Spontaneous juggling behavior in a wild urban capuchin monkey (Sapajus nigritus cucullatus).

Juggling, defined as the repeated and rhythmic throwing and catching of an object, is a rare and complex form of object manipulation among non-human animals. While object play has been described in several taxa, true juggling behavior, intentional, successive aerial manipulation of the same object, has only been formally documented in a few species such as otters, dolphins, corvids, and, more recently, in gibbons and macaques. In this study, we report the first known case of juggling behavior in a wild free-ranging Platyrrhini, a juvenile black-horned capuchin monkey (Sapajus nigritus cucullatus) inhabiting an urban forest fragment in southern Brazil, with access to human foods. The event was recorded opportunistically during a behavioral study of object manipulations by capuchins. The juvenile, positioned alone on the ground in a green open area, picked up a coconut and performed a sequence of seven successive throws and recoveries, each executed with precision, rhythm, and apparent intentionality. This observation expands the known taxonomic and ecological range of juggling-like behaviors and underscores the cognitive and motor flexibility of Sapajus species. It also raises questions about the influence of urban environments on behavioral innovation in wild primates, where exotic objects are present and predation and competition may be more relaxed, freeing up time for innovations. We propose that this object manipulation represents an innovative play behavior in a juvenile capuchin, which, beyond serving as a ludic activity, may function as a means of cognitive engagement, motor practice, and possibly cultural transmission.