Carol M. Berman

Mother-infant relationships among free-ranging rhesus monkeys on Cayo Santiago : a comparison with captive pairs

The general course of mother-infant relationships among free-ranging rhesus monkeys (Macaca mulatta) on Cayo Santiago is remarkably similar both qualitatively and quantitatively to that observed in the socially living captive colony at the MRC Unit at Madingley, England. Nevertheless, small but consistent differences appear to be due to differences between mothers in the two environments rather than differences between infants. Captive mothers may be described as more protective and less encouraging of early independence in their infants than free-ranging mothers. Moreover, captive pairs have become more like free-ranging pairs over the years, perhaps as captive mothers have been allowed to raise their infants in the presence of kin. A unitary concept of environmental complexity is not useful in accounting for the results.

The ontogeny of social relationships with group companions among free-ranging infant rhesus monkeys I. Social networks and differentiation

Abstract Social networks of infant rhesus monkeys ( Macaca mulatta ) in a free-ranging, lineage-based group on Cayo Santiago are described by assessing the extent to which four measures of positive interaction between infants and finely-divided categories of companions are associated with (1) degree of relatedness through maternal lines; (2) sex of the companion; (3) age of the companion; and (4) dominance rank of the infants lineage. The results suggest that the infants social network mirrors that of its mother both in the first weeks of life and as late as 30 weeks of age. Infants have more positive social interaction with close kin than with distant kin or with unrelated individuals, and thus function as members of their lineage from the beginning. They associate more with female companions than with male companions, and more with younger immatures than with older immatures. Finally, infants in the top-ranking lineage spend more time with their own relatives than do infants in other lineages. The fact that these patterns change little as the infant gains independence from the mother supports suggestions that early maternal influence serves to pass on aspects of the mothers social network. It is suggested that the ontogeny of early social relationships resembles a process of differentiation.

Dominance Style Among Macaca thibetana on Mt. Huangshan, China

The dominance style concept has proven useful for understanding covariation patterns in relationship qualities, particularly among macaques. However, the dominance styles of many macaques, including Tibetan macaques (Macaca thibetana), have not been examined in detail. We describe patterns of bidirectionality of aggression, postconflict affiliation and kin bias in a group of wild, but provisioned Tibetan macaques over a 2-yr period in order make an initial assessment of their dominance style. Bidirectional aggression, including percentage of counteraggression (1.9%), and conciliatory tendencies (6.4%) were consistently low across partner combinations, seasons and locations (forest vs. provisioning area). In addition, females consistently displayed high levels of kin bias in affiliation and tolerance. Compared with macaque species with better known dominance styles, the Tibetan data generally fell within the range for despotic species and outside the range for relaxed species. Although other researchers have tentatively classified them as tolerant or relaxed, we conclude that Tibetan macaques display a despotic dominance style. This conclusion poses complications to explanations based both on phylogenetic inertia and socio-ecological models.

Group size, infant development and social networks in free-ranging rhesus monkeys

Abstract The hypothesis that demographic processes are important in determining social structure among non-human primates through their effects on the development of individual social relationships was tested. Changes in maternal behaviour, infants’ social milieux and infants’ social networks were examined as a function of changes in group size and composition among free-ranging rhesus monkeys, Macaca mulatta on Cayo Santiago, Puerto Rico. Data were analysed for 10 group-years collected between 1974 and 1990 representing a single social group during periods of rapid expansion and fissioning, two daughter groups following fissioning and an unrelated group that did not undergo fissioning. As group size expanded, infants found themselves near (

Immature siblings and mother-infant relationships among free-ranging rhesus monkeys on Cayo Santiago

This report examines the possible influence of the presence of immature siblings on measures of mother-infant interaction and on the timing of the mothers resumption of mating among free-ranging rhesus monkeys, Macaca mulatta, on Cayo Santiago, Puerto Rico. Data for 124 mother-infant pairs, collected between 1974 and 1986, were analysed using analysis of covariance methods. The results suggest that mothers with one or more immature daughters in addition to their infants are in contact with their infants less than those with no older immature daughters, perhaps because their infants need less protection from other group members. High-ranking mothers with older immature daughters also reject their infants significantly more than those without older daughters, and tend to begin mating earlier in the mating season than expected based on their dates of parturition the preceding birth season. In contrast, the presence of sons has relatively little impact on mother-infant interaction, or on the timing of the mothers resumption of mating.

Hierarchical steepness and phylogenetic models: phylogenetic signals in Macaca

Phylogenetic models of primate social behaviour posit that core social traits are inherent species characteristics that depend largely on phylogenetic histories of species rather than on adaptation to current socioecological conditions. These models predict that aspects of social structure will vary more between species than within species and that they will display strong phylogenetic signals. We tested these predictions in macaques focusing on dominance gradients, a relatively little studied, yet central, aspect of social structure. We used data from 14 social groups representing nine macaque species living in a variety of conditions. We examined proportions of counteraggression and two recently developed measures of dominance gradients (hierarchical steepness) for phylogenetic signals in nine phylogenetic trees constructed using (1) available genetic data sets and (2) Bayesian Markov Chain Monte Carlo (MCMC) and maximum likelihood algorithms. Hierarchical steepness and counteraggression showed significant variation between species but inconsistent variation within species. Both steepness and counteraggression showed evidence of phylogenetic signals, with results being particularly strong for one steepness measure and for counteraggression. Our results suggest that between-species variation in some core aspects of social structure are shaped by species’ evolutionary relationships, despite differences in living conditions. As such, they provide broad support for the phylogenetic model.

