Birth-season interactions of adult female Japanese Macaques(Macaca fuscata) without newborn infants

The affiliative interactions of 11 adult female Japanese macaques that did not deliver an infant during the 1981 birth season of the Arashiyama West troop were examined. Consideration was given to the effects of kinship as a structuring element in these birth-season interactions and to the degree of association with various categories of troop members based on age, sex, and (in the case of adult females) whether or not the females were new mothers. Females without infants interacted predominantly with their yearling off-spring, although it was the behavior of the offspring that precipitated the interaction. These females were active in soliciting affiliation with nonkin new mothers, whereas female matrilineal relatives with new infants approached and remained in proximity to them more than did nonrelated new mothers. Females without newborns groomed and approached nonkin infants more than infants within their own matriline, and these infants were predominantly those of females in the highest-ranking matriline of the troop. Adult males were responsible for 40% of all grooming received from nonkin by the females without newborns, and these males approached them significantly more than did other adult females without infants. These patterns demonstrate that the structure of social relationships is influenced by the particular dynamics of troop contexts such as birth seasons, as well as by enduring, broad-based affinities which are less affected by cyclic changes in troop context.     

Patterns of affiliation among immature rhesus monkeys (Macaca mulatta)

The affiliative interaction patterns of the immature members of a group of rhesus monkeys at the Yerkes Regional Primate Research Center reflected a strong bias toward matrilineal kin, although this effect was modified by age and sex variables. Association with kin decreased with age, particularly for males. Juvenile males showed less of a kin bias in their behavior than did juvenile females, especially for grooming. Juvenile males also exhibited a preference for interaction with other males. The diminished association with kin and the same-sex bias may be reinforced in adolescence as adult males begin to aggressively target adolescent males involved in agonistic encounters with females or immatures. Adolescent males did not decrease their levels of social interaction relative to those of adolescent females; however, these males preferentially associated with other males (predominantly their own age-sex class) and specifically avoided females and younger animals, both kin and nonkin. Avoidance may diminish conflicts with females or immatures which could result from association, thereby decreasing the potential for selective aggressive interference by adult males. Juvenile and adolescent females maintained strong ties with their kin and preferentially associated with other females and immatures. The breadth of interaction of females with other females may facilitate the establishment of dominance relationships as females mature. Familiarity and predictability may also decrease the necessity of more severe agonistic interaction.     

Bonds of bros and brothers: Kinship and social bonding in postdispersal male macaques

Group‐living animals often maintain a few very close affiliative relationships—social bonds—that can buffer them against many of the inevitable costs of gregariousness. Kinship plays a central role in the development of such social bonds. The bulk of research on kin biases in sociality has focused on philopatric females, who typically live in deeply kin‐structured systems, with matrilineal dominance rank inheritance and life‐long familiarity between kin. Closely related males, in contrast, are usually not close in rank or familiar, which offers the opportunity to test the importance of kinship per se in the formation of social bonds. So far, however, kin biases in male social bonding have only been tested in philopatric males, where familiarity remains a confounding factor. Here, we studied bonds between male Assamese macaques, a species in which males disperse from their natal groups and in which male bonds are known to affect fitness. Combining extensive behavioural data on 43 adult males over a 10‐year period with DNA microsatellite relatedness analyses, we find that postdispersal males form stronger relationships with the few close kin available in the group than with the average nonkin. However, males form the majority of their bonds with nonkin and may choose nonkin over available close kin to bond with. Our results show that kinship facilitates bond formation, but is not a prerequisite for it, which suggests that strong bonds are not restricted to kin in male mammals and that animals cooperate for both direct and indirect fitness benefits.     

