Capuchin monkey rituals: an interdisciplinary study of form and function

Abstract

Many white-faced capuchin monkey dyads in Lomas Barbudal, Costa Rica, practice idiosyncratic interaction sequences that are not part of the species-typical behavioural repertoire. These interactions often include uncomfortable or risky elements. These interactions exhibit the following characteristics commonly featured in definitions of rituals in humans: (1) they involve an unusual intensity of focus on the partner, (2) the behaviours have no immediate utilitarian purpose, (3) they sometimes involve "sacred objects", (4) the distribution of these behaviours suggests that they are invented and spread via social learning, and (5) many behaviours in these rituals are repurposed from other behavioural domains (e.g. extractive foraging). However, in contrast to some definitions of ritual, capuchin rituals are not overly rigid in their form, nor do the sequences have specific opening and closing actions. In our 9,260 hours of observation, ritual performance rate was uncorrelated with amount of time dyads spent in proximity but is (modestly) associated with higher relationship quality and rate of coalition formation across dyads. Our results suggest that capuchin rituals serve a bond-testing rather than a bond-strengthening function. Ritual interactions are exclusively dyadic, and between-dyad consistency in form is low, casting doubt on the alternative hypothesis that they enhance group-wide solidarity.

What Makes Inventions Become Traditions?

“…Which aspects are most relevant could depend on the complexity of the trait to be learned: e.g., learning fine motor details of a foraging technique might require extensive close-range observation, whereas learning that a particular resource can be eaten might require quick observation from afar; see also Q1. Perry and Smolla (2020) describe a fairly general relationship quality measure, which assesses the propensity of individuals to interact affiliatively rather than agonistically; this, combined with a measure of time learners spend in proximity with models, would characterize the most relevant relationship properties in a wide range of species.…”

Are demographic correlates of white‐faced capuchin monkey (Cebus capucinus) “Gargle and Twargle” vocalization rates consistent with the infanticide risk assessment hypothesis?

“…White‐faced capuchins are known to produce risky signals and perform Zahavian Bond Tests (Perry et al, 2003; Manson, 1999; Perry & Manson, 2008; Perry & Smolla, 2020; Perry, 2011). Females test bonds by holding allies' infants in risky acts of trust (Manson, 1999).…”

“…Females test bonds by holding allies' infants in risky acts of trust (Manson, 1999). Both individuals within dyads of all age‐sex classes engage in risky rituals; for example, individuals stick sharp and dirty objects or body parts (such as wood chips, fingers, or feet) into another individual's eye‐socket, nose or mouth which is potentially costly for both parties, and can reveal each individual's attitude towards the other (Perry et al, 2003; Perry & Smolla, 2020; Perry, 2011, 2012).…”