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Dominance hierarchies reduce the costs of competitive aggression in social animals, and testosterone is a proposed mediator of aggressive behaviour and social dominance. While the effects of testosterone on male behaviour are well studied, effects on female aggression and dominance within mixed-sex groups are less clear. We tested how short-term testosterone treatment influences aggressive behaviour and dominance hierarchies in the common waxbill, Estrilda astrild, a bird with mild social hierarchies. In captive mixed-sex groups, we administered intramuscular testosterone to either males or females and, using a test of competition for food, compared aggressive behaviour and social dominance to those of a control treatment (saline) with no testosterone administered. Testosterone treatment to males increased their social dominance, without increasing aggression. We observed a decrease in female aggression towards treated males, suggesting that females were reacting to subtle cues of male dominance (e.g. vocal cues). In contrast, female treatment with testosterone did not increase their dominance, which could either be due to a lack of effect on females, or because males reacted to and opposed cues of female dominance. Together, our results indicate a sex-dependent role of testosterone on social hierarchies.

The formation of male-female social bonds and the resulting competition among females for male partners is a core element of human societies. While female competition for a male partner outside the mating context is well studied in humans, evidence from non-human primates is scarce, and its evolutionary roots remain to be explored. We studied two multi male – multi female groups of wild Assamese macaques (Macaca assamensis), a species where females gain benefits from selectively affiliating with particular males. Using a behavioral data set collected over several years, we tested whether females competed over access to male social partners, whether success in competition was driven by female dominance rank, and which male traits were most attractive for females. We found assortative bonding by dominance rank between females and males, which together with females initiating and maintaining contact suggests direct female competition over males. Two male traits independently predicted male attractiveness to females: (1) current dominance rank, a measure of 'power' or a male's ability to provide access to resources, and (2) prior male affiliation with immatures, a measure of a male's potential paternal proclivity or 'commitment' to infant care. Both traits have been consistently identified as drivers of female partner choice in humans. Our study adds to the evidence that female competition for valuable male partners is not unique to humans, suggesting deep evolutionary origins of women's mate choice tendencies for ‘power’ and ‘commitment’.

Introductions of new males into captive primate groups are often necessary to prevent inbreeding, but also bear high social risks. To minimize these risks, it is crucial to understand the social behaviour accompanying male introductions. While the behaviour of new males is generally understood, information on resident female behaviour during introductions is lacking. We studied female behaviour towards the new male during introductions of three adult male rhesus macaques (Macaca mulatta)—each into a different captive group. All three males were successfully introduced; respectively 100%, 92%, and 83% of the females tolerated the male as a group-member at the end of the introductions. Older females started tolerating the male significantly faster than younger females, while no additional effect of female dominance rank, fertility, or the number of female coalitionary partners on timing of tolerance was found. During the course of the integration, female aggression and submission towards the male, and male mating access decreased, while female affiliation towards the male increased. The increase of female tolerance and the changes in social behaviour were similar between the introductions, indicating a general pattern in female behaviour, although some variation in effect size and significance level was observed. Based on these results, we suggest that low female submission levels towards an introduced male may constitute a criterion to assess the risk of leaving the male in the group full-time. Moreover, low female aggression levels at the end of the introduction may signal long-term group stability. Overall, we conclude that female behaviour can provide valuable information about the male introduction process and should not be overlooked.

It is well established that social rank in a large group confers a higher adaptive value to a dominant individual relative to others, although there is scant evidence that members of small social groups either have similar social standing or maintain strict dominance. We aimed to determine whether members of small social groups, using the southern bamboo lemur, Hapalemur meridionalis, as a model, gain rank-related benefits. We first established a dominance hierarchy through a network-based analysis of win–loss interactions, which showed that adult females maintained social dominance within their groups, similar to many strepsirrhine species. To address whether dominant individuals gained rank-related benefits, we then explored how social dynamics may permit access to resting huddles, which provide a physiological benefit. Social thermoregulation, i.e. huddling, is a behavioural energy conservation mechanism, and among many mammals is a direct response to decreasing ambient temperatures. As such, huddling behaviour may have evolved among social animals because of its potential direct and indirect benefits. To examine the effect of dominance rank within small social groups on huddling inclusion, we used generalized linear mixed-effects models to predict the likelihood of huddling occurring during resting bouts from climatic (e.g. temperature, precipitation), social (e.g. affiliation, dominance rank, grooming) and reproductive (e.g. access, infant protection) variables. We found that lower temperatures, especially during shorter resting bouts, increased the likelihood of huddling. Grooming between partners with a high discrepancy in rank increased huddling. Additionally, huddling increased during the reproductive season, potentially offering greater opportunity for males to gain favour with sexually receptive females, and when new-borns were present, providing essential thermal maintenance and potential antipredator protection to infants. Together, our results suggest that even in small social groups, females gain rank-related benefits by controlling access to huddles, i.e. the intrinsic benefits of social thermoregulation.

