Formation Of Social Hierarchies Research Articles

Characterization of social hierarchy formation and maintenance in same-sex, group-housed male and female C57BL/6 J mice

Social hierarchies are a prevalent feature of all animal groups, and an individual's rank within the group can significantly affect their overall health, typically at the greatest expense of the lowest-ranked individuals, or omegas. These subjects have been shown to exhibit various stress-related phenotypes, such as increased hypothalamic-pituitary axis activity and increased amygdalar corticotropin-releasing factor levels compared to higher-ranked subjects. However, these findings have been primarily characterized in males and in models requiring exhibition of severe aggression. The goals of the current study, therefore, were to characterize the formation and maintenance of social hierarchies using the tube test and palatable liquid competition in same-sex groups of male and female C57BL/6 J mice. We also aimed to examine the effects of tube test-determined social rank on plasma and hypothalamic oxytocin and vasopressin levels, peptides with established roles in social behaviors and the stress response. Lastly, we assessed the effects of environmental enrichment and length of testing on the measures outlined above. Overall, we demonstrated that males and females develop social hierarchies and that these hierarchies can be determined using the tube test. While we were unable to establish a consistent connection between peptide levels and social rank, we observed transient changes in these peptides reflecting complex interactions between social rank, sex, environment, and length of testing. We also found that many male and female omegas began to exhibit passive coping behavior after repeated tube test losses, demonstrating the potential of this assay to serve as a model of chronic, mild psychosocial stress.

5-HT1A receptor in the central amygdala and 5-HT2A receptor in the basolateral amygdala are involved in social hierarchy in male mice

Most social animals self-organize into dominance hierarchies that strongly influence their behavior and health. The serotonin (5-HT) system is believed to play an important role in the formation of social hierarchy. 5-HT receptors are abundantly expressed in the amygdala, which is considered as the central node for the perception and learning of social hierarchy. In this study, we assessed the functions of various 5-HT receptor subtypes related to social rank determination in different subregions of the amygdala using the confrontation tube test in mice. We revealed that most adult C57BL/6 J male mice exhibited a linear social rank after a few days of cohousing. The tube test ranks were slightly related to anxiety-like behavioral performance. After the tube test, the amygdala and 5-HT neurons in the dorsal raphe nucleus were activated in lower-rank individuals. Quantitative real-time polymerase chain reaction analysis revealed that despite the high expression of 5-HT1A receptor mRNA in the central amygdala (CeA), 5-HT2A receptor mRNA expression was downregulated in the basolateral amygdala (BLA) in higher-rank individuals. The dominant–subordinate relationship between mouse pairs could be switched via pharmacological modulation of these receptors in CeA and BLA, suggesting that these expression changes are essential for establishing social ranks. Our findings provide novel insights into the divergent functions of 5-HT receptors in the amygdala related to social hierarchy, which is closely related to our health and welfare.

The Effects of Social Hierarchy Establishment in Resident–Intruder Model on Testicular Function in Laboratory Mice of Different Inbred Strains

Male reproductive success is known to be related with ability to social dominance and number and quality of spermatozoa as well as the production of reproductive hormones. The relationships between social dominance and testicular function are affected by genotype and environmental conditions of social hierarchy formation, and male territorial status (resident or intruder). However, the mechanisms of these relationships are still poorly understood. The aim of this study was to investigate effects of genotype and of familiarization with the habitat on testicular function during social hierarchy formation in experimental model of social hierarchy in laboratory mice using resident-intruder paradigm. Male of certain inbred strain (PT or CBA/Lac strain) was placed to experimental cage where male (resident) of other inbred strain (PT or CBA/Lac strain) has been living two days with female of DD/He strain. Social rank for each male was assessed after social hierarchy formation. Then testosterone level in serum and testes and epydidymal sperm quality were estimated after five days after the group formation. It was shown that social hierarchy formation did not affect testosterone level in serum and testes as well as percentage of sperm heads with abnormal morphology. However, the establishment of social hierarchy resulted in decreased sperm number in dominant-intruders of PT strains as well as decreased progressive sperm motility in subordinants of CBA/Lac strain regardless territorial status. To conclude, social hierarchy formation in experimental model of social hierarchy in laboratory mice affects epididymal sperm quality already five days after group formation, with pattern of these relationships depending on genotype, social rank and territorial status.

