Testosterone and Linear Social Dominance Status in Captive Male Dabbling Ducks in Winter

Dominance hierarchies play an important role in avoidance and/or solving conflicts in gregarious species. In dabbling ducks (Anas species), dominance allows for feeding‐site monopolization in winter quarters where resources are generally limited. In addition, male social rank should theoretically favour access to mates. Dominance rank can be associated with morphological traits, and is often correlated with aggressiveness, a behavioural trait generally related to high testosterone levels. In this study, we investigated the existence of a winter group structure based on dominance relationships and tested for a linear hierarchy, in three species of captive male dabbling ducks (mallard Anas platyrhynchos, pintail A. acuta and wigeon A. penelope). We then analysed the relationship between dominance ranks, morphological parameters and testosterone levels measured in early (Oct.) and mid‐winter (Dec./Jan.). We found that the three male groups of the three species exhibited a linear hierarchy. Testosterone levels differed during winter and between species. Morphologic measurements, body mass and body condition were not correlated with individual dominance ranks, whereas dominant males had higher testosterone levels than subordinates. The slopes of the relationships were similar between species and winter period, but the y‐intercepts differed between species and between early and mid‐winter phases. The linear hierarchy found in the three species indicates that dominance relationships strongly structure dabbling duck groups in winter. Lack of correlation between rank and morphological characters, but correlation of rank with testosterone levels suggests that social rank is more dependent on behavioural traits such as aggressive behaviour. The differences between species and winter periods are discussed in relation to migration and wintering phenology.     

A 15-year study of the association between dominance rank and reproductive success of male rhesus macaques

The reproductive success (RS) of 32 males in a captive group of rhesus macaques (Macaca mulatta) between 1978 and 1992 was determined using paternity exclusion analysis. Dominance rank of each male over age 4 was assessed at the end of each breeding season based on agonistic dyadic interactions. The dominance rank and RS of these males were strongly correlated whether or not subadult males were included. The high reproductive success of males that eventually reached alpha rank is primarily responsible for this outcome. These results support the theory that social dominance has evolved in genusMacaca by sexual selection but some changes in male dominance rank and RS during the 15-year period suggest that priority of access is not the sole focus for such selection.     

Sex differences in the impact of social status on hair cortisol concentrations in rhesus monkeys (Macaca mulatta)

Social status impacts stress in primates, but the direction of the effect differs depending on species, social style, and group stability. This complicates our ability to identify broadly applicable principles for understanding how social status impacts health and fitness. One reason for this is the fact that social status is often measured as linear dominance rank, yet social status is more complex than simply high or low rank. Additionally, most research on social status and health ignores the effects of sex and sex-specific relationships, despite known differences in disease risk, coping strategies, and opposite-sex dominance interactions between males and females in many species. We examine the influence of social status, sex, and opposite-sex interactions on hair cortisol concentrations (HCC) in a well-studied species, rhesus macaques, where the literature predicts low ranking individuals would experience more chronic stress. Animals in three captive, seminaturalistic social groups (N = 252; 71 male) were observed for 6 weeks to obtain metrics of social status (rank and dominance certainty [DC]). DC is a measure of one's fit within the hierarchy. Hair samples were collected from each subject and analyzed for HCC. Generalized linear mixed models were used to examine (a) whether rank, DC, or sex predicted HCC; (b) whether same- or opposite-sex dominance relationships differentially impacted HCC; and (c) whether aggressive interactions initiated or received could explain any observed relationships. Results indicated that DC, not rank, predicted HCC in a sex-specific manner. For males, high HCC were predicted by receiving aggression from or having high DC with other males as well as having low DC with females. For females, only high DC with males predicted high HCC. These results likely relate to sex-specific life history pattern differences in inherited versus earned rank that are tied to female philopatry and male immigration.     

Behavioural Correlates of Female Social Status and Birth Mass of Male and Female Calves in Reindeer

In polygyny, male breeding success depends more than female success on body size, and male birth mass may therefore be more strongly correlated with mother's social dominance status. Among female reindeer, Rangifer tarandus, the rate at which a female took over winter feeding craters from conspecifics depended on rank and the mass loss decreased with increasing rank. Birth mass of male calves depended on mother's social rank, but that of female calves did not. Male foetuses appeared to be more effective than females to utilize resources associated with mother's phenotypical superiority.     

