Male–male combats in a polymorphic lizard: residency and size,but not color,affect fighting rules and contest outcome

Theoretical models predict that the outcome of dyadic agonistic encounters between males is influenced by resource‐holding potential, resource value, and intrinsic aggressiveness of contestants. Moreover, in territorial disputes residents enjoy a further obvious competitive advantage from the residency itself, owing to the intimate familiarity with their territory. Costs of physical combats are, however, dramatically high in many instances. Thus, signals reliably reflecting fighting ability of the opponents could easily evolve in order to reduce these costs. For example, variation in color morph in polymorphic species has been associated with dominance in several case studies. In this study, we staged asymmetric resident‐intruder encounters in males of the common wall lizard Podarcis muralis, a species showing three discrete morphs (white, yellow, and red) to investigate the effects of asymmetries in color morph, residency, and size between contestants on the outcome of territorial contests. We collected aggression data by presenting each resident male with three intruders of different color morph, in three consecutive tests conducted in different days, and videotaping their interactions. The results showed that simple rules such as residency and body size differences could determine the outcome of agonistic interactions: residents were more aggressive than intruders, and larger males were competitively superior to smaller males. However, we did not find any effect of color on male aggression or fighting success, suggesting that color polymorphism in this species is not a signal of status or fighting ability in intermale conflicts. Aggr. Behav. 35:274–283, 2009. © 2009 Wiley‐Liss, Inc.     

Pheromone‐mediated intrasexual aggression in male lizards,Podarcis hispanicus

Sex recognition is based on color signals in many species of lizards. However, olfactory stimuli are also clearly involved, and many species might rely primarily on chemoreception. We aimed to examine whether color pattern or odors, or a combination of both factors, induce the aggressive response of males of the lizard P. hispanicus. We experimentally manipulated the coloration and odor of male P. hispanicus, thereby creating groups with all combinations between coloration and odor of males or females. Using data from staged encounters, we compared the responses of resident males to the experimental groups of manipulated males and their response to unmanipulated individuals (males and females). Responding males reacted significantly more aggressively to intruders with male odors independent of their coloration, whereas intruders with female odors did not elicit aggressive responses but were preferentially courted, irrespective of their actual sex and body coloration. In addition, intruders with female odors elicited a higher number of tongue‐flick explorations than male odor ones. Comparisons with unmanipulated male and female intruders agreed with these expectations. Therefore, at least at close range, odoriferous cues seem to be more important than color patterns in sex recognition and intrasexual aggression by male P. hispanicus. We suggest that this might be a pattern commoner than expected in many species of reptiles.Aggr. Behav. 28:154–163, 2002. © 2002 Wiley‐Liss, Inc.     

Maternal aggression toward infanticidal males of different social status in wild house mice (Mus musculus domesticus)

Maternal aggression was examined in wild female mice (Mus musculus domesticus) derived from animals trapped in Alberta, Canada. Lactating females were tested for their behavior toward intruder males during the time of postpartum estrus while housed in a two-cage apparatus containing a defensible nest area. Prior to being used as intruders, sexually naive males were screened for their behavior toward a newborn pup (83% exhibited infanticide). Only infanticidal males were then housed in pairs and allowed to establish a dominance hierarchy. Dominance status was further verified by a urine marking test. The dominant and subordinate infanticidal males were then placed into a lactating female's cage and observed for 1 hr. The test was terminated immediately when a male began to attack the pups. Lactating females attacked the males in both groups, but subordinate males received more intense attacks than dominant males. Dominant males elicited significantly more fear/defense behavior than subordinate intruders. All of the dominant males and only one submissive male attacked the pups. Females were thus successful in blocking infanticide only by infanticidal subordinate males. Since females do not persist in attacking males with high fighting ability, one function of maternal aggression could be to assess the fighting, and resource holding, potential of a future mate. © 1994 Wiley-Liss, Inc.     

Sexual Assault,Overweight, and Suicide Attempts in U.S. Adolescents

Associations between overweight, sexual assault history, and suicide attempts were examined among 31,540 adolescents from the combined 2009 and 2011 nationally representative Youth Risk Behavior Surveys samples. These variables have not previously been studied concurrently. It was hypothesized that overweight and sexual assault, together, would interact and result in increased suicide attempts. Findings across analyses included (a) no significant associations between sexual assault and overweight in females or males (p = .65 and p = .90, respectively), (b) statistically significant associations between female (but not male) overweight status and suicide attempts (p = .001), (c) a strong association between sexual assault and suicide risk in males (p < .001) and females (p < .001), and (d) an elevated risk for suicide in overweight males with co‐occurring sexual assault, with over 33% of males with such histories attempting suicide. Preliminary findings have powerful implications for research and secondary prevention.     

