Dominance Hierarchy Research Articles

Negative feedback regulation in the hypothalamic-pituitary-interrenal axis of rainbow trout subjected to chronic social stress

The formation of dominance hierarchies in pairs of juvenile rainbow trout (Oncorhynchus mykiss) results in subordinate individuals exhibiting chronically elevated plasma cortisol concentrations. Cortisol levels reflect a balance between cortisol production, which is coordinated by the hypothalamic-pituitary-interrenal (HPI) axis in teleost fish, and negative feedback regulation and hormone clearance, which act to lower cortisol levels. However, the mechanisms contributing to the longer-term elevation of cortisol levels during chronic stress are not well established in fishes. The current study aimed to determine how subordinate fish maintain elevated cortisol levels, by testing the prediction that negative feedback and clearance mechanisms are impaired by chronic social stress. Plasma cortisol clearance was unchanged by social stress based on a cortisol challenge trial, hepatic abundance of the cortisol-inactivating enzyme 11-beta hydroxysteroid dehydrogenase type 2 (11βHSD2), and tissue fate of labelled cortisol. The capacity for negative feedback regulation in terms of transcript and protein abundances of corticosteroid receptors in the preoptic area (POA) and pituitary appeared stable. However, changes in 11βHSD2 and mineralocorticoid receptor (MR) expression suggest subtle regulatory changes in the pituitary that may alter negative feedback. The chronic cortisol elevation observed during social subordination likely is driven by HPI axis activation and compounded by dysregulated negative feedback.

Reciprocated competition between two forest carnivores drives dietary specialization.

Competition shapes animal communities, but the strength of the interaction varies spatially depending on the availability and aggregation of resources and competitors. Among carnivores, competition is particularly pronounced with the strongest interactions between similar species with intermediate differences in body size. While ecologists have emphasized interference competition among carnivores based on dominance hierarchies from body size (smaller = subordinate; larger = dominant), the reciprocity of exploitative competition from subordinate species has been overlooked even though efficient exploitation can limit resource availability and influence foraging. Across North America, fishers Pekania pennanti and martens (Martes spp.) are two phylogenetically related forest carnivores that exhibit a high degree of overlap in habitat use and diet and differ in body size by a factor of 2-5×, eliciting particularly strong interspecific competition. In the Great Lakes region, fishers and martens occur both allopatrically and sympatrically; where they co-occur, the numerically dominant species varies spatially. This natural variation in competitors and environmental conditions enables comparisons to understand how interference and exploitative competition alter dietary niche overlap and foraging strategies. We analysed stable isotopes (δ13 C and δ15 N) from 317 martens and 132 fishers, as well as dietary items (n = 629) from 20 different genera, to compare niche size and overlap. We then quantified individual diet specialization and modelled the response to environmental conditions that were hypothesized to influence individual foraging. Martens and fishers exhibited high overlap in both available and core isotopic δ-space, but no overlap of core dietary proportions. When the competitor was absent or rare, both martens and fishers consumed more smaller-bodied prey. Notably, the dominant fisher switched from being a specialist of larger to smaller prey in the absence of the subordinate marten. Environmental context also influenced dietary specialization: increasing land cover diversity and prey abundance reduced specialization in martens whereas vegetation productivity increased specialization for both martens and fishers. Despite an important dominance hierarchy, fishers adjusted their niche in the face of a subordinate, but superior, exploitative competitor. These findings highlight the underappreciated role of the subordinate competitor in shaping the dietary niche of a dominant competitor.

Graffiti Writing as Creative Activism: Getting Up, Sheeplike Subversion, and Everyday Resistance

Abstract Is graffiti writing creative activism? In this paper, I challenge commonly held beliefs that graffiti writing is politically inert. On the contrary, I argue that graffiti writing is an example of creative activism. Rather than being a narcissistic form of vandalism, primarily directed at increasing one’s fame in front of an esoteric group, that is, fellow writers, writing is a form of everyday resistance allowing its practitioners to challenge authoritarian power. In questioning dominant hierarchies, graffiti is a powerful tool to help correct a specific instance of spatial injustice: the unequal distribution of access to urban surfaces for self-expression in the city, where corporations and political elites hold an unjustified monopoly over visual communication.