Social parameters and urinary testosterone level in male chimpanzees (Pan troglodytes)

Studies investigating relationships between social parameters (such as dominance rank, rates of aggressive and sexual behaviors) and androgen (particularly, testosterone) levels in male primates have yielded inconsistent results. In the present study, we address the relationship between androgens, male dominance rank and rank-associated behaviors in two groups of captive chimpanzees, a species characterized by a pronounced dominance hierarchy between adult males. By combining behavioral observations with urinary testosterone (T) measurements, we found that the differences in T concentrations between males were small and not obviously related to their dominance rank. T levels were not related to the rates of initiated aggression and copulatory behavior, but a significant negative relationship between male T level and the rates of strong aggression received was apparent. Our findings, combined with those of others, suggest that any relationship between dominance rank and T depends upon the extent to which individual rank-associated behaviors (e.g. aggressive/sexual) are themselves related to T.     

Dominance in Domestic Dogs: A Quantitative Analysis of Its Behavioural Measures

A dominance hierarchy is an important feature of the social organisation of group living animals. Although formal and/or agonistic dominance has been found in captive wolves and free-ranging dogs, applicability of the dominance concept in domestic dogs is highly debated, and quantitative data are scarce. Therefore, we investigated 7 body postures and 24 behaviours in a group of domestic dogs for their suitability as formal status indicators. The results showed that high posture, displayed in most dyadic relationships, and muzzle bite, displayed exclusively by the highest ranking dogs, qualified best as formal dominance indicators. The best formal submission indicator was body tail wag, covering most relationships, and two low postures, covering two-thirds of the relationships. In addition, both mouth lick, as included in Schenkel’s active submission, and pass under head qualified as formal submission indicators but were shown almost exclusively towards the highest ranking dogs. Furthermore, a status assessment based on changes in posture displays, i.e., lowering of posture (LoP) into half-low, low, low-on-back or on-back, was the best status indicator for most relationships as it showed good coverage (91% of the dyads), a nearly linear hierarchy (h’ = 0.94, p<0.003) and strong unidirectionality (DCI = 0.97). The associated steepness of 0.79 (p<0.0001) indicated a tolerant dominance style for this dog group. No significant correlations of rank with age or weight were found. Strong co-variation between LoP, high posture, and body tail wag justified the use of dominance as an intervening variable. Our results are in line with previous findings for captive wolves and free-ranging dogs, for formal dominance with strong linearity based on submission but not aggression. They indicate that the ethogram for dogs is best redefined by distinguishing body postures from behavioural activities. A good insight into dominance hierarchies and its indicators will be helpful in properly interpreting dog-dog relationships and diagnosing problem behaviour in dogs.     

Social Dominance Hierarchies and Phenotypic Correlates of Dominance in Captive Groups of the Grey‐cheeked Fulvetta Alcippe morrisonia in Taiwan

Dominance hierarchies usually form quickly among avian foraging groups because they are beneficial to most individuals by reducing conflict. Several characteristics that correlate with dominance rank have been identified in birds, but most of these conclusions rely on studies of temperate species. Hence, we studied whether captive group members of a subtropical species, grey‐cheeked fulvetta Alcippe morrisonia, form social dominance hierarchies when competing for food during the non‐breeding season. We also investigated whether sex, age, body condition and fat score were related to an individual's dominance rank which was established by counting aggressive interactions in six captive groups of nine individuals each. In all groups, linear dominance hierarchies were formed whereby yearlings dominated over adult birds, and individuals with a better body condition were also more dominant, while sex and fat score had no discernable effect. Male yearlings had significantly higher body masses and body condition indices than male adults, while female yearlings had significantly higher body masses, body condition indices and fat scores than female adults. However, there were no significant differences between male and female yearlings or adults for any of these variables. We suggest possible reasons for the dominance of yearlings, such as captive conditions or the higher body weight of yearlings.     

