Social Dominance Behavior Research Articles

Coat darkness is associated with social dominance and mating behaviour in a mountain sheep hybrid lineage

Natural hybridization can produce novel traits when morphologically different populations hybridize, and can introduce variation in traits that become associated with sexual selection. Evidence from breeding experiments and genetic markers indicate that the great variation in coat darkness and the unique coat patterns found in Stone's sheep Ovis dalli stonei , populations, have resulted from an ancient hybridization event between thinhorn sheep, O. dalli, and bighorn sheep, O. canadensis . Behavioural evidence gathered in 2003 and 2004 in Yukon Territory, Canada, showed that higher dominance rank was correlated with increasing darkness in rams, and comparatively darker rams were seen more often tending oestrous ewes. The relationship between ram darkness and dominance and use of the tending mating tactic was still significant after age or horn size were controlled. In sum, our study demonstrates an interesting example of the potential for hybridization to generate diversity. In the case of mountain sheep an ancestral hybridization has resulted in a subspecies with unique coat colour characteristics that are associated with social dominance and mating behaviour.

Phenotypic characterization of spatial cognition and social behavior in mice with ‘knockout’ of the schizophrenia risk gene neuregulin 1

Neuregulin-1 (NRG1) has been identified as a candidate susceptibility gene for schizophrenia. In the present study the functional role of the NRG1 gene, as it relates to cognitive and social processes known to be disrupted in schizophrenia, was assessed in mice with heterozygous deletion of transmembrane (TM)-domain NRG1 in comparison with wildtypes (WT). Social affiliative behavior was assessed using the sociability and preference for social novelty paradigm, in terms of time spent in: (i) a chamber containing an unfamiliar conspecific vs. an empty chamber (sociability), or (ii) a chamber containing an unfamiliar conspecific vs. a chamber containing a familiar conspecific (preference for social novelty). Social dominance and aggressive behavior were examined in the resident–intruder paradigm. Spatial learning and memory were assessed using the Barnes maze paradigm, while spatial working memory was measured using the continuous variant of the spontaneous alternation task. Barnes maze data revealed intact spatial learning in NRG1 mutants, with elevated baseline latency to enter the escape hole in male NRG1 mutants reflecting an increase in activity level. Similarly, although a greater number of overall arm entries were found, spontaneous alternation was unaffected in NRG1 mice. Social affiliation data revealed NRG1 mutants to evidence a specific loss of WT preference for spending time with an unfamiliar as opposed to a familiar conspecific. This suggests that NRG1 mutants show a selective impairment in response to social novelty. While spatial learning and working memory processes appear intact, heterozygous deletion of TM-domain NRG1 was associated with disruption to social novelty behavior. These data inform at a novel phenotypic level on the functional role of this gene in the context of its association with risk for schizophrenia.

Social Dominance in Romantic Relationships: A Prospective Longitudinal Study of Non‐verbal Processes

AbstractThe study of social dominance has a long tradition within the peer relationships literature, but rarely has the topic been investigated observationally and longitudinally within other salient close relationships. The present study investigated the role of experiences in social relationships and adjustment indices in childhood in predicting later observed non‐verbal social dominance behaviors in the context of romantic relationships in emerging adults. Analyses from a subsample (N = 70) from a 29‐year prospective longitudinal study revealed links between early peer behavior and subsequent romantic relationship interactions for men and women. Non‐verbal social dominance behaviors were concurrently associated with poor romantic relationship quality, conflict, and physical and verbal aggression within the dyad. Both childhood externalizing and internalizing behaviors significantly predicted non‐verbal social dominance behaviors in the romantic partner interactions.

Behavioral alterations in mice lacking the translation repressor 4E-BP2

The requirement for de novo protein synthesis during multiple forms of learning, memory and behavior is well-established; however, we are only beginning to uncover the regulatory mechanisms that govern this process. In order to determine how translation initiation is regulated during neuroplasticity we engineered mutant C57Bl/6J mice that lack the translation repressor eukaryotic initiation factor 4E-binding protein 2 (4E-BP2) and have previously demonstrated that 4E-BP2 plays a critical role in hippocampus-dependent synaptic plasticity and memory. Herein, we examined the 4E-BP2 knockout mice in a battery of paradigms to address motor activity and motor skill learning, anxiety and social dominance behaviors, working memory and conditioned taste aversion. We found that the 4E-BP2 knockout mice demonstrated altered activity in the rotating rod test, light/dark exploration test, spontaneous alternation T-maze and conditioned taste aversion test. The information gained from these studies builds a solid foundation for future studies on the specific role of 4E-BP2 in various types of behavior, and for a broader, more detailed examination of the mechanisms of translational control in the brain.