Precursors and aftermath of severe targeted aggression in captive cotton-top tamarins.

We observed a zoo-housed group of cotton-top tamarins (Saguinus oedipus) before and after a bout of severe targeted aggression directed towards two of its members. The aggression was so severe and repeated that the zoo personnel was forced to remove the two victims and the main aggressor. In the tense period that preceded removal, the tamarins showed increased aggression, a steeper and linear dominance hierarchy, and reduced post-conflict reconciliation compared to the period following removal. In contrast, affiliative interactions such as grooming and peaceful food transfers did not differ in the two periods of observations. Patterns of reciprocity also remained stable. These results highlight the flexibility of tamarin social relationships and provide useful information for managing captive colonies and improving animal welfare.

Turtle-mediated dispersal of anostracan dormant eggs: Evidence for dominance hierarchy effects.

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Social zebrafish: Danio rerio as an emerging model in social neuroendocrinology.

The fitness benefits of social life depend on the ability of animals to affiliate with others and form groups, on dominance hierarchies within groups that determine resource distribution, and on cognitive capacities for recognition, learning and information transfer. The evolution of these phenotypes is coupled with that of neuroendocrine mechanisms, but the causal link between the two remains underexplored. Growing evidence from our research group and others demonstrates that the tools available in zebrafish, Danio rerio, can markedly facilitate progress in this field. Here, we review this evidence and provide a synthesis of the state-of-the-art in this model system. We discuss the involvement of generalized motivation and cognitive components, neuroplasticity and functional connectivity across social decision-making brain areas, and how these are modulated chiefly by the oxytocin-vasopressin neuroendocrine system, but also by reward-pathway monoamine signaling and the effects of sex-hormones and stress physiology.

115 Effect of an enriched social environment on social maturation of horses

Conventional husbandry practices rarely allow for sociality of horses. Under natural conditions, horses learn the social codes of their group mates during the first years of life. Horses raised in box stalls have more aggressive interactions with humans than horses housed in a group setting in a pasture. Such conditions can potentially compromise the well-being of the horses. The study aimed at providing Information on the temporal evolution of the young horse's behavior in a social group to estimate better the exact age of social maturity. The study was run in a breeding stud for sport horses born and raised in large social all-age groups (20–60 horses), always outdoors on large pastures and fed roughage only. Salt lick was available. From the age of 4 years, the behavior of 9 horses was observed daily during daytime (6 h between 8:00 a.m. and 8:00 p.m.) between June and August each year for 3 consecutive years. Each horse was observed for a total of at least 90 h and its social interactions (defensive, offensive, or affiliative) were recorded. The data was analyzed with a GLMM. The type of interaction was considered a fixed factor in interaction with age and season. The identity of horses was considered a random factor. We found that 4yrs-old horses had fewer defensive interactions than 5- and 6yrs-old horses (4yrs-5yrs P < 0.0001, 4yrs-6yrs P < 0.001). The affiliative and offensive interactions decreased continuously fromthe age of 4 to 6 yrs with 5yrs old showing in between levels (Affiliative: 4yrs-5yrs P < 0.0001, 5yrs-6yrs P < 0.001, 4yrs-6yrs P < 0.001; Offensive: 5yrs-6yrs P = 0.009, 4yrs-5yrs P < 0.001, 4yrs-6yrs P < 0.001). While getting older, horses expressed less offensive agonistic behavior and more defensive behavior suggesting a phenomenon of social maturation from the age of 4 to 6 years. This might be the consequence of a better ability to establish and respect the group's dominance hierarchy. It is also possible that more mature horses stay closer to same-rank individuals, unlike younger ones, decreasing then the risk of offensive interactions. The fact that the decrease in affiliative interactions was associated with a decrease in offensive interactions go along with the hypothesis of a social maturation and the development of better socio-cognitive skills. This development of social behavior questions the fact that many horses are traditionally isolated from congeners when they start working, from the age of 2, latest 3 years old. Our results suggest that such horses are excluded from a social group during a sensitive period of social maturation. This could induce a lack of social skills that could be necessary later for interacting normal with congeners and humans.

