Habitual tool use on monopolizable resources alters group cohesion

Zoë Goldsborough , Margaret Crofoot, Pranav Minasandra, Julián León, Pedro Luis Castillo-Caballero, Evelyn del Rosario-Vargas, Brendan James Barrett 

Tool-aided extractive foraging expands access to novel foods, but its effects on social dynamics are less understood. When tool-use resources are monopolizable, tool use may increase intragroup competition.
While intragroup competition encourages reduced cohesion, this comes at the cost of increased vulnerability to predation and intergroup conflict. We examined how use of spatially fixed, monopolizable resources, anvils, influences cohesion by comparing groups of tool-using and non-tool-using white-faced capuchins (Cebus capucinus imitator) on Jicarón Island in Coiba National Park, Panama.Jicarón lacks terrestrial mammalian predators and stone tool use is locally restricted to a ~2 km stretch of coast. We deployed two grids of camera traps to compare daily activity patterns, and temporal variation in party size, party composition, and spatial cohesion. We compared observed patterns with simulations of groups exhibiting different cohesion regimes. We found that tool-using capuchins showed smaller, less variable party sizes than non-tool-using capuchins. Adult females and adult males were less likely to co-occur in a sequence. Tool-using and non-tool-using capuchins differed in their patterns of spatiotemporal cohesion. Simulations support that these patterns are consistent with the tool-using group engaging in fission-fusion subgrouping. Although only male capuchins use tools, the entire tool-using group shows reduced cohesion, suggesting that increased competition for one sex can have cascading effects within the group. Our findings suggest that habitual tool use relying on monopolizable resources incentivizes lower group cohesion. This creates differences in the social environment of tool-using and non-tool-using animals sharing a habitat, and reveals culture as a potential driver of social organization.