Promiscuity drives self-referent kin recognition

Kin selection theory has been one of the most significant advances in our understanding of social behavior . However, the discovery of widespread promiscuity has challenged the evolutionary importance of kin selection because it reduces the benefit associated with helping nestmates . This challenge would be resolved if promiscuous species evolved a self-referent kin-recognition mechanism that enables individuals to differentiate kin and nonkin . Here, we take advantage of an asymmetry in the level of promiscuity among males of alternative life histories in the bluegill sunfish (Lepomis macrochirus). We show that, as a consequence of this asymmetry, offspring of "parental" males have a high level of relatedness to nestmates, whereas offspring of "cuckolder" males have a low level of relatedness to nestmates. We find that offspring of parentals do not use a direct recognition mechanism to discriminate among nestmates, whereas offspring of cuckolders use kin recognition by self-referent phenotype matching to differentiate between kin and nonkin. Furthermore, we estimate that the cost of utilizing such self-referent kin recognition is equivalent to a relatedness (R) of at least 0.06. These results provide compelling evidence for adaptive use of kin recognition by self-referent phenotype matching and confirm the importance of kinship in social behavior.     

Female rank instability in newly formed groups of familiar sooty mangabeys (Cercocebus torquatus atys)

The formation of two new groups of sooty mangabeys (N=6; N=11) comprised of individuals removed from their natal group of 98 animals led to dominance rank challenges with aggression and wounding, though this occurred after an interval of months. Dominance rank challenges were not expected because, unlike rhesus macaques, adult female sooty mangabeys do not affiliate with adult kin significantly more than nonkin and show minimal agonistic aiding even with adult kin, thus rank would seem to be independent of aiding. Moreover, during the last nine years, severe wounding of adults in a large stable group of sooty mangabeys has been virtually absent and agonistic behavior in a stable group of sooty mangabeys is exhibited at a low rate compared to some macaque species. New members in the group of six maintained their relative ranks for 12 weeks after which the beta supplanted the alpha female with no serious wounding. This ranking remained stable for 29 weeks after which the alpha and beta females were supplanted with fatal wounds inflicted to the alpha and less severe wounds to the beta female. The second subgroup also kept their relative ranks initially. However, after 27 weeks the lowest ranking female severely wounded the next to last ranking female and 1 week later attacked and displaced the alpha female with minimal wounding. Fourteen weeks later the beta female (formerly the alpha) attacked and severely wounded the new alpha female and regained the top dominance position. These events suggest that although sooty mangabeys do not exhibit strong kin preferential behavior among adults, they do have defined relationships within the long term, stable group. Removal from those defined relationships allows the possibility of social reorganization that may be mediated by serious aggression.     

Affiliative behavior of adult female sooty mangabeys (Cercocebus atys)

A 14-month study of 30 adult female members of a captive group of sooty mangabeys investigated their affiliative interactions with group members of varying age and sex. The adult females preferentially affiliated with other adults and interacted less than expected with immature group members. Dyadic frequencies suggested especially frequent affiliation with the three resident adult males, although the pattern of interaction with each male was distinct and apparently was related to age and dominance status of the males. Females of the alpha matriline showed significantly greater affiliation with the males than did those of other matrilines, but this preference was not reciprocated by the males. A preference for grooming older group members (some of the matriarchs and the oldest adult male) was also suggested. In consideration of the taxonomic distinctness of the sooty mangabey from the gray-cheeked mangabey, comparison of these results with those available for albigena were made. Few differences were apparent. Comparisons with the affiliative behavior of Papio females also suggested limited differences, despite the apparently isolated position of the sooty mangabey within the tribe Papionini.     

