. We argue that sociosexuality may be expressed flexibly, but contextual factors such as the presence of women seem more important than changes in testosterone levels.

Social regulation of arginine vasopressin and oxytocin systems in a wild group-living fish.

The neuropeptides arginine vasopressin (AVP) and oxytocin (OXT) are key regulators of social behaviour across vertebrates. However, much of our understanding of how these neuropeptide systems interact with social behaviour is centred around laboratory studies which fail to capture the social and physiological challenges of living in the wild. To evaluate relationships between these neuropeptide systems and social behaviour in the wild, we studied social groups of the cichlid fish Neolamprologus pulcher in Lake Tanganyika, Africa. We first used SCUBA to observe the behaviour of focal group members and then measured transcript abundance of key components of the AVP and OXT systems across different brain regions. While AVP is often associated with male-typical behaviours, we found that dominant females had higher expression of avp and its receptor (avpr1a2) in the preoptic area of the brain compared to either dominant males or subordinates of either sex. Dominant females also generally had the highest levels of leucyl-cystinyl aminopeptidase (lnpep)-which inactivates AVP and OXT-throughout the brain, potentially indicating greater overall activity (i.e., production, release, and turnover) of the AVP system in dominant females. Expression of OXT and its receptors did not differ across social ranks. However, dominant males that visited the brood chamber more often had lower preoptic expression of OXT receptor a (oxtra) suggesting a negative relationship between OXT signalling and parental care in males of this species. Overall, these results advance our understanding of the relationships between complex social behaviours and neuroendocrine systems under natural settings.

Classical and Modern Prejudice toward Individuals with Intellectual Disabilities: The Role of Experienced Contact, Beliefs in a Just World and Social Dominance Orientation.

This study investigates the impact of experienced contact on prejudiced attitudes towards individuals with intellectual disabilities (IDs), examining beliefs in a just world (BJW) and social dominance orientation (SDO) as potential serial mediators. Data were collected from 224 university students (M = 23.02, SD = 2.48). Path analysis modelling assessed the structural relationships between the study variables. The findings revealed that experienced contact was negatively and significantly associated with BJW and SDO. Additionally, BJW and SDO fully mediated the relationship between experienced contact and overt prejudice. These findings underscore the influence of individual differences on attitudes towards individuals with ID, establishing a crucial foundation for future research and the development of interventions aimed at reducing prejudice and discrimination.

The use of social information in vulture flight decisions.

Animals rely on a balance of personal and social information to decide when and where to move next in order to access a desired resource. The benefits from cueing on conspecifics to reduce uncertainty about resource availability can be rapidly overcome by the risks of within-group competition, often exacerbated toward low-ranked individuals. Being obligate soarers, relying on thermal updraughts to search for carcasses around which competition can be fierce, vultures represent ideal models to investigate the balance between personal and social information during foraging movements. Linking dominance hierarchy, social affinities and meteorological conditions to movement decisions of eight captive vultures, Gyps spp., released for free flights in natural soaring conditions, we found that they relied on social information (i.e. other vultures using/having used the thermals) to find the next thermal updraught, especially in unfavourable flight conditions. Low-ranked individuals were more likely to disregard social cues when deciding where to go next, possibly to minimize the competitive risk of social aggregation. These results exemplify the architecture of decision-making during flight in social birds. It suggests that the environmental context, the context of risk and the social system as a whole calibrate the balance between personal and social information use.

Many faces of dominance: the manifestation of cohabiting companion dogs' rank in competitive and non-competitive scenarios.

There are indications that companion dogs of multi-dog households form a hierarchy, maintained by formal and agonistic dominance. Although it was found that the behaviour of dogs depends on their rank in several contexts, so far, the assessment of their rank itself has been based on owner-completed questionnaires. With this research we endeavoured to find associations between rank scores from the Dog Rank Assessment Questionnaire (DRA-Q) and cohabiting dogs' behaviour in a competitive test (Toy Possession test-32 dog pairs) and a non-competitive, citizen science scenario (Greeting test-20 dog pairs). Based on the grabbing the toy first and keeping the toy at the end variables, the dogs' rank score provided a reliable indication of the dominant and subordinate dogs' behaviour in the Toy Possession test. Similarly, the occurrence of dominant and submissive behaviours in the Greeting Test showed a good match with the agonistic and leadership subscores of the composite rank score from the DRA-Q. Our results provide a pioneering case for validating a questionnaire-based rank scoring method with biologically meaningful behavioural tests in the case of companion dogs. The finer analysis of the results highlighted that in the case of a multi-question scoring system, some components might provide more effective prediction of the dogs' rank-related behaviour in some situations, while other components are more relevant in others, with traits related to agonistic dominance having relevance across contexts.

Learning from fights: Males' social dominance status impact reproductive success in Drosophila melanogaster.

