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.     

Sexually dimorphic transitions revealed in the relationships of yearling rhesus monkeys following the birth of siblings

We report here that in a large captive group of monkeys, Macaca mulatta,sudden sex-related changes occur in social interactions in one short phase of an infant’s development. Social interactions of 1-year-old animals (males, N =12; females, N =8) 6 weeks before the birth of siblings were compared with interactions occurring 6 weeks after the birth. On the day of the siblings’ birth, depression-like postures were seen in two yearling males (YMs); 10 YMs showed hyperactivity. In the postbirth period, YMs refocused their attentions away from their mother and toward other, often unrelated members of the group. Although YMs initiated disengagement of interactions with their mothers, there was evidence that mothers attempted to lessen this disengagement. The YMs had close relationships with specific (“preferred”) male individuals. These relationships (particularly those with adult males) became more pronounced following the birth of the sibling. The adult-male group also took an active role in maintaining interactions with YMs. The preferred partners in the YM-other male relationship before the birth of the sibling were, however, not always the same as those in the period after the birth. Dominance relationships and probably genetic factors determined patterns of interaction between YMs and their preferred male partners. Among yearling females (YFs), no dramatic changes in interactions with their mothers or with other group members were detected after their mothers gave birth. Relationships in YF-mother and YF-other-individual pairs (especially when the other individual was kin) seemed to be consolidated during the postbirth interval. There was little evidence of jealousy between the YFs and their younger siblings. Thus, sibling birth acted as a stimulus for the occurrence of sexually dimorphic interactions in yearlings. We suggest that in natural environments, social interactions in YFs promote relationships that will serve to integrate them into the matrilineal social structure, whereas comparable behavior in YMs encourages relationships with males that they may emigrate with into, or meet again in, nonnatal troops.     

Social relationships of nulliparous young adult females beyond the ordinary age of the first birth in a free-ranging troop of Japanese macaques (Macaca fuscata)

We describe the social relationships of young adult female Japanese macaques (Macaca fuscata) in a free-ranging troop in Arashiyama, Kyoto, Japan, who remained nulliparous beyond the ordinary age of first birth because of contraceptive administration. We observed 12 young nulliparous adult females (6–9 years old) for 270 h and 10 min from 2 February to 5 October 2010. The majority maintained close relationships with their mothers through proximity and grooming, whereas a few had very infrequent social interactions with their mothers. Most had asymmetrical grooming relationships; the grooming they received from unrelated adult females was less than the grooming they gave. Young adult females who had less frequent interactions with their mothers by either proximity or grooming received more grooming from a larger number of unrelated adult females than did those who had more frequent social interactions with their mothers. These results indicate that most young adult females who remained nulliparous beyond the ordinary age of first birth tended to maintain close relationships with their mothers, and their grooming relationships with unrelated adult females were inversely related to the degree of closeness with their mothers.     

Reciprocity in play,grooming, and proximity in sibling and nonsibling young rhesus monkeys

Play, grooming, and proximity, and the degree to which these were reciprocated between pairs, were studied in immature sibling and nonsibling rhesus monkeys (Macaca mulatta)in four established captive groups over two seasons. “Interaction reciprocity” and “partner reciprocity” were assessed for each dyad for each of the three behaviors. In play, interaction reciprocity was based on the ratio between the play initiations by each dyad member,in grooming on the ratio between the grooming durations by each dyad member, and in proximity on the relative responsibility for proximity maintenance. Two or three most frequent (top) partners for each behavior were found for each individual. If two monkeys were among each other’s top partners, they were said to be reciprocal partners. Monkeys played with nonsiblings as much as with siblings but spent more time grooming and in proximity with siblings than with nonsiblings. Same-age nonsiblings (peers) were more frequent partners than other nonsiblings for each behavior. Siblings’ grooming interactions were more reciprocal than those of nonsiblings. There was no such effect for play and proximity. All-male dyads tended to be more reciprocal in play interactions, and all-female dyads tended to be more reciprocal in grooming interactions. In play, but not in grooming or proximity, the interaction reciprocity of reciprocal partners was higher than that of nonreciprocal dyads. It is argued that the three behaviors have similar roles in infant’s social development but they differ in the expression of this role. Hence the reciprocity patterns vary with the behavior.     