High maternal aggression in dwarf hamsters (Phodopus campbelli and P. sungorus)

The defense of offspring, termed maternal aggression, is a highly conserved behavior in mammals, including rodents. This study examined relative levels of maternal aggression in two closely related dwarf hamster species, Phodopus campbelli and P. sungorus, that normally inhabit high latitude, boreal environments. When tested with first litters and with the breeder male remaining with the female (for P. campbelli the male is necessary for successful rearing of offspring), both species exhibited high levels of maternal aggression with average duration of aggressive behavior>80 sec for a 10 min test. For P. sungorus, males are not required to rear offspring. P. sungorus females with either one or multiple litters (singly housed after impregnation) exhibited significantly higher levels of aggression (>300 sec) relative to females co‐housed with the sires. In terms of species differences in attack style, P. campbelli exhibited a boxing or clawing strategy for ～50% of total attack time, but for P. sungorus, this form of attack occurred<5% of the time. For P. sungorus, attacks to the vulnerable belly and flank constituted>90% of all attacks, but these regions were attacked ～50% of the time for P. campbelli. A survey of levels of maternal aggression of rodents in other genera suggests that maternal aggression in Phodopus is at the high end of the spectrum. Results of this study suggest that the presence of the breeder male may actually suppress aggression in P. sungorus. This fact, as well as its high level of aggression and its distant relationship to mice and rats, suggest P. sungorus as a possible model for future studies on the neurobiological basis of maternal aggression. The relationship between the high rates of maternal aggression and life history strategy in Phodopus is discussed. Aggr. Behav. 00:000–000, 2005. © 2005 Wiley‐Liss, Inc.     

Offensive and defensive bite-target topographies in attacks by lactating rats

The attacks by resident lactating Wistar rats on sexually naive conspecifics of both sexes were examined. Male and female intruders were equally attacked in terms of frequency and number of bites, but the topographies of biting seen in these encounters were different. Similarly to male-male agonistic interactions, females were attacked in a fashion which avoided bites to the head and snout (“offensive” attack), whereas males were frequently bitten on such vulnerable regions (“defensive” attack). This dichotomy in bite pattern suggests that different motivations and functions underlay maternal aggression in these situations. The defensive attack on males may be a deterrent to infanticide since only male intruders counterattack lactating females and kill their pups. The attack on females may be concerned with resource competition.     

Psychophysiological correlates of organizational change and threat of unemployment among police inspectors

The study examined psychosocial work-conditions and physiological reactions among thirty-six police inspectors (median age 45 years, 81% males) who participated in a reorganization. At this time, subjects were threatened by unemployment and had to reapply for their positions in a new police district. Data were collected during the reorganization and at three years follow-up, by means of questionnaires (Stress Profile) and blood samples. The blood samples were used to determine serum levels of gammaglutamyltransferase (GGT), glucose, lipids, prolactin, testosterone and cortisol. The results show a positive association betweenworry about employment and symptoms ofburnout during the reorganization. Mean scores for the Stress Profile sub-scalesworry about employment (p<.01) andwork-load (p<.05) decreased between measurements but an impairment inrelationships with management was noticed (p<.05). No significant changes were observed in terms of self-rated health complaints. Significant decreases in total cholesterol (p<.0001), LDL-cholesterol (p<.0001), LDL/HDL-ratio (p<.01), prolactin (p<.0001), as well as increases in testosterone (p<.01) and cortisol (p<.001) were observed for the whole sample. Glucose decreased with marginal significance (<.07). Controlling for age and gender, multivariate regression analyses showed that subjects who reported deteriorations insatisfaction with work manifested the most modest decreases in prolactin (p<.05). Also, the decrease in glucose was larger for subjects who experienced impairments in,satisfaction with work (p<.05), information (p<.05), task-oriented leadership, (p<.05), andrespect and dignity (p<.05). Subjects who perceived deteriorations in theethical and moral standards of the organization increased their cortisol level to a lower degree than their counterparts (p<.05). Favorable changes in employment status and psychosocial work environment seem to be related to improved physiological functioning.     

