Affiliative relationships and reciprocity among adult male bonnet macaques (Macaca radiata) at Arunachala Hill, India

In captivity, male bonnet macaques (Macaca radiata) frequently express "friendship" toward one another, including affiliative behavior such as huddling, grooming, coalitionary support, and sitting in close proximity. The purpose of this study was to determine whether wild adult male bonnet macaques also express "friendship" by investigating whether or not (1) adult male bonnet macaques have affiliative social relationships with other males, (2) the strength of social relationships varies among dyads, (3) there is time-matched reciprocity in allogrooming among dyads, and if so, whether the level of reciprocity occurs within a bout of grooming, a day, or over 2 months (the limit of this study), and (4) a correlation exists between the strength of social relationships and dominance ranks among adult males. Focal samples totaling 150 hr on all seven adult males in one study group were conducted to record both agonistic and affiliative interactions. Agonistic interactions were used to construct a dominance hierarchy, whereas affiliative interactions (sitting in proximity to within 1 m with and without grooming) were used to quantify the existence and strength of social bonds within dyads. Results show that adult male bonnet macaques had differentiated affiliative relationships with other males in their group. There was little reciprocity of grooming within a bout of grooming or within a day, but greater reciprocity over the study period of 2 months. There was no correlation between dominance ranking distance and the strength of affiliative relationship within dyads; however, within dyads lower-ranking males groomed higher-ranking males more than vice versa. This study suggests that friendships in male bonnet macaques are characterized not by immediate tit-for-tat reciprocal altruism, but by reciprocity over a longer time span, and that affiliative social relationships may be less constrained by agonistic relationships than is the case in more despotic species of macaques.     

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.     

Dominance hierarchy and social grooming in female lion- tailed macaques (Macaca silenus) in the Western Ghats, India

This article reports the structure of dominance and its relationship with social grooming in wild lion-tailed macaque females. The strength of dominance hierarchy was 0.79 on a scale of 0 to 1 indicating a moderate linearity in the ranking system. Dominance scores were converted into an ordinal as well as an interval scale. Grooming scores were also converted into interval scales using standard scores. Grooming received and grooming given correlated positively and negatively respectively with dominance ranks indicating that high ranking females received more and gave less grooming. Grooming was also positively related to encounter rates for dyads of females. More grooming among adjacent ranks, and grooming being more reciprocal, occurred only in the case of dominant females. The grooming patterns, therefore, appeared to be more of despotic than egalitarian nature. While ranking macaques into different Grades of social systems ranging from despotic to egalitarian, Thierry (2004) has placed lion-tailed macaques in Grade 3 corresponding to the ‘relaxed’ social system. Our results indicate that the grooming and dominance relationships in this species are more despotic, and hence, the Grade for this species requires to be shifted toward 2 or 1.     

The functions of the "Greeting Ceremony" among male mantled howlers (Alouatta palliata) on Agaltepec Island, Mexico

Nonhuman primates use greeting behaviors as nonaggressive communicatory signals in multiple social contexts. Adult male mantled howlers (Alouatta palliata) perform a ritual greeting that has been associated with bond-strengthening functions. The aim of this study is to explore the greeting patterns of male howlers living on Agaltepec Island, Mexico. Specifically, we analyzed the relationships between greetings and several individual, relational, and contextual variables, such as the expression of affiliation and agonism, dominance rank, age, kinship relationships, spatial organization, activity patterns, and subgrouping patterns. Greetings were more frequent between males with closer dominance ranks. Among those dyads that greeted at least once, dominant males initiated greetings more frequently than less-dominant males. On the other hand, more greetings were observed when one of the participants had recently returned to a subgroup and during locomotion. On the basis of these results, we propose that on Agaltepec greetings are a conflict management mechanism used between males of similar ranks. The fission-fusion social system of this group of howlers allows males with conflicting interests to remain separated, and greetings may reduce tension during fusion events.     

Dominance and its Behavioral Measures in a Captive Group of Bonobos (Pan paniscus)

