Foraging rehabilitation in rescued capuchin monkeys (Sapajus spp.): Assessing the role of personality in a tool-use protocol

Capuchin monkeys ( Sapajus spp.) are the second most common primates found in Brazilian rescue centers, most often as victims of wildlife trafficking. Although legislation prioritizes reintroduction, detailed rehabilitation protocols remain scarce. In this study, we tested a tool-use protocol with 23 captive capuchins at a rescue center in Paraíba, northeastern Brazil, to examine how individual traits, such as personality, influence performance. After a four-week baseline observation, we implemented a 12-session protocol structured in three phases: (1) offering whole nuts, (2) offering partially cracked nuts, and (3) demonstrating the cracking technique. Personality was assessed using the Hominoid Personality Questionnaire (HPQ), and behavioral data were analyzed with Generalized Linear Mixed Models (GLMMs). We identified three personality dimensions: Assertiveness, Neophilia, and Agreeableness. Neither age nor sex had significant effects, but assertiveness consistently predicted performance. More assertive monkeys engaged in complex tool-use behaviors (“Hit 1” and “Hit 2”) more frequently and spent more time manipulating tools and feeding. Despite the short duration of training phases, the protocol was effective, with the tool use behavior increasing fortyfold across the training sessions. Our findings indicate that personality, particularly assertiveness, plays a central role in shaping rehabilitation outcomes. Standardized “one-size-fits-all” protocols may therefore be inadequate. Instead, flexible and personalized strategies that account for individual personality differences are crucial to improving welfare and enhancing the chances of successful reintroduction. • We tested a stone tool-use rehabilitation protocol on 23 naive rescued capuchin monkeys • Total success was achieved after only 12 training sessions, although the behavior did not become customary • No ages or sex differences in stone tool use • Assertiveness trait influences how individuals learn this essential survival skill • Tool use behavior increased fortyfold across the phases.