Behavioral tactics control the energy costs of aggression: The example of Macropodus opercularis

Previous experiments on Betta splendens have shown that energy expenditures related to aggression are under social control. The present paper examines the biochemical energetics of social cohabitation in groups of Macropodus opercularis. The species is closely related to Betta splendens, however, dominants use somewhat different behavioral tactics against intruders. In contrast to Bettas, submissive Macropoduses are not harassed by dominants, but are confined to the bottom of the tank. This results in a reduced rate of oxygen consumption in defeated animals (Anabantid fish mainly use atmospheric oxygen). The only metabolic change, compared to isolated controls, is a reduction in hepatic glycogen content. Submissive animals have shifted carbohydrate metabolism towards anaerobic glycolysis. Substantial reductions in muscle proteins, lipids, and glycogen occurred in submissive Betta splendens. Thus, the sharp difference in behavioral strategy results in a sharp difference in the energetic consequences of aggression. A theory is presented regarding the possible role of energetic constraints in the control of behavior. © 1996 Wiley-Liss, Inc.     

The potential effects of protected nests and cage complexity on maternal aggression in house mice

I studied the behavior of nursing house mice (Mus musculus) in captivity and used a two-by-two factorial design to test the hypothesis that the combination of a protected nest along with a chance for the intruders to retreat would improve the ability of resident females to defend their litters from infanticidal males. A chance for the intruder to retreat was manipulated by testing the resident females in either a single- or a two-compartment cage. The effect of a protected nest was examined by providing females with a nest box having a narrow entrance. During each test, an infanticidal adult male was introduced into the cage of a resident female and her pups. I observed that neither the presence of a protected nest nor the chance for the intruders to retreat to a different compartment, or a combination of the two, increased the ability of a female to defend her litter against an intruder male. Moreover, neither of these two factors influenced the overall behavior of the resident females. I obtained similar results after using data from previous studies to examine the influence of both of these factors on the efficiency of maternal aggression. Overall, these two approaches showed that females are often unable to prevent intruders from committing infanticide. I discuss the validity of the hypothesis that maternal aggression evolved as a mechanism to protect offspring from infanticide. Aggr. Behav. 24:385–396, 1998. © 1998 Wiley-Liss, Inc.     

Violent video games and anger as predictors of aggression

Considerable research has demonstrated that playing violent video games can increase aggression. The theoretical framework upon which a good deal of this research has rested is known as the General Aggression Model (GAM; [Anderson, C. A., & Bushman, B. J. (2002). Human aggression. Annual Review of Psychology, 53, 27–51]). The current study tested an assumption of the GAM by examining if the dispositional trait of anger moderated the relation between violent video games and aggression. A total of 167 undergraduate students (79 females, 88 males) first completed a measure of anger and were then randomly assigned to play either a non-violent or violent video game. After the video game play period, participants completed ambiguous story stems in order to assess aggression. Consistent with predictions of the GAM, anger significantly moderated the effect of video game violence on aggression. Specifically, participants who were angry were more affected by violent video games than participants who were not angry.     

Infanticide and maternal aggression: Synchrony of male and female reproductive strategies in mice

Thirty-six percent of male mice from three strains attacked newborn pups sired by another male. No male attacked its own offspring. Females did not show differential aggression toward males likely (strangers) or unlikely (sires) to attack their pups. Both forms of aggression were unaffected by housing in rooms which did or did not contain the aggression targets. The three strains differed in strength of maternal aggression but not in the incidence of infanticide. Females showed more aggression when mated with males of the same, rather than a different, strain but no differences with intruders of the same or a different strain. Infanticide by males is best viewed as a postcopulatory, intermale-competition strategy, and maternal aggression as a counter strategy.     

Sex differences in aggressive behaviour in various strains of mice

Two nonalbino inbred (C57 BL/6 and C3H/He) and one albino strain (Swiss) of mice were compared for female aggression toward intruders: 1 in period of lactation, 2 in nonlactating state and (3) in nonlactating state but previously rubbed with urine of lactating females; and for male aggression toward familiar or unfamiliar opponents. The results showed that resident females of the C57 and Swiss strain vigorously attack lactating intruders introduced into their cages. This effect was mediated by urinary cues emitted by the latter mice. It was also shown that Swiss residents displayed aggression towards nonlactating females, irrespective of their strain. Groups of C57 residents reacted most aggressively towards Swiss females, less aggressively towards C3H intruders, but did not show any aggression towards their own nonlactating conspecifics. In contrast, none of the C3H resident female groups displayed aggression towards intruding females of any category or strain. The results also showed that the males of the three strains displayed little (Swiss and C3H) or no aggression (C57) towards familiar opponents, whereas they directed increased aggressive responses towards unfamiliar ones. Comparisons among the three strains of mice revealed that Swiss males were the most aggressive in either situation. On the other hand, the finding that C3H males showed aggressive responses suggested that male and female aggression are, in this strain, under separate genetic or hormonal control.     