Summary In this paper, we consider whether it is the gender of the decision maker or the extent of agency that they wield that is crucial to increasing household welfare. This is an important question as development policy is often formed on the basis that placing resources in the hands of women results in greater household welfare. Indonesia provides the ideal opportunity to study this issue because it is home to ethnic groups with very different gender norms from male dominance (the patrilineal Batak) to female dominance (the matrilineal Minangkabau). Using IFLS data for three rounds, we consider the impact of decision-making by the dominant spouse on household expenditure on education. We find that, in Indonesia, when the dominant spouse (male or female) has sole control of decision-making, there is an overall negative impact on education expenditure. This leads us to argue that it is more important to consider the issue of spousal dominance, than to wholly focus on gender.

Female social dominance over males can only be found in a small number of mammalian species, but is unusually concentrated among Malagasy lemurs. Three major hypotheses are currently discussed to explain this phenomenon, namely the energy conservation hypothesis, sleeping site hypothesis and ancestral lemur condition hypothesis. Since proximate determinants of female dominance have rarely been studied, this study aimed to investigate the influence of factors connected to these hypotheses, focusing on sex-specific differences in energy requirements and group composition in two closely related nocturnal lemur species. More specifically, the effects of species, season and age on agonistic behaviour and the expression of female dominance were tested, while the effects of individuality, body mass, breeding experience and habituation were controlled. Seasonal variations in intersexual dominance relationships were investigated in captivity in grey mouse lemurs, Microcebus murinus , a prominent female-dominant species, and Goodman's mouse lemurs, Microcebus lehilahytsara , whose agonistic behaviour was studied for the first time. Data were collected during a series of encounter experiments between one male and one female (15 dyads of M. murinus and nine of M. lehilahytsara ) during the reproductive and nonreproductive seasons. Moderate female dominance was expressed in both species with females winning the majority of conflicts year round, independently of context. However, effects of season and species were found in conflict rates, in the probability for females to win conflicts, and in the number of dominant females. Moreover, the age difference between dyad partners and the breeding experience of females influenced whether conflicts were decided in favour of males or females. It can be concluded that female dominance probably represents an ancestral trait in mouse lemurs and it is proposed that its evolution might have been driven by sex-specific energetic constraints prevailing in the species-specific ancestral habitats, and may moreover be influenced by the species-specific social organization.

In group-living mammals, social dominance can be achieved and maintained via kin support, winner–loser effects and individual differences in resource-holding potential (RHP). When dominance is based on RHP, the likelihood of winning is also influenced by the incentive to compete. For females, this equation can be quite complex, as both age and reproductive state can alter the relative value of resources and the risks associated with fighting. For example, females that are young, pregnant or lactating may have high nutritional demands, while lactating females also face risks associated with offspring survival. To date, however, there have been few studies investigating how such factors influence female agonistic relationships. Here, we use 2 years of data to evaluate how age and reproductive state influence the probability of winning, focusing on two groups (5–9 and 10–12 females) of wild Phayre's leaf monkeys, Trachypithecus phayrei crepusculus, at Phu Khieo Wildlife Sanctuary, Thailand. Consistent with previous studies, we found that young females and pregnant females were more likely to win dyadic interactions in the smaller group, PA. By contrast, the likelihood of winning was unrelated to age in the larger group, PB. Moreover, differences between reproductive states were less pronounced in PB, with females that were pregnant or in early lactation being more likely to win compared to females that were cycling. The deviating results for PB were likely associated with a greater number of competitors and small age differences intensifying intrasexual competition. These results highlight the importance of individual as well as demographic factors in female dominance relationships. In this population, females with high nutritional demands are more likely to win agonistic encounters, suggesting that female–female competition occurs primarily over access to resources.

In most mammals, male–male contests over access to resources select for males to be larger, more aggressive and better armed than females. However, the functional significance of male–male aggression has been little studied in sex-role-reversed species, such as spotted hyaenas, Crocuta crocuta. This species has highly aggressive, socially dominant females, to which male access cannot be directly improved by fighting. Here, we first demonstrated that males nevertheless display intrasexual aggression at rates similar to rates of intrasexual aggression displayed by adult females. We then tested three hypotheses suggesting functions of this aggression among males. Males aggressed significantly less in the presence of an adult female than when adult females were absent, suggesting that they do not use aggression to prevent other males from remaining in close proximity to females. New immigrants received significantly more aggression from other immigrants than did established immigrants, but new and established immigrants were treated equally by adult natal males. These results supported a hypothesis suggesting that male–male aggression functions to restrict clan membership, although the data indicated that immigrants, not adult natal males, engage in aggression for this reason. Finally, a hypothesis suggesting that this behaviour functions to provide access to food was supported by data showing that male–male aggression occurred significantly more frequently, and at higher intensities, in the presence than the absence of food. In contrast to male–male contests in most mammals, those in spotted hyaenas appear to increase a male's access to females only indirectly, which is presumably due to the sex-role-reversed nature of social dominance in spotted hyaenas.