Relationships between musk extraction, social rank and tail-rubbing in male Alpine musk deer, Moschus sifanicus

Musk deer (Moschus spp.) are small, solitary forest ruminants well-known for the musk secreted by adult males. Because of illegal hunting and habitat degradation and loss, the five species of musk deer are classified as endangered. Musk deer farming has been a positive example of ex situ conservation, maintaining deer numbers whilst sustaining musk production. This study was conducted at the Xinglongshan Musk Deer Farm in Gansu Province in northwest China, and was designed to explore the relationships among musk extraction, fighting ability and social rank in captive, male alpine musk deer (Moschus sifanicus). Results showed that musk production was related to a male’s rank in the dominance hierarchy. Males in the middle rank of the dominance hierarchy tended to produce more musk than deer of higher and lower ranks. This is due to the time-energy budgeting patterns and captive stress of males with different status in the dominance hierarchy. That is, high-ranking males need to budget more time and energy to maintain their higher rank, while low-ranking males are exposed to more aggression from higher-ranking individuals, thus limiting their access to resources such as food and shelter. Accordingly, high-ranking and low-ranking males endured more stress than middle-ranking males, negatively affecting their annual musk production. Supporting the correlation between musk production and the frequency of tail-rubbing behavior was not significant, average musk extraction could not be predicted based on the frequency of tail-rubbing alone. Status in the dominance hierarchy, however, was positively correlated with tail-rubbing frequency, with males of higher rank tending to tail-rub more frequently. Conflict winners tended to initiate tail-rubbing after the conflict; tail-rubbing accounted for 83.33% of the post-conflict behavior expressed by the winner. Tail-rubbing was one of the behavioral rewards of winning a conflict and was also related to releasing aggression; not solely for scent marking territory and trails. Based on the results of this study, there was no direct relationship between musk production and captive males’ status in the dominance hierarchy (and, therefore, in the intensity of aggression displayed). If the sole aim of musk deer farms is to domesticate musk deer for maximum production of musk, we suggest that highly aggressive males be removed from the population. Musk production will remain unchanged, however, aggression level and intensity of fighting could be lessened thus reducing farming costs.     

Dominance hierarchy in a herd of female eland antelope (Taurotragus oryx) in captivity

The dominance hierarchy of a group of adult female elands (n=10) kept in captivity was followed for 34 months. Outcomes of dominance relationships at the beginning and end of the study were compared. A clear dominance hierarchy existed in the herd. The dominance pattern was complex, but triads were predominantly (95%) transitive or linear. Reversal of dominance occurred in 12 dyads (27%), of which eight (67%) involved a single female. Two females shared the most dominant rank at the beginning of the study. One of these two females and another female later assumed the highest dominance rank on different occasions. A single female remained most subordinate throughout the study period. The correlation between body weight and dominance rank was not significant (r=0.46; P=0.21). Similarly, dominance rank was not associated with the taming potential of the females. However, the median dominance value increased in females with good taming potential, while it decreased in those with poor taming potential. In conclusion, captive eland antelope have a dynamic and complex dominance hierarchy that is predominantly linear. Zoo Biol 23:323–333, 2004. © 2004 Wiley‐Liss, Inc.     

Agonistic Interactions and Matrifocal Dominance Rank of Wild Bonobos (Pan paniscus) at Wamba

I studied dominance relations in a wild group of bonobos at Wamba, Democratic Republic of Congo. Although agonistic interactions between males occurred frequently, most of them consisted only of display, and physical attacks were infrequent. Dominance rank order seemed to exist among males, but its linearity is unclear. Dominant males rarely disturbed copulatory behavior by subordinate males. However, high-ranking males usually stayed in the central position of the mixed party and, so, would have more chance of access to estrous females. Among females, older individuals tended to be dominant over younger individuals. However, agonistic interactions between females occurred rather infrequently, and most consisted of displacement without any overt aggressive behavior. Dominance between males and females is unclear, but females tended to have priority of access to food. The close social status between males and females may be related to the prolonged estrus of females and their close aggregation during ranging. Existence of a male's mother in the group and her dominance status among females seemed to influence his dominance rank among males. Young adult males whose mothers were alive in the group tended to have high status. In some cases, change in dominance between high-ranking males was preceded by a corresponding change in dominance between their mothers. As the dominance status of females is similar to that of males, mothers may be able to support their sons to achieve high status, stay in the center of the mixed party, and so have greater access to females, which may maximize the number of descendants of the mothers.     