Kinship Bonds Are Not Necessary for Maintaining Matrilineal Rank in Captive Japanese Macaques

Although kinship is of central importance in matrilineal (nepotistic) dominance systems, various lines of evidence indicate that its role has probably been overestimated. For example, alliances among nonkin, patterned on the basis of dominance per se, contribute to the maintenance of rank and to the remarkable stability of matrilineal rank orders. But because kin and nonkin alliances exert their stabilizing effects on the rank order simultaneously, the effect of nonkin alliances per se is unknown. We tested whether nonkin alliances are sufficient to ensure the stability of matrilineal rank relations in a laboratory-housed group of Japanese macaques (Macaca fuscata). We first created a group composed of two female subgroups: (1) a subordinate subgroup of close kin known to constitute an effective revolutionary alliance and (2) a dominant subgroup composed mostly of nonkin and distant kin known to support each other against lower-ranking females. In the course of 12 consecutive experimental manipulations, we reduced progressively the relative power of the dominant subgroup by manipulating its size and age composition. The members of the dominant subgroup maintained their rank in all experimental situations except when alone. Thus, nonkin alliances remained effective up to extremely pronounced levels of power imbalance. These results suggest that the remarkable stability of matrilineal rank orders is not conditional upon the existence of nepotistic alliances and strong matrilines of close kin.     

Significance of the social relationships of Efe Pygmy men in the Ituri forest,Zaire

Efe Pygmies in northeast Zaire exhibit features of social organization (small group size, flexible but predominantly patrilocal residence, close relations with kin, and pair bonds) that are common to many hunting and gathering societies. This study uses methods commonly employed in studies of nonhuman primates to investigate the associations of Efe men with other individuals as a function of their age, sex, and kinship, and it tests the hypothesis that Efe are patrilocal because hunting efficiency is improved by hunting with male relatives. The analyses of 376 hours of focal behavior observations on 16 Efe men and observations of 71 cooperative group hunts show that the majority of associations between Efe men were with other adult men. Men associated preferentially with kin over nonkin, and they associated with close kin more than with distant kin. Men's close relationships (what we call “Companionships” sensu Smuts' “Friendships” in baboons) were predominantly with other adult men, but each man who cohabited with a woman had his strongest Companionship by far with that woman. Neither the efficiency of hunts nor the hunting success of individual men were found to be related to the degree of relatedness of hunters nor the proportion of relatives on the hunt. Alternative hypotheses concerning the functional significance of patrilocality and male kin groups are considered. We conclude that strong affiliative bonds between male kin and between males and females may arise as much from the need for strong allies in the face of competitive social situations as from economic or ecological necessity.     

Social behavior of infant and mother Japanese Macaques (Macaca fuscata): Effects of kinship,partner sex,and infant sex

The behavioral interactions of 22 infant and mother Japanese macaques with other group members were studied. Focal-animal observations were made from the time of each infant’s birth until 1 year of age. Infants and mothers both displayed exceedingly strong preferences for associating with matrilineal kin and, specifically, for female kin. The degree of genetic relatedness was positively correlated with levels of spatial proximity, contact, grooming, aggression, and play. Overall frequencies of interactions with nonkin were very low, and partner sex was not an important factor in interactions with nonkin. There were no significant differences between male and female infants in interactions with kin versus nonkin. There was only one significant difference between male and female infants in interactions with males versus females: female infants showed stronger preferences for initiating proximity with females over males than did male infants. Because mothers provide the focal point for infant interactions during the first year of life, we compared the behavior of infants and mothers. Mothers were the recipients of more social interactions than were infants, mothers engaged in more grooming than did infants, and infants engaged in more social play than did mothers. These findings are only partially consistent with kin-selection theory, and the inadequacies of studying matrilineal kin discrimination to test kin selection are reviewed. The near-absence of infant sex differences in associations with social partners suggests that although maternal kin other than the mother are important to infant socialization, they probably do not contribute to the development of behavioral sex differences until after the first year of life.     

