Sex differences in vocal communication among adult rhesus macaques

In female-bonded primate species, females invest more time in grooming than males, and the majority of this grooming occurs in intra- rather than intersexual interactions. These clear sex differences in sociability reflect females' need to forge and maintain complex networks of social relationships with other females in the group. Increasing evidence indicates that vocal signals can have a similar function to grooming in mediating social interactions and relationships, and sex differences in patterns of use of vocal communication comparable to those seen for grooming might therefore be expected to occur. In this study of free-ranging adult rhesus macaques, we tested for such patterns, focusing on the frequency of utterance of three types of vocalisations given during close-range social interactions: coos, grunts, and girneys. As predicted, we found that females gave such calls significantly more frequently than males and also directed more of these vocalisations towards other females than to males; males' rate of vocalising towards the two sexes was not significantly different. To our knowledge, these results provide the first evidence for a sex difference in the rate of production of social vocalisations among adult nonhuman primates. The finding that increased sociability is associated with increased reliance on vocal communication may have important implications for theories of language evolution.     

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.     

Social segregation in male,but not female yearling rhesus macaques (Macaca mulatta)

Males and females of many species sex‐segregate, ranging from complete separation of habitats to social segregation within the same space, sometimes varying across seasons and lifespan development. Mechanisms for such segregation are not well understood, though some have suggested that sex differences in preferred juvenile behaviors lead to greater behavioral compatibility within than between sexes. This within‐sex behavioral compatibility may be the source of sex‐segregation. As juvenile behavioral sex differences are well‐documented in rhesus monkeys, we examined sex‐segregation patterns of yearling rhesus monkeys engaged in three different types of behavior: rough play, parallel play, and grooming. We observed male and female rhesus yearlings from five stable long‐term age‐graded social groups of 67–183 animals. Behavioral observations were designed to collect equal numbers of rough play, grooming, and parallel play bouts. In addition, sex composition and proximity to adults was recorded for each bout. Across all behaviors, more all‐male groups and fewer mixed sex‐groups were observed than expected by chance. All‐female groups occurred at the level expected by chance. Thus, males sex‐segregated regardless of type of behavior, while females did not sex‐segregate. Female groups were observed in proximity to adults more often than expected by chance. These results suggest that behavioral compatibility may produce sex‐segregation in male yearling rhesus monkeys, possibly preparing males and females for different social roles and segregation as adults. Am. J. Primatol. 72:87–92, 2010. © 2009 Wiley‐Liss, Inc.     

Male Mating Tactics in Captive Rhesus Macaques (Macaca mulatta): The Influence of Dominance, Markets, and Relationship Quality

Male mating success in a multimale–multifemale group can depend on several variables: body condition, dominance, coalitions, “friendship,” or an exchange of services for mating access. Exchange patterns may also be determined by market effects or social relationships. We studied the mating tactics of males in a captive, multimale–multifemale group of rhesus macaques and the resulting patterns of mating and paternity to determine the influence of dominance rank, mating markets, and relationship quality on their mating tactics. Male rank was positively related to the total number of copulations and the number of mating partners, but did not explain male mating distribution completely. Moreover, male fertilization success was not related to male rank. Males did not exchange grooming for mating access on the same day and neither the supply nor the rank (as a proxy for quality) of receptive females affected the amount of male grooming, suggesting that market effects did not explain male mating access. However, there was a positive correlation between long-term grooming patterns of both males and females and mating access, indicating that social relationships were important for male mating access. Paternity data revealed that these social relationships were also important for male reproductive success. We conclude that both male rank and male–female “friendship” determined male mating access in these rhesus macaques, but that “friendship” was more important in determining paternity, emphasizing the importance of intersex social bonds in male mating success in multimale primate societies.     

