Male-biased stone tool use by wild white-faced capuchins (Cebus capucinus imitator)

Abstract

Tool-using primates often show sex differences in both the frequency and efficiency of tool use. In species with sex-biased dispersal, such within-group variation likely shapes patterns of cultural transmission of tool-use traditions between groups. On the Panamanian islands of Jicarón and Coiba, a population of white-faced capuchins (Cebus capucinus imitator) — some of which engage in habitual stone tool use — provide an opportunity to test hypotheses about why such sex-biases arise. On Jicarón, we have only observed males engaging in stone tool use, whereas on Coiba, both sexes are known to use tools. Using 5 years of camera trap data, we show that this variation reflects a true sex difference in tool use rather than a sampling artefact, and then test hypotheses about the factors driving this pattern. Differences in physical ability or risk-aversion, and competition over access to anvils do not account for the sex-differences in tool-use we observe. Our data show that females are physically capable of stone tool use: females on Coiba and juveniles on Jicarón as small and smaller than adult females regularly engage in tool use. Females also have ample opportunity to use tools: the sexes are equally terrestrial, and competition over anvils is low. Finally, females rarely scrounge on left-over food items either during or after tool-using events, suggesting they are not being provisioned by males. Although it remains unclear why white-faced capuchin females on Jicarón do not use stone-tools, our results illustrate that such sex biases in socially learned behaviors can arise even in the absence of obvious physical, environmental and social constraints. This suggests that a much more nuanced understanding of the differences in social structure, diet and dispersal patterns are needed to explain why sex-biases in tool use arise in some populations but not in others.

Primate archaeology 3.1

“…There are also sex biases in some of the Panamanian Cebus groups, with males using tools more than females (Barrett et al, 2018), which joins examples such as male bias in probing tools among some Sapajus groups (Fal otico et al, 2021) to aid discussions going beyond technology into the social and developmental realms of past primates. While the most recent reports of Cebus tool use appeared too late for inclusion in the review (e.g., Goldsborough, Crofoot, Alavi, et al, 2023;Goldsborough, Crofoot, & Barrett, 2024)…”