Female behavior in populations of mice in the presence and absence of male hierarchy

Female aggression may be the regulator of population size in small mammals. Freely growing populations of house mice showed several differences in aggressive female behavior in the presence and the absence of a male hierarchy. Territoriality in females and not in males appeared to maintain social order and regulate population density. Certain females were seen patrolling and guarding the territory and chasing and fighting with both male and female intruders. These females did not fight amongst themselves, suggesting that they were not fighting for rank (as do the males) but for territory. Although these aggressive females produced young, the pups were neglected, and few were weaned. The non-aggressive females were the successful breeders. Aggression by the females only occurred when there was reproduction and increased densities. Assembled females with no males present never show this aggression. The occurrence of “male-type” behavior became most apparent when the males were removed at peak population densities. The removed males were then castrated and injected with testosterone cyprionate. Doses were increased by population cage, and therefore all males returned to each freely growing population were given the same dose. The males given oil placebo injections showed no return of a male hierarchy and the females showed high levels of aggression toward them. Males injected with testosterone cyprionate showed return of male aggression and fighting and mounting of females. But the new “dominant” females continued their patrols and chased males away from their territories and did not permit these males to mount. Male-male fighting consisted primarily of frontal attacks to the face and roll and tumble fights. Female-male aggression consisted primarily of attacks to the posterior region targeted at the base of the tail and the genitals of the male. The males were rarely seen attacking females and then only during mating. Females only attacked each other in defense of their territories.     

Effect of conspecific sex on aggression during pregnancy and lactation in golden hamsters

The effect of conspecific sex on maternal aggression in hamsters was determined by comparing the frequency of aggressive responses by dams continuously housed with either a virgin male or female cagemate during pregnancy and lactation. Dams easily established aggressive dominance over male cagemates soon after pairing, and their aggression was low thereafter for the duration of pregnancy and lactation. The aggression of dams with females, on the other hand, tended to fluctuate with highs during mid pregnancy and mid lactation and lows around birth. When dam aggression was low around birth, female cagemates frequently became aggressively dominant, and several dams lost their litters. The higher aggression of dams toward females than males is probably a reflection of greater intrasexual competition for environmental resources that includes pups.     

Effects of early exposure to intermale aggression on the aggressiveness of adult male mice varying in their genetic disposition for aggressive behavior

This study examined whether adult male aggression is influenced by either visual or olfactory exposure in early postnatal life to brief episodes of aggression. Another focus of interest was the interplay between a genetic disposition for aggressive behavior and early exposure experiences. The subjects used in the study were male mice of the 49th generation of selection for high (Turku Aggressive, TA) and low (Turku Non-Aggressive, TNA) levels of aggressiveness. Moderately aggressive males of the parental strain (Normal, N) were also used. Subjects of each strain were exposed from 21 to 32 days of age to fighting males either behind a wire mesh or glass screen. Control subjects were isolated during the entire experimental period. At 90–100 days of age, each subjects was tested three times for its aggressiveness. Exposure to fighting males behind a wire mesh screen enhanced later aggressiveness of juvenile male mice. Juveniles exposed solely to visual cues were comparable to isolates, both groups showing less adult aggression. Early experience and the genetic disposition for aggression were correlated; TA males showing the greatest increase in aggressive behavior. The role of early olfactory learning is discussed. © 1993 Wiley-Liss, Inc.     

70-kHz vocalizations by male mice do not inhibit aggression in lactating mice

Two experiments investigated the relationship between adult male 70-kHz vocalizations and aggression by lactating female mice (Mus domesticus). Intact, vocalizing males, surgically devocalized males, and naturally nonvocalizing males were used to assess the effects of high frequency vocalizations on maternal aggression. The emission of high frequency vocalizations promoted aggressive behavior by the females. In both experiments, lactating females attacked the vocalizing males more rapidly and showed a higher incidence of aggressive behaviors toward these males than they did to the nonvocalizing male. We suggest that these vocalizations are only one of many situational cues that the female uses to determine her final behavioral response.     