The role of androgens in shaping “masculine” traits in males is a core focus in behavioral endocrinology, but relatively little is known about an androgenic role in female aggression and social dominance. In mammalian models of female dominance, including the ring-tailed lemur (Lemur catta), links to androgens in adulthood are variable. We studied the development of ring-tailed lemurs to address the behavioral basis and ontogenetic mechanisms of female dominance. We measured behavior and serum androgen concentrations in 24 lemurs (8 males, 16 females) from infancy to early adulthood, and assessed their ‘prenatal’ androgen milieu using serum samples obtained from their mothers during gestation. Because logistical constraints limited the frequency of infant blood sampling, we accounted for asynchrony between behavioral and postnatal hormone measurements via imputation procedures. Imputation was unnecessary for prenatal hormone measurements. The typical sex difference in androgen concentrations in young lemurs was consistent with adult conspecifics and most other mammals; however, we found no significant sex differences in rough-and-tumble play. Female (but not male) aggression increased beginning at approximately 15 months, coincident with female puberty. In our analyses relating sexually differentiated behavior to androgens, we found no relationship with activational hormones, but several significant relationships with organizational hormones. Notably, associations of prenatal androstenedione and testosterone with behavior were differentiated, both by offspring sex and by type of behavior within offspring sexes. We discuss the importance of considering (1) missing data in behavioral endocrinology research, and (2) organizational androgens other than testosterone in studies of female dominance.

Fecal glucocorticoid (fGC) concentrations are reliable, non-invasive indices of physiological stress that provide insight into an animal's energetic and social demands. To better characterize the long-term stressors in adult members of a female-dominant, seasonally breeding species - the ring-tailed lemur (Lemur catta) - we first validated fecal samples against serum samples and then examined the relationship between fGC concentrations and seasonal, social, demographic, genetic, and reproductive variables. Between 1999 and 2006, we collected 1386 fecal samples from 32 adult, semi-free-ranging animals of both sexes. In males and non-pregnant, non-lactating females, fGC concentrations were significantly elevated during the breeding season, specifically during periods surrounding known conceptions. Moreover, group composition (e.g., multi-male versus one-male) significantly predicted the fGC concentrations of males and females in all reproductive states. In particular, the social instability introduced by intra-male competition likely created a stressor for all animals. We found no relationship, however, between fGC and the sex, age, or heterozygosity of animals. In reproducing females, fGC concentrations were significantly greater during lactation than during the pre-breeding period. During pregnancy, fGC concentrations were elevated in mid-ranking dams, relative to dominant or subordinate dams, and significantly greater during the third trimester than during the first or second trimesters. Thus, in the absence of nutritional stressors, social dominance was a relatively poor predictor of fGC in this female-dominant species. Instead, the animals were maximally challenged by their social circumstances and reproductive events-males by competition for mating opportunities and females by late-term gestation and lactation.

In most vertebrates, aggression and dominance are tightly linked to circulating testosterone. Fish, however, have two androgens (testosterone, T and 11-ketotestosterone, 11KT) that influence aggression and dominance. To date, few studies have compared the relationship between androgen levels and the outcome of aggressive contests in both females and males of the same species. To investigate sex differences in androgens we staged size-matched, limited-resource (territory) contests with 14 female–female and 10 male–male pairs of the highly social cichlid Neolamprologus pulcher. We then examined androgen levels in recently established dominants, who won the contest and subsequently acquired a territory (for 3 h), and subordinates, who lost and did not acquire a territory. Newly dominant females had higher plasma T but similar 11KT levels to newly subordinate females. In contrast, newly dominant males had higher 11KT but similar T levels to subordinate males. The ratio of 11KT to T, which demonstrates physiological importance of T conversion to 11KT, was positively correlated with submissive behavior in female winners, and correlated weakly with aggressive behavior in male winners (p = 0.05). These findings provide support for the hypothesis that different androgens play equivalent roles in female versus male dominance establishment, and suggest that relative levels of 11KT and T are implicated in female dominance behavior and perhaps behavior of both sexes.

The function of olfactory signalling in social species is less well understood than in asocial species. Consequently, we examined olfactory communication in the ringtailed lemur, a socially complex primate that retains a functional vomeronasal organ, has well-developed scent glands and shows a suite of scent-marking behaviour. To assess the information content of different types of scent gland secretions, we decoupled olfactory cues from the visual and behavioural modalities with which scent marking is normally associated. We presented male and female subjects (signal receivers) with a series of choice tests between odours derived from conspecific donors (signal senders) varying by sex, age, social status and reproductive condition. We additionally examined the influence of the receivers' reproductive state and familiarity with the signaller. The reproductive condition, social status and familiarity of senders and receivers affected signal transmission; specifically, male receivers attended most to the odours of conspecifics in breeding condition and to the odours of familiar, dominant animals. By contrast, females varied their responses according to both their own reproductive state and that of the sender. Based on male and female patterns of countermarking, we suggest that scent marking serves a function in intergroup spacing and intrasexual competition for both sexes, as might be expected in a female-dominant species. By contrast, minimal female interest in male odours counters a female mate choice function for scent marking in this species. Nevertheless, scent marks are critical to male–male competition and, therefore, may be subject to sexual selection.