We investigated the existence of a social dominance hierarchy in the captive group of six adult bonobos at the Planckendael Zoo. We quantified the pattern of dyadic exchange of a number of behaviors to examine to what extent each behavior fits a linear rank order model. Following de Waal (1989), we distinguish three types of dominance: agonistic dominance, competitive ability and formal dominance. Fleeing upon aggression is a good measure of agonistic dominance. The agonistic dominance hierarchy in the study group shows significant and strong linearity. The rank order was: 1. female (22 yr), 2. female (15 yr)., 3. male (23 yr.), 4. female (15 yr.), 5. male (9 yr.), 6. male (10 yr.). As in the wild, the females occupy high ranks. There is prominent but nonexclusive female agonistic dominance. Teeth-baring does not fulfil the criteria of a formal submission signal. Peering is a request for tolerance of proximity. Since its direction within dyads is consistent with that of fleeing interactions, it is a useful additional measure to determine agonistic ranks in bonobos. In competitive situations, the females acquire more food than other group members do. The rank obtained from access to food resources differs from the agonistic rank due to female intrasexual social tolerance, expressed in food sharing. We typify the dominance styles in the group as female intrasexual tolerance and male challenging of rank differences. The agonistic rank order correlates significantly with age and has a strong predictive value for other social behaviors.     

Female dominance and female social relationships among yellow baboons (Papio hamadryas cynocephalus)

Adult females in a female-bonded, cercopithecine species such as baboons are characterized by hierarchically ranked matrilines, i.e., female offspring assume rankings just beneath those of their mothers. In this system of closely ranked matrilines, a female should engage in significantly more affiliative interactions with those individuals who are closely ranked to herself than with those individuals who are more distantly ranked. We examine the hypothesis that females in this troop of feral yellow baboons (Papio hamadryas cynocephalus) who are closely ranked will also show close social affiliation. We collected focal data on 23 feral, adult female subjects (253 possible dyads) over approximately 1 year at the Tana River National Primate Reserve, Kenya. Following Bramblett's [Behav Brain Sci 4: 435, 1981] method of dominance tabulation and utilizing a modified version of Smuts' [Sex and friendship in baboons, Hawthorne: Aldine Publishing Co., 1985] preferred partner index, we describe and compare the dominance matrix and hierarchy, preferred proximity partner and grooming partner sociograms, and the social networks of these 23 focal females. Over 1,400 interactions were utilized in the dominance tabulations, 41 statistically significant proximity partner preferences were documented, and 100 grooming dyads were recorded. We examine both partners' ranks and the presence of an infant as possible factors influencing proximity and grooming partner preferences. We find that in this population there is no direct correspondence between females' ranks and their affiliation partners. Neither proximity nor grooming preferences are consistently predictable from partners' ranks. While proximity preferences were not significantly influenced by the presence of an infant, grooming partner preferences were. Females with infants had more grooming partners and were more often involved in unidirectional grooming relationships as the recipients than were females without infants. We conclude that females' dominance rankings are not good predictors of either proximity partner or grooming partner preferences and that the presence of an infant does have a significant impact on grooming partner preferences in this population.     

Effect of testosterone and melatonin on social dominance and agonistic behavior in male Tscheskia triton

Social dominance and agonistic behavior play important roles in animal societies. Melatonin and testosterone are closely related to social dominance and agonistic behavior in rodents, but interactions between both of them remain unknown. In this study we investigated the effects of testosterone and melatonin by manipulating photoperiod and castration on social dominance and agonistic behavior in male Tscheskia triton. Castration significantly decreases social dominance of both short- and long-day males, suggesting that testosterone benefits social dominance of males in both breeding and non-breeding seasons. In intact conditions, long-day males tended to dominate short-day males, suggesting that the effect of testosterone on social dominance was a little stronger than melatonin. However, castrated short-day males became dominant over their castrated long-day opponents meaning that high melatonin levels obviously benefit social dominance in males. Hormone implantation indicated that testosterone had no effect on non-breeding condition, but that melatonin was important during the breeding season. Our results indicate that both testosterone and melatonin are important in determining social dominance in male hamsters, and the effect of testosterone appears to be stronger than melatonin. Testosterone is responsible for aggression and social dominance in male hamsters during the breeding season, while melatonin regulates behavior during non-breeding, probably due to the different seasonal secretory patterns of the hormones.     

Matrilineal rank Inheritance varies with absolute rank in Japanese macaques

In many cercopithecine primates, females form linear dominance hierarchies based on kinship. It is known that female rank follows the rules of matrilineal rank inheritance (MIR): (1) maternal rank inheritance, (2) maternal dominance, and (3) youngest ascendancy among sisters. Although, several determining such variation remain largely unknown. In this paper, I investigate the dominance relation-ships of 69 adult (>6 yr old) female Japanese macaques (Macaca fuscata fuscata) in a free-ranging provisioned troop living in Shiga-Heights (Nagano Prefecture, Japan) and report new evidence of intra-group variation. Dominance relationships among high-ranking females followed MRI within kin units, those among low-ranking females did not. Maternal rank inheritance and youngest ascendancy operated between mother/daughter dyads and sister dyads of high-rank, but not in the dyads of low-rank. The dominance ranks of females from low-ranking kin units were dispersed and less predictable. These findings suggest that MRI varies with absolute dominance rank, and are discussed in relation to other asymmetries between high-and low-rank     