Socialization in spectacled parrotlets (Forpus conspicillatus): how juveniles compensate for the lack of siblings

  Socialization, that is, the process of the integration of an individual into the social system and the acquisition of basic social traits, has been studied in a variety of vertebrate species. Deprivation experiments have shown that the lack of early affiliative relationships has negative long-term effects on social behaviour and reproduction. Most studies emphasized the importance of the mother-infant relationship. However, it soon became evident that peer relationships to like-aged conspecifics, such as siblings and unrelated juveniles of nearly the same age, are also important for socialization. Whether individuals, deprived of one of these important social components, are able to compensate for this lack is not known. Here I tested the hypothesis that in spectacled parrotlets (Forpus conspicillatus), singletons (i.e., those that grew up without siblings) were able to compensate for this social lack by establishing and strengthening other relationships. In spectacled parrotlets socialization depends on the formation of long-lasting sibling groups. However, singletons without nest mates are quite common (about 6%), both in captivity and in nature. In this study I analysed the affiliative interactions with other group members of five singletons in comparison to eight siblings, from fledging to the 36th week after fledging, within a group of adult and juvenile conspecifics. In contrast to siblings, the singletons prolonged the relationships with their parents. Then they established a ”host sibling group” with other like-aged individuals. All singletons became well integrated into the group and established exclusive pair bonds. It is concluded that juvenile singletons of spectacled parrotlets are able to compensate for the lack of siblings by the development of alternative socialization tactics. Received: 12 December 1998 / Received in revised form: 17 May 1999 / Accepted: 7 June 1999     

A preliminary study of kinship and social organization in a semi-free-ranging group ofLemur catta

From long-term studies of a number of anthropoid species, many investigators have shown that kinship affinities affect social relationships. Factors such as proximity, social grooming, dominance rank, and mating patterns have been shown to be related to kinship. In this paper, we report the results of a preliminary study of the social organization of a group of prosimians (Lemur catta) in which individuals were identified and kinship affinities were known. We found that close matrilineal kin preferred to groom one another and to remain in close proximity more than did nonkin and distantly related animals. Furthermore, no copulations were observed within matrilines. These results are similar to those found in a number of species of anthropoids. This research was conducted on a semi-free-ranging group at the Duke University Primate Facility, Durham, North Carolina.     

Grooming interactions among adult chimpanzees at Bossou,Guinea, with special reference to social structure

Grooming and proximity interactions among chimpanzees at Bossou, Republic of Guinea, were analyzed as an index of friendly and affinitive relationships among adult males, among adult females, and between the sexes. Data from the first (1976–1977) and the third (1982–1983) study period were used. The expected value of their interactions was calculated from the number of adult males and females in the group and also from the observed frequency of combinations of adult males and females in the parties (temporary foraging groups). In the pooled data from the two periods, there was little difference between grooming and proximity (without grooming). The frequency of male-female grooming and proximity interactions was lower than expected, and that of female-female interactions was higher than expected. The frequencies of male-male grooming and proximity were intermediate but fluctuated. Male-male grooming frequency was lower than that recorded in chimpanzees of East Africa. Characteristics of same-sex affinitive interactions, especially between Bossou chimpanzee females, clearly differ from those of East African chimpanzees and are more like those recorded for female-related groups of Japanese macaques (Macaca fuscata).These differences indicate the variability and flexibility of chimpanzee social structure.     

Children Love Their Pets: Do Relationships between Children and Pets Co-vary with Taxonomic Order,Gender, and Age?

Generally, children love their pets. However, a deeper insight into the beneficial effects of pets on the physical, psychological, and social wellbeing and development of children is needed. This study investigated whether children have more intense relationships with animals which are behaviorally similar to humans (according to the scala naturae), and whether the relationship patterns between 11- to 14-year-old children (n = 72) and their pets differ from those in prepubescent children, between 6 and 10 years of age (n = 84). We also investigated whether pet-relationship quality is associated with children’s age, gender, and number of siblings. Data about individual bonding type and attachment quality between the children and their pet were collected using a questionnaire. The results indicate that the younger children’s relationships clearly co-varied with taxonomic order of the pet. In contrast, 11- to 14-year-old children reported similarly high scores of attachment with their mouse or iguana as with their dog or cat, and the relationship patterns did not co-vary with taxonomic order. Gender effects on relationship quality were found in both age groups; especially girls reported intense relationships with their pets. In addition to gender, children without siblings had stronger attachment to their pet than children who had siblings. Our data suggest that young children develop high-quality relationships with pets, particularly those which are taxonomically closely related, such as dogs and cats, and less so with other pet species, such as birds or fish. Older children were also able to strongly attach to other pet species. We argue that mental relationship representations change during puberty and that older (11- to 14-year-old) children may no longer make attachments to pets based on them being behaviorally similar to people.     