Female baboons (Papio hamadryas spp.) must contend with myriad potential stressors on a daily basis. In a previous study on female chacma baboons, Papio hamadryas ursinus, living in the Okavango Delta of Botswana, increases in glucocorticoid (GC) concentrations were associated with female reproductive stage, male immigration and the threat of infanticide. Here, we extend this previous analysis to a larger data set with several additional potential stressors, including actual infanticide and instability in the female dominance hierarchy. A general linear mixed model showed that reproductive state, male immigration, infanticide, female rank instability and predation all had significant effects on GC levels. Lactating females’ GC levels increased in response to the arrival of immigrant males and increased even further when infanticide occurred. In contrast, cycling and pregnant females’ GC levels did not change. Females also showed elevated GCs in response to instability within their own dominance hierarchy, especially if their own ranks were at risk. Females’ stress responses were frequent, but specific to events that threatened their own lives, the lives of their offspring, or their dominance ranks.

The present study argues that pressures associated with the threat of paternal uncertainty shaped a male mate-preference for relatively subordinate partners in the context of long- (high investment) but not short-term (low investment) relationships. Using a hypothetical scenario depicting a workplace setting, 120 male and 208 female undergraduates were randomly assigned to one of six experimental conditions in which they were asked to judge a male or female target, described as either their supervisor (higher dominance), coworker (equal dominance), or their assistant (lower dominance). Participants exposed to an opposite-sex target rated their attraction to the target for varying types of investment (e.g., desire for a one-night stand, desire to affiliate, or desire for a long-term relationship), and participants exposed to a same-sex target rated their desire to affiliate with the target. Results supported predictions and indicated that males preferred the subordinate over the dominant target for affiliation and high-investment items, and females were unaffected by the target's dominance status. The results of same-sex ratings indicated that dominance status did not influence females' ratings of the female target, and that dominance did not influence males' ratings of the male target. These results are discussed in terms of the role of relational dominance in shaping male mate-preferences.

The spatial position of young animals within a brood affects their survival, so that marginal individuals are at greater risk of predation. Spatial brood structuring may be caused by differences in offspring size, age, hunger, or active parental manipulation through aggression. Nepotistic manipulation of brood structure would confer fitness benefits for parents accepting nondescendant young. However, insufficient kin recognition has often been considered to preclude such nepotism in birds, particularly in precocial waterfowl. We explored the spatial structure of ducklings within broods of eiders, Somateria mollissima ,a seaduck with frequent brood amalgamation. We compared the distribution of ducklings of different origin relative to reference females whose kinship to the ducklings was known. We also observed female aggression towards ducklings, to evaluate the role of parental manipulation of brood structure. We found a nonrandom distribution of ducklings within broods; a female’s own young were on average closer to her than unrelated young were. We also found evidence for parental nepotism: whether the brood contained unrelated young was the strongest predictor of female aggression towards ducklings. The spatial position, hatch weight and relative size of ducklings showed no significant correlations with each other, suggesting that active parental manipulation may be needed to explain the observed spatial structure. Our study conflicts with previous anecdotal evidence suggesting that brood amalgamation in eiders results in the disintegration of parent–offspring bonds, preventing parental exploitation of nondescendant young. It also opens up the possibility that the spatial position of ducklings depends on their mother’s status in the female dominance hierarchy.

Many studies have shown that low dominance status within a social group is associated with elevated glucocorticoid hormone production, a common index of physiological stress. However, the reverse may be true among cooperatively breeding female mammals with high reproductive skew; that is, high dominance status is associated with elevated glucocorticoid levels. Elevated glucocorticoid levels in these dominant females may be a product of their being the only breeder within a group or may result from other challenges associated with high status. To test this difference, we studied fecal corticoid levels in cooperative breeding females with low reproductive skew (i.e., where reproduction is not limited to dominant group members): ring-tailed lemurs (Lemur catta). We collected behavioral and fecal corticoid data from 39 ring-tailed lemur females from eight groups across three sites. In seven of the eight groups, either one or both of the two most dominant females (ranks 1 and 2) exhibited the highest fecal corticoid levels in the groups. The best predictor of corticoid levels in high-ranking females was the proportion of aggressive agonistic interactions they initiated. For the lower-ranking females the best predictors of elevated corticoid levels were being the recipient of aggressive attacks and being relatively close to one’s nearest neighbors. These results differ from many studies of caged male mammals where subordinate individuals often exhibit the highest glucocorticoid levels of a group. Furthermore, the results indicate that reproduction itself is not the primary reason for higher glucocorticoid levels among dominant cooperative-breeding females, but that some other factor must account for these elevated levels.

