Organization of Group Members at Departure Is Driven by Social Structure in Macaca

Researchers have often explained order of progression of group members during joint movement in terms of the influence of ecological pressures but rarely that of social constraints. We studied the order of joining by group members to a movement in semifree-ranging macaques with contrasting social systems: 1 group of Tonkean macaques (Macaca tonkeana) and 1 group of rhesus macaques (M. mulatta). We used network metrics to understand roles and associations among individuals. The way the macaques joined a movement reflected the social differences between the species in terms of dominance and kinship. Old and dominant male rhesus macaques were more often at the front of the movement, contrary to the Tonkean macaques, which exhibited no specific order. Moreover, rhesus macaques preferred to join high-ranking or related individuals, whereas Tonkean macaques based associations during joining mostly on sexual relationships with a subgroup of peripheral males.     

Balancing contest competition,scramble competition,and social tolerance at feeding sites in wild common marmosets (Callithrix jacchus)

Models of primate sociality focus on the costs and benefits of group living and how factors such as rank, feeding competition, alliance formation, and cooperative behavior shape within‐group social relationships. We conducted a series of controlled field experiments designed to investigate how resource distribution (one or three of four reward platforms) and amount of food on a reward platform affected foraging strategies and individual feeding success in four groups of wild common marmosets (Callithrix jacchus) living in the Caatinga of northeastern Brazil. At our field site, common marmoset groups are characterized by a single breeding female who can produce twin litters twice per year, strong social cohesion, and cooperative infant care provided principally by several adult male helpers. We found that except for the dominant breeding female, rank (based on aggression) was not a strong predictor of feeding success. Although the breeding female in each group occupied the highest rank position and obtained the greatest daily feeding success, all other group members, including adults and juveniles experienced relatively equal feeding success across most experimental conditions. This was accomplished using a balance of behavioral strategies related to contest competition, scramble competition (associated with a finder's advantage), and social tolerance (sharing the same feeding platform). Based on these results, the social structure of common marmosets is best described as “single female dominance,” with the breeding female maximizing food intake needed to offset the energetic costs associated with reproductive twinning and the ability to produce two litters per year. Cooperative infant caregiving, in which the number of helpers is positively correlated with offspring survivorship, requires a set of behavioral strategies that serve to reduce contest competition and promote prosocial behaviors at feeding sites.     

Group size,composition, and reproductive success in wild common marmosets (Callithrix jacchus)

Data from published sources about size and composition of wild common marmoset groups (Callithrix jacchus) were analyzed to see if the number of juveniles in a group is closely related to the number of other group members. Mean group size was 8.7 members including 4.4 adults (1.8 females, 2.5 males), 2.9 subadults, and 1.4 juveniles. The number of juveniles was significantly positively correlated to the number of adult males. Groups with one or two adult males had significantly fewer juveniles (mean: 1:1 juveniles) than groups containing more than two adult males (mean: 2.0 juveniles). Apart from a different number of subadults, results showed obvious similarities between common marmosets and tamarins of the genus Saguinus in size and composition of subgroups of adults as well as the key role of adult males in mediating the reproductive success of a breeding female. Common marmoset females seem to gain direct fitness benefits in increased reproductive success from the presence of a larger number of adult males. Whether or not other group members get fitness benefits depends on the reproductive strategy of adult males (monogamy vs. polyandry), their kinship, and on the genetic relationship of nonbreeders to the offspring of the breeding female. © 1995 Wiley-Liss, Inc.     

Dominance relations in captive groups of adult and juvenile arctic blue foxes (Alopex lagopus)

Dominance relationships were studied in captive Arctic blue fox (Alopex lagopus) groups comprising adults (four males, five females) and juveniles (four males, five females). The results showed that Arctic blue foxes easily formed a social organization with an observable hierarchy, in which adults typically dominated over juveniles. Within the same age group, males usually dominated over females. Dominance correlated most significantly with body weight in autumn, but later that correlation decreased. Urine marking activity was very low during autumn and early winter, but increased significantly prior to and during the breeding season when aggressive encounters were also most pronounced. In addition to several adults, the social status of some juveniles was high at breeding time. Altogether 7 out of 11 females (63.6%) whelped, but the survival rate of litters was low and kits of only two adult females survived (18.2%). It can be concluded that hierarchical development and reproduction in Arctic blue fox groups are markedly influenced by dominance relationships.     

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.     