The acquisition of dominance among free-ranging rhesus monkey siblings

In several species of Cercopithecine monkeys, younger sisters reverse dominance with older sisters during the course of maturation. Proximate hypotheses to account for the phenomenon are based on few and incomplete data, and tend to be unifactorial. This paper (1) presents systematic data on ‘youngest ascendancy’ among free-ranging rhesus monkey, Macaca mulatta, siblings; and (2) attempts to identify its proximate basis. Early social influences were inadequate to explain reversal. Older siblings resisted outranking, and only those younger siblings (including orphans) with powerful long-term support rebelled successfully. Supporters tended to be close relatives (such as the mother and other siblings) dominant to both siblings. Rebellion did not occur at some absolute age of the younger sibling. Its timing depended partly on the relative size of siblings, and partly on the extent of support the younger sibling had against the older. The study strongly suggests that the occurrence and timing of reversal depends on an interaction between factors predictive of individual fighting ability (such as body size) and those predictive of social power (such as alliances). Observed variation in the regularity with which ‘younges ascendancy’ occurs is discussed in relation to these findings.     

Aggression, grooming and group-level cooperation in white-faced capuchins (Cebus capucinus): insights from social networks

The form of animal social systems depends on the nature of agonistic and affiliative interactions. Social network theory provides tools for characterizing social structure that go beyond simple dyadic interactions and consider the group as a whole. We show three groups of capuchin monkeys from Barro Colorado Island, Panama, where there are strong connections between key aspects of aggression, grooming, and proximity networks, and, at least among females, those who incur risk to defend their group have particular "social personalities." Although there is no significant correlation for any of the network measures between giving and receiving aggression, suggesting that dominance relationships do not follow a simple hierarchy, strong correlations emerge for many measures between the aggression and grooming networks. At the local, but not global, scale, receiving aggression and giving grooming are strongly linked in all groups. Proximity shows no correlation with aggression at either the local or the global scale, suggesting that individuals neither seek out nor avoid aggressors. Yet, grooming has a global but not local connection to proximity. Extensive groomers who tend to direct their efforts at other extensive groomers also spend time in close proximity to many other individuals. These results indicate the important role that prosociality plays in shaping female social relationships. We also show that females who receive the least aggression, and thus pay low costs for group living, are most likely to participate in group defense. No consistent "social personality" traits characterize the males who invest in group defense.     

Spatial proximity among adult siblings in greylag geese (Anser anser): evidence for female bonding?

By staying close to allies, individuals may enjoy benefits through social support. In the socially monogamous greylag goose (Anser anser), pair-partners, parents, and even human foster parents may provide social support, facilitating access to resources or reducing agonistic pressure. In the present work, we analysed the spatial distribution of individuals within a semi-feral flock of 120 greylag geese, which contained 23 adult sibling groups of 2–4 individuals from 2 to 12 years old. During resting periods we scored dyadic distances between 28 focal individuals of different social categories, their siblings and unrelated control individuals of the same age. Adult female siblings (i.e. those hatched in the same year and raised together) rested significantly closer to each other than to either their brothers or unrelated control individuals. We attribute this to social attraction rather than to just a common preference for the same resting site. Thus, kinship bonds as expressed by cohesion might persist into adulthood, at least in the females. We discuss the potential benefits of proximity between related individuals with regard to reduced social stress via social support. Received: 21 February 2000 / Received in revised form: 16 May 2000 / Accepted: 17 May 2000     

Group harmony in gibbons: Comparison between white-handed gibbon (Hylobates lar) and siamang (H. syndactylus)

