Social Learning and Developmental Stages of Probe Tool-Use in Captive Bonobos
Bonobos (Pan paniscus) are capable of diverse tool-use; however, research on the role of social learning on vertical tool-use transfer and the developmental stages of juveniles has been limited. Captive bonobo populations provide novel opportunities to study juvenile skill development in naturalistic social settings.This study was conducted using film taken at the San Diego Zoo over four consecutive years. The bonobo enclosure included an artificial termite mound which was provisioned to provide enrichment. All bonobos demonstrated the proper application of probe tools required to extract bait during the study, and “fishing” was a common activity. This bonobo group included two infants, a mother-raised female, and an effectively orphaned male. Both infants observed and interacted with older members as they fished. As they aged, their contacts with the artificial termite mound increased, and eventually both successfully used probe tools like their conspecific models. The skill development process involved five distinctive stages, the identification of which allowed for detailed evaluation of the social learning process of the young bonobos. The order and rate at which the juvenile bonobos acquired critical fishing skills paralleled the processes described for probe-fishing juvenile chimpanzees. Despite this inter-species concordance, the social learning environment the juvenile bonobos experienced involved a higher level of expert tolerance than that reported among probe-fishing chimpanzees. Two observed behaviors of primary models, active tool transfer to juveniles and repetitive dip exaggeration, are indicative of scaffolding, or parental modeling, in bonobos. Identified individual fishing technique preferences did not appear to be vertically transmitted.