Impact of Translocation, Provisioning and Range Restriction on a Group of Macaca thibetana

We examined the possible long-term impact of translocation and subsequent provisioning and range restriction on recruitment rates in a group of rare Tibetan macaques (Macaca thibetana) in Anhui Province, China. We compared demographic data recorded in the group (and in its fission products) during the 6 years before and after translocation and in a group with no history of management. We also compared preliminary data related to nutritional condition, habitat characteristics, and group activities. Infant losses markedly increased following translocation and management. Estimated measures of nutritional condition varied more among adults in the managed group than among those in the never managed group, suggesting that members of the managed group may have experienced higher levels of intragroup competition. We hypothesize that increased levels of intragroup competition for provisioned food may have put infants at increased risk.

Hierarchical Steepness, Counter-Aggression, and Macaque Social Style Scale

Nonhuman primates show remarkable variation in several aspects of social structure. One way to characterize this variation in the genus Macaca is through the concept of social style, which is based on the observation that several social traits appear to covary with one another in a linear or at least continuous manner. In practice, macaques are more simply characterized as fitting a four‐grade scale in which species range from extremely despotic (grade 1) to extremely tolerant (grade 4). Here, we examine the fit of three core measures of social style—two measures of dominance gradients (hierarchical steepness) and another closely related measure (counter‐aggression)—to this scale, controlling for phylogenetic relationships. Although raw scores for both steepness and counter‐aggression correlated with social scale in predicted directions, the distributions appeared to vary by measure. Counter‐aggression appeared to vary dichotomously with scale, with grade 4 species being distinct from all other grades. Steepness measures appeared more continuous. Species in grades 1 and 4 were distinct from one another on all measures, but those in the intermediate grades varied inconsistently. This confirms previous indications that covariation is more readily observable when comparing species at the extreme ends of the scale than those in intermediate positions. When behavioral measures were mapped onto phylogenetic trees, independent contrasts showed no significant consistent directional changes at nodes below which there were evolutionary changes in scale. Further, contrasts were no greater at these nodes than at neutral nodes. This suggests that correlations with the scale can be attributed largely to species’ phylogenetic relationships. This could be due in turn to a structural linkage of social traits based on adaptation to similar ecological conditions in the distant past, or simply to unlinked phylogenetic closeness. Am. J. Primatol. 74:915‐925, 2012.

Development of kin bias among rhesus monkeys: maternal transmission or individual learning?

We examined the possible roles of maternal transmission and independent learning in the development and perpetuation of kin networks across generations of free-ranging rhesus monkeys, Macaca mulatta, on Cayo Santiago, Puerto Rico. We tested predictions derived from maternal transmission and independent learning hypotheses by examining the extent to which variation in the degree of kin bias displayed by individual infants was related to variation in mother-infant interaction and aspects of the infants social environment. High levels of kin bias in infants were related independently to high levels of both proximity to the mother and to potential social risk. At 25-30 weeks of age, infants displayed degrees of kin bias that were moderately correlated with those of their mothers. However, infants that spent large amounts of time near the mother did not necessarily develop degrees of kin bias that were highly similar to those of their mothers. The extent to which infants developed degrees of kin bias similar to their mothers was significantly correlated with the degree to which they experienced similar levels of social risk. The results suggest that, while intense mother-infant interaction contributes to the development of high degrees of kin bias in infants, the perpetuation of similar degrees of kin bias across generations may depend on mothers and infants having similar experiences with mutual kin and nonkin. We suggest that the perpetuation of kin bias across generations may be viewed as socially biased independent learning (Galef 1995, Animal Behaviour, 49, 1325-1334). Copyright 1999 The Association for the Study of Animal Behaviour.

Supportive and tolerant relationships among male Tibetan macaques at Huangshan, China

Tibetan macaque males at Huangshan ( Macaca thibetana huangshanensis ) display highly skewed mating success and highly asymmetric patterns of aggression, but also high levels of tolerance. We examined affiliation, tolerance and agonistic support to test the hypothesis that increased tolerance in otherwise despotic males may occur when high-ranking males require support from other males to prevent (1) potentially destabilizing revolutionary coalitions against them, or (2) young adult males from usurping the alpha position. Several predictions of the first hypothesis were supported: Support was unrelated to kinship or affiliation and was generally conservative, serving to reinforce the current hierarchy. Nevertheless revolutionary coalitions posed a threat, particularly to alpha males. High-ranking males displayed tolerance in the form of co-feeding toward lower ranking males that supported them, and alpha males showed the most cooperation with the males that targeted them in revolutionary coalitions. Predictions of the second hypothesis were not consistently supported; male coalitions targeted young potential usurpers of the alpha position during only one of two periods of hierarchical stability. We suggest that high ranking males discourage revolutionary alliances by using two strategies. They primarily rely on conservative alliances, but also offer tolerance in cases in which conservative coalitions are less effective.