The siamang (Hylobates syndactylus) is exceptional among gibbons in that its area of distribution almost completely overlaps those of other gibbons, namely the white-handed gibbon (H. lar) and the agile gibbon (H. agilis) of the lar group. The siamang has almost twice the body weight of the gibbons of the lar group (ca. 11 kg vs. 5–6 kg), and it has been suggested that distinct ecological and behavioural differences exist between the siamang and its two sympatric species. The siamang has been claimed to differ from the white-handed gibbon “in the closer integration and greater harmony of group life” (Chivers, 1976, p. 132). However, few quantitative data exist to support this hypothesis. In the present study, intra-group interactions in captive family groups of white-handed gibbons and siamangs (two groups of each species) were recorded by focal-animal sampling. These data failed to show a consistent association between species and most of the behavioural patterns recorded, such as frequency of aggression, percentage of successful food transfer, frequency of social grooming bouts, and duration of social grooming/animal/hr. A significant difference was found for only two of the variables: Individual siamangs in this study showed longer grooming bout durations, and made fewer food transfer attempts than lar individuals. Only the first of these two differences is consistent with the hypothesis mentioned above, whereas the lower frequency of food transfer attempts in siamangs is the opposite of what should be expected under the hypothesis. On the other hand, two of these behavioural patterns showed a significant correlation with the parameters group size and individual age: Both individuals in larger groups and younger individuals tended to show shorter grooming bouts and a smaller proportion of successful food transfers. Our findings indicate that social cohesion within these gibbon groups may be much more flexible according to and depending on social or ecological influences and less rigidly linked to specific gibbon taxa than previously assumed. A considerably larger number of gibbon groups would have to be compared to provide reliable evidence for or against species-specific differences in group cohesion. Another finding of this study—a positive correlation between the frequency of aggression and grooming—is discussed in the light of the functional interpretations commonly attributed to allogrooming behaviour in primates.     

Effect of kinship on social behaviors in Brandt's voles (<Emphasis Type="Italic">Microtus brandti</Emphasis>)

The roles of kinship in agonistic behavior and mate choice were evaluated in Brandt's voles (Microtus brandti). In chambers bedded with familiar or unfamiliar substrates, the aggressive behavior and social investigation towards adult unfamiliar same-sex siblings and non-siblings were examined, and no significant kin bias was found. Males sniffed and followed unfamiliar unrelated females significantly more than unfamiliar sibling sisters, but males did not show significant preferences in copulatory behavior and agonistic behavior. Females spent significantly more time copulating with unfamiliar unrelated males than with their unfamiliar sibling brothers, while they did not show a significant preference in social investigation between them. Our study shows that kinship might play a role in the inbreeding avoidance based on preweaning familiarity or/and phenotype matching, but the role of kinship in agonistic behavior remains unclear.     

Adolescent male chimpanzees (Pan troglodytes) form social bonds with their brothers and others during the transition to adulthood

Social relationships play an important role in animal behavior. Bonds with kin provide indirect fitness benefits, and those with nonkin may furnish direct benefits. Adult male chimpanzees (Pan troglodytes) exhibit social bonds with maternal brothers as well as unrelated adult males, facilitating cooperative behavior, but it is unclear when these bonds develop. Prior studies suggest that social bonds emerge during adolescence. Alternatively, bonds may develop during adulthood when male chimpanzees can gain fitness benefits through alliances used to compete for dominance status. To investigate these possibilities and to determine who formed bonds, we studied the social relationships of adolescent and young adult male chimpanzees (N = 18) at Ngogo in Kibale National Park, Uganda. Adolescent male chimpanzees displayed social bonds with other males, and they did so as often as did young adult males. Adolescent and young adult males frequently joined subgroups with old males. They spent time in proximity to and grooming with old males, although they also did so with their age peers. Controlling for age and age difference, males formed strong association and proximity relationships with their maternal brothers and grooming relationships with their fathers. Grooming bonds between chimpanzee fathers and their adolescent and young adult sons have not been documented before and are unexpected because female chimpanzees mate with multiple males. How fathers recognize their sons and vice versa remains unclear but may be due to familiarity created by relationships earlier in development.     

Social Relationships among Males in Multimale Siamang Groups

I quantified social and spatial interactions among adults in 4 multimale siamang (Symphalangus syndactylus) groups to evaluate the importance of aggression and avoidance in mediating male-male relationships. Actual genetic relationships among adults are unknown, but available mitochondrial data suggest that in 3 of 4 groups, neither male was the offspring or maternal sibling of the female, whereas in the fourth group, a matrilineal relationship between the female and 1 adult male was not excluded. Rates of aggression involving male-male dyads were very low. One male-female dyad maintained closer spatial cohesion than those of other adult dyads in 3 of 4 groups. Nonetheless, all adult males spent substantial percentages of their time ≤20 m from other adults in their groups. The percentages of time that male-male dyads spent in social grooming interactions did not differ from those of male-female dyads. In 3 groups, both males copulated with the group female. While previous studies have reported high rates of aggression between adult males and subadult male group members in siamangs, my results suggest that male-male relationships in multimale groups at Way Canguk were relatively harmonious. Acceptance of multimale grouping (and in some cases sexual polyandry) suggests that the benefits outweigh the costs under some circumstances. If there was a genetic relationship between males, then tolerance of delayed dispersal and copulation with the adult female may function as a form of parental investment. Males may also benefit from multimale grouping via enhanced territorial defense or reduced costs of mate defense.     