In animals, the access to vital resources often relies on individuals' behavioural personality, strength, motivation, past experiences and dominance status. Dominant individuals would be more territorial, providing them with a better access to food resources and mate. The so-called winner and loser effects induce individuals' behavioural changes after experiencing a victory or a defeat, and lead to an individual persistent state influencing the outcome of subsequent fights. However, whether and how development of winner and loser effects affect individuals' fitness is controversial. The aim of this study is to evaluate how individuals' fitness can be influenced by previous fighting experience in Drosophila melanogaster. In this study, we assess various behavioural performances as indicators for dominant and subordinate fitness. Our results show that subordinates are less territorial than dominants although their locomotor abilities are not affected. We also demonstrate that in a non-competitive context, experiencing a defeat reduces males' motivation to court females but not the reproductive success while in a competitive context, it negatively affects males' reproductive success. However, we found no impact upon either males' ability to distinguish potential mates nor on females' choice of a specific mating partner. Overall, these results indicate that previous defeats reduce reproductive success, a commonly used estimate of individual fitness.

Agonistic interactions and social behaviors in the Saharan Dorcas gazelle (Gazella dorcas neglecta): Using social network analysis to evaluate relationships and social structure in captive male groups.

Social interactions, including agonistic behavior, are very important for the management and welfare of individuals forming groups in captivity. One of the main concerns for the stability and durability of adult male groups is a noticeable level of intraspecific aggression. This study comprises a Social Network Analysis to illustrate social structure in different groups of captive Saharan Dorcas gazelles (Gazella dorcas neglecta). Our main objectives were to examine the relationship between agonistic, affiliative, and association networks and their reciprocity, assessing also whether the agonistic networks can conform to a linear dominance hierarchy. For these purposes, we recorded the behavior of 23 adult males organized in five herds, three composed only of Saharan Dorcas gazelle males and two mixed herds in which there were also Mhorr gazelle males (Nanger dama mohor). Observations were carried out during 295 h through scan sampling. We found no correlation between the affiliative and association networks in any group, although there was a significant correlation between the agonistic and association networks in mixed-species groups which was not present in single-species groups. Overall, there was no consistent reciprocity in either affiliative nor agonistic networks and none of the agonistic networks showed a linear structure. These results indicate that affiliative behavior in Saharan Dorcas gazelles offers distinctive and valuable information about the bonds between individuals, however, their dominance structure is far more complex than previously thought. As information provided by affiliative and proximity behaviors is different in this species, we suggest considering affiliative interactions to stablish affinity between individuals. Evaluating different social behaviors and not only agonistic interactions in later studies, is also recommended to develop a more accurately daily management in zoos that guarantee group stability and individuals' welfare, which will improve the conservation of captive populations.

Steep Hierarchies without Skew? Modeling How Ecology and Decision-Making Shape Despotism of Relationships.

AbstractAnimals can form dominance relationships that vary from highly unequal, or despotic, to egalitarian, and this variation likely impacts the fitness of individuals. How and why these differences in relationships and fitness exist among groups, populations, and species has been the subject of much debate. Here, we investigated the influence of two major factors: (1) spatial resource distribution and (2) the presence or absence of winner-loser effects. To determine the effects of these factors, we built an agent-based model that represented 10 agents directly competing over food resources on a simple landscape. By varying the food distribution and using either asymmetry of strength or experience, we contrasted four scenarios from which we recorded attack decisions, fight outcomes, and individual energy intake to calculate dominance hierarchy steepness and energetic skew. Surprisingly, resource distribution and winner-loser effects did not have the predicted effects on hierarchy steepness. However, skew in energy intake arose when resources were distributed heterogeneously, despite hierarchy steepness frequently being higher in the homogeneous resource scenarios. Thus, this study confirms some decades-old predictions about feeding competition but also casts doubt on the ability to infer energetic consequences from observations of agonistic interactions.

A systematic review and meta-analysis of how social memory is studied.

Social recognition is crucial for survival in social species, and necessary for group living, selective reproduction, pair bonding, and dominance hierarchies. Mice and rats are the most commonly used animal models in social memory research, however current paradigms do not account for the complex social dynamics they exhibit in the wild. To assess the range of social memories being studied, we conducted a systematic analysis of neuroscience articles testing the social memory of mice and rats published within the past two decades and analyzed their methods. Our results show that despite these rodent's rich social memory capabilities, the majority of social recognition papers explore short-term memories and short-term familiarity levels with minimal exposure between subject and familiar stimuli-a narrow type of social memory. We have identified several key areas currently understudied or underrepresented: kin relationships, mates, social ranks, sex variabilities, and the effects of aging. Additionally, reporting on social stimulus variables such as housing history, strain, and age, is limited, which may impede reproducibility. Overall, our data highlight large gaps in the diversity of social memories studied and the effects social variables have on social memory mechanisms.