Objectives To assess the degree of sexual dimorphism for Preterm Birth (PTB), Pregnancy Induced Hypertensive Disorders (PIHD) and Gestational Diabetes Mellitus (GDM) in an Australian population. Methods Retrospective population-based study of 574,358 South Australian singleton live births during 1981–2011 in the South Australian Perinatal Statistics Collection of three major adverse pregnancy outcomes (PTB (divided by PTB [birth before 37 weeks] and ePTB [birth before 34 weeks]), PIHD and GDM) in relation to fetal sex. Results There were 295,724 male (51.5%) and 278,634 (48.5%) female neonates (sex-ratio 1.06). Among all pregnancies there was a significant male dominance in pregnancies complicated by PIHD (RR 1.053, 95%-CI 1.034–1.072), PTB (PTB – RR 1.115, 95%-CI 1.092–1.139 & ePTB – RR 1.151, 95%-CI 1.104–1.199) and GDM (RR 1.042, 95%-CI 1.011–1.074). The pattern for PIHD by gestational age was markedly different (Fig. 1). Preterm PIHD showed a significant female dominance [RR’s ranging from 0.686, 95%-CI 0.581–0.811 (25–29 weeks) to 0.925, 95%-CI 0.870–0.982 (34–36 weeks)], while term PIHD showed a significant male dominance [RR 1.064, 95%-CI 1.037–1.093 (37–39 weeks) and RR 1.074, 95%-CI 1.044–1.105 (40–42 weeks)]. Conclusions This large South Australian cohort confirms the presence of marked sexual dimorphism for PTB, PIHD and GDM. The striking associations of male fetal sex with PTB and female sex with preterm PIHD could indicate that a certain degree of placental dysfunction in the male fetus would lead to PTB while the female fetus may be able to temporarily improve intrauterine life by increasing maternal blood pressure and thereby placental perfusion pressure with the attendant risk of PIHD. Disclosures P.E. Verburg: None. G. Tucker: None. W. Scheil: None. J.H. Erwich: None. C.T. Roberts: None. G.A. Dekker: None.

Research on both mammals and birds suggests that parental features, such as body condition and dominance rank, could influence sex ratios. This study examined the effect of male and female dominance rank on hatching sex ratios in domestic chickens,Gallus gallus domesticus. Twenty-four dominant males and 24 subordinate males were each placed in a pen with eight females. Females that were mated to a dominant male in the first 3 weeks of the experiment were mated to a subordinate male in the second 3 weeks and vice versa. Sex ratios (number of females/male) at hatch were not directly affected by male and female dominance status. Females that were mated to a subordinate male in the first trial, however, produced more variable sex ratios in the second trial. This effect was not evident for females mated to dominant males first. In addition, both groups of females produced more daughters in the second trial than in the first, although this effect was only significant for females that mated with subordinate males first. The results did not support the hypothesis that females should alter the sex ratio of their offspring based on their own dominance status or that of their mates. They did provide evidence, however, that sex ratios in chickens may be indirectly influenced by the status of the male. 1996 The Association for the Study of Animal Behaviour

Spotted hyaenas, Crocuta crocuta, live in clans characterized by a matrilineal social system, with female dominance over males. As part of an ongoing study of the development of hyaena social behaviour, the ‘de novo’ emergence of a natural social system was documented in captive groups of peer-reared hyaenas that had not acquired their mother's rank prior to removal to a captive situation. The acquisition of rank in their descendants was examined. Dominance relationships were studied in six breeding groups using competitive feeding tests administered in different social contexts. Founding members of these groups had been collected in Africa as infants (

The development of intra-litter competition and cooperation is described in free-living and captive spotted hyaenas. Field data were collected on dominance relations in 26 twin litters, and additional behavioural analyses were performed on different subsets of this group. Intra-litter dominance relations were assessed on the basis of the direction of aggressive and appeasement behavior patterns. In all wild litters, one cub clearly dominated the other by the time cubs were observed above-ground, at 2–3 weeks of age. Within the 17 twin litters of mixed sex, female dominance over male litter-mates was significantly more common (N = 14) than the reverse (N = 3). When males were the dominant litter-mates, they were as aggressive towards their siblings as were females. Rates of intra-litter aggression were highest in the youngest age interval observed (1–2 months), and dropped significantly the next month. Peak monthly rates of intra-litter aggression correlated significantly with maternal rank, such that offspring of low-ranking females fought more than of those high-ranking females. High levels of intra-litter cooperation were observed in the context of coalition formation, and youngster affiliated more with litter-mates than with any other hyaena. In captivity, seven twin and two triplet litters were videotaped during the first 2 months of life, and were scored for aggressive interactions. Results showed that dominance between litter-mates is established as early in development as the first day of life.

Inferences for female bonding in humans have drawn on models derived from studies of nonhuman primates. In primates, strong affiliative relationships between unrelated females are rare. This is true for the social systems of apes and particularly for those of the closest living relatives of humans, the chimpanzee ( Pan troglodytes ). However, the other member of the genus Pan , the bonobo ( Pan paniscus ) is strikingly different in this regard as evidenced from the present comparative study that was conducted at the Wilhelma Zoo, Germany. A group of bonobos and of chimpanzees was each provided with limited access to an artificial "fishing" site (a simulated termite mound) filled with desirable food. In chimpanzees, the adult male was dominant over all females and able to monopolize the food. In bonobos, on the other hand, the adult bonobo male was low ranking, and females controlled food access. Sex between bonobo females apparently facilitated affiliative encounters between females in the context of feeding. Until now, studies of exchanges of sex-for-food focused on heterosexual interactions. This study reveals that trading of sex for food occurs regularly between bonobo females. These exchanges appear to reduce tension and facilitate female cofeeding and cooperation. They help create stable long-term relationships among females that result in coalition formation, control of food resources, and ability to elevate their dominance status relative to males well above that of their chimpanzee counterparts. The strong affiliative relationships between unrelated female bonobos provide an alternative model from which predictions for bonding among human females can be generated.