Social interactions affect physiological consequences of sublethal copper exposure in rainbow trout, Oncorhynchus mykiss

The interactions of sublethal waterborne copper exposure and social dominance behavior were examined in juvenile rainbow trout. Dominance hierarchies were determined between pairs of fish by behavioral observations and among groups of 10 fish by the use of passive integrated transponder (PIT) tagging equipment. The present study is one of the first to utilize this novel PIT tag method for behavioral assessment. Feeding behavior was quantified by placing a PIT tag recorder at the entrance to the feeding area. Linear dominance hierarchies were documented based on these observations of feeding behavior. Dominance hierarchies established in control water were not altered by exposure to 30 microg/L of copper; however, physiological responses of fish to sublethal concentrations of copper were related to social rank. Subordinate fish exhibited a higher accumulation of copper in both gill and liver tissue. Subordinates of paired fish were also shown to have a higher uptake of sodium than dominant fish, and the uptake of sodium was correlated with uptake of copper from the water. Therefore, within a population of fish, it cannot be assumed that individuals of different social status will exhibit the same physiological responses to the presence of copper.

Serotonergic intervention affects both social dominance and affiliative behaviour

Deficiencies in serotonin function have been associated with irritability and aggression but enhancing serotonin has also been shown to promote social status and affiliative behaviour in non-human primates and more recently in humans. To investigate the effects of citalopram, a selective serotonin reuptake inhibitor (SSRI), on social behaviour with a flatmate and a stranger. Ten pairs of healthy volunteers took part in a randomized double-blind crossover study of 2 weeks treatment with citalopram (20 mg/day) and placebo with a 2-week washout period. In each pair, one person (subject) took the tablets and the other (flatmate) received no treatment. On the last day of each treatment period, the subjects socially interacted with a confederate behaving as a responsive person in a stranger-dyadic social interaction paradigm. After the interaction, subjects played the Mixed-motive game, which measures cooperative behaviour and communication, with the confederate. The flatmates evaluated the social behaviour of the subjects before and at the end of the treatment periods. On citalopram, the subjects were rated as significantly less submissive by their flatmates and they showed a dominant pattern of eye contact in the stranger-dyadic social interaction paradigm. They also reduced the number of points they awarded themselves and sent more cooperative messages during the game. These results indicate that administration of an SSRI can modify social status in different interactions and increase affiliative behaviour. They implicate a role for serotonin in modulating social aspects of behaviour.

Reproductive skew and the threat of eviction: a new perspective

Most recent models of the partitioning of reproduction attempt to explain patterns of skew on the assumption that dominant individuals have complete control over breeding opportunities within the group, but may nevertheless concede a share of direct reproduction to subordinates as an incentive to remain peacefully in the association. Although these models may be applicable to some animal societies, we argue that they fail to provide a comprehensive theory of skew. Instead, we suggest that subordinates may often be able to claim unsanctioned reproduction for themselves, but will be forced to exercise a degree of reproductive restraint lest they incite ejection by the dominant. Reproductive skew, in other words, may reflect the threat of ejection (inducing subordinate restraint) rather than the threat of subordinate departure (inducing reproductive concessions by dominants). We present a simple ESS model of reproductive skew under these circumstances, which demonstrates that a shift in emphasis from reproductive concessions by dominants to reproductive restraint on the part of subordinates, radically alters the predictions of skew models. High group productivity, high relatedness and (when group members are related) strong ecological constraints are all expected to lead to reduced skew (the opposite conclusions to those of previous, concession-based analyses). The reason is that these factors reduce the benefits (or increase the costs) of ejection to the dominant, who therefore does best to tolerate more subordinate reproduction.

Permanent and Transient Effects of Repeated Preweaning Stress on Social and Sexual Behaviors of Rats