雄性短尾猴的等级顺位、睾酮水平与肠道寄生虫感染强度的关系

在等级森严的非人灵长类群体中,睾酮对雄性顺位维持有着重要作用,且影响着体内寄生虫种类和荷虫量。本研究以栖息于安徽黄山的雄性短尾猴为研究对象,通过计算成年雄性的等级顺位,测定其粪便中睾酮含量以及寄生虫的荷虫量,探讨雄性等级顺位、睾酮水平与健康间的平衡关系。结果表明：共检测出10种肠道寄生虫,包括4种蠕虫、5种原虫和1种螨虫;其中雄性短尾猴个体间睾酮水平（1.00±0.42） ng/g和肠道寄生虫荷虫量（112.44±83.62）EPG均存在显著差异（Kruskal-Wallis H,P<0.05）;等级顺位与睾酮水平呈正相关（Spearman, N=8,ρ= 0.326, P<0.05）,与肠道原虫类的荷虫量呈负相关（Spearman, N=8,ρ= - 0.345, P<0.05）,与肠道蠕虫类的荷虫量无相关性（Spearman, N=8,ρ= 0.065, P>0.05）;睾酮水平与肠道原虫类寄生虫的荷虫量呈负相关（Spearman, N=8,ρ= -0.546, P<0.05）,与肠道蠕虫类的荷虫量无相关性（Spearman, N=8,ρ= -0.013, P>0.05）。本研究表明高顺位雄性拥有更高的睾酮水平,这不仅对其顺位的维持具有重要作用,对原虫类寄生虫也具有明显的抑制作用。     

Longitudinal study of dominance relations among captive patas monkeys

Eight and a half years of dominance relations within a captive group of patas monkeys were analyzed. It was found that matrilineal kinship significantly influenced individuals' ranks. In contrast, with the exception of certain intramatriline changes, increasing age had no predictable effect on overall rank, at least for females (this was untestable for males). Offspring typically challenged maternal dominance and in eight of twelve dyads, offspring either rose fully over their mothers (three cases, all daughters) or at least achieved dominance ambiguity with them. Additionally, two of the four younger sisters with an opportunity to rise in rank over an older sister did so. The group dominance hierarchy was unstable for 75% of the study due to a combination of agonistically induced and demographically induced rank changes. Concentration of the highest ranks in a single matriline showed a stronger association with group hierarchy stability than did the presence of an adult, nonnatal male. Group hierarchy stability was associated with increased affiliation (sitting close and sitting touching), but otherwise there were no behavioral correlations. Individuals' ranks within the group hierarchy were unrelated to their chances of being wounded or having diarrhea. Adult females' ranks were over twice as stable as the group hierarchy (57.1% stability), but stability/instability was not correlated with any behavioral changes. Available evidence suggests that dominance relations play only a minor role in the organization of patas monkeys' intragroup behavior. Am. J. Primatol. 42:41–51, 1997. © 1997 Wiley-Liss, Inc.     

The relation between dominance and exploratory behavior is context-dependent in wild great tits

Individual differences in personality affect behavior in novelor challenging situations. Personality traits may be subjectto selection because they affect the ability to dominate others.We investigated whether dominance rank at feeding tables inwinter correlated with a heritable personality trait (as measuredby exploratory behavior in a novel environment) in a naturalpopulation of great tits, Parus major. We provided clumped resourcesat feeding tables and calculated linear dominance hierarchieson the basis of observations between dyads of color-ringed individuals,and we used an experimental procedure to measure individualexploratory behavior of these birds. We show that fast-exploringterritorial males had higher dominance ranks than did slow-exploringterritorial males in two out of three samples, and that dominancerelated negatively to the distance between the site of observationand the territory. In contrast, fast-exploring nonterritorialjuveniles had lower dominance ranks than did slow-exploringnonterritorial juveniles, implying that the relation betweendominance and personality is context-dependent in the wild.We discuss how these patterns in dominance can explain earlierreported effects of avian personality on natal dispersal andfitness.     