Kinship shapes affiliative social networks but not aggression in ring-tailed coatis

Animal groups typically contain individuals with varying degrees of genetic relatedness, and this variation in kinship has a major influence on patterns of aggression and affiliative behaviors. This link between kinship and social behavior underlies socioecological models which have been developed to explain how and why different types of animal societies evolve. We tested if kinship and age-sex class homophily in two groups of ring-tailed coatis (Nasua nasua) predicted the network structure of three different social behaviors: 1) association, 2) grooming, and 3) aggression. Each group was studied during two consecutive years, resulting in four group-years available for analysis (total of 65 individuals). Association patterns were heavily influenced by agonistic interactions which typically occurred during feeding competition. Grooming networks were shaped by mother-offspring bonds, female-female social relationships, and a strong social attraction to adult males. Mother-offspring pairs were more likely to associate and groom each other, but relatedness had no effect on patterns of aggressive behavior. Additionally, kinship had little to no effect on coalitionary support during agonistic interactions. Adult females commonly came to the aid of juveniles during fights with other group members, but females often supported juveniles who were not their offspring (57% of coalitionary interactions). These patterns did not conform to predictions from socioecological models.     

Influence of kinship and spatial density on reconciliation and grooming in rhesus monkeys

Some cercopithecine primates direct disproportionate amounts of grooming, huddling, and agonistic support toward maternal kin. Disproportionate amounts of aggression are also directed toward maternal kin, however, suggesting that mechanisms that restore relationships damaged by aggression, such as reconciliation, might be biased toward these preferred social partners. Studies investigating kinship effects and reconciliation are inconsistent, however, perhaps because of differences in the environmental conditions under which behavior was observed. In order to test the effects of kinship and spatial density on affiliative and reconciliation behavior, we conducted focal and scan sampling on a group of rhesus monkeys (Macaca mulatta) living in an outdoor corral under low spatial density conditions. We then compared this data to previously published data on a group of the same species living under higher spatial density conditions. Neither overall grooming nor reconciliation were affected by spatial density once correction procedures were applied. Grooming was kin biased at both study sites, whereas reconciliation was kin biased only in the low-density group. Although data failed to support a Coping Model according to which grooming and reconciliation should go up under higher densities, we suggest that coping may be reflected not so much in overall rates of behavior but in strategic partner choices, such as the increased importance monkeys under crowded conditions appear to attach to nonkin partners. © 1996 Wiley-Liss, Inc.     

Social relationships in a herd of Sorraia horses Part II. Factors affecting affiliative relationships and sexual behaviours

The influence of age, dominance rank, kinship and aggressiveness over affiliative relationships and sexual behaviours were analysed in a herd of Sorraia horses, Equus caballus, kept under extensive management. Subjects were 10 adult mares 5-18 years old that had known each other since birth, and a stallion introduced into the group for breeding for the first time. Kinship coefficient and dominance rank were the most important factors affecting affiliative relationships. Bonds were reciprocal and stronger among mares with higher kinship. Mares spent more time in proximity to close-ranking and lower-ranking females. Mares with stronger affiliative relationships or higher relatedness were not less aggressive towards each other. Affiliative relationships between the stallion and the mares were not reciprocal: lower-ranking mares formed stronger bonds with the stallion but he preferred the less genetically related mares for proximity. However, the stallion was involved in sexual behaviours more frequently with the mares that were more genetically related to him. These results suggest that kinship beyond close relatives may affect affiliative relationships both among familiar and among unfamiliar horses. However, the influence of kinship does not imply that horses possess a kin recognition system and alternative explanations are discussed.     

Testing kin altruism in long-tailed macaques (Macaca fascicularis) in a food-sharing experiment

Social grooming and coalition formation have been main foci in studies concerning altruism in monkeys. Results have been inconclusive because the altruistic nature of these behaviors remains unclear. I investigated altruism in a more transparent context via an apparatus in which captive long-tailed macaque females had the choice to exploit a food source themselves or to yield the food to a test partner. I hypothesized that if potential donors behaved altruistically toward kin, they would yield the food sources longer to kin than to nonkin. Of 11 tested potential donors, 8 did not discriminate between daughters or sisters and nonkin. Thus, the experiments do not support the kin altruism hypothesis. Three females let their youngest offspring have more food than matched juvenile nonrelatives. Behavioral observations strongly suggested,however, that it was primarily spiteful behavior toward juvenile nonrelatives that caused the differences between kin and nonkin in these three cases.     