Huddling relationships in night sleeping groups among wild Japanese macaques in Kinkazan Island during winter

Huddling groups at sleeping sites, and allogrooming and proximity in the daytime during winter, were examined in a wild Japanese macaque (Macaca fuscata) troop on Kinkazan Island in the non-snowy district of northern Japan. All sleeping groups, defined as a cluster in which individuals huddle at sleeping sites, were formed on the ground. Their sizes tended to increase when the temperature was lower. The number of adults with mutual physical contact in sleeping groups increased when the size of sleeping groups increased. These results suggest that the physiological function of huddling is protection from low temperatures, and that macaques select the ground as sleeping sites to form large sized groups. Huddling was performed most frequently among kin dyads. Non-related dyads which appeared to be affiliative in the daytime also huddled frequently at sleeping sites. Even non-related dyads which showed affiliative behavior less frequently in the daytime exhibited huddling, at night, however, they did so less often than those of kin dyads and affiliated dyads. It appears that huddling at night by pairs that did not normally affiliate in the daytime was made possible by the increased tolerance of individuals responding to colder temperatures at night in winter. Furthermore, huddling, grooming, and proximity were exhibited at greater frequency between kin dyads, and between high-ranking males and specific females of kin groups, although the dyads of individuals older than 15 years often were involved only in huddling. These results suggest that two types of social bonds exist at sleeping sites in winter. One is the social bond common to both the daytime and nighttime, the other is peculiar to nighttime. Consequently, the social function of huddling is that, troop integration might increase at sleeping sites in winter as close social relationships among adults are extended more widely than those in daytime.     

Longitudinal observations of care and development of infant titi monkeys (Callicebus moloch)

The purpose of this study was to describe patterns of infant care and development in family groups of the monogamous titi (Callicebus moloch). Three infant titis were observed with their natal family groups over the first six months of life. Field observations of extensive male involvement with infants were confirmed. Adult males were clearly the infants' primary social companions, and infants spent more time in contact with adult males at all ages than with mothers or older siblings. However, mothers and siblings also carried infants at times and interacted with them in affiliative ways (e.g., grooming, nuzzling, play). Mothers often invited nursing, but otherwise it was infants who primarily initiated transfers between carriers and approaches to parents, reminding us that the infants' own activities and their effects on caregivers should not be overlooked in considerations of the patterns of infant care. This is particularly important for those species exhibiting extensive parental involvement by males. It is suggested that substantial male care of young titi infants leads to several important consequences for the infant's social development, including the development of a stronger attachment to the father than the mother.     

Whom do the sparrows follow? The effect of kinship on social preference in house sparrow flocks

Non-aggressive social interactions between group-mates, e.g. maintenance of spatial proximity or activity synchrony are basic elements of a species’ social structure, and were found to be associated with important fitness consequences in group-living animals. In the establishment of such affiliative relationships, kinship has often been identified as one of the key predictors, but this has rarely been studied in simple social groups such as flocks of gregarious birds. In this study we investigated whether kinship affects social preference, as measured by the tendency to associate with others during various social activities, in captive house sparrow (Passer domesticus) flocks where birds could interact with differently related flock-mates. We found that preference between flock-mates was correlated with familiarity from early nestling period: same-brood siblings followed their sib initiating new activities more often than non-sib birds. The strength of association between birds also tended to correlate with genetic relatedness, but this was mainly due to the effect of siblings’ affiliation. Thus we concluded that house sparrows prefer the company of their siblings during social activities even well after fledging, which may facilitate kin-biased behaviours.     

Social organization in a wild population ofCallithrix jacchus: II. Intragroup social behavior

The social behavior of the common marmoset has been well studied in captivity, but little is known about the social dynamics of this species in its natural habitat. Social relationships were studied in three polygynous groups of common marmosets,Callithrix jacchus, in northeastern Brazil. Breeding adults appeared to be the center of social life and were the most frequent grooming partners or nearest neighbors for most adult group members. The observations of unidirectional agonistic interactions suggest that breeding adults were also dominant over all other group members, but that neither sex was dominant over the other. The dynamics of within-group social relationships are likely to be important determinants in the reproductive strategies employed by marmoset females.