Mixed-species groups and the question of dominance in the social ecosystem.

Dominance interactions and hierarchies are of long-standing interest in the field of animal behaviour. Currently, dominance hierarchies are viewed as complex social structures formed by repeated interactions between individuals. Most studies on this phenomenon come from single-species groups. However, animals are constantly surrounded by and interact with individuals of other species. Behaviour and social interactions of individuals can be shaped by the presence or behaviour of other species in their social ecosystem, which has important implications for social behaviour in groups. Given how ubiquitous mixed-species animal groups are, deeper study of the relationships between mixed-species group (MSG) structure and dominance will be key to understanding constraints on individual behaviour and decision making. Here we call for more research into dominance interactions among individuals in MSGs. Greater understanding of the dynamics of dominance relationships among individuals in MSGs, whose size and composition can change considerably over shorter and longer term time frames, will be crucial to understanding their structure and functioning. This article is part of the theme issue 'Mixed-species groups and aggregations: shaping ecological and behavioural patterns and processes'.

Incorporating neurological and behavioral mechanisms of sociality into predator-prey models.

Consumer-resource population models drive progress in predicting and understanding predation. However, they are often built by averaging the foraging outcomes of individuals to estimate per capita functional responses (functions that describe predation rate). Reliance on per-capita functional responses rests on the assumption that that individuals forage independently without affecting each other. Undermining this assumption, extensive behavioral neuroscience research has made clear that facilitative and antagonistic interactions among conspecifics frequently alter foraging through interference competition and persistent neurophysiological changes. For example, repeated social defeats dysregulates rodent hypothalamic signaling, modulating appetite. In behavioral ecology, similar mechanisms are studied under the concept of dominance hierarchies. Neurological and behavioral changes in response to conspecifics undoubtedly play some sort of role in the foraging of populations, but modern predator-prey theory does not explicitly include them. Here we describe how some modern approaches to population modeling might account for this. Further, we propose that spatial predator-prey models can be modified to describe plastic changes in foraging behavior driven by intraspecific interaction, namely individuals switching between patches or plastic strategies to avoid competition. Extensive neurological and behavioral ecology research suggests that interactions among conspecifics help shape populations' functional responses. Modeling interdependent functional responses woven together by behavioral and neurological mechanisms may thus be indispensable in predicting the outcome of consumer-resource interactions across systems.

Invasive cichlids (Teleostei: Cichliformes) in the Amacuzac River, Mexico: Implications for the behavioral ecology of the native Mexican mojarra Amphilophus istlanus

The introduction of species is a leading cause of biodiversity loss and habitat alteration. Several species have invaded Mexican freshwater ecosystems, adversely affecting native fishes. Specifically, in the Amacuzac River of the Balsas Basin (Central Mexico), at least four non-native cichlids have been recorded: tilapia Oreochromis sp., convict cichlid Amatitlania nigrofasciata, spotcheek cichlid Thorichthys maculipinnis, and green terror Andinoacara rivulatus. These species co-occur with the Mexican mojarra Amphilophus istlanus, the only native cichlid in the Basin. Invasive cichlids compete for resources such as shelter and food, and prey on offspring of the Mexican mojarra. In the presence of invasive cichlids, the costs and risks of foraging and finding available shelter increase for the native cichlid. Predation pressure from invasive cichlid fishes on the Mexican mojarra increases the time invested by parents in caring for offspring and their stress levels, potentially contributing to Mexican mojarra population declines. Here, we gathered the best evidence available to discuss some mechanisms and consequences of such co-occurrences in relation to reproductive behaviors, parental care, competition for resources, and dominance hierarchy, and how the four invasive cichlids have negatively affected the Mexican mojarra.