个体亲近程度对藏酋猴攻击行为的影响

友好和冲突行为决定了群居动物的社会结构及其表现形式,表现为个体间近距差异。但目前尚不清楚藏酋猴个体间亲近关系的差异性是否会影响冲突和攻击的强度。本研究于2020年9月至2021年5月对栖息于安徽黄山的藏酋猴鱼鳞坑YA1群进行跟踪观察,采用目标动物取样法采集行为数据,全事件记录法用于攻击行为数据的补充,分析个体间近距、理毛和攻击行为矩阵的关系,并采用GLMM模型探讨攻击行为的影响因素。结果显示：藏酋猴个体间近距指数越大,理毛时间越长;个体间近距指数矩阵与攻击总次数、轻度攻击和重度攻击次数矩阵均呈显著正相关;个体间亲近关系越紧密,攻击次数和强度越大,但相较雄性间和异性间,雌性间攻击次数和强度最小。这些结果表明,个体间近距持续时间会增加理毛和攻击行为的可能性,雌性个体间社会关系更稳定,但并未发现藏酋猴根据个体间亲近关系调整攻击强度。本研究为进一步了解多雌多雄的藏酋猴群体的社会关系和社会结构提供了数据支持。     

Mating patterns,mate choice,and birth season heterosexual relationships in free-ranging rhesus macaques

Birth season adult heterosexual nonkin relationships of 50 free-ranging female rhesus macaques (Macaca mulatta) in two social groups at Cayo Santiago, Puerto Rico were examined using focal follow (289 hr) and ad lib data. Eighty-eight percent of subjects had at least one relationship characterized by particularly high frequencies of spatial proximity, grooming, or both. These were designated “friendships.” Males intervened in aggressive interactions more frequently on behalf of Friends than non-Friends. Female aggressive support of males was extremely rare. Higher-ranking males experienced more friendships than lower-ranking males. High-ranking females had higher-ranking Friends than low-ranking females. Older females had higher-ranking Friends than younger females. Females groomed high-ranking Friends more than they were groomed by them, whereas they groomed low-ranking Friends less than they were groomed by them. In one social group, high-ranking females were more likely than low-ranking females to groom their Friends more than they were groomed by them. Males were more responsible than females for spatial proximity maintenance in 9 of 14 Friend dyads for which sufficient data were available. Neither male nor female dominance rank affected responsibility for proximity maintenance in Friend dyads. Eight of 24 females had friendships with males with whom they had completed copulations during their conception peri-ovulatory period of the preceding mating season. Two of 19 females completed peri-ovulatory copulations with Friends during the following mating season. Friendship was not correlated with either of two demonstrated female mate choice indicators: (1) proximity maintenance during estrus; or (2) cooperation with male “hip-grasp” courtship attempts. Males directed “muzzle-up” courtship signals at lower rates toward Friends than toward non-Friends. These and other investigators' results indicate that (1) protection from aggression is the primary benefit to female rhesus macaques of birth season heterosexual relationships; (2) the most effective protectors are in greatest demand as Friends; and (3) friendship has no effect or an inhibitory effect on mate choice in this species. Benefits to males of friendships were not apparent from this study but may include coalitional support against lower-ranking males.     

Effects of provisioning on the social behaviour of Japanese and rhesus macaques: Implications for socioecology

Long-term studies have shown remarkable similarity in the social behaviour and relationships of Japanese and rhesus macaques living in free-ranging groups. The vast majority of these studies have been of provisioned groups and many key principles have been derived from them. Provisioning is known to influence various aspects of life history and demography, as well as quantitative aspects of social behaviour, such as the frequencies of grooming and aggression. It has been widely assumed, however, that the fundamental characteristics of social behaviour and relationships observed in provisioned populations are representative of those that would occur under natural conditions. This paper reviews findings from fieldwork on Japanese macaques living under natural conditions, and compares them with patterns of social behaviour reported by multiple studies of provisioned groups of both species. Differences are apparent in the nature of social relationships between adult females, between adult males, and between adult males and females. Some of these differences can be attributed to the increased levels of aggression associated with provisioning. Others appear to be related to demographic peculiarities of provisioned groups, such as large size and skewed sex ratio. These differences can be used to generate predictions concerning the influence of ecological variables on the dynamics of social relationships and social structure. Ways in which these predictions could be tested by further fieldwork on provisioned and natural populations are discussed.     