Kin recognition by paternal half-siblings in captive Papio cynocephalus

Our objective in this study was to evaluate whether a group of paternally related, subadult baboons (Papio cynocephalus) would preferentially interact with kin or nonkin when they had been raised apart from kin other than their mothers. Subjects and their mothers were removed from the breeding group and placed in alternate housing within 24 h after birth to ensure that the subjects would not have a social history with either their sire or their half-siblings. At 90 days of age, the 23 subjects were separated from their mothers and assigned to a peer–peer social group. Behavioral performance was measured using focal animal sampling techniques and 12 molecular behavioral criteria. Analyses of the data indicate that in dyadic interactions kin did not interact more frequently than nonkin in performance of affiliative, sociosexual, and agonistic behaviors. The hypothesis that baboons recognize kin in the absence of maternal associations was not supported by the data; moreover, we suggest that social learning and social history are the most likely mechanisms for kin recognition. Am. J. Primatol. 43:147–157, 1997. © 1997 Wiley-Liss, Inc.     

Paternal Relatedness Predicts the Strength of Social Bonds among Female Rhesus Macaques

Forming strong, equitable, and enduring social bonds with a few individuals in a group carries adaptive benefits in terms of increased longevity, offspring survival and paternity success in birds and mammals, including humans. These recent insights generated a new interest in the factors creating variation in the strength of social relationships. Whether and how animals discriminate paternal kin from non-kin and bias their social behavior accordingly is being debated. This study explores the relative importance of dominance rank, age, maternal and paternal relatedness in shaping dyadic affiliative relationships in a group of 30 captive rhesus macaque females. The strength of social relationships, measured by the composite sociality index from observational data, was independently predicted in GLMMs by both maternal and paternal relatedness as well as rank similarity. In addition, social bonds between paternal half-sisters were stronger than between distantly related kin suggesting that females biased their affiliative effort towards paternal relatives. Despite identical relatedness coefficients bonds between mothers and their daughters were three times as strong as those between full sisters. Together these results add to the growing body of evidence for paternal kin biases in affiliative behavior and highlight that females prefer descendent over lateral kin.     

Greeting behavior during party encounters in captive chimpanzees

Party encounter situations were experimentally produced in a group of captive chimpanzees (Pan troglodytes verus) at the Primate Research Institute of Kyoto University, Japan. During weekends all subjects (two adult males and five adult females) usually stayed together in the rooms (Baseline condition). Under experimental conditions, we shut passages between rooms to divide the subjects into two groups. We examined the effects of temporal separation of group members on affiliative interactions, aggressive interactions, and simple proximity. The frequency of affiliative interactions between male and female chimpanzees and between female chimpanzees increased when they encountered one another after separation, irrespective of male identity or housing history. Therefore we considered affiliative interactions between males and females during party encounters as being the response between separated individuals. The same tendency was not found in the frequency of affiliative interactions between females or between males. Unlike affiliative interactions, neither aggressive interactions nor simple proximity were influenced by separation.     

The effects of temporary removal of the alpha male on the behavior of subordinate male vervet monkeys

The effects of temporary removal of the alpha male on the behavior of subordinate adult male vervet monkeys were evaluated. Twelve subordinate males from six captive multimale, multifemale vervet monkey groups were observed in two conditions: when all group members were present and when the alpha male was temporarily removed from each group. In the absence of the alpha male, subordinate males initiated more affiliative behavior and increased the amount of time spent in proximity to females but their rates of aggression were unaltered. Increased affiliative behavior was selectively directed to high-ranking females and their offspring. Under removal conditions, subordinate male behavior did not resemble that of alpha males in intact conditions: they differed in their proximity to and affiliative behavior towards other group members. In the absence of the alpha male, females increased their aggression towards subordinate males. These observations suggest that the presence of alpha males strongly inhibits subordinate males' behavior. When the constraints of the alpha male's presence are removed, subordinate males rapidly engage in behavior that may enhance their likelihood of attaining high rank. In combination with prior studies, the data also indicate that the behaviors involved in the maintenance of high rank by alpha males differ from those subordinates use to acquire dominance. Finally the current study supports the view that aggression by female vervets may be highly influential in determining male ascendency to dominant rank.     

