Percussive manipulations distinguish object play in capuchin and patas monkeys

Object play has been proposed as a developmental precursor of flexible tool use. We applied a standardized object play protocol, previously used with corvids and parrots, to tufted capuchin monkeys ( Sapajus apella ), a member of a genus known for tool use, and patas monkeys ( Erythrocebus patas ), for which tool use has not been reported. Both groups were tested in a zoo across 15 sessions with a standardized set of objects and activity plates. All capuchins smashed objects, whereas only two patas monkeys did so, a difference consistent with the percussive foraging of capuchins. The species did not differ significantly in behavioral variability, object combinations, manipulation time, number of body parts used, or tail use, and combination rates were low in both. The species thus differed in a specific form of manipulation rather than in overall or combinatory object play. With one species per category and small samples, these results cannot establish whether combinatory object play is associated with tool use in primates.