Social interactions among female rhesus macaques (Macaca mulatta) during the nonbreeding season: Responses to the introduction of males

When rhesus monkeys are observed in social groups during the breeding season, increases in interfemale aggression coincide with midcycle increases in sexual activity between males and females. However, some investigators have suggested that both aggressive and affiliative interactions between females are influenced by the presence or absence of males, irrespective of menstrual cycle stage. In the present study, social interactions among members of a captive group of rhesus females were measured during the non-breeding season in response to the introduction of rhesus males. Ovariectomized rhesus females (estrogen-treated or untreated) served as stimulus controls. Tests with males were characterized by significantly decreased interfemale proximity and grooming and significantly increased aggression from that seen in tests with stimulus females or in the absence of stimulus animals. Only interfemale proximity declined significantly during stimulus female tests, but results suggest that this may merely reflect a decline in this behavior that occurs across the course of the day. Estrogen treatment did not alter either the aggressive or affiliative behavior of stimulus females or group female response to stimulus females. The possibility is discussed that changes in interfemale interactions during tests with males reflect female interest in interacting with the male, particularly under social conditions that may limit such interactions.     

Symmetrical patterns in non-agonistic social interactions found in unprovisioned Japanese macaques

Non-agonistic social interactions in an unprovisioned troop of Japanese macaques (Macaca fuscata yakui) were analyzed with the spacing between individuals, leading-following interactions, and exchange of social grooming. The most frequent interactions were found between kin-related females. Unrelated females stayed with one another rather frequently, but rarely exchanged social behaviors. Interactions between males and females were infrequent though they were occasionaly observed between high-ranking males and high-ranking females. Very frequent exchange of grooming was observed between males, and even high-ranking males exchanged grooming more frequently with males than with females. Most non-agonistic social interactions in the study troop were based on bidirectional exchange of social behaviors, in which no clear tendency relevant to dominance or sex was found; while in provisioned Japanese macaque troops, associations between males and females, between unrelated females, and between males were formed mainly be subordinates' active roles in associative behaviors. This seems relevant to the idea that dominance grealty influence social life in provisioned troops. The present study provides guidelines for interspecific comparison of social interaction patterns of macaque species.     

Quantitative observations of grooming behavior in free-rangingMacaca mulatta

Quantitative methods of observation and analysis were used in a 12-month study of grooming behavior of free-rangingMacaca mulatta on La Cueva Island at La Parguera, Puerto Rico. Observations lasting 30–120 minutes were made from eight positions on the island at a standard time of day when monkeys were either feeding or resting. Two dependent variables were obtained: (1) the number of monkeys present in the observation area were noted by age and sex class at five-minute intervals throughout each observation, and (2) the frequency of grooming encounters was tabulated by the age and sex class(es) of groomer and recipient. These data were computed as grooms/hour/possible interacting combination of monkeys. Grooming frequencies were higher in non-feeding situations than when monkeys were feeding. The largest social group had the lowest mean grooming rates, while the smallest group had the highest grooming frequencies. More grooming occurred during the November-to-February mating season than at other periods of the year. Adult females were involved in over 60% of all grooming behavior, juveniles participated in 25% of the grooming, while adult males groomed females, primarily during the mating season, and rarely groomed other males or juveniles. Genealogical relationships, levels of group aggression and the feeding or resting context all influenced the frequency of grooming. This study provides support for the hypothesis that the basic social unit for rhesus macaques consists of a core of adult females with their juvenile and infant progeny.     

Allogrooming in two species of macaque (Macaca nemestrina andMacaca radiata)

This paper analyzes allogrooming (social grooming) data collected from two large, fully integrated and long established social groups of macaques (one of pigtail macaques and one of bonnet macaques). The data demonstrates a species and sex difference for total allogrooming given with females of both species giving more grooming than the males and with pigtails as a species giving more grooming than bonnets. Also, pigtail females gave more allogrooming to clan members than to nonclan members, but this was not true for pigtail males, bonnet males, and bonnet females. Allogrooming given and allogrooming received by age class for both species showed development of a sexual dichotomy at three to four years. The analysis characterized some of the social structures extant in two closely related species of macaque, particularly the somewhat different use of allogrooming in pigtail females as opposed to the other three categories of animals. Social implications with relation to macaque societies are discussed.     