The impact of paternity on male–infant association in a primate with low paternity certainty

In multimale groups where females mate promiscuously, male–infant associations have rarely been studied. However, recent studies have shown that males selectively support their offspring during agonistic conflicts with other juveniles and that father's presence accelerates offspring maturation. Furthermore, it was shown that males invest in unrelated infants to enhance future mating success with the infant's mother. Hence, infant care might provide fitness gain for males. Here, we investigate male–infant associations in rhesus macaques (Macaca mulatta), a primate with low paternity certainty as females mate with multiple partners and males ensure paternity less efficiently through mate‐guarding. We combined behavioural data with genetic paternity analyses of one cohort of the semi‐free‐ranging population of Cayo Santiago (Puerto Rico) and recorded affiliative and aggressive interactions between focal subjects and adult males from birth to sexual maturation (0–4 years) of focal subjects. Our results revealed that 9.6% of all interactions of focal subjects involved an adult male and 94% of all male–infant interactions were affiliative, indicating the rareness of male–infant aggression. Second and most interestingly, sires were more likely to affiliate with their offspring than nonsires with unrelated infants. This preference was independent of mother's proximity and emphasized during early infancy. Male–infant affiliation rose with infant age and was pronounced between adult males and male rather than female focal subjects. Overall, our results suggest that male–infant affiliation is also an important component in structuring primate societies and affiliation directed towards own offspring presumably represent low‐cost paternal care.     

Egg-dumping lace bugs preferentially oviposit with kin

Egg dumping, or abandoning eggs and young to the care of other conspecifics, results in an extreme form of alloparental care. It is unclear, however, if egg dumpers discriminate among kin and nonkin egg recipients. In the lace bug Gargaphia solani (Heteroptera: Tingidae), some females with eggs (guards) also accept and defend eggs of conspecifics. Other females (egg dumpers) abandon their offspring after oviposition, leaving a single guard as the caregiver. We asked if egg dumpers preferentially dump their eggs among unguarded eggs of kin or nonkin. When given a choice between dumping among eggs of full siblings and eggs of nonsiblings, most eggs (67%) were dumped with full siblings' eggs. Furthermore, egg dumpers were just as likely to oviposit among eggs of kin with whom they had interacted on a shared host plant during juvenile development as they were to oviposit with kin reared on different host plants. Thus, egg dumpers discriminate kin by using cues associated with eggs, and such cues are not likely to be acquired through interaction on a common host plant environment. Copyright 2000 The Association for the Study of Animal Behaviour.     

Kin discrimination in prepubescent and adult Long-Evans rats

The present study investigated the preference of prepubescent and adult rats for an unrelated conspecific over a closely related conspecific (e.g., father, mother). Preference was measured by the amount of time spent in the vicinity of the stimulus animals as well as who was visited first. To prevent mating behavior, stimulus animals were housed behind wire-mesh. Experiment 1 determined if adult female offspring prefer an unrelated, unfamiliar adult male or their father. The preference of adult female rats was independent of kinship. Experiment 2 evaluated the preference of prepubescent female and male offspring for an unrelated, unfamiliar adult male or their father. The preference of prepubescent female and male rats was also independent of kinship. Experiment 3 evaluated the preference of adult male offspring for an unrelated, unfamiliar adult female or their mother. The preference of adult male rats was independent of kinship. In summary, prepubescent and adult rats do not demonstrate preference for kin vs. non-kin (as measured by time spent near stimulus animals or who was visited first). Although kin recognition provides a mechanism for inbreeding avoidance (Wilson, 1987), in the present study adult rats show no evidence of inbreeding avoidance.