Maternal neglect alters reward-anticipatory behavior, social status stability, and reward circuit activation in adult male rats.

Adverse early life experiences affect neuronal growth and maturation of reward circuits that modify behavior under reward predicting conditions. Previous studies demonstrate that rats undergoing denial of expected reward in the form of maternal contact (DER-animal model of maternal neglect) during early post-natal life developed anhedonia, aggressive play-fight behaviors and aberrant prefrontal cortex structure and neurochemistry. Although many studies revealed social deficiency following early-life stress most reports focus on individual animal tasks. Thus, attention needs to be given on the social effects during group tasks in animals afflicted by early life adversity. To investigate the potential impact of the DER experience on the manifestation of behavioral responses induced by natural rewards, we evaluated: 1) naïve adult male sexual preference and performance, and 2) anticipatory behavior during a group 2-phase food anticipation learning task composed of a context-dependent and a cue-dependent learning period. DER rats efficiently spent time in the vicinity of and initiated sexual intercourse with receptive females suggesting an intact sexual reward motivation and consummation. Interestingly, during the context-dependent phase of food anticipation training DER rats displayed a modified exploratory activity and lower overall reward-context association. Moreover, during the cue-dependent phase DER rats displayed a mild deficit in context-reward association while increased cue-dependent locomotion. Additionally, DER rats displayed unstable food access priority following food presentation. These abnormal behaviours were accompanied by overactivation of the ventral prefrontal cortex and nucleus accumbens, as assessed by pCREB levels. Collectively, these data show that the neonatal DER experience resulted in adulthood in altered activation of the reward circuitry, interfered with the normal formation of context-reward associations, and disrupted normal reward access hierarchy formation. These findings provide additional evidence to the deleterious effects of early life adversity on reward system, social hierarchy formation, and brain function.

Peculiarities of Agonistic and Marking Behavior in Male Laboratory Mice (Mus musculuc) of Different Inbred Strains during the Formation of Social Hierarchy

Peculiarities of Agonistic and Marking Behavior in Male Laboratory Mice (Mus musculuc) of Different Inbred Strains during the Formation of Social Hierarchy

Effects of local versus global competition on reproductive skew and sex differences in social dominance behaviour.

Social hierarchies are often found in group-living animals. The hierarchy position can influence reproductive success (RS), with a skew towards high-ranking individuals. The amount of aggression in social dominance varies greatly, both between species and between males and females within species. Using game theory we study this variation by taking into account the degree to which reproductive competition in a social group is mainly local to the group, emphasizing within-group relative RS, or global to a larger population, emphasizing an individual's absolute RS. Our model is similar to recent approaches in that reinforcement learning is used as a behavioural mechanism allowing social-hierarchy formation. We test two hypotheses. The first is that local competition should favour the evolution of mating or foraging interference, and thus of reproductive skew. Second, decreases in reproductive output caused by an individual's accumulated fighting damage, such as reduced parenting ability, will favour less intense aggression but should have little influence on reproductive skew. From individual-based simulations of the evolution of social dominance and interference, we find support for both hypotheses. We discuss to what extent our results can explain observed sex differences in reproductive skew and social dominance behaviour.

Using Machine Learning to Identify Associations between the Environment, Occurrence, and Outcomes of Songbird Displacements at Supplemental Feeders

The context and outcome of aggressive interactions between individuals has important fitness consequences. Displacements—an aggressive interaction wherein one individual is chased from a location by another—also have implications for social hierarchy formation and geographic distribution in songbirds. Morphological correlates, like body size, and social correlates, such as dominance rank, have been shown to mediate displacements in songbirds. However, the role of the physical environment, namely temperature, humidity, and time of day, which may influence an individual’s energy needs and thus displacement motivation, has remained understudied. We monitored songbird feeding and displacement behaviors using computerized automated feeders. We observed asymmetric differences across species in displacement involvement. To identify the conditions of the social and physical environment that are associated with the occurrence and outcome of songbird displacements at supplemental feeders, we use the machine learning approach, random forest, which is a novel method to the fields of ornithology and animal behavior. From our random forest models, we found that the attributes of the physical environment (i.e., humidity and the time of day) are associated with the occurrence of a displacement event, whereas the attributes of the social environment (i.e., species of the displacer and displaced individuals) are associated with which species are involved. These results provide context to develop further observational and experimental hypotheses to tease apart the inner workings of these multifactorial behaviors on a larger scale and provide a proof of concept for our analytical methods in the study of avian behavior.

