Matrilineal Cohesion and Social Networks in Macaca fuscata

In a provisioned troop of Japanese macaques (Macaca fuscata) in Arashiyama, Japan, greater adherence to Kawamura's rules of matrilineal rank inheritance and youngest ascendancy occurred among high-ranking females versus low-ranking females. Accordingly, high-ranking females formed more clustered hierarchies and low-ranking females had more dispersed hierarchies. A proximate explanation for this finding may be related to differences in how females maintain their social networks. To determine whether the clustering in the hierarchy was reflected in patterns of social cohesiveness, I compared network sizes of coalition and grooming partners for females in each third of the hierarchy. I calculated the proportion of available partners that were coalition and grooming partners within each category of relatedness (0.5 r 0.004 and r = 0). High-ranking females formed coalitions with a large proportion of their close relatives and a small proportion of their distant relatives; middle-ranking females supported an intermediate proportion of their close relatives and a small proportion of their distant relatives; and, low-ranking females formed coalitions with very few available close and distant relatives. High-ranking females groomed nearly all available close relatives and an intermediate proportion of distant relatives, whilst middle- and low-ranking females groomed a large proportion of available close relatives and a very small proportion of distant relatives. Thus, levels of clustering within the hierarchy appeared to reflect levels of social cohesion, in terms of grooming and coalition formation.     

Age-related differences in social grooming among adult female Japanese monkeys ( Macaca fuscata)

The present study investigated the influence of dominance rank in combination with kinship on age-related differences in social grooming among adult females in a free-ranging group of Japanese monkeys (Macaca fuscata). Eighty-three adult females were divided into six sub-groups according to age-class (younger: 5–9 years old; middle: 10–14 years old; older: 15–22 years old) and dominance rank (high and low rank). The ratio of the number of unrelated females that each female groomed to the total number of available unrelated females and grooming bouts which she gave to unrelated females decreased with increasing age for both high- and low-ranking females, whereas age did not appear to affect corresponding values for related females. On the other hand, compared with low-ranking females, high-ranking females of all age-classes received grooming more often from a larger number of unrelated females. Moreover, older females of low rank received grooming less often from a smaller number of unrelated females than younger females of low rank. These results indicate that with increasing age females are more likely to concentrate on related females when they have grooming interactions with other females. This tendency seems to be more apparent for low-ranking females. Moreover, the present findings also indicate that older high-ranking females could maintain their social attractiveness as high as younger high-ranking females.     

Dominance in assamese macaques (Macaca assamensis)

A field study of 64 assamese macaques (Macaca assamensis) was conducted at a temple site in Assam, India. Focal and all occurrence scan techniques were used to collect data on agonistic, grooming, and sexual behavior. More than 1,000 hr of data were summarized into agonistic dominance, grooming, and mounting matrices. Rank hierarchies were constructed for all three and compared. We also directly compared each cell in each matrix with the corresponding cells in the other matrices. A nearly linear agonistic dominance hierarchy was found, but it did not correlate with the directionality of mounting or grooming. Adult males mounted females, generally were dominant to females and groomed females more often than they were groomed by females. Younger males groomed older males and were also generally subordinate to older males. These age and sex effects produced some inter‐correlations among grooming, mounting, and dominance but only for specific age‐sex classes. Theoretical models of social exchange were not considered useful in predicting the complex patterns of grooming, mounting, and dominance seen in the present group. Whereas such models may "explain" existing data for some groups and have gained widespread acceptance, they must be empirically tested. Am. J. Primatol. 48:283–289, 1999. © 1999 Wiley‐Liss, Inc.     

Affiliative relations among male Japanese macaques (Macaca fuscata yakui) within and outside a troop on Yakushima Island

Male Japanese macaques (Macaca fuscata yakui) in a troop on Yakushima Island frequently groom other males. However, previous studies have not compared the social relations of troop males to those of non-troop males. I followed all troop males and non-troop males in and near a troop during a mating season and during the following non-mating season and recorded their neighbors, grooming, and agonistic interactions. Comparisons of the social relations of troop males and non-troop males with other troop members revealed that grooming and agonistic interactions with females during the mating season were similar between troop and non-troop males. However, troop males groomed each other more often and had fewer agonistic interactions among themselves than did non-troop males. Compared to what occurred in the mating season, troop males groomed females less often and exchanged grooming bouts more often with other troop males during the non-mating season. One non-troop male groomed females more frequently than did any troop male in both seasons, and this male groomed troop males more frequently than did any troop male in the non-mating season. This male immigrated into the troop during the following mating season. Regardless of their competition with respect to reproduction, male Japanese macaques on Yakushima Island maintain affiliative relations, probably to cooperatively defend fertile females from non-troop males.     

