Carlson, M. K. W. | bioRxiv Science

bioRxiv2025

White-faced capuchins (Cebus capucinus imitator) exhibit selectivity for stone tools

Over the last few decades, the developing field of primate archaeology has used archaeological methods to reconstruct primate behaviors, especially tool use. We expand the possibilities of primate archaeology with an inverse approach: using living primates to address archaeological questions. In particular, we investigate tool selectivity, a phenomenon that not only represents a significant milestone for tool users, also for the emergence of stone tool technology in human evolution. Observing extant primate tool use can establish clear expectations for a percussion-based archaeological record across taxa. Here, we describe stone tools assemblages produced by two independent populations of white-faced capuchin monkeys (Cebus capucinus imitator) in Coiba National Park, Panama, and provide evidence of stone tool selectivity in both populations. We demonstrate that capuchins select for tool dimensions, and select different sizes for different tool functions. This selectivity analysis reveals that primate stone tool use results in assemblages of artifacts that are distinct from natural accumulations of unused material in the surrounding landscapes. These variations further suggest that stone tool use has a recognizable signature at the assemblage level, even where no lithic flaking occurs. The existence of such assemblage-level signatures offer new avenues for the archaeological identification of tool use both in unhabituated living primates and extinct taxa. The presence of selectivity in multiple capuchin populations suggests that, along with percussion, tool selectivity is ancestral to stone tool flaking, and is shared by phylogenetically distant branches of the primate tree.

animal behavior and cognition↗

bioRxiv2025

Development and social dynamics of stone tool use in white-faced capuchin monkeys

Percussive tool use for extractive foraging allows animals to access otherwise inaccessible resources and forage more efficiently, with potentially important implications for their fitness. The development of tool use proficiency has been well-documented in nut-cracking chimpanzees and robust capuchins, and in shellfish-cracking long-tailed macaques, where mothers and proficient tool users are the most important models for social learning. However, little is known about how tool use develops in populations where opportunities for social learning are scarce. White-faced capuchins (Cebus capucinus imitator) on Jicaron Island, Panama, provide a unique case to consider this question: stone tool use is entirely male-biased, meaning juveniles cannot learn from their mothers, and reduced group cohesion further limits social learning opportunities. Here, we investigate the acquisition and development of stone tool proficiency in this population using a year-long dataset from camera traps placed at two experimental anvils. We assess differences in proficiency between age classes, examine the development of tool use proficiency over time, and explore patterns of social attention during tool use. We show that juvenile capuchins are less proficient than subadults and adults, but their proficiency remains stable over the course of one year, suggesting that skill development may require prolonged practice or physical maturation. In contrast to other primates, social learning opportunities on Jicaron appear limited and scrounging is rare, yet when social attention occurs, we find robust patterns. Social attention to tool use mostly comes from juveniles too young to use tools themselves, who observe proficient subadults that tolerate scrounging. Our results contribute to the understanding of how complex tool use behaviours are acquired and maintained in primates. They highlight that even when tool use is largely solitary, directed social attention and social tolerance play an important role in the development of tool use proficiency. HighlightsO_LIJuvenile white-faced capuchins are less proficient tool users than (sub)adults C_LIO_LIDevelopment of capuchins tool use proficiency is a slow process C_LIO_LISocial learning opportunities on Jicaron island are limited and social attention rare C_LIO_LIAttention was selective, juveniles to proficient sub(adults) who tolerated scrounging C_LIO_LINon-tool-using juveniles paid most attention, so likely important for acquisition C_LI

animal behavior and cognition↗