A group of Capuchin monkeys is entering the Stone Age

Research has documented the first instance of habitual stone-tool use in white-faced capuchins (Cebus capucinus imitator) in Coiba National Park, Panama. Unlike their robust counterparts (genus Sapajus), gracile capuchins have rarely been observed using tools, particularly stone tools. This study highlights the capuchins' reliance on hammerstone and anvil techniques to access food items such as Terminalia catappa seeds, hermit crabs, marine snails, and terrestrial crabs. The behavior has been consistent on one island since at least 2004. Camera trapping over a year revealed that stone-tool use is predominantly male-driven, with adult females never recorded using tools, although they were present and engaged in scrounging. Tool use was observed year-round, with over half of identifiable individuals participating. At the most active site, 83.2% of days with capuchin sightings coincided with tool use. The population's terrestrial lifestyle, reduced predation pressure, and potential resource limitations compared to mainland groups may contribute to the evolution of this behavior. This finding provides a unique opportunity to investigate the ecological and evolutionary factors influencing stone-tool use in primates, offering insights into the behavioral differences between Cebus and Sapajus species. The study underscores the significance of environmental context in the development of tool use among primates.