We have reported that exposure of preweaning male and female rats to a model of unpredictable mild physical stressors (Neo-A) can decrease the behavioral and hormonal responses to acute and chronic stress as adults. In this paper we have analyzed the effect of Neo-A on development of social behaviors, including aggressiveness, social dominance, and sexual behavior in adulthood. The subjects were divided into two groups: Neo-A (daily exposed to unpredictable mild stresses- from day 2 up to day 15 of suckling; n = 30 litters) and controls (C) (undisturbed rats, except for testing, during the same period of life; n = 26 litters). When day 6 pups were submitted to a social clustering test the Neo-A group showed a higher rate of litter-mate clustering than C. The 35 days Neo-A males and Neo-A females submitted to a social behavior test after 24 h of social isolation also showed higher scores of time spent in active social interaction than controls, as well as a higher ratio of animals showing aggressive playing. A second social behavior test performed after 48 h of social isolation at days 75–80 of age revealed that only Neo-A females displayed increased social behavior and aggressive behaviors, whereas controls did not. A water competition test performed at 24 and 48 h after water deprivation showed that Neo-A adult males spent more time in possession of the drinking device and drank more frequently than C. When adult proestrous females were exposed to a sexual behavior test, the Neo-A group showed shorter latency and higher scores of lordosis quotient. These results support the view that exposure to this model of repeated mild stress early in life stimulates the development of social behavior, dominance and sexual behavior.

Testosterone, Physical Aggression, Dominance, and Physical Development in Early Adolescence

The associations among testosterone, physical development, social dominance, and antisocial behaviour during early adolescence were assessed in a sample of boys followed from 6 to 13 years. Saliva testosterone level was positively correlated with height, and uncorrelated with measures of fatness, including the body mass index. Physical aggression and social dominance were not significantly correlated. Regression analyses revealed that testosterone level and body mass additively predicted social dominance, whereas only body mass predicted physical aggression. Thus, early adolescents with high levels of testosterone were more likely to be socially dominant, especially if they had a large body mass. Those who had a large body mass were more likely to be physically aggressive, independently of their testosterone level. The observed pattern of correlations between testosterone, body mass, dominance, and physical aggression offers an interesting example of the complex hormone-physique-behaviour relations at puberty. They support the hypothesis that testosterone level and social dominance are related, and that the association between testosterone level and physical aggression is probably observed in contexts where physical aggression leads to social dominance.

Porcine reproductive and respiratory syndrome virus: routes of excretion

This study was conducted to delineate potential sites of exit and duration of shedding of porcine reproductive and respiratory syndrome virus (PRRSV). Two experiments of 6 pigs each were conducted. Pigs were farrowed in isolation, weaned at 7 days of age, and housed in individual HEPA filtered isolation chambers. In each experiment, 3 pigs served as controls and 3 were inoculated intranasally with PRRSV (ATCC VR-2402) at 3 weeks of age. In a first experiment, on days 7, 14, 21, 28, 35, and 42 post inoculation (PI), pigs were anesthetized and intubated. The following samples were collected: serum, saliva, conjunctival swabs, urine by cystocentesis, and feces. Upon recovery from anesthesia, the endotracheal tube was removed, rinsed, and the rinse retained. In the second experiment, the sampling schedule was expanded and serum, saliva, and oropharyngeal samples were collected from day 55 to day 124 PI at 14 day intervals. Virus was isolated in porcine alveolar macrophages up to day 14 from urine, day 21 from serum, day 35 from endotracheal tube rinse, day 42 from saliva, and day 84 from oropharyngeal samples. No virus was recovered from conjunctival swabs, fecal samples, or negative control samples. This is the first report of isolation of PRRSV from saliva. Virus-contaminated saliva, especially when considered in the context of social dominance behavior among pigs, may play an important role in PRRSV transmission. These results support previous reports of persistent infection with PRRSV prolonged recovery of virus from tonsils of swine.

A nonhuman primate model of type II excessive alcohol consumption? Part 1. Low cerebrospinal fluid 5-hydroxyindoleacetic acid concentrations and diminished social competence correlate with excessive alcohol consumption.

Developmental, biochemical, and behavioral concomitants of excessive alcohol consumption were investigated using a nonhuman primate model. The variables of interest were: (1) interindividual stability of cerebrospinal fluid (CSF) 5-hydroxyindoleacetic acid (5-HIAA) from infancy to adulthood, (2) effect of parental deprivation early in life on adult CSF 5-HIAA concentrations; (3) correlations between CSF 5-HIAA and 3-methoxy-4-hydroxyphenylglycol (MHPG) concentrations and alcohol consumption; and (4) correlation between the frequency of competent social behaviors and alcohol consumption. Twenty-nine rhesus macaques were reared for their first 6 months either with their mothers or without adults in peer-only conditions. At 6 and 50 months of age, each subject underwent a series of four, 4-day social separations. Cisternal CSF was sampled before and during the first and last separations; concomitantly, observational data were collected on social dominance behavior in the home-cage. When they reached 50 months of age, the monkeys were provided free access to a palatable alcohol solution daily for 1-hr periods before, during, and after the social separations. Before and after the 50-month separations, data were collected on all types of social behavior in the home-cage. Results showed that peer-reared subjects consumed more alcohol than mother-reared subjects during baseline conditions. Mother-reared subjects, however, increased their rates of consumption to equal peer-reared subjects' rates of consumption during the conditions of a social separation stressor. Peer-reared subjects also exhibited lower CSF 5-HIAA concentrations in infancy and adulthood than their mother-reared counterparts. With rearing condition held constant, interindividual differences in CSF 5-HIAA, MHPG, and homovanillic acid were stable from infancy to adulthood, and high rates of alcohol were consumed by the young adult monkeys with low CSF 5-HIAA and MHPG concentrations, particularly when the CSF was obtained during the social separations. High rates of alcohol consumption were also observed in subjects with infrequent social interactions and less competent social behaviors. In contrast to the human data, we found no gender differences in rates of alcohol consumption, nor in the correlations between alcohol consumption and the other variables. With some exceptions, findings from the study are generally consistent with predictions from Cloninger's type II model of excessive alcohol consumption in men with low CSF 5-HIAA, who also exhibit impaired impulse control and violent and antisocial behaviors.