Long-term grooming partnerships between unrelated adult females in a free-ranging group of Japanese monkeys (Macaca fuscata)

In order to examine the presence of long-term grooming relationships among unrelated females, grooming interactions of 18 adult females (range: 16-32 years) in a free-ranging group of Japanese monkeys (Macaca fuscata) were recorded in 2003 and compared with those recorded 10 years earlier, i.e., in 1993. In 2003, on average, each female who had survived the 10 years had grooming interactions with 2.2 surviving old partners with whom she was recorded to have grooming interactions in 1993, 3.5 females related to the surviving old partners, and 4.5 unrelated females who were other than the surviving old partners or their related females. By calculating the ratio of actual grooming partners to available females in 2003, we concluded that females had a greater possibility of selecting surviving old partners as their grooming partners than other unrelated partners, and that they also had a greater possibility of selecting females related to surviving old partners than females other than surviving old partners and their related females. These findings indicate that with regard to grooming relationships, female Japanese monkeys are basically conservative, showing a tendency to concentrate their grooming interactions on closely related females and certain familiar unrelated females such as surviving old partners and some females closely related to these partners. At the same time, however, female Japanese monkeys also showed a progressive trait for grooming since they formed grooming relationships with new partners. The necessity of long-term psychological bonding for long-term grooming relationships between unrelated females is discussed in this work.     

Grooming reciprocity in female tibetan macaques macaca thibetana

Grooming among nonhuman primates is widespread and may represent an important service commodity that is exchanged within a biological marketplace. In this study, using focal animal sampling methods, we recorded grooming relationships among 12 adult females in a free-ranging group of Tibetan macaques (Macaca thibetana) at Huangshan, China, to determine the influence of rank and kinship on grooming relationships, and whether females act as reciprocal traders (exchange grooming received for grooming given) or interchange traders (interchange grooming for social tolerance or other commodities). The results showed that: (1) grooming given was positively correlated with grooming received; (2) kinship did not exert a significant influence on grooming reciprocity; and (3) grooming reciprocity occurred principally between individuals of adjacent rank; however, when females of different rank groomed, females tended to groom up the hierarchy (lower ranking individuals groomed higher ranking individuals more than vice versa). Our results support the contention that both grooming reciprocity and the interchange of grooming for tolerance represent important social tactics used by female Tibetan macaques.     

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.     

Male Social Behavior and Dominance Hierarchy in the Sulawesi Crested Black Macaque (Macaca nigra)

In a 6-week study of the social behavior of wild Sulawesi crested black macaques (Macaca nigra), we found a linear and transitive dominance hierarchy among the six adult males in one social group. Dominance rank, as determined by the direction of supplantations, correlated strongly with percentage of time near more than four neighbors, frequency of grooming received from adult females, and percentage of time with an adult female as nearest neighbor. These results suggest that high-ranking males are socially attractive. Adult females sexually solicited high-ranking males more often than low-ranking males, but frequency of copulation was not correlated with dominance rank. Frequency and intensity of aggression between males are strongly correlated with rank distance, but aggression toward females was greatest for mid-ranking males. Males of all rank displayed significantly more aggression toward sexually receptive females than toward females in other estrous states. These data indicate that male Sulawesi crested black macaques display a social organization similar to that reported for multimale groups in other macaque species rather than the egalitarian social organization described for female Sulawesi macaques.     

Weaving a tight social net: Allogrooming in free-ranging female langurs (Presbytis entellus)

We studied grooming among adults of a one-male multifemale troop of free-ranging Hanuman langurs (Presbytis entellus)living near Jodhpur, India, for 9 years. The 11–13 females devoted about 6% of their day to allogrooming. Adult males, whose tenures averaged 2.2 years, were transient figures in the troop's history, as reflected by their rather peripheral role in the grooming network. Females groomed males 4–40 times more frequently (1006 episodes) than vice versa- (176 episodes). Adult females received 97% of all grooming from other adult females (6655 episodes). Although females exhibited an age- inversed dominance hierarchy, they did not compete for grooming access to particular troop mates. Dyads of all possible rank differences occurred as frequently as expected: 51% of grooming was directed up the hierarchy and 49% down it. Young, high- ranking individuals gave and received significantly more grooming than the oldest, low- ranking females did. The pattern seemed to be influenced by kin selection because of the presumably high degree of female relatedness. They invested most in troopmates with the highest reproductive value, i.e., the youngest individuals. This trend was coupled with a preference of closest kin (mothers and daughters). Reciprocity was the outstanding feature since all adult females groomed and were groomed by all others. Such a tight social net might establish the necessary cohesion during frequent territorial disputes with neighboring troops.     

