Our interest in social traditions began when a group of 10 capuchin researchers collaborated on a study of traditions in white-faced capuchin monkeys. We concentrated our efforts on three behavioral domains: social conventions, foraging techniques, and interactions with members of other species. We have worked at 4 different research sites in Costa Rica, which are ecologically similar and close enough geographically that there is unlikely to be much genetic variation between sites. This map indicates the locations of the research sites within Costa Rica. We have collectively observed these monkeys for nearly 70,000 hours over a 13-year period. Researchers involved in this cross-site collaborative project included Susan Perry, Linda Fedigan, Katharine Jack, Lisa Rose, Katharine Mackinnon, Mary Baker, Melissa Panger, Joe Manson, Julie Gros-Louis, and Kendra Pyle.
Much of our work thus far has focused on social conventions: dyadic social behaviors or communicative behaviors that are unique to particular groups or cliques. We began this phase of the project by nominating various quirky social interactions or communicative signals that we had witnessed, soliciting data on these behaviors from the researchers at all sites, and subjecting them to a set of operational criteria that allowed us to classify a subset of the nominations as traditions.
What is a Tradition?
We defined a tradition as “a behavioral practice that is relatively long-lasting and shared among members of a group, each new practitioner of the behavior relying to some extent upon social influence to learn to perform the behavior.” We subjected candidate behaviors to the following criteria to determine whether they qualified as traditions:
- There must be intergroup variation in the behavior, such that it is common (i.e. seen at a rate of at least once/100 hours) in one or more group and absent in other groups that have been observed for at least 250 hours.
- The behavior must be observed to spread through a social network.
- The behavior must endure in the repertoire for at least a 6-month period.
Observed Traditions at Lomas Barbudal
Five behavior patterns were nominated as likely traditions: hand-sniffing, sucking of body parts, finger-in-mouth game, hair-in-mouth game, and toy game. The last three behavior patterns are referred to as games because they involved two roles and occurred in a relaxed social context, often stemming from slow-motion play wrestling, play biting, or grooming of the mouth. Another variant, eyeball poking, comes close to meeting the criteria. This chart shows the distribution of each behavior pattern across the study groups.
Sucking of body parts
In this variant, one individual bites a large tuft of hair from the face or shoulders of the partner. The partner may flinch, but does not exhibit much pain. The partner then typically tries to pry open the mouth and retrieve the hair. The hair is passed with gentle force from mouth to mouth until most of it has fallen to the ground. Then one of the monkeys bites another tuft of hair from the partner so they can continue. The hair game is observed only at Lomas Barbudal. This video clip shows two males from Flakes group at Lomas Barbudal playing the hair game. Adult male Napoleon has juvenile male Jade’s hair in his mouth, and Jade is trying to remove the hair from his mouth. When Jade starts to lose interest, Napoleon once again shows him the remaining hair.
The research described on this site is based in part upon work supported by the National Science Foundation under grants No. SBR-9870429, SBR-0613226 and BCS-0848360, and several grants from the Leakey Foundation and National Geographic Society. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation or other funding agencies.