Sex and age differences in juvenile social priorities in female philopatric,nondespotic blue monkeys

Juveniles should choose social partners on the basis of both current and future utility. Where one sex is philopatric, one expects members of that sex to develop greater and sex‐typical social integration with group‐mates over the juvenile period. Where a partner's position in a dominance hierarchy is not associated with services it can provide, one would not expect juveniles to choose partners based on rank, nor sex differences in rank‐based preferences. We tested these ideas on 39 wild juvenile (3.2–7.4 years) blue monkeys (Cercopithecus mitis stuhlmanni), cercopithecines with strict female philopatry and muted hierarchies. We made focal animal observations over 6 months, and computed observed:expected amounts of proximity time, approaches and grooming given to various social partners. Overall, our results agree with the hypothesis that juvenile blue monkeys target social partners strategically. Spatial proximity, approaches and active grooming showed similar patterns regarding juvenile social preferences. Females were far more sociable than males, groomed more partners, reciprocated grooming more frequently, and preferred—while males avoided—infants as partners. Older juveniles (5–7 years) spent more time than younger juveniles (3–4 years) near others, and older females were especially attracted to infants. Close kin, especially mothers and less consistently adult sisters, were attractive to both male and female juveniles, regardless of age. Both sexes also preferred same‐sex juveniles as social partners while avoiding opposite‐sex peers. Juveniles of both sexes and ages generally neither preferred nor avoided nonmaternal adult females, but all juveniles avoided adult males. Partner's rank had no consistent effect on juveniles' preference, as expected for a species in which dominance plays a weak role. Juveniles' social preferences likely reflect both future and current benefits, including having tolerant adult kin to protect them against predators and conspecifics, same‐sex play partners, and, for females, infants on which to practice mothering skills. Am. J. Primatol. 72:193–205, 2010. © 2009 Wiley‐Liss, Inc.     

Male–Female Association Patterns Among Free-ranging Chimpanzees (Pan troglodytes schweinfurthii)

Although male–female relationships can offer a number of advantages such as protection or social support, they are poorly studied among primates compared to same-sex relationships. We used 12 yr of data from the Kanyawara chimpanzee community to compare three independent measures of association (party association, 5m association, and grooming) among all adult dyads. Party association exhibited by male–female dyads was of intermediate strength between strong male–male and weak female–female association. Male–female dyads were less likely to be within 5m of one another and to groom as male–male dyads, but equally likely to be within 5m and more likely to groom as female–female dyads. Variation in male–female association strength was not related to male rank but was affected by female ranging patterns and female reproductive states. Females with core areas in the center of the home range were more likely to be in parties with males but did not show higher spatial proximity or grooming indices compared to females ranging in the periphery. Party association and 5m indices were higher for dyads of males and estrous females compared to those with anestrous females. These results indicate that male–female dyads are likely to associate with one another more often than female–female dyads because of overlapping ranging patterns and short-term changes in female reproductive state. We conclude that male and female chimpanzees do not exhibit proximity and grooming patterns indicative of strong affiliative bonds. This study also highlights the importance of using multiple independent measures of bond strength in studies of primate social dynamics.     

Social Relationships in Free-Ranging Male Macaca arctoides

Macaque social relationships differ greatly between species. Based on captive studies that focus mainly on females, researchers have classified stumptail macaque (Macaca arctoides) social relationships as tolerant, as indicated by a high rate of affiliation, frequent aggression, and symmetrical conflicts. To accumulate more data on male social relationships, which are relatively understudied, and to generate comparative data, we investigated male social relationships in a provisioned group of 68 free-ranging, naturally dispersing stumptail macaques in southern Thailand. We collected continuous focal animal and ad libitum data on 7 adult and 2 subadult males, recording social behavior during 283 contact hours between December 2006 and March 2007. Stumptail macaques of this population were less tolerant than predicted based on previous studies on captive groups: Rates of spatial proximity, affiliation, and aggression were low, most males directed affiliative behavior toward higher-ranking males, and conflicts were generally of low intensity and relatively asymmetrical. Thus, male stumptail macaques of the focal group appear to differ in their social style from a previous study of a captive group that mainly comprised of females. In some traits, they are even more intolerant than rhesus macaques, an intensively studied intolerant macaque species. We also compare our data on stumptail macaque males to those on other male macaques, but available data are too sparse to draw final conclusions.     