Dominance versus Prestige Hierarchies: How Social Hierarchy Base Shapes Conspicuous Consumption

Abstract Consumers are known to seek out and display conspicuous goods—items that are exclusive and signal wealth and high social standing. Though many factors can drive such conspicuous consumption, the present work looks at an unexplored element: whether consumers find themselves in a dominance versus prestige-based hierarchy. Dominance-based hierarchies encourage consumers to use threatening, assertive, and manipulative behaviors to navigate the hierarchy. In contrast, prestige-based hierarchies encourage consumers to show their talent, skills, and motivation to operate within the hierarchy. The present research reveals how these two main bases of hierarchy shape consumers’ consumption of conspicuous goods. Specifically, dominance, relative to prestige hierarchies, is proposed to foster greater social anxiety, which leads people to seek conspicuous goods as a means of psychological security. Consequently, dominance-based hierarchies are more likely to encourage conspicuous consumption relative to prestige-based hierarchies. Multiple experiments, which utilize real employees’ behaviors, experimental manipulations of hierarchy, as well as incentivize-compatible decisions, reveal that dominance-based hierarchies, relative to prestige-based hierarchies, increase consumers’ preference for conspicuous goods. Moreover, evidence for a psychological mechanism in the form of social anxiety is demonstrated via both mediation and moderation.

The Missed Fork in the “Forked-Road Situation”

The Missed Fork in the “Forked-Road Situation”

Postcolonial Black Motherhood: Dismantling Controlling Images in Jesmyn Ward's Bois Sauvage Novels

Abstract Centering on Jesmyn Ward's two recent novels, this article begins with the literary through line from Toni Morrison's early novels to Ward's constructions of Black mothers in the twenty-first century of a fictional rural Mississippi. As Morrison before her, Ward archives Black women's lived experiences to reconfigure not only an American literary imagination but also the past itself to explore Black women's oppressions from the slave era to our contemporary moment. Ward's novels Salvage the Bones and Sing, Unburied, Sing express the social constructions that have burdened Black women, especially mothers, since the slave era. Through the social framework of controlling images as defined by Patricia Hill Collins, this article dissects U.S. social hierarchies that discriminate against Black mothers’ intersectional identities while theorizing how Black women feminist writers have strived toward self-definition and liberation. Implicit in the construction of these dominant social hierarchies is the postcolonial condition of Black mothers and women who have contested the colonial project of slavery, the imperial project of expansionism, and the postcolonial project of mass incarceration and lynchings. Most importantly, Ward illustrates how these controlling images and social constructions of racialized motherhood have concealed the structural oppressions experienced by Black women every day. Thus, I argue these two novels dismantle the controlling images surrounding Black mothers while examining how motherwork and othermothering constitute radical interventions that disrupt our racist, sexist culture and society. By reappropriating their past and self-defining their present, the Black mothers in Ward's novels uncover structural oppressions and reveal the critical connections between enslaved mothers and contemporary Black mothers.