Control of aggression and dominance in white-throated sparrows by testosterone and its metabolites

In three experiments, we investigated whether testosterone itself or its metabolites activate aggression and dominance in white-throated sparrows Zonotrichia albicollis. Groups of five to six sparrows, each treated with a different steroid implanted subcutaneously, were observed in outdoor aviaries during late winter to determine the birds' rates of aggression (supplantations and attacks scaled to the number of available subordinates) and dominance rankings with opponents not previously encountered. In Experiment 1, testosterone (T) had a greater effect on aggression and dominance than did androstenedione, 5α-dihydrotestosterone (D), androsterone, or estradiol (E). In Experiment 2, birds with T or D + E had higher aggression scores and dominance ranks than birds with either D or E alone. Birds with T and D + E did not differ. The testosterone metabolites, D and E, thus acted synergistically to determine rates of aggression and dominance ranks. To corroborate these results, in Experiment 3 we treated T-implanted birds with the following blocking agents: ATD, expected to reduce conversion of T to E (AT birds); progesterone, expected to reduce conversion of T to D (PT birds); or both (APT birds). The APT birds had lower aggression scores and dominance ranks than did AT or PT birds, despite having higher mean levels of circulating T than AT or PT birds or birds implanted with T alone. Cyproterone acetate also reduced aggression scores and dominance in T-implanted birds. We conclude that the hormonal control of aggression and dominance in these birds requires conversion of testosterone to both androgenic and estrogenic metabolites.     

Serum testosterone, male dominance, and aggression in captive groups of vervet monkeys (Cercopithecus aethiops sabaeus)

The relationship of serum testosterone concentration to male dominance rank and frequency of aggression was investigated in stable vervet monkey social groups, each containing two or three adult males, several adult females, and their offspring. Dominance relationships were determined by noting an animal's success in intermale aggressive encounters. A striking finding was the marked within-subject variation in testosterone concentration: 5- to 10-fold fluctuations were often observed on successive days. When all 15 groups were considered together, testosterone concentration was unrelated to dominance rank. Although mean testosterone concentration for all dominant males was higher than the mean for all subordinate males, this difference was not significant. In a subset of 4 groups, the rate of aggression initiated was significantly correlated with same-day testosterone in dominant but not in subordinate males.     

Linear social dominance hierarchy and corticosterone responses in male mallards and pintails

In winter, dabbling ducks gather in large flocks and males compete not only for food resources but also for mates. Setting up a social hierarchy is one way to reduce the costs of conflicts, but the position in the hierarchy has implications for individuals, for instance their susceptibility to conflict and interference, hence to social stress. We investigated relationships between linear social dominance and corticosterone levels, baseline levels and induced-stress response, in captive male mallards Anas platyrhynchos and pintails Anas acuta during the winter period. We hypothesised that corticosterone responses would reflect the costs associated with social stress. From previous work on dominance and corticosterone in wintering birds, we expected that, where the social hierarchy is linear, there would be (1) no relationship between social ranks and baseline corticosterone levels and (2) a significant positive relationship between dominance ranks and responses to acute stress. Our results demonstrated the existence of a linear hierarchy in both species (h' = 0.95 for mallards and h' = 0.97 for pintails), and we found that pintails had on average more corticosterone than mallards. The relationship between dominance and corticosterone responses followed the predictions, with no differences for baseline levels and an attenuated response to induced-stress for subordinates. We discuss these results in the perspective of the cost-benefits of dominance and wintering strategies of waterbirds.     

Testosterone and cortisol jointly regulate dominance: Evidence for a dual-hormone hypothesis

Traditional theories propose that testosterone should increase dominance and other status-seeking behaviors, but empirical support has been inconsistent. The present research tested the hypothesis that testosterone's effect on dominance depends on cortisol, a glucocorticoid hormone implicated in psychological stress and social avoidance. In the domains of leadership (Study 1, mixed-sex sample) and competition (Study 2, male-only sample), testosterone was positively related to dominance, but only in individuals with low cortisol. In individuals with high cortisol, the relation between testosterone and dominance was blocked (Study 1) or reversed (Study 2). Study 2 further showed that these hormonal effects on dominance were especially likely to occur after social threat (social defeat). The present studies provide the first empirical support for the claim that the neuroendocrine reproductive (HPG) and stress (HPA) axes interact to regulate dominance. Because dominance is related to gaining and maintaining high status positions in social hierarchies, the findings suggest that only when cortisol is low should higher testosterone encourage higher status. When cortisol is high, higher testosterone may actually decrease dominance and in turn motivate lower status.     