Kinship and social bonds in female chimpanzees (Pan troglodytes)

A large body of theoretical and empirical research suggests that kinship influences the development and maintenance of social bonds among group‐living female mammals, and that human females may be unusual in the extent to which individuals form differentiated social relationships with nonrelatives. Here we combine behavioral observations of party association, spatial proximity, grooming, and space use with extensive molecular genetic analyses to determine whether female chimpanzees form strong social bonds with unrelated individuals of the same sex. We compare our results with those obtained from male chimpanzees who live in the same community and have been shown to form strong social bonds with each other. We demonstrate that party association is as good a predictor of spatial proximity and grooming in females as it is in males, that the highest party association indices are consistently found between female dyads, that the sexes do not differ in the long‐term stability of their party association patterns, and that these results cannot be explained as a by‐product of the tendency of females to selectively range in particular areas of the territory. We also show that close kin (i.e. mother–daughter and sibling dyads) are very rare, indicating that the vast majority of female dyads that form strong social bonds are not closely related. Additional analyses reveal that “subgroups” of females, consisting of individuals who frequently associate with one another in similar areas of the territory, do not consist of relatives. This suggests that a passive form of kin‐biased dispersal, involving the differential migration of females from neighboring communities into subgroups, was also unlikely to be occurring. These results show that, as in males, kinship plays a limited role in structuring the intrasexual social relationships of female chimpanzees. Am. J. Primatol. 71:840–851, 2009. © 2009 Wiley‐Liss, Inc.     

Social relationships between adult females and the alpha male in wild tufted capuchin monkeys

Primates are notable for the widespread presence of long-term female-male associations which go beyond the mating context. However, little attention has been given to the factors that affect within-species variation in female-male relationships, especially among New World primates. Although detailed accounts of heterosexual relationships in Cebus species are scarce, a few studies have suggested the occurrence of strong associations between adult females and high-ranking males. This study explores affiliative relationships between females and the alpha male during the nonbreeding season in wild tufted capuchin monkeys (Cebus apella nigritus). Affiliative relationships were explored through female-male patterns of spatial proximity and grooming. By adopting a social network approach, we analyzed: (1) whether the alpha male is the preferred male partner for females and, (2) whether variation (if any) in female-alpha male affiliation can be explained through both female individual characteristics and social network metrics. Our results showed that alpha males were the favorite male partner for adult females in the proximity networks, but this did not hold true in the grooming networks. In addition, female-alpha male interaction patterns showed considerable variation, with only some females being strongly associated with the alpha male. Our results suggest that such a variation can be explained by female dominance rank, level of centrality (the quantity and intensity of spatial connection with other females) and prestige (the quantity of grooming received by other females) in female-female social networks. Taken together, these findings highlight two aspects of female-alpha male relationships in tufted capuchin monkeys: the alpha male represents the most socially integrated male in the group, and females with high dominance ranks and high centrality in both proximity and grooming networks show stronger relationships with the alpha male.     

Proximity and grooming patterns reveal opposite-sex bonding in Rwenzori Angolan colobus monkeys (<Emphasis Type="Italic">Colobus angolensis ruwenzorii</Emphasis>)

Close proximity and social grooming are important bonding mechanisms in primates. These behaviors show the social structure of a species and many studies have found positive correlations between the degree of kinship and grooming and proximity. We used 1 year of data collected via instantaneous scan sampling on a large “supertroop” of Colobus angolensis ruwenzorii at Lake Nabugabo, Uganda, to examine partner preferences for grooming and nearest neighbors in each age-sex class. Little is known about this species, so we based our hypotheses on congeners. Of the five species of black-and-white colobus, data on sex-biased dispersal patterns are available for three (C. guereza, C. vellerosus, and C. polykomos), all of which show male-biased dispersal with occasional female dispersal. We thus predicted that female C. a. ruwenzorii would be more strongly bonded than males, showing greater proximity and grooming. We did not expect bonding between the sexes since congeners do not show this pattern. We found that among adult dyads, males and females were more likely to be found in loose proximity, and to groom, than would be expected given group composition. Conversely, both males and females had relatively weak same-sex relationships. Between the sexes, adult males had higher proximity and grooming indices with adult females without infants than with females with infants. These observations indicate that this subspecies is cross-bonded and that both sexes may disperse. Furthermore, our findings suggest that the social organization and social structure of C. a. ruwenzorii differ greatly from other black-and-white colobus species.     

