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Duets in pair-bonding primates serve as a primary mode of communication between pairs, and duets may provide cues to conspecifics regarding the calling individual or pair. Here, we test the hypothesis that pulse elements in coppery titi monkey duets vary with condition and identity of the caller. We predicted that pulse elements would vary with age, sex, or pair-bond length. We estimated pulse rate and duration for 378 pulse elements from the duets of 74 captive titi monkeys (Plecturocebus cupreus). We found inter-individual variation in both features, and evidence for vocal convergence among pair mates in pulse rate. Age was the best predictor of pulse rate, and pulse rate decreased with age. Age and pair-bond length reliably predicted pulse duration. Our results suggest that variation in titi monkey duets reflects differences in caller condition and pair identity, and contribute to growing evidence for vocal plasticity in nonhuman primates. [ABSTRACT FROM AUTHOR]

Cooperative relationships among male primates are emerging as an important aspect of primate social behavior. What remains unclear is the extent to which male associations with coresident males vary within species, and what social and demographic factors drive these associations. This information provides an important contribution to our understanding of how cooperative relationships play an adaptive role in the evolution of male social and reproductive strategies. To examine the nature of male associations and the influence of social and demographic factors, including rank and age, we collected 1751 h of focal behavioral data on adult males in two large multimale-multifemale groups of mantled howlers {Alouatta palliata) at La Pacifica, Costa Rica. Both groups inhabited upland forest area, were of similar size and sex ratio, and exhibited strongly linear male hierarchies. Based on observed .spatial associations within 3 m proximity, dyadic patterns varied from strongly preferred to strongly avoided associations that were largely consistent among dyads over the study period. In contrast to reports from other mantled howler study sites, neither rank nor age differences among males predicted whether dyads spent any time in proximity to one another, nor the amount of time in proximity. However, higher-ranked males within dyads were more likely to maintain close proximity than their lower-ranked counterparts. Our results provide important data on the nature of male associations within mantled howler groups with linear dominance relationships, and are suggestive of the adaptive value of cooperative relationships. [ABSTRACT FROM AUTHOR]

Research on Old World primates provided the foundation for understanding competitive strategies resulting from social and ecological pressures. The neotropical primate, Cebus capucinus shares many social patterns with Old World cercopithecines (e.g., female philopatry, male dispersal), which may contribute to similar expression of competitive strategies. To clarify the nature of dominance patterns among female white-faced capuchins we examined hierarchical linearity, rank acquisition, matrilineal rank inheritance, hierarchical strength and stability. We collected focal data on 22 adult females (2008) and long-term dominance data (1986–2008) on 33 adult females in Sector Santa Rosa, Costa Rica. Females displayed linear hierarchies based on the direction of dyadic submission. At sexual maturity females quickly acquired rank positions beneath their mother and older sisters. Hierarchies were considered strong based on high proportions of food-related agonism, short latency to detection of hierarchies (21 h/female) and low directional inconsistency scores (<5%). Hierarchies were considered stable based on lack of tied submissive interactions (indicative of uncontested rank positions), low rates of rank change (0.510 changes/year), and long-term stability in matrilineal rank order. These findings enhance our understanding of capuchin social systems and how the competitive strategies of white-faced capuchins compare to those of Old World primates. [ABSTRACT FROM AUTHOR]