Does bullying others at school lead to adult aggression? The roles of drinking and university participation during the transition to adulthood

This study uses a three‐wave longitudinal study of young Australians to identify developmental processes underlying the relationship between school bullying and physical aggression in early adulthood. The central question is whether and how drinking and participation in work or university study disrupt or entrench aggressive pathways from school bullying to adult aggression. Self‐report data were collected from 88 females and 63 males (N = 151) during childhood (age 10), adolescence (age 14), and early adulthood (age 20). Participants who bullied other students during childhood and adolescence, or during adolescence only, reported more physical aggression during early adulthood than those who never bullied. However, those who had bullied during adolescence only reported significantly higher adult aggression if they were also drinking at above‐average frequencies. Conversely, participation in university, compared to being in the workforce, was associated with significantly less adult aggression among the at‐risk groups. Findings suggest that particular contexts during early adulthood can offer youth on aggressive trajectories (as evidenced by bullying at school) unique opportunities to turn their behaviour around. Other contexts, however, may exacerbate aggressive behaviour patterns.     

Rare male aggression directed toward females in a female‐dominated society: Baiting behavior in the spotted hyena

Spotted hyenas (Crocuta crocuta) are gregarious carnivores. The females are socially dominant to males, and adult males rarely direct aggression toward adult females. This study analyzed all cases in which adult immigrant males behaved aggressively toward adult females in a large population of free‐living hyenas in Kenya, observed for 11 years. Our goals were to describe the conditions under which male attacks on females occur, and address possible adaptive functions. Most aggression directed by adult immigrant males against females occurred when coalitions of two or more males attacked a single adult female, who typically responded by defending herself and fighting back. Male aggression against females frequently occurred at sites of ungulate kills, but males never behaved aggressively toward females over food, and all male attacks on females were unprovoked. Although no mounting or other copulatory behaviors ever occurred during or immediately after an attack, the number of male attacks on females peaked around the time of conception. Daily rates at which males attacked females did not vary with female social rank. However, daily attack rates did vary significantly with female reproductive state, and the highest rates of male attack on females were observed during the two stages of the reproductive cycle during which females were most likely to conceive litters. The adaptive significance of male aggression against females in this species remains unknown, but a tight association between male attacks on females and a female's time of conception provides strong evidence of some role for male aggression in hyena sexual behavior. In particular, our data are consistent with hypotheses suggesting that male aggression toward females in this species either serves to inform females about male fitness or represents sexual harassment. Aggr. Behav. 29:457–474, 2003. © 2003 Wiley‐Liss, Inc.     

The introduction of a group of alien mice (Mus musculus L.) into hierarchically organized groups of five male mice

Groups of 3 male or female Mus musculus were introduced into hierarchically organized colonies of 5 male mice for a period of 8 days. The colonies were of 2 kinds; high-level aggressive (HLA), which had been set up 3 days prior to the introduction of the aliens, and low-level aggressive (LLA), which had been established for 21 days before strangers were introduced. Both males and anestrous females were attacked, but males were attacked 5 times more frequently than females. In HLA colonies most of the attacks on the aliens were by the dominant; in LLA colonies there was no difference in the behavior of dominant and subordinate mice toward strangers. Both aggression toward aliens and intracolony aggression declined over the 8 day experimental period. In HLA colonies the dominant mouse mounted females 5 times more frequently than did either his subordinates or male mice in the LLA colonies. In HLA colonies aliens huddled with subordinates to form a single colony with 1 dominant and 7 subordinates. In LLA colonies alien males remained as a discrete group spatially separated in the cage. Female aliens were incorporated into the main colony. In all cases dominant male mice made more attacks on aliens as compared with familiar mice.     