Personality-dependent passage behaviour of an aquatic invasive species at a barrier to dispersal

Intraspecific variation in personality traits is increasingly recognized as an important determinant of invasion success and is associated with the dispersal ability of several invasive species. However, previous studies have focused on the dispersal of invasive species through continuous habitats, despite the high levels of anthropogenic fragmentation in modern environments. This study investigated how personality influences the behaviour of aquatic invasive species at an anthropogenic barrier to dispersal, using the passage behaviour of American signal crayfish, Pacifastacus leniusculus , at an experimental Crump weir as a model system. Personality was characterized by determining the repeatability of boldness, activity and sociability, with correlations between traits indicating behavioural syndromes, while passage behaviour was quantified as motivation and subsequent ability to pass the weir. Boldness and activity were repeatable and positively correlated, indicating a boldness–activity syndrome. However, sociability was not repeatable and was therefore not classified as a personality trait, potentially as a result of the confounding effects of social hierarchy formation. Bolder individuals tended to be more motivated to pass the weir, although motivation was not related to activity. Few individuals passed the weir, and personality was not related to passage success. This study evidences the presence of behavioural syndromes in signal crayfish and demonstrates that personality can influence the motivation of invasive species to expand their range in a fragmented habitat. Although no relationship with passage success was observed, the higher levels of motivation in bold individuals may lead to differential passage success in natural situations where the time to attempt passage is not constrained by experimental conditions. • Signal crayfish personality and barrier passage behaviour were assessed. • Boldness and activity, but not sociability, were repeatable personality traits. • Crayfish demonstrated a boldness–activity behavioural syndrome. • Bolder crayfish were more motivated to pass the weir, but were not more successful. • Activity and sociability were not related to crayfish passage behaviour.

Pumping iron for strength and power: prisoners’ perceptions of a stable body

ABSTRACT Prior studies emphasise that prisons are violent places and strong social hierarchies exist between inmates. Against the background that a large number of inmates engage in strength training, this paper explores the significance of self-organised weight training and muscle building by reconstructing the meanings and relevance of these activities particularly with regard to power relations and social hierarchy formation. Using an ethnographic approach, the study is based on 80 field visits over 27 months in a German prison and 19 problem-centred interviews with male prisoners. The material shows that social hierarchies among inmates are largely based on physical strength and often manifest in acts of violence. In addition, inmates frequently face minor provocations, verbally or physically, that establish relations of dominance and submission. Interviewees interpret a stable, muscular body in combination with a self-confident, sometimes deliberately grim appearance as a signal that one is determined to defend oneself and does not serve as an easy victim. Accordingly, inmates see it as a necessity to build up muscle strength, which is why all forms of strength training are extremely popular within the prison. However, since the prison studied here actually forbids weight training with barbells, prisoners have to find informal ways and sometimes trick guards when carrying out muscle building exercises. It is concluded that weight training can best be understood as a functional adaptation to the prison context with its widespread aggression and (fear of) violence.

Low-rank Gallus gallus domesticus chicks are better at transitive inference reasoning

A form of deductive reasoning, transitive inference, is thought to allow animals to infer relationships between members of a social group without having to remember all the interactions that occur. Such an ability means that animals can avoid direct confrontations which could be costly. Here we show that chicks perform a transitive inference task differently according to sex and rank. In female chicks, low-ranking birds performed better than did the highest ranked. Male chicks, however, showed an inverted U-shape of ability across rank, with the middle ranked chicks best able to perform the task. These results are explained according to the roles the sexes take within the group. This research directly links the abilities of transitive inference learning and social hierarchy formation and prompts further investigation into the role of both sex and rank within the dynamics of group living.

Individual history of winning and hierarchy landscape influence stress susceptibility in mice.

