Female grooming markets in a population of gray-cheeked mangabeys (Lophocebus albigena)

Primate female allogrooming models based on biological marketstheory predict that grooming is "time matched" within bouts,that is, the amount of time the first female grooms predictsthe amount of time the second one grooms. The models also predictthat when female–female contest competition is weak, groomingis traded for grooming, but when female–female contestcompetition is strong, grooming may be traded for other commoditiessuch as feeding tolerance, and grooming discrepancy betweenmembers of dyads is rank related. We tested these predictionsusing data collected from adult and subadult female gray-cheekedmangabeys (Lophocebus albigena) (N = 26) in 5 groups in KibaleNational Park, Uganda. We found that, overall, females reciprocatedin 33% of grooming bouts. Among reciprocated bouts, femalesin all 5 groups showed time matching. In 2 groups, we also foundrank-related grooming discrepancies but showing opposite patternsto each other. Consistent with predictions based on biologicalmarkets theory, these groups may have been under greater feedingcompetition, revealed more by adjustments in ranging behaviorthan increased agonistic rates. Although these results supportcurrent allogrooming models, they also suggest that the modelsmay become more robust if the influence of scramble competitionis incorporated. In addition, they emphasize the flexibilityand dynamic nature of female competitive relationships withinthe same population of primates.