Social relationships between adult male and female rhesus macaques: II. non-sexual affiliative behaviour

The social relationships of adult male rhesus macaques (Macaca mulatta) in Group I of the Cayo Santiago colony were studied over a period of 14 months. Relationships were found in which adult males and sexually mature females were persistently close to one another in nonsexual contexts, both within and across seasons. Males of long tenure and high dominance rank tended to have more female partners, and more persistent relationships, than more recent immigrants of lower rank. Correlations with length of tenure were stronger than those with dominance rank. Closely-related females tended to have persistent relationships with the same male. In most cases the female was primarily responsible for maintaining proximity in non-sexual contexts. Dyads which were persistently within 5 m of each other in the birth season were more likely to form a consortship in the subsequent mating season than those which had a brief relationship. A similar tendency was apparent in the 1 m data but it was not statistically significant. There was no association between persistent proximity during the birth season and the occurrence of long, or multiple consortships, nor with the maintenance of proximity or direction of grooming between consort partners. The pattern of consortships was not closely related to the formation of persistent relationships in the subsequent birth season. Females occasionally received protection from their male partners and, in some cases, spent more time in the feeding corral with them than did other females. Affiliative relationships can be very enduring and may have long-term benefits that were not apparent during the study period.     

Social Behavior,Reproductive Strategies,and Population Genetic Structure of <Emphasis Type="Italic">Lagothrix poeppigii</Emphasis>

For species of primates in which females emigrate, we would expect males within groups to be related to one another. Kin selection theory suggests that these males should associate preferentially with one another, be more affiliative and cooperative with one another than females are, and compete less overtly with one another over reproductive opportunities than males in female philopatric taxa do. Precisely these patterns of social behavior characterize well-studied populations of 2 of the 3 atelin primate genera: spider monkeys (Ateles) and muriquis (Brachyteles). For the third atelin genus, Lagothrix, patterns of intragroup social behavior have been less well-documented. We studied the social and reproductive behavior of lowland woolly monkeys (Lagothrix lagotricha poeppigii) in Ecuador during a one-year observational study and subsequently used molecular techniques to investigate population genetic structure and dispersal patterns for this taxon. Among adult male woolly monkeys, both affiliative and agonistic interactions were rare, and males were seldom in close proximity to one another. Relationships among male woolly monkeys are best characterized as tolerant, especially in the context of mating wherein direct competition among males was minimal despite the fact that females mated with multiple males. Relationships among females were likewise generally tolerant but nonaffiliative, though females often directed harassment towards copulating pairs. Affiliative interactions that did occur among woolly monkeys tended to be directed either between the sexes—primarily from female to male—or from younger towards older males, and the proximity partners of females tended to be members of the opposite sex. These results suggest that bonds between the sexes may be more important than same-sex social relationships and that direct female-female competition is an important feature of woolly monkey reproductive biology. Our genetic results indicate that, as in other atelins, dispersal by females is common, but some male dispersal likely occurs as well. In some but not all groups we studied, nonjuvenile males within social groups were more closely related to one another on average than females were, which is consistent with greater male than female philopatry. However, differences in these patterns among our study groups may reflect local variation in dispersal behavior.     

Social grooming in assamese macaques (Macaca assamensis)

Reciprocity and social bonding hypotheses were evaluated as explanations for observed patterns of social grooming in assamese macaques (Macaca assamensis). In accordance with social bonding, females, as the long-term residents of this matrifocal group, groomed each other and juveniles more often than males groomed one another or juveniles. On the other hand, males groomed females more often and for longer durations than females groomed males and, whereas both males and females groomed juveniles more often than juveniles groomed them, juveniles groomed their elders for longer durations. Male grooming of females did not seem directly related to matings as males are single mount ejaculators and use coercive mating tactics. Male grooming of females could not be accounted for in terms of reciprocity; it was not a simple function of dominance. Although both sexes groomed subordinate females more than vice versa, males groomed dominant males more and females groomed subordinate males more than they received grooming from them. Grooming was concluded to function to establish and maintain affiliative social bonds rather than as a specific mechanism to obtain matings or any other specific reciprocation in terms of services or favors.