Female dominance hierarchies influence responses to psychosocial stressors

Social species form dominance hierarchies to ensure survival and promote reproductive success. Traditionally studied in males, rodent hierarchies are considered despotic, and dominant social rank results from a history of winning agonistic encounters. By contrast, female hierarchies are thought to be less despotic, and rank is conferred by intrinsic traits. Both social buffering and elevated social status confer resilience to depression, anxiety, and other consequences of chronic stress. Here, we investigate whether female social hierarchies and individual traits related to social rank likewise influence stress resilience. We observe the formation of dyadic female hierarchies under varying conditions of ambient light and circadian phase and subject mice to two forms of chronic psychosocial stress: social isolation or social instability. We find that stable female hierarchies emerge rapidly in dyads. Individual behavioral and endocrinological traits are characteristic of rank, some of which are circadian phase dependent. Further, female social rank is predicted by behavior and stress status prior to social introduction. Other behavioral characteristics suggest that rank is motivation-based, indicating that female rank identity serves an evolutionarily relevant purpose. Rank is associated with alterations in behavior in response to social instability stress and prolonged social isolation, but the different forms of stress produce disparate rank responses in endocrine status. Histological examination of c-Fos protein expression identified brain regions that respond to social novelty or social reunion following chronic isolation in a rank-specific manner. Collectively, female rank is linked to neurobiology, and hierarchies exert context-specific influence upon stress outcomes.

Dynamics of Changing Rural Demography (A Case Study of Villages in National Capital Region –Delhi)

Migrants preferring to settle in the villages abutting urban centers avoiding slums and ghettos in metropolitan cities influences and changes rural demographics as migrants outnumber the host denizens who shift to the cities to leverage urban amenities for quality life and convenience. In this context of new dynamics in the rural socioeconomic setup the focus of the paper is to highlight positive factors which entice migrants towards villages and local denizens shifting to the cities. The study elucidates contributions of migrants in making rural economy vibrant and thriving with myriad new avenues for the host communities to prosper. In spite of being the harbinger of dynamism in rural landscapes, migrants are deprived of socio economic amenities and denied roles in local governess by supremacist thinking dominant status and local hierarchy. The need is to address there denied rights for inclusive and harmonious rural societies. Keywords: Dynamics, Migration, Demographics, Prosper Friction

Morphological characteristics convey social status signals in captive tree sparrows (Passer montanus).

In social animals that form flocks, individuals compete or cooperate to gain access to shared resources. In particular, group-foraging individuals frequently engage in aggressive interactions with conspecifics, including threat displays and physical attacks, in order to acquire food resources. Here, we investigated social interactions in flocks of captive tree sparrows (Passer montanus) to observe the formation of dominance hierarchies. We also examined correlations between social status and morphological traits to identify which physical traits act as indicators of dominance. To do so, we recorded aggressive behaviours (attacks and threats) of tree sparrows caught in two distinct regions in the Republic of Korea (Gwangju and Gurye). After merging the two groups, we examined dominance structures using David's scores for one month, and we recorded 1,051 aggressive interactions at a feeder in a group of 19 individuals. Using the number of aggressions and attack and threat behaviours, we tested whether morphological traits and sex influenced dominance structures. Aggressions were significantly more frequent in males than in females. However, no significant difference was observed the frequency of between- and within-sex aggression. In addition, differences in the frequency of aggression behaviours were observed between capture-site groups. Dominance structure was significantly correlated with certain morphological traits; specifically, the frequency of attacking behaviours was correlated with bill-nose length, and the frequency of threat displays was correlated with sex and badge size. These results suggest that social signals are closely related to morphological traits that are used to form dominance hierarchies in tree sparrow flocks.

Perturbations highlight importance of social history in parakeet rank dynamics

Abstract Dominance hierarchies can provide many benefits to individuals, such as access to resources or mates, depending on their ranks. In some species, rank can emerge as a product of a group’s history of social interactions. However, it can be difficult to determine whether social history is critical to rank in observation-based studies. Here, we investigated rank dynamics in three captive groups of monk parakeets (Myiopsitta monachus). We used experimental social perturbations to test whether social history shapes rank emergence in these groups. Using targeted removals and reintroductions, we tested whether differently ranked individuals could re-take their ranks in hierarchies after reintroduction following their removal period from the group. We performed perturbations that consisted of an 8-day removal and an 8-day reintroduction period of 15 differently ranked focal birds. We found that no focal birds could regain their previous rank immediately following reintroduction and that the top-ranked birds showed greater relative rank loss than middle/low-ranked birds. We also found that morphology, specifically bodyweight, was unassociated with rank. Combined with previous results, this experiment supports the hypothesis that rank in monk parakeet dominance hierarchies is more likely to be an emergent outcome of past interactions and memory rather than based on individual characteristics. Gaining a better understanding of how individuals achieve and maintain rank can give insight into the role of cognition on rank acquisition, as rank position can have significant biological effects on individuals in hierarchically structured groups.