The aggression test as a taxonomic tool: Evaluation in sympatric and allopatric populations of wood-ant species

Ant-workers of Formica lugubris and F. rufa from colonies living sympatrically (from the same area) and allopatrically (from different areas) were tested in pairs using a laboratory aggression test. The aim was to verify whether sharing the same area of origin influences the relationships among heteroeolonials between and within these species which belong to the F. rufa group. The results suggest that a similar degree of agonistic behaviour (ritualised aggression) was shown in sympatric and allopatric conspecific dyads of both species studied. The interactions between F. lugubris and F. rufa were characterised by a low level of overt aggression both in sympatric and allopatric pairs, confirming the interspecific tolerance observed in our previous studies on these wood-ant species. This reduced aggressiveness between workers of F. lugubris and F. rufa coming from the same or a different area can be interpreted on the basis of their sharing common signals, such as odours and patterns of behaviour. Therefore, their mutual tolerance and acceptance can be indicative of a phylogenetic closeness between such species. We propose that an aggression test can be a valid tool for elucidating systematic problems in this taxonomically difficult group of ants. © 1993 Wiley-Liss, Inc.     

The aggression test as a possible taxonomic tool in the Formica rufa group

The intra- and interspecific aggressive behavior of Formica polyctena, a species of the Formica rufa group, was analyzed and quantified both in the laboratory and in the field. This behavior was used as a potential taxonomic tool for gaining a better understanding of the phyletic relationships among the species within the group. No overt aggression was recorded toward members of the same species. To examine interspecific relationships, F. polyctena was first confronted with F. cunicularia, to ascertain its aggressiveness toward a distantly related species. All such encounters led immediately to overt and prolonged attacks with virtually no initial mutual inspection. This suggests that recognition of strangeness of the unrelated species is almost immediate in F. polyctena, as previously observed in F. lugubris and F. rufa toward the same antagonist. Subsequently, F. polyctena was contrasted with F. lugubris and F. rufa (also belonging to the F. rufa group) in order to compare these related species. Fierce attacks accompanied by all the elements of conflict behavior were observed in all encounters. Moreover, the degree of aggression in the field was higher than in laboratory-paired ants, possibly because of a territorial effect. These data and our previous and similar research indicate that the relationships between F. lugubris and F. rufa are closer than between these two species and F. polyctena. In considering different viewpoints on this problem, the validity of the aggression test is discussed and the opportunity to compare levels of aggressiveness among strictly sympatric samples of red wood ant species gathered from the same ecological environment are considered.     

Influence of school-level and family-level variables on Chinese college students’ aggression

With the frequent occurrence of campus violence, scholars have devoted increasing attention to college students’ aggression. This study aims to estimate the prevalence of aggression in Chinese university students and identify factors that could influence their aggression. We can thus find methods to reduce the incidence of college students’ aggression in the future. A multi-stage stratified sampling procedure was used to select university students (N = 4565) aged 16–25 years in Harbin. The Aggression Questionnaire, the Adolescent Self-Rating Life Events Checklist and the Social Support Revalued Scale were used to collect data. Females reported lower levels of aggression than males (p < .001). A multiple linear regression analysis was conducted to determine the influence of factors of aggression, and the model was highly significant (R² = .233, Ad R² = .230, p < .01). The results show that the aggression is affected by gender, family-level and school-level variables. Aggression scores are significantly correlated with not only family-level or school-level variables independently, but their combination as well. We find that the risk factors for aggression include a dissatisfying profession, higher levels of study pressure, poor parental relationships, poor interpersonal relationships, the presence of siblings, punishment, health maladjustment, less subjective support, and lower levels of utilization of social support.     