Social hierarchy formation is strongly evolutionarily conserved. Across species, rank within social hierarchy has large effects on health and behavior. To investigate the relationship between social rank and stress susceptibility, we exposed ranked male and female mice to social and non-social stressors and manipulated social hierarchy position. We found that rank predicts same sex social stress outcomes: dominance in males and females confers resilience while subordination confers susceptibility. Pre-existing rank does not predict non-social stress outcomes in females and weakly does so in males, but rank emerging under stress conditions reveals social interaction deficits in male and female subordinates. Both history of winning and rank of cage mates affect stress susceptibility in males: rising to the top rank through high mobility confers resilience and mice that lose dominance lose stress resilience, although gaining dominance over a subordinate animal does not confer resilience. Overall, we have demonstrated a relationship between social status and stress susceptibility, particularly when taking into account individual history of winning and the overall hierarchy landscape in male and female mice.

The Dominance Hierarchy of the Female Yunnan Snub-Nosed Monkeys, Rhinopithecus bieti

Dominance hierarchies are common in social mammals, especially primates. The formation of social hierarchies is conducive to solving the problem of the allocation of scarce resources among individuals. From August 2015 to July 2016, we observed a wild, provisioned Yunnan snub-nosed monkey ( Rhinopithecus bieti ) group at Xiangguqing in Baimaxueshan National Nature Reserve, Yunnan Province, China. Aggressive and submissive behaviors were used to investigate dominance hierarchies between female individuals in the same one-male unit (OMU), and the grooming reciprocity index was used to detect reciprocal relationships between these females within the OMU. The results showed that loose social hierarchies exist among the females in each OMU, and more dominant individuals have higher grooming incomes. These results are consistent with the aggressive-submissive hypothesis and the resource control hypothesis.

Reproductive status effects of pair-housed male pigs on natural, agonistic and sexual behaviours

Boar rearing, which avoids pain and suffering caused by surgical castration, provides better performance, a greater deposition of muscle tissue and leaner carcasses and thus has beneficial effects on both animal welfare and the product. Some countries that do not slaughter boars must consider their boar taint and aggressive and sexual behaviours. Considering that pigs are housed in large groups, which may complicate the formation of social hierarchies and increase fighting and mounting behaviours, some studies have conducted research with reduced numbers of pigs per pen, but these behaviours continued to be observed. However, a study of the reproductive status of pair-housed male pigs has yet to be reported. The aim of this study was to determine whether the reproductive status of uncastrated, immunocastrated and surgically castrated pair-housed male pigs alters their natural, agonistic and sexual behaviours. A total of 48 male pigs from Agroceres PIC™ genetics were assigned to three groups: surgically castrated (barrows), immunocastrated and uncastrated (boars). Natural, aggressive and sexual behaviours of the pigs were assessed by direct observations during four periods of 12 h each (six, five and three weeks before slaughter and the slaughter week). The pigs were housed in pairs from the growing phase until slaughter. Animal behaviour was observed from the finishing phase to slaughter. Carcass lesions were assessed according to five different classes (one: no injury; two to five: severely injured). Overall, boars spent more time lying and less time eating and drinking than barrows. In total of all the periods (48 h), boars expressed more aggressive and sexual behaviours than barrows, whereas immunocastrated pigs displayed similar behaviours to boars, before and after the second vaccine dose. No differences in carcass lesions between treatments and no prevalence of carcasses with severe injuries were observed. In conclusion, the reproductive status of pair-housed male pigs did not change the natural behaviour of boars, immunocastrated pigs or barrows. The agonistic and sexual behaviours of boars and barrows remained unchanged. When housing pigs in pairs, immunocastrated pigs presented similar agonistic and sexual behaviours to boars before and after the second immunocastration vaccine dose. The use of pair-housed uncastrated male pigs has generated welfare benefits for these animals, as the number of carcasses with injuries did not differ from barrows and immunocastrated pigs.

Changes in Aggressive Behavior, Cortisol and Brain Monoamines during the Formation of Social Hierarchy in Black Rockfish (Sebastes schlegelii).

