cultural phylogeny

UCLA Dept. of Anthropology


Capuchin Traditions Project

Current Projects


Positions available


Current Projects

Developmental study:

Since 2001, we have been conducting a longitudinal study of infant development on 50 subjects residing in 5 social groups of wild white-faced capuchins at Lomas Barbudal. These animals have been the subject of intensive focal sampling (over 7,000 hours of focal data as of 2006). We are interested in the effects of demographic factors, social learning opportunities, personality, and experience on the development of these animals’ foraging skills and social strategies.

  infant development study Specific goals:

The primary goal of this study has been to document the precise nature of the role of social influence on the acquisition of various traits, such as relationship negotiation skills, food processing techniques, and classification of animal species as dangerous, edible, or neutral. We also hope to be able to document how various personality traits influence the ability to learn, either asocially or socially.

There are many other questions that we would also like to address with this data set, in addition to the questions pertinent to social learning. For example, how do sex differences in behavior emerge developmentally? What can developmental studies tell us about the emergence of a female-bonded society in capuchins (note that female philopatry is anomalous among platyrrhine primates) and the manner in which females attain their dominance ranks? What factors affect the timing of juvenile males’ migration decisions, their choice of destination, and their selection of co-migration partners? Are young capuchins capable of detecting who are their kin through the paternal line? What factors contribute to adolescent females’ mothering styles?
  The database:
Our focal individuals are members of 5 social groups which vary according to size, stability of male membership, and degree of relatedness among individuals. (Click here for more information on the study groups.)

All social groups are completely habituated and most have been the subjects of long-term observation (ranging from 1-15 years of observation preceding the onset of this phase of study). Geneologies, constructed on the basis of behavioral and genetic information, are complete or virtually complete for these groups.

The core database for the longitudinal study consists of 10-minute focal follows of each infant, in which we record all occurrences of social interactions (including gestural, olfactory and vocal communication), manipulations of plants and insects, food processing and ingestion, and interactions with members of other species. Continuous observations are supplemented by instantaneous scans recording the proximities of other group members. During focal follows, we also record the activities of all group members within 5 body lengths of the focal, and note whether the focal is visually attending to these behaviors, so that we have a record of learning opportunities for each animal as it develops. As of June 2006, we have well over 6,500 hours of focal follows. The entire data set since the inception of the monkey project in 1990 includes over 35,000 hours of contact time with the study groups.

This core database is supplemented by various other types of data collection:

  (a)We collect group scans every 30 minutes in which we note the spatial structure of the group and the activities of each group member. These data help us document social networks for those animals that are not included among our focal subjects. Ad libitum sampling is used to note important events that help us monitor changes in social dynamics among the adults: e.g. dominance interactions, coalitions, sex, grooming, and bonding rituals of various kinds.  
  (b)When the animals are foraging on foods that require particularly complex forms of processing, we have a special protocol for capturing the precise motor details of the techniques used for all group members and the extent to which group members monitor one another during these activities.  

(c) We have made approximately 190 hours of audio recordings, documenting vocal development in our focal subjects and also the adults. This can help us document the extent to which there is variability in acoustic structure across study groups, and also determine the degree to which call structure is developmentally flexible.

  eyeball-poking(d) We make video recordings, focusing primarily on the details of culturally variable “bonding rituals” such as handsniffing and eyeball-poking that occur in some of our study groups.  
  (e) We have collected fecal or tissue samples from all members of our study groups, with the exception of a few early infanticide victims in which the bodies could not be recovered, in order to obtain DNA for paternity assignment.  
  (f)Experienced field assistants (i.e. those who have been with the project for a year or more) complete questionnaires on the monkeys’ personality traits.  

(g) We collect fecal samples in order to measure corticosteroids and testosterone levels.

  (h) We conduct longer focal samples (up to 12 hours in length) on those monkeys who exhibit interesting bonding rituals, to study the effects of these communicative behaviors on relationship quality.  
UCLA Dept. of Anthropology - Susan Perry