Female choice of multiple male criteria in guppies: interacting effects of dominance, coloration and courtship

I experimentally examined the relative importance of social dominance, color patterns, and courtship behavior in male mating and reproductive success in the guppy Poecilia reticulata. Female choice of males is based on a complex set of behavioral and morphological traits. The results of 59 paired-male one-female visual choice and mating trials showed that male mating success was positively correlated with dominance, courtship intensity, and male coloration. Only dominant males engaged in full copoulations, and they sired two-thirds of the broods. An analysis of the paternity of broods and results of mating trials showed that a female's visual response when the sexes are separated by a glass partition is a good predictor of a male's reproductive success when the partition is removed and they are allowed to mate. A canonical correlation analysis of male behavioral and morphological traits indicated that female visual response and male mating success were positively correlated with male courtship and with agonistic behavior. However, the relative importance of color varied. Carotenoid and iridescent spots were important both in attracting the female's attention and in enhancing male mating success. Melanins were not correlated with either mating success or female response. There was a relatively low correlation (48%) between male behavioral and morphological variables and female response variables (full copulation and female visual response). These results suggest that female choice is subtle, and is based on a complex suite of male behavioral and morphological traits as well as on competitive interactions among males.

Relationships Between Social Dominance and Feeding Behaviour in Lactating Heifers During Periods of Heavy Competition

Previous research has shown that social dominance in dairy herds can be measured using replacements of one cow by another at feed stations (Rutter et al,1987). When there is competition for feed or space, the motivation to engage in physical and non-physical agonistic interactions will be stronger than if resources are freely available. When resources are limited, social dominance becomes very important and high ranking animals have priority.This becomes especially important after cows are returned from milking and/or when fresh feed is added when the number of cows is far greater than the number of feeding spaces (Campling and Morgan, 1981). This experiment aimed to further investigate the way in which social interaction between cows affects the feeding behaviour, particularly at times of peak feeding activity.

Changes in the social behaviour of drafthorse ( Equus caballus) mares coincident with foaling

It has been suggested that equid mares may undergo significant changes in social behaviour coincident with foaling. To examine this, two herds of drafthorse mares were observed prior to and after foaling. One herd consisted of six Belgian and two Percheron mares; the other consisted of 15 Belgian mares. Using focal animal sampling, a variety of agonistic and affiliative behavioural patterns and spatial relationships were examined. Results indicated no changes in social dominance or agonistic behaviour. There were changes in the patterns of affiliative behaviour among adults. Mares were more likely to make changes in their adult associates after foaling than before, and they were less affiliative to other mares after foaling. Furthermore, new dams put more distance between themselves and other adults and actively socially disengaged themselves from their herd. The results are consistent with the hypothesis that new dams are less socially active post-partum to facilitate the mare-foal bond and to prevent others from interfering with that bond.

Winter Distribution of Age and Sex Classes in an Irruptive Migrant, the Evening Grosbeak (Coccothraustes vespertinus)

I used bird--banding data (1955-1988) and logistic regression analyses to test the prediction that male Evening Grosbeaks (Coccothraustes v. vespertinus) winter farther north than females, and to investigate whether age groups (first-winter vs. older) differ in their winter distribution. Males wintered farther north than females in 28 of 31 winters in eastern North America (<85°W), and in 12 of 31 winters in central regions. Males typically comprised 53-65% of individuals wintering at the northern edge of the winter range, and 18-27% in the south. No differences in distribution between age classes were observed. Differential migration of the sexes in this species is most likely related to social dominance behavior or to the ability of the larger-bodied males to tolerate harsh winter conditions in northern regions.