Simple SummaryBlack rockfish (Sebastes schlegelii) are naturally solitary animals. Under a high stocking density in aquaculture, juvenile black rockfish frequently show aggressive interactions, resulting in welfare issues (e.g., body injury). Aggressive interactions can lead to a social hierarchy and influence the responses of animal behavior and physiology. However, the responses of fish behavior and physiology to social hierarchy is limited. This study examined the differences in the growth performance, aggression, cortisol level, brain serotonergic activity, and brain dopamine activity between the dominant individuals and the subordinate individuals in the short-term contest and in the long-term contest. Ultimately, our results suggest that subordinate hierarchy inhibits aggression but does not impact growth in black rockfish. The cortisol-related change in brain monoaminergic activity could be a potential indicator to predict aggressive behavior in black rockfish in captivity with an obvious social hierarchy. This study has provided new insight into the understanding of the regulatory mechanisms between social hierarchy and aggressive behavior in black rockfish, and contributed to building the theoretical basis for behavioral management to solve the welfare issues in captive fish.Aggressive interactions can lead to a social hierarchy and influence the responses of animal behavior and physiology. However, our understanding on the changes of fish behavior and physiology during the process of social hierarchical formation is limited. To explore the responses of fish behavior and physiology to social hierarchy, we examined the differences in the growth performance, aggression, cortisol level, brain serotonergic activity, and brain dopamine activity between the dominant individuals and the subordinate individuals of black rockfish (Sebastes schlegelii) in two time scenarios. In the short-term contest, the cortisol level and the ratio of telencephalic 5-hydroxyindoleacetic acid (5-HIAA)/5-hydroxytryptamine (5-HT) was significantly higher in subordinate individuals than in dominant individuals. In the long-term contest, the ratios of 5-HIAA/5-HT in all brain regions were significantly higher, and the frequency of aggressive acts were significantly lower in subordinate individuals than in dominant individuals. In contrast, no difference was detected in growth performance. Significant positive correlations between the cortisol level and serotonergic activity were observed in the short-term contest, but the serotonergic activity was negatively correlated with the aggressive behavior in the long-term contest. These results suggest that subordinate hierarchy inhibits aggression but does not impact growth in black rockfish. The cortisol-related change in brain monoaminergic activity could be a potential indicator to predict aggressive behavior in black rockfish in captivity with an obvious social hierarchy.

Reestablishment of Social Hierarchies in Weaned Pigs after Mixing.

Simple SummaryAggression after mixing has negative effects on growth performance and animal welfare in pigs. To analyze the temporal dynamics of social hierarchy formation and maintenance, a total of 102 weaned pigs (47 females and 55 barrows) were selected and blocked by sex and body weight. The pigs were mixed into 10 single-sex pens (10 to 11 pigs/pen) avoiding original littermates. Their behavior was recorded and observed for 72 h after mixing for the analysis of dominance hierarchy indices in each pen. The three hierarchical indices: I&SI, Elo rating, and Glicko rating, were associated with each other (|r| = 0.681~0.942, p < 0.001). I&SI was associated with the logarithms of frequency of active attack (|r| = 0.65, p < 0.05) and tended to be associated to logarithms of frequency of standoff (|r| = 0.48, p < 0.1). Elo rating, and Glicko rating were associated with logarithms of duration of being bullied (|r| = 0.393~0.401, p < 0.05). In addition, Glicko rating tended to be associated with the logarithms of duration of active attack and frequency of active attack (|r| = 0.416~0.439, p < 0.1). Multiple linear regression analyses of logarithms of dyadic behavior indicators for hierarchical indices indicated the same effects. The rank of pigs became stable earlier (p < 0.001) in females (23.06 ± 4.15 h post mixing) than in barrows (40.55 ± 4.71 h post mixing). The first ranked pig quickly appeared within a few hours after mixing and remained stable. Our study provided new insights into the re-establishment of social hierarchies in weaned pigs after mixing.Pigs are animals that live in groups and have social hierarchies within the group. After mixing, they can re-establish social hierarchies within several days through fighting. Dominance hierarchical indices, such as I&SI, Elo rating, and Glicko rating, have been used to analyze social hierarchies of some social animals but not pigs. I&SI index involves iterative calculations that first minimize the number of inconsistencies (I) in a dominance matrix, and then minimize the strength of those inconsistencies (SI). Elo rating and Glicko rating indices are based on the sequence in which interactions occur, and continuously update ratings by looking at interactions sequentially. To study the temporal dynamics of social hierarchy formation and maintenance in weaned pigs after mixing, a total of 102 pigs (47 females and 55 barrows) were selected by similar body weight and mixed in 10 pens (10 or 11 females or barrows per pen). Their behavior was recorded and observed for 72 h after mixing. Results showed that hierarchical indices I&SI, Elo rating, and Glicko rating were associated with each other (|r| = 0.681 ~ 0.942, p < 0.001). I&SI was associated with logarithms of frequency of active attack (|r| = 0.65, p < 0.05) and tended to associated with logarithms of frequency of standoff (|r| = 0.48, p < 0.1). Elo rating, and Glicko rating were associated with the logarithms of duration of being bullied (|r| = 0.393~0.401, p < 0.05). In addition, Glicko rating tended to be associated with the logarithms of duration of active attack and frequency of active attack (|r| = 0.416~0.439, p < 0.1). Multiple linear regression analyses of logarithms of dyadic behavior indicators for three hierarchical indices indicated the same effects. The time (hours) to achieve social stability of pigs after mixing was lower for females than barrows (23.06 ± 4.15 vs. 40.55 ± 4.71 h; p < 0.001). The most dominant pig (the first ranked) in each pen quickly appeared within a few hours after mixing and remained stable. Overall, our study demonstrated that the ranks calculated by the three dominance hierarchical indices: I&SI, Elo rating, and Glicko rating, were consistent and partially associated with part of the dyadic behavioral indicators in weaned pigs after mixing.