Social organization and endocrine profiles of <Emphasis Type="Italic">Australoheros facetus</Emphasis>, an exotic freshwater fish in southern Portugal

Australoheros facetus is a neotropical cichlid and an exotic species in the Guadiana and Odelouca basins (Southern Portugal). In this research, we aimed to characterize the main behavioural patterns and circulating hormones, 17β-estradiol (E₂) for females, and testosterone, 11-ketotestosterone (11KT) and cortisol for both sexes, during the formation of social groups, a crucial step in the life-history of A. facetus. A pair-breeding strategy with territorial behaviour and aggressive interactions was found, with a positive correlation between dominance and size for both sexes. There were no significant differences between non-territorial and territorial individuals in the baseline levels of hormones, but 11KT was higher in males when they became territorial, as E₂ for territorial females, while there was no clear pattern for testosterone. In contrast, cortisol was higher in non-territorial males and correlated negatively with social dominance. These results suggest that size is the main driver for social dominance and that formation of stable hierarchies result in higher circulating 11KT and lowers stress in territorial males. Related to A. facetus’ behaviour, aggressiveness and biparental care may be an advantage during the invasion process of A. facetus, facilitating colonization of new habitats.     

Testosterone and cortisol jointly regulate dominance: Evidence for a dual-hormone hypothesis

Traditional theories propose that testosterone should increase dominance and other status-seeking behaviors, but empirical support has been inconsistent. The present research tested the hypothesis that testosterone's effect on dominance depends on cortisol, a glucocorticoid hormone implicated in psychological stress and social avoidance. In the domains of leadership (Study 1, mixed-sex sample) and competition (Study 2, male-only sample), testosterone was positively related to dominance, but only in individuals with low cortisol. In individuals with high cortisol, the relation between testosterone and dominance was blocked (Study 1) or reversed (Study 2). Study 2 further showed that these hormonal effects on dominance were especially likely to occur after social threat (social defeat). The present studies provide the first empirical support for the claim that the neuroendocrine reproductive (HPG) and stress (HPA) axes interact to regulate dominance. Because dominance is related to gaining and maintaining high status positions in social hierarchies, the findings suggest that only when cortisol is low should higher testosterone encourage higher status. When cortisol is high, higher testosterone may actually decrease dominance and in turn motivate lower status.     

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.     

Stress, social behaviour, and secondary sexual traits in a male primate

We examined variation in glucocorticoid levels in the mandrill, a brightly coloured primate species, to identify major social influences on stress hormones, and investigate relationships among glucocorticoid levels, testosterone and secondary sexual ornamentation. We collected a total of 317 fecal samples for 16 adult male mandrills over 13 months, including mating and non-mating periods and periods of both dominance rank stability and instability, and compared fecal glucocorticoid levels with dominance rank, rank stability, presence of receptive females, gastro-intestinal parasite infection, fecal testosterone and facial red coloration. Glucocorticoid levels did not vary systematically with dominance rank, but increased when the dominance hierarchy was unstable, and increased in the presence of receptive females. The relationship between dominance rank and glucocorticoid levels changed direction according to the stability of the dominance hierarchy: glucocorticoid levels were higher in subordinate males under stable conditions, but under conditions of instability higher ranking males had higher glucocorticoid levels. The influence of dominance rank also interacted with the presence of receptive females: glucocorticoids were higher in dominant males than in subordinates, but only during mating periods, suggesting that dominant males are more stressed than subordinates during such periods. These findings support previous studies showing that the relationship between glucocorticoids and dominance rank in male baboons is dependent on the social environment. We also found that males with higher glucocorticoids suffered a higher diversity of gastrointestinal parasite infection, in line with evidence that glucocorticoids suppress the immune system in other species. However, we found no support for the stress-mediated immunocompetence handicap hypothesis for the evolution of condition-dependent ornaments: glucocorticoid and testosterone levels were positively related, rather than the negative relationship predicted by the hypothesis, and we found no relationship between red colour and glucocorticoid levels, suggesting that glucocorticoids do not play a role in translating social conditions or physical health into ornament expression in this species.     

Maternal testosterone in tree swallow eggs varies with female aggression

Variation in the investment of maternal resources in eggs, such as proteins and lipids, can have a profound influence on the growth and development of young. Maternal resources transferred to eggs also include androgens found in the yolk. In several species of birds the concentration of testosterone in the yolk either increases or decreases with laying order. Yolk testosterone has been shown to have various effects on the young including enhanced growth and dominance as well as reduced survival. Previous work suggested that the concentration of testosterone in the yolk may be influenced by the female's social conditions, specifically the frequency of aggressive interactions. In tree swallows, Tachycineta bicolor, we found that yolk testosterone was correlated with the aggressive interactions of the female before and during egg laying. In contrast to other species, yolk testosterone did not vary with laying order in tree swallows. Thus, patterns of yolk testosterone are more variable than thought previously and may be influenced by the social conditions experienced by the female during laying.