Hair plucking in captive bonobos (Pan paniscus)

Both wild and captive studies of grooming in non-human primates emphasize the adaptive role of this behavior. Indeed, social grooming is frequently characterized as “social glue” in the life of primates. Grooming behavior is studied to reveal dominance, kin relations, and social networks. Many captive primates, including apes, are observed to over-groom which may result in denuding of individuals. This study focused on a discrete pattern of grooming, specifically hair plucking-a rapid jerking away of the hand or mouth to remove the hair and hair follicle, often accompanied by inspection and consumption of the hair and follicle. This pattern has never been reported for wild bonobos (Pan paniscus) but is routinely observed in many individuals in captive colonies. Subjects were 17 bonobos (4 wild-born and 13 captive-born) housed at the Columbus Zoo. Data on grooming behavior were collected using all-occurrence sampling. Approximately 21% of self-directed and dyadic grooming bouts involved hair plucking. The four wild-born individuals were never observed to hair pluck. While plucking was not significantly different between males and females, subadult males plucked significantly more than adult males. Self-directed plucking appears to be influenced by dominance-the dominant male and female showed the highest percent of self-directed plucking behavior, 54% and 57%, respectively. This is the first study to document the significance of plucking in bonobo grooming behavior and contributes to discussions of visitors' perception of ape well being.