Factors in childhood that predict later criminal behavior

A follow-up study was conducted on the aggressive and delinquent behavior of an original sample of 220 pupils of two age groups. The subjects were 7 and 9 years old in 1978 when they were interviewed for the first time. The present paper focuses on predictors of the subjects' aggressive and criminal behavior in adolescence and in young adulthood. Four different groups of variables were chosen as possible predictive factors: 1) parental aggression, punitivity, and attitudes of rejection toward the child, 2) previous acts of aggression by the subjects, 3) the viewing of violence on television during childhood, and 4) aggressive, indifferent, and delinquent behavior in adolescence. Physical aggression in adolescence and the number of arrests and traffic violations in young adulthood were used as dependent variables. The analyses established that for the male subjects, the best predictor of physical aggression in adolescence was previous aggression, whereas for the female subjects the best predictor of physical aggression in adolescence was previous viewing of violence on television. The number of arrests in young adulthood was best predicted for the male subjects on the basis of previous aggression and viewing of violence on television. The best predictors of the number of arrests in young adulthood for the female subjects were, apart from previous aggression and viewing of violence on television, also aggressive and delinquent behavior in adolescence as well as parental aggression, punitivity, and attitudes of rejection. The results emphasize the importance of the atmosphere of socialization in childhood and previous aggressive behavior as significant predictors of physical aggression in adolescence and criminal behavior in young adulthood. © 1996 Wiley-Liss, Inc.     

Sex,race, and experiences of aggression

Most previous research on sex differences in experienced aggression has confounded the sex of the aggressor and of the target by considering married or dating couples. In the present study, black and white male and female college students were asked about specific acts of aggression which they had received from or directed toward a male or female. As predicted, males were likely to have both received and exhibited more forms of aggressive behavior, although females were somewhat more likely to have been honked at, to have been forced by a male to have sex, and to have slapped someone. Few racial differences were found, but it appeared that blacks might have been relatively more likely to exhibit physical aggression and whites to exhibit nonphysical aggression. Some differences were found in specific behaviors directed toward and received from males and females, but in general subjects said that they received more aggressive behaviors than they directed toward others. © 1992 Wiley-Liss, Inc.     

The relationship between family aggression history and expressed aggression among college males

The relationship between family of origin aggression and aggression across numerous relationship types was examined among a sample of 197 college‐aged males. Participants completed a self‐report questionnaire assessing the frequency and severity of family aggression (aggression between parents, parental aggression directed toward participants), as well as the frequency and severity of participants' aggression across a number of relationship types (dating, friends, strangers, people in bars, co‐workers, bosses, police officers). The results of the present study indicate that a substantial proportion of college‐aged males report a history of aggressive behavior, both in dating/spousal relationship and other‐relationship types. Analyses revealed that observing parental aggression and receiving aggression from parents was related to aggression in dating relationships. However, only received aggression from parents was related to more general aggressiveness in other non–dating/spousal relationship types. The pattern of findings also suggest that it is important to assess the aggressive behavior of both parents to get a better understanding of the link between family aggression and later expressed aggression. Aggr. Behav. 25:255–267, 1999. © 1999 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.     

Intersexual aggression and male sexual activity in captive rhesus macaques

Rape has been posited to be an outgrowth of male reproductive strategies. Forced copulations may have evolved as a consequence of the low parental investment made by males in producing and raising offspring. We designed a laboratory experiment which paired rhesus macaque males with females in order to assess the influence of intersexual aggression on male sexual activity. Younger and older adult males had comparable levels of sexual behavior, but younger males were more aggressive towards females than were older males. In addition, females threatened younger males more than older males. Male attacks on females did not result in sexual intercourse. On the contrary, a negative correlation existed between male aggression towards females and male success at achieving intromissions. Female aggression towards males appeared to be an effective tactic which reduced the chances of sexual intercourse. We conclude that intersexual aggression acts either as a mechanism of dominance assertion or as a means to increase spatial distance between individuals. These data do not support the idea that rape in humans has an evolutionary foundation derived from male reproductive strategies.     

