Agonism and dominance in female blue monkeys

Abstract

Agonistic behavior features prominently in hypotheses that explain how social variation relates to ecological factors and phylogenetic constraints. Dominance systems vary along axes of despotism, tolerance, and nepotism, and comparative studies examine cross-species patterns in these classifications. To contribute to such studies, we present a comprehensive picture of agonistic behavior and dominance relationships in wild female blue monkeys (Cercopithecus mitis), an arboreal guenon, with data from 9 groups spanning 18 years. We assessed where blue monkeys fall along despotic, tolerant, and nepotistic spectra, how their dominance system compares to other primates, primarily cercopithecines, and whether their agonistic behavior matches socioecological model predictions. Blue monkeys showed low rates of mainly low-intensity agonism and little counter-aggression. Rates increased with rank and group size. Dominance asymmetry varied at different organizational levels, being more pronounced at the level of interactions than dyad or group. Hierarchies were quite stable, had moderate-to-high linearity and directional consistency and moderate steepness. There was clear maternal rank inheritance, but inconsistent adherence to Kawamura's rules. There was little between-group variation, although hierarchy metrics showed considerable variation across group-years. Overall, blue monkeys have moderately despotic, moderately tolerant, and nepotistic dominance hierarchies. They resemble other cercopithecines in having significantly linear and steep hierarchies with a generally stable, matriline-based structure, suggesting a phylogenetic basis to this aspect of their social system. Blue monkeys most closely match Sterck et al.'s [1997] Resident-Nepotistic-Tolerant dominance category, although they do not fully conform to predictions of any one socioecological model. Our results suggest that socioecological models might better predict variation within than across clades, thereby incorporating both ecological variables and phylogenetic constraints. Our findings also highlight the need for clearer definitions of socioecologically relevant dominance categories, which would ideally derive from quantitative measures of dominance behavior. Intraspecific and methodological variation may, however, be a challenge.

Stronger between-clan than within-clan contests and their ecological correlates in a non-territorial, fission-fusion species, the Asian elephant

“…This has been reported many times before in primates (see van Schaik et al . 1983, Wittig and Boesch 2003, Klass and Cords 2015, Wheeler et al . 2013) although not in elephants.…”

Stronger social bonds do not always predict greater longevity in a gregarious primate

“…Those savings and their benefits remain to be quantified on a mechanistic level. Because within‐group agonism and alliances are rare in blue monkeys (Klass & Cords, ), the function of their social bonds in general may be to maintain group cohesiveness rather than orchestrate competitive power relations within groups. Group‐wide cohesion may not require particularly strong bonds.…”

Aggression and dominance: an interdisciplinary overview

“…However, much of the variation in primate rank relationships cannot be explained by socio-ecological models, so alternative efforts have focused on the possibility that phylogenetic inertia constrains social evolution by limiting animals' responses to specific ecological pressures [e.g., 85; see also Box 2). Indeed, the degree of despotism in societies of multiple clades of primates reveals a strong phylogenetic signal [87,88,85]. Clearly, both socioecological and phylogenetic effects must be considered in attempts to explain the evolution of animal societies.…”

“…Quantification of dominance relationships permits testing of hypotheses concerning the function of dominance, assessment of the properties of societies that emerge from dyadic interactions, and comparisons among groups; it also enhances our understanding of the role dominance plays in various types of societies (Fig 1). To date, efforts to quantify, compare, and explain dominance hierarchies have suffered from a lack of consensus on methods and difficulties in dealing with unresolved relationships, which occur when two individuals in a society are never observed to interact [87]. Estimates of hierarchy linearity and steepness decrease with an increasing proportion of unresolved relationships, as does the reliability of rank assignments [87].…”

“…To date, efforts to quantify, compare, and explain dominance hierarchies have suffered from a lack of consensus on methods and difficulties in dealing with unresolved relationships, which occur when two individuals in a society are never observed to interact [87]. Estimates of hierarchy linearity and steepness decrease with an increasing proportion of unresolved relationships, as does the reliability of rank assignments [87]. Researchers should report the proportion of unresolved relationships in their data, but many do not.…”