Brown capuchin (Sapajus apella) in French Guiana repeatedly inserts in-situ palm-trunk spines between teeth

Capuchin monkeys are known for their dexterity, risk-taking, and object manipulation skills, including tool use. Animal populations on islands often produce novel behaviors, especially when the location is absent of key predators. On Île Royale in French Guiana, predators such as large felids are absent, and introduced robust capuchin monkeys (Sapajus apella) are abundant and fed both directly and indirectly by tourists. Here we provide a photo sequence of a juvenile robust capuchin monkey using the in-situ spines on a palm tree trunk as toothpicks. The capuchin interacted with stationary, dangerous and delicate objects, the sharp and numerous in-situ palm spines, and positioned the mouth three times consecutively so that a spine entered between two of the teeth. While observations of dental cleaning, probing or flossing in other primate species, including S. libidinosus, are considered tool use as they involve the use of movable objects to manipulate the environment, here careful body orientation to utilize a potentially harmful stationary object is not considered tool use, but expands previous findings that capuchins are cognitively skilled, dexterous, highly exploratory and willing to risk pain in foraging and other activities. We hope this observation stimulates further research on capuchin behavior within the Guianas and throughout the Amazon biome, where robust capuchins are abundant but relatively little studied in regards to tool use behavior and object manipulation.