Response of male and female Siberian hamsters towards pups

The influence of sex, reproductive maturity, and parental experience on the behavior of Siberian hamsters (Phodopus sungorus sungorus) toward strange pups was examined in this study. Immature, mature, or parentally experienced male and female Siberian hamsters were presented with 3- to 8-day-old pups. We recorded pup carrying during the initial 10 min, nesting with pups after 8 or 14 h, and attacking pups during the test period. Among inexperienced animals, more mature males attacked pups than did immature males or mature females. Parental experience significantly decreased pup attacks by males and increased nesting with pups by both males and females. Repeated testing did not modify the responses to pups. We conclude that in Siberian hamsters both caretaking and aggressive responses to pups may be shown by immature and mature animals of both sexes. Parental experience resulted in increased caretaking by males and females and decreased aggressive responses by males.     

The association of irritability and impulsivity with suicidal ideation among 15- to 20-year-old males

Information on the association of impulsivity and measures of aggression with suicidal ideation in adolescents and young adults is limited. Data were gathered from a community sample of 625 adolescent and young adult males. Analyses were based on multivariate generalized estimating equations. Impulsivity and irritability were associated strongly with suicidal ideation after accounting for alcohol dependence and other aggression-related constructs including psychopathy. Given that irritable, impulsive adolescent males appear to contemplate suicidal behavior, their heightened suicide risk may be anticipated and mitigated.     

Ethnicity,gender, and evaluations of aggression

In order to investigate some of the ways in which ethnicity and gender influence interpretations of aggression, 363 Anglo and Hispanic university students responded to a questionnaire soliciting their evaluations of aggression in three situations. Consistent with previous research and with the stereotype of machismo, Hispanics, particularly Hispanic males, were more likely to endorse some aggressive behaviors than Anglos. However, the same pattern of gender influences emerged for both ethnic groups. As predicted, males were more aggressive and more supportive of fighting back and punishing an aggressor than females, whereas females were more likely to show self-control about aggression and to endorse restraint. Respondents, particularly males, said that they would behave more aggressively toward a male, and they encouraged a male to behave more aggressively. These results are consistent with the social constructionist view that performance and evaluations of aggression are largely influenced by cultural factors. © 1995 Wiley-Liss, Inc.     

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.     

Aggression toward female partners by at-risk young men: the contribution of male adolescent friendships

Deviancy training was examined as a risk factor for physical and psychological aggression toward a female partner among boys and young men in the Oregon Youth Study. Hostile talk about women during videotaped male friendship interactions was hypothesized to indicate a process by which aggression toward women is reinforced within male peer networks. Both antisocial behavior and hostile talk were predicted to be associated with later aggression toward a female partner. Prospective developmental models were tested from 9-10 years of age through young adulthood. Findings indicated that the relation of deviant peer association in adolescence and later aggression toward a partner was mediated by antisocial behavior; observed hostile talk about women with male peers explained additional variance in aggression toward a partner.     

Who victimizes whom and who defends whom? A multivariate social network analysis of victimization,aggression, and defending in early childhood

The aim of this research was to investigate the interplay between victim‐aggressor relationships and defending relationships in early childhood to test the proposition that young aggressors are less selective than older children in their choice of vulnerable targets. Cross‐sectional multivariate statistical social network analyses (Exponential Random Graph Models) for a sample of 177 preschoolers from seven classes, 5‐ to 7‐years‐old, revealed that boys were more aggressive than girls, toward both boys and girls, whereas defending relationships were most often same‐sex. There was significant reciprocity in aggression, indicating that it was more often bidirectional rather than unidirectional. In addition, aggressors clearly defended each other when they shared their targets of aggression, whereas a marginally significant trend appeared for defending between victims who were victimized by the same aggressors. Furthermore, teacher‐rated dominance was positively associated with children's involvement in both aggression and victimization, and teacher‐rated insecurity was associated with less aggression, but not with victimization. These findings suggest that those who are reported as being victimized may retaliate, or be aggressive themselves, and do not display some of the vulnerabilities reported among older groups of victims. The findings are in line with the proposition that young aggressors are less strategic than older children in targeting vulnerable victims. The network approach to peer victimization and defending contributes to understanding the social processes facilitating the development of aggression in early childhood.     