Coalitions among gelada baboons

Geladas spend an unusually large amount of time in quiet, mutual grooming in this captive sample, part of which is presumably due to the effects of captivity and part is a reflection of the gelada pattern of social interactions. The most frequent signals associated with threat or displacement (lid) occurs only at a rate of 5.3 times per hour. Herding and displacement activities are important, but infrequent.One-male bisexual units are extremely cohesive. A male does not tolerate the positioning of another male between himself and any of his females, and the adults of the groups react antagonistically to each other's proximity.The solitary male is not groomed by other adults, but stays withChief's group and backsChief in interactions with the other group.Chief's group is a two-male unit in some ways, but withDemon being excluded from any activity or location which interferes withChief's interactions with his group.The females inEcho's group exhibit a dominance hierarchy, as measured in displacement, or denial of desirable social space. Interactions between individuals ofEcho's group reflect strong preferences between individuals, prohibitions toward certain relationships by more dominant individuals, and the ability to enlist the support of others in coalitions. Coalitions are simply another expression of social relationships that are more frequently expressed in grooming, proximity, and displacement.     

Do snakes represent the principal predatory threat to callitrichids? Fatal attack of a viper (<Emphasis Type="Italic">Bothrops leucurus</Emphasis>) on a common marmoset (<Emphasis Type="Italic">Callithrix jacchus</Emphasis>) in the Atlantic Forest of the Brazilian Northeast

A juvenile common marmoset (Callithrix jacchus) was attacked by a whitetail lancehead viper (Bothrops leucurus) while playing with other group members close to the ground at a site in northeastern Brazil. The attack was almost immediately fatal, but the viper was unable to ingest the body of the marmoset. After approximately 10 min, during which it attempted to swallow the marmoset a number of times, the viper moved away, abandoning the body. While raptors are the principal predators of callitrichids, this record reinforces the relative vulnerability of these primates to snakes in comparison with other platyrrhines, although the small number of recorded events precludes a more definitive analysis of the phenomenon.     

The Pair-Bond Formation and Its Role in the Stimulation of Reproductive Function in Female Common Marmosets (Callithrix jacchus)

The sociosexual relationship between male and female common marmosets (Callithrix jacchus) is characterized by pair-bond formation, which includes sexual and social interactions such as contact, huddling and allogrooming. The formation of heterosexual pairs in captivity sometimes is unsuccessful in terms of reproduction. We investigated the existence of a correlation between characteristics of sociosexual interaction of marmoset pairs and its role in stimulating reproductive function in females. We studied pair-bond formation during the first 10 weeks of pairing in eight unrelated heterosexual pairs of common marmosets (Callithrix jacchus) without prior sexual experience. In three of them, pregnancy occurred during the study period (group SR), and we compared the profile of their sociosexual interactions with that of the five other couples in which pregnancy was not registered (group NS) during that period. The results show differences between the two groups, related mainly to affiliative responses between male and female, with significantly higher levels of allogrooming and simultaneous piloerection in the SR group. Although we did not find significant differences in the frequency of mounting behavior between groups, their reproductive success was different, suggesting that some behavioral patterns related to cooperative interactions between the male and female could be expressing the pair-bond. These behaviors may be influencing the females' physiology and consequently successful reproduction in the species.     

The social behavior of a marmoset (Saguinus fuscicollis) group II: Behavior patterns and social interaction

The behavioral patterns and social interaction of a marmoset (Saguinus fuscicollis) group in a semi-naturalistic environment were observed for 14 months. The analysis showed that, of the 32 behavior patterns observed, the 10 most frequent accounted for over 97 per cent of the total behavior. One pattern, sit and look, accounted for 44 per cent of the total behavior. The two most frequent social behavior patterns, grooming and social play, were concentrated in different parts of the group. The focal point of grooming was the adult female; social play was characteristic of younger animals 4–20 months of age. These results were compared with other studies of marmosets and with primate studies on grooming and social play.     

Do Barbary macaques ‘comment’ on what they see? A first report on vocalizations accompanying interactions of third parties

Primates acquire knowledge about relationships of third parties and group structure by monitoring their conspecifics. We show that Barbary macaques (Macaca sylvanus) utter specific vocalizations while monitoring interactions of other group members. As they did not direct other behaviours to the interacting group members, we provisionally termed these vocalizations vocal comments. We investigated the acoustic properties of these comments and the social contexts in which they occurred. Most adult males and females of two studied groups produced low-amplitude calls when observing close contact interactions of other group members. The acoustic features of these calls varied with characteristics of the commented situation. Our results suggest that such calls might not be directed towards the agents of the commented situation, but towards other group members. The vocal comments may signal the callers awareness of the observed interaction and possibly attract the attention of others to the situation.     