Grooming site preferences determined by lice infection among Japanese macaques in Arashiyama

I investigated the effect of the density of louse eggs (Pedicinus obtusus andP. eurygaster) on grooming site preferences in Japanese macaques (Macaca fuscata). Louse eggs were more often found on the outer side of the body (upper back, lower back, outer arms, and outer legs) than on the inner side of the body (chest, belly, inner arms, and inner legs). Japanese macaques were more likely to be groomed on the outer side than the inner side of the body by allogrooming and autogrooming. Such grooming site preferences correlated with the distribution of louse eggs but not with the areas of body parts. Thus, the ecology of lice might affect grooming behavior of Japanese macaques. Five hundred and fifty louse eggs were estimated to parasitize an adult female Japanese macaque. Considering the intrinsic rate of natural increase of lice, monkeys need to be groomed almost every day. This suggests that Japanese macaques need grooming partners and form social bonds with others for everyday grooming.     

Gender-related factors affecting primate social behavior: Grooming,rank, age,and kinship in heterosexual and all-male groups of stumptail macaques

The structure of grooming relations was studied in three captive groups of stumptail macaques, two heterosexual (consisting mainly of females) and one all male. Compared to the heterosexual groups, social hierarchy in the all-male group was less linear, and agonistic and peaceful activity of low-ranking individuals toward high-ranking ones was higher. In addition, in the all-male group received grooming was more variable than performed grooming and showed stronger dependence on age. No effect of maternal kinship was found in the all-male group, and individual preferences were also less marked in this group than in heterosexual groups. These differences tend to be related to dominance style and dispersal patterns. © 1996 Wiley-Liss, Inc.     

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.     

Costs of Mate Guarding and Opportunistic Mating Among Wild Male Japanese Macaques

A trade-off relationship between mating and feeding effort is important when considering reproductive strategies of long-lived species. I compared the influence of male sexual activities, female mate-choice behaviors and the daily activity budget on male mating success among males in a group of wild Japanese macaques (Macaca fuscata yakui) on Yakushima Island. The 1st-ranking male, which had immigrated into the troop at this rank, more frequently approached peri-ovulatory females, spent more time grooming peri-ovulatory females and in mounting series and spent less time feeding than subordinate males did. The 1st-ranking male attained the highest mating success as a result of his high expenditure of time and energy in sexual behaviors directed toward peri-ovulatory females. Mating success of subordinate males did not relate to the amount of sexual effort, but instead to the frequency of female approaches, female rush toward males and the number of peri-ovulatory females within the group. The pattern of intermale competition shifted from nearly contest competition to scramble competition as the number of peri-ovulatory females in the group increased. Feeding time of subordinate males did not vary between the days when they copulated and the days when they did not. The findings demonstrate that mate guarding in the 1st-ranking male is a high-cost mating tactic, while opportunistic mating in subordinate males is a low-cost mating tactic. The differences in male mating tactics are probably related to male life history and to the formation of groups with a high socionomic sex ratio.     

Initiation and solicitation in male-female grooming in a wild Japanese macaque troop on yakushima island

Grooming initiation among adult males and females of a Japanese macaque troop was analyzed during the non-mating season. Some gestures (“solicitation”) elicited grooming from partners at a high rate. Grooming initiation patterns were divided into two main types: (1) a male often solicited a female to groom him immediately after approaching her and was groomed by her; and (2) a female approached an alpha male selectively, and immediately groomed him. After a female groomed a male, she rarely solicited him to groom her and instead often moved away from him. These results indicated that males were motivated to be groomed, while females were more highly motivated to groom. Sex differences in grooming motivation can be explained by sex differences in the benefit to be groomed.     

The social grooming of captive female rhesus monkeys: Effects of the births of their infants

We observed the grooming interactions of 13 female rhesus monkeys (Macaca mulatta)before and for 12 weeks after the births of their infants. Mothers groomed for similar amounts of time before and after the birth of their infants, but after the birth, the grooming they directed to their infants may have been at the expense of that directed to other partners. Lactating females did not receive more grooming from other females but were approached more often, suggesting that they were more attractive. Mothers that groomed their infants most groomed others least, as if grooming time was limited for each mother or as if she was trying to compensate for avoiding interactions with other partners. Mothers of male infants groomed others more than mothers with female infants did, which might be due to mothers with daughters receiving more aggression and therefore avoiding interaction. Experienced and high-ranking mothers groomed their newborn infants considerably more than primiparous mothers did in the 24 hr following birth. Grooming was preferentially directed at close kin before the births of the infants. Mothers tended to groom higher-ranked partners more than they were groomed by them, and they tended to receive more grooming from lower-ranked partners than they gave, as suggested in models of rank attractiveness.     

