Social inequality is a consistent feature of animal societies, often manifesting as dominance hierarchies, in which each individual is characterized by a dominance rank denoting its place in the network of competitive relationships among group members. Most studies treat dominance hierarchies as static entities despite their true longitudinal, and sometimes highly dynamic, nature. To guide study of the dynamics of dominance, we propose the concept of a longitudinal hierarchy: the characterization of a single, latent hierarchy and its dynamics over time. Longitudinal hierarchies describe the hierarchy position ( We modify three popular ranking approaches to make them better suited for inferring longitudinal hierarchies. Our three “informed” methods assign ranks that are informed by data from the prior period rather than calculating ranks Using both a simulated dataset and a long‐term empirical dataset from a species with two distinct sex‐based dominance structures, we compare the performance of these methods and their unmodified counterparts. We show that choice of method has dramatic impacts on inference of hierarchy dynamics via differences in estimates of This work provides crucially needed conceptual framing and methodological validation for studying social dominance and its dynamics.
- NSF-PAR ID:
- 10349954
- Author(s) / Creator(s):
- ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more »
- Date Published:
- Journal Name:
- Royal Society Open Science
- Volume:
- 8
- Issue:
- 7
- ISSN:
- 2054-5703
- Page Range / eLocation ID:
- 210873
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract r ) and dynamics (∆ ) associated with each individual as a property of its interaction data, the periods into which these data are divided based on a period delineation rule (p ) and the method chosen to infer the hierarchy. Hierarchy dynamics result from both active (∆a ) and passive (∆p ) processes. Methods that infer longitudinal hierarchies should optimize accuracy of rank dynamics as well as of the rank orders themselves, but no studies have yet evaluated the accuracy with which different methods infer hierarchy dynamics.de novo in each observation period and use prior knowledge of dominance correlates to inform placement of new individuals in the hierarchy. These methods are provided in an R package.∆a . Methods that calculate ranksde novo in each period overestimate hierarchy dynamics, but incorporation of prior information leads to more accurately inferred∆a . Of the modified methods, Informed MatReorder infers the most conservative estimates of hierarchy dynamics and Informed Elo infers the most dynamic hierarchies. -
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Abstract In group‐living species, integrating into a new social group after dispersal is an important life history milestone associated with physical and social challenges. Generally, this process seems to be accompanied by heightened glucocorticoid (GC) concentrations; however, most studies of physiological responses to group transfer have been conducted on species with despotic social relationships, where integrating individuals are often targets of frequent aggression. Here we present data on fecal glucocorticoid (fGC) concentrations during periods of unstable group membership for male woolly monkeys (
Lagothrix lagotricha poeppigii ), a species with extremely low rates of male–male aggression and generally tolerant male–male associations. We collected data on males in four study groups at the Tiputini Biodiversity Station, Ecuador, and observed three attempted transfer events, involving a total of four adult males, in one study group. We observed only three instances of overt aggression (chases) between males across the entire study period, though male display behaviors were more frequent. We tested whether rates of displays were higher during periods of unstable group membership using a generalized linear mixed model (LMM). We also examined whether male status, group stability, and the occurrence of intergroup encounters affected fGC concentrations using LMMs. Contrary to our predictions, rates of display behaviors were not higher during periods of unstable group membership. However, both transient/integrating males and those who were already group members showed elevated fGC concentrations during these unstable periods. Our results suggest that even in species with tolerant male–male relationships, the integration of unfamiliar individuals can provoke an increase in GCs. -
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Abstract Objectives Unidirectional dominance‐related signals can be used to communicate submission (an immediate behavioral response) or subordination (the status of an established relationship). Subordination signals are defined as emitted during peaceful interactions and are hypothesized to be critical for the evolution of social complexity and robust power structures because they reduce uncertainty in social relationships. The chatter vocalization in Verreaux's sifaka (
Propithecus verreauxi ) is a unidirectional submissive signal. I tested the hypothesis that chatter vocalizations can signal subordination and thereby reduce agonism in a dyad.Materials and Methods I examined 780 chatters from 18 dyads collected over 881 observation hours on four groups of sifaka in Kirindy Forest, Madagascar.
Results Sifaka emitted 63% of chatters in the peaceful context. Peaceful chatters significantly predicted grooming rate, fighting rate, reconciliation, and proportion of wins in a dyad but did not predict time in proximity. Dyad‐type significantly predicted the frequency of peaceful chatters, with intrasexual dyads exhibiting chatters in peaceful contexts more often than intersexual dyads.
Discussion Sifaka communicate both submission and subordination with chatter vocalizations. Subordination signaling increased tolerance and affiliation. It reduced conflicts and the probability dominant individuals usurped resources. Moreover, intrasexual power may be more institutionalized than intersexual power in sifaka. The finding of complex and cognitively demanding social communication in a lemur with low levels of cooperation (1) challenges previous assumptions that the evolution of social complexity is dependent on frequent triadic interactions and high levels of cooperation, and (2) highlights the need for taxonomic diversity in studies of social complexity.
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Animal groups are often organized hierarchically, with dominant individuals gaining priority access to resources and reproduction over subordinate individuals. Initial dominance hierarchy formation may be influenced by multiple interacting factors, including an animal's individual attributes, conventions and self-organizing social dynamics. After establishment, hierarchies are typically maintained over the long-term because individuals save time, energy and reduce the risk of injury by recognizing and abiding by established dominance relationships. A separate set of behaviours are used to maintain dominance relationships within groups, including behaviours that stabilize ranks (punishment, threats, behavioural asymmetry), as well as signals that provide information about dominance rank (individual identity signals, signals of dominance). In this review, we describe the behaviours used to establish and maintain dominance hierarchies across different taxa and types of societies. We also review opportunities for future research including: testing how self-organizing behavioural dynamics interact with other factors to mediate dominance hierarchy formation, measuring the long-term stability of social hierarchies and the factors that disrupt hierarchy stability, incorporating phenotypic plasticity into our understanding of the behavioural dynamics of hierarchies and considering how cognition coevolves with the behaviours used to establish and maintain hierarchies.
This article is part of the theme issue ‘The centennial of the pecking order: current state and future prospects for the study of dominance hierarchies’.
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Aggressive interactions among closely related species are common, and can play an important role as a selective pressure shaping species traits and assemblages. The nature of this selective pressure depends on whether the outcomes of aggressive contests are asymmetric between species (i.e., one species is consistently dominant), yet few studies have estimated the prevalence of asymmetric versus symmetric outcomes to aggressive contests. Here we use previously published data involving 26,212 interactions between 270 species pairs of birds from 26 taxonomic families to address the question: How often are aggressive interactions among closely related bird species asymmetric? We define asymmetry using (i) the proportion of contests won by one species, and (ii) statistical tests for asymmetric outcomes of aggressive contests. We calculate these asymmetries using data summed across different sites for each species pair, and compare results to asymmetries calculated using data separated by location. We find that 80% of species pairs had aggressive outcomes where one species won 80% or more of aggressive contests. We also find that the majority of aggressive interactions among closely related species show statistically significant asymmetries, and above a sample size of 52 interactions, all outcomes are asymmetric following binomial tests. Species pairs with dominance data from multiple sites showed the same dominance relationship across locations in 93% of the species pairs. Overall, our results suggest that the outcome of aggressive interactions among closely related species are usually consistent and asymmetric, and should thus favor ecological and evolutionary strategies specific to the position of a species within a dominance hierarchy.
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1098/rsos.210873