Correlates of Self-directed Behaviors in Captive <Emphasis Type="Italic">Cercopithecus aethiops</Emphasis>

Researchers have widely used self-directed behaviors (SDB) as a behavioral indicator of anxiety in nonhuman primates. We examined if SDB rates in captive vervets (Cercopithecus aethiops) were associated with 1) proximity to conspecifics in general, 2) relative dominance rank of proximity partners, and 3) postconflict situations. Subjects were members of a captive group of vervets at the Lisbon Zoo, Portugal. The group comprised 3 males and 7 females, which were focal sampled for 10.5 h each. Vervets did not engage in more SBD while in proximity of conspecifics than while alone, and individual SDB rates were not generally influenced by dominance ranks of neighbors. Yet, victims of conflicts significantly increased their SDB rates after agonistic episodes, which is consistent with the view that SDB rates are an index of anxiety in Cercopithecus aethiops.     

Within-brood social status and consequences for winter hierarchies amongst Mallard Anas platyrhynchos ducklings

Juveniles of many birds establish dominance hierarchies within family social units, only to leave and compete to acquire dominance status in new social groups. Little is known about the role of sex, body mass, size or experience during the duckling period on subsequent dominance rank and adult social relationships. We used captive Mallard Anas platyrhynchos ducklings to test for the role of individual characteristics and growth parameters in establishing within-brood hierarchies, the maintenance of within-brood hierarchies in the subsequent wintering group and differences in social ranks between broods. Strong stable linear hierarchies were present within each brood and, later, within each phase of the winter. There was a reorganisation of the hierarchical order between the duckling period and early winter, but only few modifications afterwards during the winter. None of the tested “hatching”, “duckling” and “adult” traits explained either the within-brood or the winter hierarchies, but winter rank was related to brood of origin with ducklings from the same brood having similar social ranks. These differences between broods were maintained through the whole winter in most cases, though one brood drastically progressed in the hierarchy during late-winter. These results suggest that the factors affecting the establishment of social relationships within broods differ from those in winter groups, and that brood-related mechanisms influence social relationships during winter. We discuss our results in the light of direct and indirect maternal influence.     

Social and spatial relationships in captive southern white rhinoceros (Ceratotherium simum simum)

Although critical to the conservation of white rhinoceros, captive breeding has proven challenging because of the poor and irregular reproductive health of many captive rhinos, and social interactions may play a significant role. This research investigated the social and spatial relationships of two captive groups of southern white rhinoceros (Ceratotherium simum simum) by examining the frequency of companion changes, the number of space maintenance vocalizations made per hour by each reproductively mature female, and dominant/subordinate interactions. The observed captive rhinos did not change their companionships during the study. They exhibited space maintenance vocalizations and display greater than once per hour, particularly when feeding. Females housed with four calves on 0.033 km² exhibited space maintenance vocalizations more frequently (X±SE = 6.19±0.199/hr) than females housed with one calf and more space (0.06 km², X±SE = 0.55±0.182/hr) and females housed without calves and more space (0.65 km², X±SE = 1.90±0.086/hr). Wider separation of food piles and of females with young calves is suggested to reduce the interpreted spatial stress. The presence of a large number of rhinos in restricted captive space resulted in the formation of herds with dominance hierarchies that were enforced during competition for food and shade. The most subordinate rhino in each of the herds exhibited unusual behaviors such as dung‐kicking and nonestrus urine squirting, and neither has ever reproduced. Suppression of subordinate rhinos might lead to social stress that could negatively impact reproductive success. Zoo Biol 26:487–502, 2007. © 2007 Wiley‐Liss, Inc.     