Abstract. Spotted hyaenas, Crocuta crocuta, live in social groups in which dominance relationships are organized along matrilineal lines and female dominance over males is the norm among adults. In this study the ontogeny of rank relationships between juveniles and adults was examined in a clan of free-living spotted hyaenas. Juveniles of both sexes were initially subordinate to all adult females, but at approximately 6 months of age they began to challenge adult females from matrilines of lower rank than their own. By 18 months of age, juvenile females and males dominated 76% and 50% of adult females from lower-ranking matrilines, respectively. Juveniles dominated immigrant males in 99% of aggressive interactions with them. Juvenile attacks against adults often occurred in coalitions, but as the size difference between juveniles and adults decreased, so did the relative frequency of coalitionary aggression compared with that of dyadic attacks. Whereas adult females resisted challenges from juveniles, immigrant males appeared to passively accept subordinate status relative to juveniles. Dispersal thus appeared to precipitate a dramatic decline in the social status of males.

Abstract. This study documents the development of rank relations between free-living juvenile spotted hyaenas, Crocuta crocuta , and (1) members of the peer cohort, (2) older non-sibling juveniles, and (3) older siblings. All agonistic interactions observed among 67 juvenile members of one large spotted hyaena clan were recorded, both in natural contexts and following experimental presentation of food. Within peer groups, juveniles of both sexes initially exhibited aggression and appeasement without regard to their social partners' maternal ranks. This changed during ontogeny such that juveniles came to direct aggression only towards peers from lower-ranking matrilines, and only appeased peers from higher-ranking matrilines. By 6-8 months of age, intra-cohort ranks were highly correlated with maternal rank. The same age-related trends found in juveniles' interactions with peers were also observed in aggressive and appeasement interactions between younger and older juveniles, despite their differences in body size. However, juveniles directed a greater number of coalitionary attacks against older juveniles than against peers. Presence of mothers during their offspring's aggressive interactions strongly influenced interaction outcomes of juveniles less than 6 months of age. At approximately 8 months of age, juveniles rapidly outranked their older siblings, who had previously dominated them. Juveniles 12-36 months old could be ordered in a linear hierarchy in which ranks were transitive and isomorphic with maternal ranks. Ontogenetic trends in outcomes of rank-related interactions revealed no significant sex differences. Female dominance, characteristic of rank relations among adult hyaenas, was not expressed among juveniles in their natal clan.

The social system of bighorn sheep, Ovis canadensis, was studied for 10 years in a marked population in southwestern Alberta. Yearling sons did not associate with their mothers. Males switched from ewe to ram groups between the ages of 2 and 4 years. No evidence of permanent emigration was found, but some rams left their native group to rut elsewhere, and the proportion so doing increased with the number of rams in the population. Most ewes coexisted with their mothers until 6 years of age, but other uterine kin, such as maternal sisters, rarely overlapped in time. Known matrilines were small and 29% of the ewes had no known live adult maternal kin. The mother's survival did not affect the reproductive success of young daughters. Yearling ewes were in the same group as their mother more often than predicted by a random model, but were not in the same group as their mother for most sightings. Two- and 3-year-old ewes did not associate with their mothers. The outcome of aggressive interactions among ewes was age related, the older ewe winning 92% of interactions. When age was controlled, dominance was not correlated with reproductive success and was negatively correlated with the proportion of male offspring. The social system of bighorn sheep appears to have been shaped by anti-predator and foraging strategies that rely upon learned traditions. Kinship appears to play a limited role. There is little scope for female dominance status to affect reproductive success, because bighorns seldom require resources that can be defended against conspecifics.

The relative importance of male and female dominance rank, age and other socio-demographic variables to female-male social interactions was examined for a wild population of wedge-capped capuchin monkeys, Cebus olivaceus , in Venezuela. Females groomed females more frequently than males but were equally aggressive to males and females. Females associated with the dominant male and groomed the dominant adult male more than subadult males. Females were most intolerant of middle-ranking subadult males and most female-male aggressive interactions involved these males. Female rank and male rank were the most important determinants of interactions initiated by females. During interactions initiated by males, ranks of male and female were not important. Social preference for the dominant male appears to reflect breeding preference; females do not improve access to resources or receive infant care as a result of this preference. Females may minimize the chance of infanticide by restricting social/breeding preference to the dominant male. Although subadult males represent a social cost to females, they may be tolerated because they are important for inter-group competition for resources.