Social dominance and individual aggressiveness

Male rats exhibiting high, moderate, or low levels of offensive aggressive behavior in interactions with intruders in their home cage were grouped in mixed-sex colonies with 1 male of each aggression-level group in each colony. Agonistic interactions measured 1, 2, 3, 7, 14, 21, and 22 days after colony formation indicated that highly aggressive males on pretests continued to be more aggressive, becoming the dominant colony male in five of seven colonies and attacking intruders more often than less aggressive males. In the two remaining colonies the moderately aggressive male became dominant. This relationship, which was consistent over a number of indices, including offensive and defensive behaviors, and wound counts and wound sites, was seen even when a substantial weight differential favored the less aggressive animal. Dominance relationships were rapidly established and within-group fighting declined significantly over the 21-day test period. Pretest offensive levels also influenced the behavior of subordinates, with high or moderately aggressive subordinates showing more defense in interactions with dominants and receiving more wounds than did low-aggression subordinates. Dominant males also showed more defense in interacting with those subordinates which had been more aggressive during pretests. This pattern of results suggests that aggression level of the subordinate as well as the dominant may be an important factor determining the intensity of agonistic interactions in male rats.     

Psychometric properties of the cyberbullying triangulation questionnaire: A prevalence analysis through seven roles

This study explores the psychometric properties of the Cyberbullying Triangulation Questionnaire (CTQ), which measures and triangulates the roles of cybervictimization, cyberaggression, and cyberbystanding. The study sample was composed of 5,036 Spanish students with a mean age of 14.19 years (SD = ±1.7; range = 10–23 years). Confirmatory factor analysis of the three correlated‐factor model yielded a high goodness of fit. Reliability as measured by Omega coefficients was adequate (>0.94). The measurement model was invariant for the two age groups (10–14 years and 15–23 years). Cybervictimization and cyberaggression correlated with offline victimization and aggression (r = 0.49; p < 0.001; r = 0.57; p < 0.001, respectively). The results show that the most prevalent cyberbystanding subrole was that of the Defender of the Victim (54.6%), and that cyberaggression and cyberbystanding were more prevalent among male adolescents (p < 0.001). The lack of parental control over children's use of the mobile phone was associated with cyberaggression (p < 0.001).     

Effects of reactivity to dorsal stimulation and social role on aggressive behavior in laboratory rats

Rats were selected on the basis of reactivity to dorsal tactile stimulation and then tested in a resident-intruder paradigm. While reactivity of residents did not influence the occurrence of agonistic behaviors or wounding of residents and intruders, reactivity of intruders did affect offensive and defensive patterns of interactions and the wounds sustained by residents and intruders. Subsequent to resident-intruder testing, rats were tested for shock-induced aggression. The pattern of the results and the results of additional experiments demonstrated that resident-intruder experience could affect subsequent shock-induced aggressive behavior.     

Conflict and postconflict behaviour in two lemur species with different social organizations (Eulemur fulvus and Eulemur macaco): A study on captive groups

Although the brown lemur (Eulemur fulvus) and the black lemur (Eulemur macaco) share many life parameters and are genetically closed, they show considerable difference in social organization. Dominance relationships with no systematic effect of gender characterize the former, whereas the latter is based on female dominance. The present study was done on two captive groups of brown lemurs and one semi–free‐ranging group of black lemurs. To reveal links between the specific pattern of social organization and agonistic behaviors, agonistic interactions were analyzed for each species as for their context of occurrence, symmetry, initiation, and outcome. The effect of gender in the initiation of conflicts appeared as the only notable interspecific difference, aggression being mostly initiated by females in E. macaco and by males in E. fulvus. Conflict outcome was generally in favor of the initiator, regardless of gender in both species. The analysis of postconflict behaviors revealed conciliatory processes in the brown lemur, whereas reconciliation seemed to be absent in the black lemur, a characteristic shared with the ring‐tailed lemur (Lemur catta), another lemur species with female dominance. Aggr. Behav. 28:62–74, 2002. © 2002 Wiley‐Liss, Inc.     

Intruders of differing reproductive status alter aggression differentially in early and late pregnant mice

Independent groups of early and late pregnant mice, housed individually, were observed with an intruder in their home cage. The intruders were either males, virgin, early, or late pregnant females. Male intruders were sniffed less, but more frequently and more severely attacked, than any type of female intruder, both by early and by late pregnant residents. While early pregnant females behaved similarly with the three types of female intruders, late pregnant animals treated them differently: they showed practically no aggression to late pregnant intruders, more to early pregnant ones and were most aggressive towards virgin female intruders. The possible relation of these findings to reproductive behaviour is discussed.