Genetic signatures of dominance hierarchies reveal conserved cis-regulatory and brain gene expression underlying aggression in a facultatively social bee.

Agonistic interactions among individuals can result in the formation of dominance hierarches that can reinforce individual behavior and social status. Such dominance hierarches precede the establishment of reproductive dominance, division of labor and caste formation in highly social insect taxa. As such, deciphering the molecular basis of aggression is fundamental in understanding the mechanisms of social evolution. Assessing the proximate mechanisms of aggression in incipiently social bees can provide insights into the foundations of genomic mechanisms of social behavior. Here, we measured the effects of aggression on brain gene expression in the incipiently social bee, Ceratina australensis. We examine the brain transcriptomic differences between individuals who have experienced recurrent winning, losing, or a change in rank during repeated encounters. Using comparative analyses across taxa, we identify deeply conserved candidate genes, pathways, and regulatory networks for the formation of social hierarchies.

The French Revolutionin Then-Contemporary Philosophical Consciousness: The Divergent Lines of Interpretation

The author examines the alternative interpretations of the French revolution, which were offered by outstanding thinkers, its contemporaries. For philosophical consciousness, a revolution is always an occasion to express the most common social problems, to outline this or that vision of history as such. The article reviews the main features of Barnave’s and SaintMartin’s theories, which present naturalistic and theological interpretations of the revolutionary events. While Barnave considered the revolution in light of the theory of progress, Saint-Martin understood it through the concept of original sin. Saint-Martin saw the revolution as means for religion renovation, Barnave interpreted the revolution as a phase in the course of fading of religion’s social role. While Barnave’s philosophical methodology was substantially based on Enlightenment sensationalism, the position of Saint Martin relied on its denial. Despite all the differences between Barnave’s and Saint-Martin’s points of view, they shared similar intentions, analogous motives. First of all, there was a belief in need of revolution, in its justice and importance for mankind. The revolution was not understood by them as the collapse of common sense and foundations of society. On the contrary, the revolution was inevitable payment for abuses of the past, and it symbolized the beginning of a path to the better life awaiting mankind. The more the revolution receded into the past, the more proponents of its secular interpretation appeared. The primary focus was on the interests of social estates and classes, the issues of distribution of property and formation of social hierarchy. The providential approach to history lost its popularity, looked less and less feasible in the opinion of very numerous group of scholars. Nevertheless, the various elements of this approach remain in culture, they are present in the breath, rhythm and development of culture, they are reproduced again and again.