The relationship between female dominance and flehmen was investigated in a herd of 11 female sable antelope (Hippotragus niger) maintained in a 13.2-ha pasture at the National Zoological Park's Conservation and Research Center in Front Royal, VA, U.S.A. All occurrences of aggression and flehmen by adult females were recorded during 274 h of observation over a 9 month period. Overall frequencies of flehmen were highly correlated with rank, dominant females exhibiting the highest flehmen rates. Subordinates rarely performed flehmen in response to urination by higher ranking females. When aggression immediately preceded opportunities for flehmen, dominants virtually always performed flehmen while subordinates never did. Investigation of urine on the substrate was unrelated to rank, suggesting that subordinates may exploit alternate strategies for social investigation. Flehmen may allow synchronization of reproduction by enabling females to assess each other's reproductive condition. High ranking females showed the greatest degree of reproductive synchrony within the herd.

The intensity and patterning of interference competition for food within mountain gorilla (Pan gorilla beringei) social groups is influenced in several ways by group size and composition and varies within and across age/sex classes. Data on 251 spatial displacemtnts associated with feeding, collected during a 17-month study of mountain gorilla feeding ecology, show that overall displacement rates and displacement rates for individuals were positively correlated with social group size. Silverback males were responsible for a disproportionately high number of displacements. Adult females also were involved in competitive interactions over food more often than expected from their representation in groups, and had feeding bouts interrupted disproportionately often, principally by other females and by silverbacks. Competitive relationships between females varied in association with female dominance rank and age, but were not clearly associated with relatedness between females. The results support the argument that social foraging entails a cost which is proportional to group size and which falls particularly on adult females. The comparatively low rates of competitive interactions, however, suggest that this cost is relatively low, and that female mountain gorillas sacrifice little in terms of feeding efficiency by living in social groups.

At Polonnaruwa, Sri Lanka, four out of 29, groups of toque macaques, Macaca sinica , divided in a period of 16 years. Temporary peripheral subgroups of varying sizes and compositions preceded fission by 9–40 months. Fission crystallized within a month through an increase and stabilization of subgroup membership and permanent division. All members in the newly seceded groups had been frequent participants in pre-fission subgroups, and belonged to subordinate matrilineages. Subgroups, and hence group divisions, were initiated by cores of mutually loyal females and occurred mostly along kinship lines. In the year of fissions, the rate of change in female dominance relations was significantly greater among groups that divided than among those that did not. It is hypothesized that low-ranking females secede to form new groups when the costs, especially of intragroup competition for food resources, outweigh the benefits of group membership. Such seceding females were easily available and familiar mates for group males that had recently lost rank. Final division, therefore, resulted from a coalition of subordinate females and males acting according to their respective interests. It was triggered in this population by rapid growth of some groups to large size and by environmental stress (the reduction and fragmentation of food resources caused by drought and a cyclone), which accentuated the costs of resource competition. Male aggression, such as infanticide, which negatively affects female fitness, might also have contributed to one group fission.

The reproductive, agonistic, and social interactions between the adult male and adult females of a patas monkey ( Erythrocebus patas ) harem were investigated. The occurrence of oestrus appeared to be influenced by both social and hormonal factors. Oestrus was not limited to the peri-ovulatory period, but also occurred at other times within the menstrual cycle and after conception. Mating behaviour was correlated with seasonal decreases in daylength and temperature. The male showed no clear preference for either non-pregnant or pregnant sexual partners. Female dominance rank appeared to have little influence on intrasexual competition for copulations. Of the non-reproductive behaviours studied, only two (female-to-male grooming and heterosexual sitting-close) showed significant fluctuations in frequency with changing female reproductive state. For both behaviours, non-pregnant oestrous females showed the highest frequencies.

The aggressive behaviour of female hamsters was studied while they were housed in large enclosures with males and in brief tests with males or females. Some females are not aggressive with any male, whereas others are very aggressive toward all males in both testing conditions. Females that are not aggressive toward intact males may be very aggressive toward castrated males or females. When the animals are housed together for long periods of time, males dominate only if they are much heavier. Male dominance takes a relatively long time to establish and often there is an equivocal period characterized by reversals of doinance. Female dominance is rapidly established. Unless the male is much heavier, the female determines the presence or absence of agonistic behaviour.

