The Lasting and the Passing: Behavioural Traditions and Opportunities for Social Learning in Wild Tufted Capuchin Monkeys

There is abundant evidence that allows us to consider wild tufted capuchin monkeys’ toolkits as behavioural traditions. Developmental studies show that infants’ interest in nutcracking and adults’ tolerance of scrounging enhance opportunities for social learning. Field experiments have examined the socially mediated diffusion of new behaviours. The difference between forest populations’ lack of customary tool use and the typical savannah toolkit—including stone “hammers” for nutcracking—seems sufficiently explained by terrestriality. By contrast, the narrower distribution of customary use of tools for probing cannot be accounted for by distinct diets or environmental affordances. Opportunities for social learning may be framed in Niche Construction theory, as social diffusion may depend on the conspicuousness and permanence of tools and leftovers. This is the case for nutcracking, which is highly conspicuous, leaves lasting environmental changes, and frequently allows delayed scrounging (enabling direct observation and delayed stimulus enhancement). The use of stick probes, however, creates fewer opportunities for social learning: the events are quick and less conspicuous, scrounging opportunities are minimal, and there are no lasting “tool use sites”. This may explain the observed distribution of probe use: the lesser the role of environmental niche construction, the greater the role of social dynamics in the diffusion of innovations and the establishment of traditions.