Observation of a wild Japanese macaque mother pacifying her distressed infant with an acorn

This is the first report on an observation of food transfer by a mother to her offspring in wild Japanese macaques (Macaca fuscata yakui). On November 6, 1996, an adult female wild Japanese macaque stopped grooming her 1.5–1.6 yr old daughter in order to be groomed by a young male. Her daughter protested loudly for about 1 min. In response to her daughter's protest, the mother picked up a mature nut ofQuercus phillyraeoides that was lying near her right hand, and placed it in the daughter's mouth. The daughter's cries were immediately muffled and she silently ate the acorn's contents, and spat out the pericarp. We inferred that the daughter wanted to be groomed by her mother, not to receive food. This reported example of treatment resembling tool using behavior in response to an emotional outcry was precipitated by mother-offspring conflict in the natural habitat.     

Sex Differential Behavior of Immature Hanuman Langurs (Presbytis entellus) in Ramnagar, South Nepal

We investigated sex differences in the social behavior of immature Hanuman langurs (Presbytis entellus) in the light of sex-specifically different life-courses and Hanuman langur characteristics, such as the individualistic dominance hierarchy and the rarity of intragroup coalitions among adult females. We observed four immature female and four immature male langurs—all members of the same free-ranging multimale multifemale group in Ramnagar, South Nepal—from November 1992 to February 1993 for 288 hr via focal-animal and instantaneous sampling techniques. Immature females spent significantly more time in proximity to other group members than immature males did. They had more physical contact and groomed more. Other immature females were their preferred social partners. Immature males also preferred like-aged females. They restricted their relationships with other immature males to proximity and occasional grooming. Monitoring was directed especially toward adult males. Female behavior can be interpreted as oriented toward integration into the female social network and their age-inverted dominance hierarchy. Males seem to prepare for leaving their natal group and for future strong intrasexual competition.     

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.     

Grooming relationships of adolescent orphans in a free-ranging group of Japanese macaques (Macaca fuscata) at Katsuyama: a comparison among orphans with sisters, orphans without sisters, and females with a surviving mother

The present study examined grooming relationships of adolescent females in a free-ranging group of Japanese macaques (Macaca fuscata) at Katsuyama. To assess whether the loss of the mother influenced the grooming relationships of adolescent females (5–7 years old), we compared the time spent in grooming interactions and the number of grooming partners among the following three groups: 6 adolescent orphans with sisters, 9 adolescent orphans without sisters, and 11 adolescent non-orphans with surviving mothers. In Japanese macaques, grooming most frequently occurs between mothers and their daughters. Therefore, it is expected that if the mother is lost, orphans will devote less time to grooming interactions than non-orphans. However, the time spent in overall grooming interactions did not differ among the three groups. While non-orphans maintained grooming relationships with their mothers, orphans acquired alternative grooming relationships with other group members. Orphans adopted two kinds of tactics to compensate for the loss of the mother. First, adolescent orphans with sisters developed more affiliative grooming relationships with their sisters than non-orphans with sisters. Secondly, adolescent orphans without sisters spent more time in grooming interactions with same-aged females and non-related adult females. Moreover, regarding grooming interactions with same-aged females and non-related adult females, orphans without sisters had a larger number of grooming partners than non-orphans. These results indicate that adolescent females have enough flexibility to develop their grooming network after the loss of their mothers, and that the lack of mother and sisters might accelerate socialization of adolescent females and enable them to be integrated in reciprocal adult grooming relationships.     

Female-female social relationships in wild white-faced capuchin monkeys,Cebus capucinus

A single social group of wild white-faced capuchin monkeys was studied for a period of 26 months at Lomas Barbudal Biological Reserve, Costa Rica. A total of 604 hr of focal animal data was collected on six adult females in a group of 21 monkeys. Females could be ranked in a stable, linear dominance hierarchy. Adult females spent much more time in proximity to other adult females than to adult males. Females groomed other females twice as often as they groomed males, and about 55 times more often than males groomed males. Females tended to groom up the dominance hierarchy, and dyads with smaller rank distances groomed more often. Higher-ranking females nursed infants other than their own at lower rates than did lower-ranking females; however, females nursed infants of females ranked both above and below them. Although lower-ranking females were more likely than higher-ranking females to be the victims of aggression, higher-ranking females were not necessarily more aggressive than lower-ranking females. In 96% of female-female coalitions vs. a female, the victim was lower-ranking than both coalition partners; in the remaining 4%, the victim was intermediate in rank between the two coalition partners. Higher-ranking female-female dyads formed coalitions more often than did lower-ranking dyads. Those female-female dyads that groomed more frequently also formed coalitions more frequently. The patterning of social interactions indicates that Cebus capucinus at Lomas Barbudal are female bonded. © 1996 Wiley-Liss, Inc.