Dominance relationships were studied in a rhesus monkey group during five consecutive years. The group consisted of eight stable matriarchies and an adult male class which was replaced at the start, and again at the midpoint, of the study. Immature males were selectively harvested to maintain a sex ratio typical of natural troops. Maximum group size during the study was 77 animals. Dominance relationships were remarkably stable, with only 4.4% of dyads failing to show unidirectional relationships. Despite this stability, a linear ranking of all group members was not possible. Male dominance relationships with other males were among the most stable, following the fighting which ensued on male introductions. Male introductions did not disrupt female dominance relationships. Adult female dominance relationships were also quite stable, but immature females slowly achieved dominance over older sisters and females subordinate to their mothers. Such reversals were the result of processes lasting over many months. Many dominance assertions occurred prior to puberty but a significant number occurred following sexual maturity. Maturing females did not reverse dominance relationships according to any particular hierarchial order and, as a consequence, many were subordinate to animals that were dominated by others that they dominated. Although there was an alpha male that was dominant to all animals in the group, adult females dominated most adult males. Adult males, however, often reciprocated aggression directed at them. They almost invariably threatened or countercharged aggressive immature animals regardless of matriarchial membership. Adult males dominated some adult and most young females, even in families containing matriarchs and adult females to which the adult males always submitted. The dominance relationships of young males were similar to those of their sisters, until puberty. Young males did not necessarily bypass adult males that their mothers outranked, and often failed to win against adult females that their mothers dominated. Adolescent female aggression against females is seldom interfered with by adult males, and females may actively aid one another against males. In contrast, the aggression of young males often elicits interference by adult males, and young males often become the targets of redirected aggression in the group. As a consequence, whereas young females rise in rank to positions adjacent to their mothers, adolescent males often suffer losses to animals that they had dominated as juveniles.

A 4-year study of the social organization of spotted hyaenas in a clan of 60–80 individuals showed that there is a separate dominance hierarchy within each sex. One female and her descendants dominated all others; matrilineal rankings were stable over time because maternal rank is inherited. Cubs of higher ranking females were able to feed at kills in competition with adults more successfully than other cubs, and male offspring of the alpha female were the only males able to dominate adult females. The mating system is highly polygynous: only the behaviourally dominant male was seen to mate, though all other resident males regularly courted females. Among females, there was no correlation between reproductive success and age, size, or social rank. It is postulated that the unusually aggressive sons of the alpha female would probably be highly successful competitors in the context of a polygynous mating system. A primary consequence of female dominance over males is that females and their young have priority of access to food in a highly competitive feeding situation. This competition may have been the selective force that produced female dominance and the associated syndrome of female virilization that is characteristic of the species. Cooperation among related females may be the basis for the matrilineal system, as has been suggested for certain primate species.

Aggressive dominance orders of all adults in a confined troop of Japanese macaques (Macaca fuscata) were determined each mating and birth season during a 4-year interval. Males outranked more females in the mating than in the birth season, and some males shifted back and forth from ranks lower than female ranks in the birth season to ranks higher than female ranks in the mating season. Mating behaviour (number of female partners in mount and ejaculation series and ejaculation frequency) did not differ among males with ranks higher than, as high as, or lower than those of most females, nor did individual males mate more in years, when they were high-ranking than in years when they were not. There was a correlation, however, between ejaculation frequency and the number of females defeated by males. A pattern of increasing male rank with age was found.

Eight years of reproductive data (including 248 births) from a translocated troop of Japanese monkeys (Macaca fuscata) living in a 42-ha enclosure provided three measures of female reproductive success: fecundity, survival of infants to 1 year of age, and age at first parturition. No significant relationship was found between social dominance and these measures. Social dominance was considered with respect to both matrilineal and individual female rank. Additional data on female dominance ranks over four generations of adult females revealed no significant concordance over time. The finding that ranks may not be stable over the lifetime of a female is a significant one because the variation in reproductive success among the females of a group is likely to be further diminished by any instability. For 34 females that were adults for the 8-year period considered, there was no significant correlation between the average rank of a female and either fecundity or survivorship of infants to 1 year of age. These data considered along with the results of other studies of female dominance and reproduction suggest that any effect of female social dominance on reproductive success is probably dependent upon resource availability, with significant benefits accruing to high-ranking individuals only during subsistence periods. It is suggested that dominance competition among female macaques may be a behavioural strategy with a variable payoff.

Female baboons, Papio cynocephalus, in Amboseli National Park establish linear dominance hierarchies in which maternal kin usually occupy adjacent ranks. Previous work had shown that few changes in the relative rank order of matrilines had occurred between 1971 and 1981 (Hausfater et al. 1982). During a 9-month period beginning in December 1982, the rate and magnitude of changes in matrilineal rank order accelerated. Major changes in the relative ranks of members of a few matrilines resulted in changes in the absolute ranks of females of all but one matriline. However, the ordering between many pairs of matrilines did not change and the genealogical structure of dominance relations was generally maintained. This brief period of rapid change was succeeded by a period of slow change and relative stability in dominance relations, lasting at least 27 months. Data from the 15-year period suggest that the rates of change in female dominance relations are variable: long periods of stability are sometimes punctuated by short periods of instability and change. No single explanation accounted for this variability.

Attention is drawn to the dominant demand made by the elderly female for long-stayhospital and Welfare Home care. The fact that this considerably exceeds her proportional representation in the community at large, reveals a different pattern of response and mortality in chronic illness requiring long-stay care in women in old-age, compared with men. This female dominance in survival is seen throughout life and may be due to more effective immunological mechanisms. There will be practical implications with a heavier increase in demand in future for all aspects of care as the numbers of aged women in the population rises which, because of inherent biological differences between the sexes, will be seen in men to a much smaller degree.