Interplay between various aspects in social relationships of young rhesus monkeys: Dominance,agonistic help,and affiliation

Relationships between group-living primates depend strongly on their position in the group dominance hierarchy and on their relationships with other group members. The influence of various behaviours on social relationships of immature rhesus monkeys (Macaca mulatta) was investigated here. Dominance ranks were established and related to the degree of affiliation in a dyad. Older monkeys were mostly dominant to the younger ones, regardless of kinship. Subordinate monkeys left proximity of their dominant members more often than they were left by them both among siblings and non-siblings, but the effect of dominance rank on the amount of play initiation and grooming in a dyad differed between these two types of dyads. The amount of agonistic help two individuals provided for each other was low among immatures. Nevertheless, pairs of siblings gave help to each other in agonistic conflicts more often than non-siblings, and such help was more often reciprocated between siblings than between non-siblings. Help in agonistic conflicts was positively correlated with the amount of time monkeys spent playing, grooming, or in proximity. Adults tended to interfere less in conflicts of frequent sibling play partners or non-sibling grooming partners. No evidence was found for young monkeys to exchange reciprocally grooming for agonistic help. It is argued that the time monkeys spend interacting with each other in affiliative interactions increases their familiarity and thus promotes close relationships between them. On the whole, young monkeys' relationships, like those between adults, are influenced strongly by their kinship, and position in the dominance hierarchy.     

Dominance and association among members of a captive and a free-ranging group of grey kangaroos (Macropus giganteus)

Dominance relationships and the degree of association between members of groups of eastern grey kangaroos (Macropus giganteus) were investigated by observing a small group in captivity and a larger free-ranging group. Only decisive aggressive interactions were used as a criterion of dominance, and the number of times individuals occurred together were used as a measure of association. A dominance hierarchy in which the male assumed the highest rank was found in the captive group, while in the wild hierarchies were found separately among both males and females in the group. A low level of positive association existed between members of both the groups studied and the data indicated that in general the free ranging animals tended to move about at random with respect to each other. In the captive group dispersion about the enclosure was regular but became more random during the day in winter and spring.     

The social significance of plumage variability in wintering turnstone Arenaria interpres

Wintering turnstone, Arenaria interpres, have individually variable plumage. This paper examines the possibility that individual differences in plumage signal differences in dominance status (status signalling hypothesis) and/or allow individuals to be recognized by conspecifics (individual recognition hypothesis). The status signalling hypothesis was rejected on the basis of several lines of evidence: (1) differences in status between males and females, and between adults and juveniles, were not reflected by significant differences in plumage characteristics; (2) features of the plumage of adults remain the same from year to year yet the status of the adults probably changes; (3) in two flocks of wild turnstones dominance rank orders were not correlated with rank orders predicted by individual differences in three plumage variables. The individual recognition hypothesis was supported by tests showing that when the plumage of captive turnstone was experimentally altered, flock mates acted more aggressively towards them, irrespective of the form of the alteration.     

Aggression and social support predict long‐term cortisol levels in captive tufted capuchin monkeys (Cebus [Sapajus] apella)

Many nonhuman primates live in complex social groups in which they regularly encounter both social stressors such as aggression and social support such as that provided by long‐term affiliative relationships. Repeated exposure to social stressors may result in chronically elevated cortisol levels that can have deleterious physical effects such as impaired immune function, cardiovascular disease, and reduced brain function. In contrast, affiliative social relationships may act as a buffer, dampening the release of cortisol in response to acute and chronic stressors. Understanding how social stressors and social support predict cortisol levels is therefore essential to understanding how social situations relate to health and welfare. We studied this relationship in 16 socially housed captive brown capuchin monkeys (Cebus [Sapajus] apella) by comparing long‐term hair cortisol levels with behavioral measures of social stress (dominance rank, rank certainty, and amount of aggression received) and social support (amount of affiliation and centrality in the affiliative social network of the group). Dominance rank, rank certainty, amount of affiliation, and age were not significant predictors of long‐term cortisol levels in this population. Instead, long‐term cortisol levels were positively related to the amount of aggression received and negatively related to centrality in the affiliative social network of the group. This pattern may be attributed to the species’ socially tolerant dominance system and to the availability of social support across the dominance hierarchy.     