Androgens and aggressive behavior in primates: A review

This review deals with possible central and peripheral effects of androgens upon primate aggressive behavior. One problem that clouds interpretation of experimental work is that measurements of dominance have often been employed, such as competition tests for food and water. Such measures often do not correlate with those obtained by quantifying aggressive interactions. It should be remembered that very few of the 188 primate species have been studied experimentally and that great behavioral and physiological diversity occurs within the order. Therefore, generalizations about the effects of androgens upon aggressive behavior in primates (including man) should be made with caution. Testosterone has an organizing influence upon the foetal brain of rhesus monkeys and may affect the development of neural mechanisms which govern aggression in males. More data are required on primates, however, since rhesus monkeys show some important differences from rodents as regards the effects of androgen upon sexual differentiation of the hypothalamus. In future, marmosets may provide a suitable model for such studies, because there is evidence that sexual differentiation of brain by androgen occurs postnatally in these monkeys. At puberty, male primates show a variety of behavioral changes and, during adulthood, males of seasonally breeding species may be more aggressive during the mating season, when testosterone levels are maximal. This does not indicate a causative relationship between testosterone and aggressive responses, because castration and androgen treatments have little effect upon aggression in prepubertal or adult males of several primate species. Androgens have pronounced effects on sexual responses in adult male monkeys, but their central effects upon aggression are much less important than among rodents. Elec trical stimulation of hypothalamic pathways has been employed to evoke aggressive behavior in marmosets and rhesus monkeys. In the rhesus, preliminary evidence indicates that such pathways show some sensitivity to androgens. In rodents it is known that these areas are richly supplied with monoaminergic neurons, which play an important role in aggressive behavior. There is little evidence on primates, however, and this remains a crucial topic for future research. Peripheral effects of androgens should also be considered. Many prosimians and New World monkeys use scent-marking behaviors and, in males, androgen-dependent chemical cues may be involved in sexual recognition and territorial behavior. This possibility awaits investigation. Finally, plasma testosterone levels may alter as a function of aggression itself; thus levels decrease if male rhesus monkeys are defeated by conspecifics. This might occur because neural events associated with giving (or receiving) aggression also influence pituitary function and hence alter gonadal testosterone secretion. Theoretically, it is possible that such changes in circulating testosterone might affect aggressive behavior via a feedback action on the brain, but the experimental evidence does not support such a view.     

Role of female behavior in controlling population growth in mice

Sex ratio does not appear to be a factor in generating the characteristic population growth curve. Freely growing populations of house mice, consisting of all females and one male, stopped their growth at approximately the same densities as normal sexratio populations used as references. The mechanism(s) of female control of population dynamics may be related to female aggressive behavior. As the all-female/one-male populations approached their maximum size, the females began to show wounding patterns and social hierarchies in much the same manner as males in populations with normal sex ratios. The male in each of the populations was severely wounded in the posterior region, and each lost its tail as a result of injuries which could have been inflicted only by the females. The female social hierarchy can be seen only when there has been reproduction and population growth. Assembled populations of all females rarely exhibit aggressive behavior. Female aggression becomes apparent only when the population approaches its maximum size and thereafter. These data are consistent with the hypothesis that males are competitive among themselves for territory and social rank, and ultimately to mate with the females. Other investigators have indicated that females respond to population size, which may reflect increased competition between the females with the establishment of territories. Thus female agression may control population growth, a role previously ascribed to male aggression.