Evidence of Non-Random Social Interactions between Pairs of Bait-Attracted White Sharks in Gansbaai (South Africa)

Knowledge about the social behavior of sharks is a growing research field, but not many observations are available on the social interactions between pairs of sharks in the presence of passive surface bait and mainly related to aggregations. Between 2009 and 2018, in Gansbaai, South Africa, 415 white sharks were sighted, and 525 surface-generated social interactions were identified, exhibited by 169 different white sharks. The mean sighting rate was 0.91 (range 0.18–1.53) white sharks per hour. Eight patterns of social interaction were exhibited: swim by, parallel swim, follow/give way, follow, give way, stand back, splash fights, and piggyback. Non-random interactions occurred when pairs of specimens approached the passive surface bait, confirming that the white sharks made a real choice, showing a dominance hierarchy during the ten years of data collection. Evidence of non-random social interactions in the surface behavior of bait-attracted white sharks Carcharodon carcharias in Gansbaai’s transient population was the goal of this research.

Sex-dependent control of pheromones on social organization within groups of wild house mice

Dominance hierarchy is a fundamental social phenomenon in a wide range of mammalian species, critically affecting fitness and health. Here, we investigate the role of pheromone signals in the control of social hierarchies and individual personalities within groups of wild mice. For this purpose, we combine high-throughput behavioral phenotyping with computational tools in freely interacting groups of wild house mice, males and females, in an automated, semi-natural system. We show that wild mice form dominance hierarchies in both sexes but use sex-specific strategies, displaying distinct male-typical and female-typical behavioral personalities that were also associated with social ranking. Genetic disabling of VNO-mediated pheromone detection generated opposite behavioral effects within groups, enhancing social interactions in males and reducing them in females. Behavioral personalities in the mutated mice displayed mixtures of male-typical and female-typical behaviors, thus blurring sex differences. In addition, rank-associated personalities were abolished despite the fact that both sexes of mutant mice formed stable hierarchies. These findings suggest that group organization is governed by pheromone-mediated sex-specific neural circuits and pave the way to investigate the mechanisms underlying sexual dimorphism in dominance hierarchies under naturalistic settings.

Successful Bullying Prevention: a Curriculum Based on Cooperative Learning – Theoretical Analysis

At the level of pre-university education units in Romania, there is a visible concern for identifying the most effective strategies to prevent bullying in parallel with the development of social skills for positive interaction. In accordance with these trends, this work aims to identify some educational strategies to prevent bullying that value the dynamics of cooperation. Thus, in the present study we propose to present the theory of social interdependence from the perspective of cooperative learning in the prevention of bullying. In the scientific literature it is shown that students who have more experiences of cooperation have an increased probability of not developing individualistic tendencies or engaging in intentional acts of aggression. On the other hand, social dominance theories show that through competition students compete for a place in dominance hierarchies and may have harmful intentions. The findings of various researchers show that cooperation is an effective strategy against bullying both in secondary school and in primary school. Cooperative learning significantly reduces bullying because bullies and victims share a tendency to be uncooperative. It was also observed that the results of cooperative learning on prosocial ability they have related by the improvement of the relationship between students. Given that bullies prefer to dominate rather than be cooperative, while victims lack social interaction skills, we believe that the success of bullying prevention is found in a curriculum centered on cooperative learning. Therefore, the design of such a curriculum is important from the perspective of developing students' cooperation and interrelationship skills as a strategy to prevent bullying.