Food Transfer Among Adult Lion Tamarins: Mutualism,Reciprocity or One-Sided Relationships?

Tamarins (Callitrichidae) are cooperative breeders. Groups typically contain only two or three breeding individuals and subordinate group members are reproductively suppressed. Nonreproductive individuals, which are usually the offspring of the group's breeding members, delay dispersal while providing care to infant siblings. Callitrichid breeder-infant and helper-infant relationships have been well studied but empirical studies regarding the dynamics of breeder-helper relationships are sparse. I examined food-transfer interactions among parents and natal adults in 7 groups of captive lion tamarins, Leontopithecus spp., to test whether relationships are maintained by mutualism or reciprocity or are to the benefit of one side of a dyad. Individuals that had recently received food from a group member most frequently released food to the previous donor as their next act of transfer. Conversely, food transfer was not dependent on symmetrical relationships within groups over a time frame of several weeks. These results suggest that mutualism plays a role in the maintenance of food-transfer relationships but reciprocity does not. However, there is evidence for a reciprocal relationship between grooming and food transfer in one group. Subadults and adults living in their natal groups transferred proportionally more food to mothers than to oppositely-sexed subadult and adult siblings. Thus, individuals most likely to receive aggression preferentially released food to individuals most likely to inflict injury upon them. Although these results support the coercion hypothesis, they may suggest alternatively that food transfer by helpers to breeding adults is driven by inclusive fitness considerations.     

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.     

Group unity of chimpanzees elucidated by comparison of sex differences in short-range interactions in Mahale Mountains National Park,Tanzania

Chimpanzees (Pan troglodytes) form multi-male and multi-female unit groups with fission–fusion grouping patterns. Short-range interaction (SRI) plays an important role in the unity of these groups and in maintaining social bonds among members. This study evaluated three models of chimpanzee social structure that differed according to the emphasis each placed on social bonds between the sexes, i.e., the male-only, the bisexual, and the male-bonded unit-group model. I investigated differences in SRI between the sexes among group members in well-habituated wild chimpanzees in Mahale Mountains National Park, Tanzania. I followed six focal adult males and six females, and quantified their respective SRI with other chimpanzees. Except between subordinate males and adult females, adults in general engaged in SRI with about 60–90% of the individuals with whom they made visual contact each day, whether in large or small parties. Although the number of social grooming (SGR) partners was limited, male–male SGR networks were wider than were either male–female or female–female SGR networks among adults. The number of contact-seeking behavior (CSB) partners was also limited, but dominant males had more CSB partners. Adult females mainly interacted by pant-grunt greeting (PGG) with adult males, but tended to do so mainly with the highest-ranking male(s) within visual contact. These results indicated that the social bonds among adult males were essential to group unity. Because of clear male dominance, adult females established peaceful coexistence with all group members despite less frequent SRI with subordinate males by maintaining affiliative social bonds with dominant males, thereby supporting the male-bonded unit-group model. Adult females had many female SRI partners, but these interactions did not involve performing conspicuous behaviors, suggesting that females maintain social bonds with other females in ways that differ from how such bonds are maintained with and between adult males.     

Sex differences in food acquisition and aggression in captive common marmosets (Callithrix jacchus)

Competition for food within the social group has been postulated as an important factor affecting primate social organization. This study examined how factors such as sex, aggression, dispersion of food, and amount of difficulty involved in obtaining food affect the distribution of food in common marmoset (Callithrix jacchus) social groups. Mated pairs of adultC. jacchus were presented with food that was either dispersed or concentrated, and either difficult or easy, to obtain. The number of food pieces obtained, aggressive displays, incidents of physical aggression, and amount of time spent searching for food were recorded for each animal. Neither dispersion nor difficulty in obtaining food had significant effects on the distribution of food or any of the other behaviors examined. The primary factors affecting food distribution were aggression and amount of time spent searching. Females obtained more food than males in all situations because they were more aggressive and apparently more motivated to search for food than were males.     