Injection of diethylstilbestrol on the first day of incubation affects morphology of sex glands and reproductive behavior of Japanese quail.

Japanese quail eggs were injected with DES (0.9-1,000 micrograms) dissolved in 50-microliter of corn oil on day 1 of incubation. Higher doses of DES (250-1,000 micrograms) reduced hatchability to 37-33% compared to 61% for corn oil-injected controls. Lower doses of DES (0.9-125 micrograms) had no effects on hatchability. In a second study, eggs were injected with 0.9 or 1.9 micrograms of DES and the survivors were assessed up to 12 weeks posthatch. DES did not affect hatchability, but did increase mortality during the first 4 weeks posthatch. Females were affected more than males. At 10 days of age, open-field activity of some birds was examined. The acquisition and reversal of a visual discrimination task was studied at 6 weeks of age. DES had no effect on these measurements. Ten females from each group were chosen randomly to determine egg production over a single 28-day period beginning at 6 weeks of age. Exposure to DES blocked egg production in these birds. The oviduct weights of 12-week-old females were decreased by 50%, but ovarian weights were not affected. Testicular weights were not affected. In a third study reproductive behaviors and social-dominance behaviors of males were markedly attenuated in birds exposed to 0.48 or 1.9 micrograms DES in ovo.

Social dominance and predatory behavior of chacma baboons

Members of two chacma baboon ( Papio ursinus ) groups in Botswana were observed eating 28 vertebrate prey items over a three-year interval. Adult males captured most of the prey, including all impala and vervet monkeys, the largest prey. For adult males social rank is significantly correlated with the number of times individuals were the first observed consumers of a carcass; first and second ranking males were the first observed consumers of 15 of the 28 prey. Adult females obtained carcasses seven times and lost possession of them five times. The results suggest that the lincar dominance hierarchy of these troops limits the meat eating potential for most troop members.

Social dominance and female reproductive behaviour in rhesus monkeys ( Macaca mulatta)

The relationship between dominance rank and female sexual behaviour was examined in rheusus monkeys ( Macaca mulatta) living in a social group. High-ranking females engaged in copulatory series as frequently as lower-ranking females. Furthermore, lower-ranking females copulated with as many available males as did high-ranking females. Social rank did appear to influence the pattern of sexual activity exhibited, in that copulatory series were more often initiated by the higher-ranking animal of the mating pair. Copulatory series involving high-ranking females were characterized by more mounts by males and were longer in duration. Higher-ranking animals interfered more often with copulatory series involving other animals, but such interference was not effective in preventing completion of the series. These data indicate that any reproductive advantage conferred to high-ranking females is not the result of sexual competition in social-living rhesus monkeys.

Altrusim in children: A naturalistic study of reciprocation and an examination of the relationship between social dominance and aid-giving behavior

Dyadic fights between children on a playground may be terminated by intervention of a third child on behalf of the one losing the fight. A small cluster of children repeatedly served as aid-givers within the playgroups monitored in study 1; little reciprocity was observed within this situational context. Study 2 was performed to examine the relationship between aid-giving and playgroup social status. Children who intervened during fights were consistently rated as dominant members of the playgroup by naive raters who viewed randomly selected videotaped segments of general playgroup activity. Another index of dominance, visual regard by other members of the playgroup, also provided evidence that documented the relationship between peer group social status and aid-giving. The generality of this relationship was examined in study 3. Children ranked as good leaders by their fourth-grade classmates demonstrated significantly more prosocial sharing than lower ranked peers. Thus, status within a social group hierarchy may be an important dimension related to a variety of prosocial behavior exhibited by children.

Flock Stability in Relation to Social Dominance and Agonistic Behavior in Wintering Dark-Eyed Juncos

Abstract This paper examines some consequences of changes in the membership and location of winter flocks of Dark-eyed Juncos (Junco hyemalis). Among captives, intragroup social relationships seldom were affected by separation from or subsequent reunion with another portion of the home flock, by amalgamation with or separation from a foreign flock, or by changes in flock location. Foreign flock members usually were subordinate to, and preferentially attacked by, residents. Juncos rejoining their home flocks after a 1-week separation retained their previous social positions but engaged temporarily in a disproportionate amount of agonistic behavior with former flockmates. Some proximate and ultimate implications of winter flock stability in juncos are discussed in the light of these and other findings. Social and ecological costs that may be incurred by juncos attempting to change their flock membership or home range during the winter should select for behavior that reduces the likelihood of such changes, including geographic differentiation in the migratory habits of the sexes.