Agonistic behaviour and control of access to hiding places in two intertidal blennies, Lipophrys pholis and Coryphoblennius galerita (Pisces: Blenniidae)

In this study we investigated the relationships between dominance rank and access to shelters in captive groups of Lipophrys pholis and Coryphoblennius galerita, as well as the effects of group size and shelter availability. Dominance rank was strongly correlated with size in juvenile L. pholis and with sex and size in adult C. galerita, males being dominant over females of similar size. Access to shelters was significantly correlated with dominance rank. For both species, most interactions occurred out of shelters. Direct disputes over shelters were always initiated by the dominant fish and the initiator was always the winner. The rate of aggression per fish per unit time decreased with an increase in the number of fish in L. pholis but not in C. galerita. No significant differences were found in groups differing in the number of shelters. C. galerita showed a higher rate of agonistic interactions and a higher proportion of overt aggression than L. pholis. It is suggested that one of the functions of agonistic interactions in these fishes is the control of a set of shelters, in the network of pathways used by each individual within its home range, minimising the time required to hide in case of danger. Received in revised form: 29 January 2001 Electronic Publication     

Examination of the interrelationships of behavior,dominance status,and ovarian activity in captive Asian and African elephants

Ovarian inactivity has been identified in captive African (Loxodonta africana) and Asian (Elephas maximus) elephants and is thought to be mediated in part by social influences. Thus, a survey was conducted to determine how behavior and dominance status relate to each other and to ovarian cyclicity. For both Asian and African elephants, dominance status was positively correlated with relative size, age, temperament, disciplinary nature, and willingness to share novel objects. Relative size and temperament were also related to disciplinary nature toward herdmates. Behavior toward keepers was a good indicator of the willingness of elephants to follow commands, whereas sharing novel objects was positively correlated with object curiosity. Finally, dominance status, temperament, and disciplinary nature were all correlated with willingness to share. Comparisons of ovarian cyclicity status with behavior rankings were conducted only for African elephants because of the low number of noncycling Asian elephants surveyed. Overall, social status appeared to be the best predictor of ovarian activity in African elephants. Noncycling African elephant females ranked higher in the dominance hierarchy and gave more discipline to herdmates than cycling cohorts. It remains to be determined whether these are cause or effect relationships, but clearly it is important to understand how physical and social attributes impact physiological processes, such as reproduction. Captive management now needs to focus on optimizing social and environmental conditions to maximize reproductive potential in elephants. Zoo Biol 23:431–448, 2004. © 2004 Wiley‐Liss, Inc.     

圈养马麝(Moschus sifanicus)个性特征及与麝香分泌的关系

采用焦点取样和扫描取样方法,对甘肃兴隆山麝场圈养马麝(Moschus sifanicus)交配季节及非交配季节进行行为取样。通过行为样本,对个体个性特征(活跃性、领域性、刻板性、探索性、行为冗余性)进行标准化处理,分析了年龄及性别对个性特征的效应,以及交配季节与非交配季节之间个性特征的差异,同时分析了马麝个性特征与泌香量的相互关系。结果表明:年龄增加对活跃性具有降低的效应(P0.05),并对非交配季节领域性具有降低效应(P0.05);非交配季节里雌性活跃性高于雄性(P0.05);不同季节间个性特征存在差异,交配季节活跃性与领域性均有高于非交配季节的趋势,并且活跃性与领域性在两季节间呈正相关关系(P0.05);雄麝泌香量与活跃性存在正相关关系(交配季节:r=0.518,P0.05;非交配季节:r=0.397,P0.05),与交配季节领域性同样具有正相关关系(r=0.406,P0.05)。本研究通过行为取样方法首次对马麝个性特征进行定量分析,探讨了将个性特征,特别是活跃性和领域性,作为泌香量预测指标的方法,对圈养动物个性研究的理论创新具有指导作用,同时对麝香及麝类资源的发展具有实践意义。