Intergroup encounters in wild white-faced capuchins (Cebus capucinus)

Wrangham (1980) hypothesized that knowledge of the nature of intergroup encounters is crucial to understanding primate social relationships and social organization. I studied a single social group of wild white-faced capuchins over a period of 26 months and observed 44 encounters between social groups during 3703 hr of observation. All intergroup encounters consisted of predominantly hostile social interactions. However, nonaggressive interactions between males of different social groups occurred in a few cases. Adult males were the sole participants in 39 encounters and the primary participants in all 44 encounters. The alpha male was the most frequent participant. High-ranking females participated aggressively in five encounters, and low-ranking females never participated. There was no stable intergroup dominance hierarchy. I hypothesize that the need for male-male cooperation in intergroup aggression is an important factor influencing the quality of intragroup male-male relationships. Behavior during intergroup encounters is consistent with the idea that intergroup behavior is related to male reproductive strategies, but inconsistent with the idea that intergroup aggression is related to female defense of resources. The possibility that males are “hired guns” (Wrangham, 1980) cannot be ruled out.     

Social Dominance Hierarchies and Phenotypic Correlates of Dominance in Captive Groups of the Grey‐cheeked Fulvetta Alcippe morrisonia in Taiwan

Dominance hierarchies usually form quickly among avian foraging groups because they are beneficial to most individuals by reducing conflict. Several characteristics that correlate with dominance rank have been identified in birds, but most of these conclusions rely on studies of temperate species. Hence, we studied whether captive group members of a subtropical species, grey‐cheeked fulvetta Alcippe morrisonia, form social dominance hierarchies when competing for food during the non‐breeding season. We also investigated whether sex, age, body condition and fat score were related to an individual's dominance rank which was established by counting aggressive interactions in six captive groups of nine individuals each. In all groups, linear dominance hierarchies were formed whereby yearlings dominated over adult birds, and individuals with a better body condition were also more dominant, while sex and fat score had no discernable effect. Male yearlings had significantly higher body masses and body condition indices than male adults, while female yearlings had significantly higher body masses, body condition indices and fat scores than female adults. However, there were no significant differences between male and female yearlings or adults for any of these variables. We suggest possible reasons for the dominance of yearlings, such as captive conditions or the higher body weight of yearlings.     

Food Transfer and Development of Feeding Behavior and Food-Associated Vocalizations in Cotton-Top Tamarins

Food transfer between adults and infants is common in many marmoset and tamarin monkeys, and is often accompanied by vocalizations. We hypothesized that vocalizations by adults in a food transfer context creates an opportunity for infants to learn not only what foods are appropriate but what vocalizations are appropriate in feeding contexts. We studied the development of feeding behavior and food-associated vocalizations in 10 infant cotton-top tamarins through the first 20 wks of life. Infants obtained solid food through transfers from older group members, primarily the adult male, beginning at weeks 5–6. Both adults and infants vocalized during food transfers with adults, producing rapid sequences of the call types adults normally give when feeding. Infants were usually successful in obtaining food primarily when the adult was vocalizing. The sooner infants were active participants in food transfers, the sooner they began to feed independently. In the early weeks, infants produced a large number of vocal types during food transfers, but with increasing age there was a steady increase in the number of adult-form food calls and a reduction in other, non-food-associated calls. Infants that fed independently at an early age produced fewer non-food-associated calls by the last month of observation. Infants called at higher rates to their most preferred food. Food transfers accompanied by vocalizations may provide an opportunity for infants to learn about appropriate foods as well as the vocalizations that accompany feeding in adults, and may represent a form of 'coaching' or information donation by adults.     

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.     

Dynamics of the fungal symbionts in the gallery system and the mycangia of the ambrosia beetle,Xylosandrus mutilatus (Blandford) (Coleoptera: Scolytidae) in relation to its life history

The dynamics of the fungal symbionts in the gallery system and the mycangia of the ambrosia beetle,Xylosandrus mutilatus, were studied in relation to its life history using both isolation experiments and scanning electron microscopy (SEM). In the galleries,Ambrosiella sp. was predominant during the larval stages but its relative dominance gradually decreased during the development of the larvae. In contrast, yeasts (mainlyCandida sp.) andPaecilomyces sp. dominated continuously in the galleries after eclosion.Ambrosiella sp. was consistently stored in the mycangia in all adult stages, except in the teneral and overwintering adults when the other fungi were dominant. No fungal spores occurred in the mycangia of the adult beetles reared under aseptic conditions from the pupal stage, while onlyAmbrosiella sp. was stored in those reared from the teneral-adult stage. These results suggest that: (i) Xmutilatus is associated with at least three fungal species, among whichAmbrosiella sp. is the most essential food resource for development of the broods; (ii) immediately after eclosion, new female adults may take at least four associated fungal species, with no or incomplete selection, into their mycangia from the walls of the cradles; and (iii) conditions may well be produced in the mycangia of both matured and dispersing beetles whereby only the spores ofAmbrosiella sp. can proliferate.