“Diz que em corumbá tem muita conversa fiada”: fofoca, política e moralidade em uma cidade do Pantanal

A cidade de Corumbá-MS possui pouco mais de cem mil habitantes e a fofoca é um fato social reconhecido pelos seus moradores em seus efeitos e alcance. Baseado na leitura de Bailey (1971), o estudo busca pensar nas relações que se estabelecem entre a fofoca e a política em torno das reputações pessoais e no pertencimento a uma ou mais “comunidades morais” na cidade, aqui nomeada de circuitos sociais da fofoca. Além disso, o estudo da fofoca pode contribuir etnograficamente para investigações sobre vários elementos da estrutura social da cidade: as relações de trabalho, os modos de se fazer negócios na fronteira, sobre a política local e a formação das hierarquias sociais, sobre a chegada de migrantes, sobre os significados de relacionamentos amorosos, relações de gênero, sobre a construção dos papéis sociais e do status e o posicionamento social dos indivíduos no “mapa” da cidade.

Social competition in red drum (Sciaenops ocellatus) is influenced by crude oil exposure

The present study examined impacts of crude oil exposure on dyad competition in juvenile red drum. Following the 2010 Deepwater Horizon oil spill, it has become well established that oil exposure can constrain maximum metabolic rate, reduce aerobic scope and exercise performance in marine fish. Aerobic scope is one of the physiological characteristics that is a known determinant of dominance in fish social hierarchy formation. As such, oil exposure may predispose individuals to subordinate social status, complete with the concomitant ecological costs. We tested this hypothesis on the gregarious Gulf of Mexico species, the red drum (Sciaenops ocellatus). Using a standard dyad, one-on-one, test design, we first assessed the parameters – including size and aerobic scope– that predict social dominance. Of the tested parameters, only aerobic scope was predictive of social dominance, with dominant individuals consistently having higher aerobic scopes than subordinates. Hierarchy formation between individuals exposed to one of two oil concentrations (5.7 ± 0.5 and 9.0 ± 0.2 μg l–1 ΣPAH50) and unexposed conspecifics were then investigated. As hypothesized, fish exposed to both oil concentrations were more likely to be subordinate than what would occur by random chance. These results demonstrate that the physiological constraints imposed by oil exposure can affect social status and behavior in fishes, which can have downstream consequences for ecological fitness.

Who is the boss? Individual recognition memory and social hierarchy formation in crayfish.

Under laboratory conditions, crayfish establish hierarchical orders through agonistic encounters whose outcome defines the dominant one and one, or more, submissive animals. These agonistic encounters are ritualistic, based on threats, pushes, attacks, grabs, and avoidance behaviors that include retreats and escape responses. Agonistic behavior in a triad of unfamiliar, size-matched animals is intense on the first day of social interaction and the intensity fades on daily repetitions. The dominant animal keeps its status for long periods, and the submissive ones seem to remember 'who the boss is'. It has been assumed that animals remember and recognize their hierarchical status by urine signals, but the putative substance mediating this recognition has not been reported. The aim of this work was to characterize this hierarchical recognition memory. Triads of unfamiliar crayfish (male animals, size and weight-matched) were faced during standardized agonistic protocols for five consecutive days to analyze memory acquisition dynamics (Experiment 1). In Experiment 2, dominant crayfish were shifted among triads to disclose whether hierarchy depended upon individual recognition memory or recognition of status. The maintenance of the hierarchical structure without behavioral reinforcement was assessed by immobilizing the dominant animal during eleven daily agonistic encounters, and considering any shift in the dominance order (Experiment 3). Standard amnesic treatments (anisomycin, scopolamine or cold-anesthesia) were given to all members of the triads immediately after the first interaction session to prevent individual recognition memory consolidation and evaluate its effect on the hierarchical order (Experiment 4). Acquisition of hierarchical recognition occurs at the first agonistic encounter and agonistic behavior gradually diminishes in the following days; animals keep their hierarchical order despite the inability of the dominant crayfish to attack the submissive ones. Finally, blocking of protein synthesis or muscarinic receptors and cold anesthesia impair memory consolidation. These findings suggest that agonistic encounters induces the acquisition of a robust and lasting social recognition memory in crayfish.