Tool making and use by captive bonobos: functional & behavioral strategies
Résumé
Primates have highly developed capacities for gripping and manipulating that differ between species. In this context, the human hand is considered as unique based on its functional characteristics. However, the real dynamic manual abilities of primates remain poorly known. The aim of the present study was to quantify the behavioral strategies (tool selectivity and modification) and functional strategies (manual postures and in-hand movements) used by 8 captive adult bonobos (Pan paniscus) during two tool use tasks: food extraction and a new, more complex task consisting of recovering food in a wooden maze placed outside the cage. We found that 1) bonobos were able to plan, chose and modify their tools according to the task; 2) that each individual presented his own manipulation techniques with more variability for the maze task than extractive food tasks; 3) more in-hand movements for the maze task than extractive food task; 4) a difference between males and females with a greater variability in manual postures for males for both tasks, and more in-hand movements for females. Bonobos had individual specificities that could reflect the specialization of their manipulation strategies, especially for the more complex task. They were able of in-hand movements similar to humans and chimpanzees. The observed sex effect could reflect an effect of the hierarchy with females taking more their time to perform a task. These preliminary results show the necessity to pursue the quantification of object manipulation in different species for new tasks and with new methods to better understand the manual specificities of each species.