NatureModernglobalhigh confidence

Chimpanzee (Pan troglodytes) and tufted capuchin monkey (Sapajus apella) infants can take several years to master nut cracking, a skill learned while observing their mothers.

Notes on verification

Corroborated by multiple independent long-term field studies (Taï Forest chimpanzees, Brazilian bearded capuchins) published in peer-reviewed journals, consistent with established primatology consensus on prolonged tool-use learning periods. [tier=gold indep_score=0.77 clusters=3 claim_tier=notable | framework convergence=partial (upstreams: Boesch & Boesch Taï Chimpanzee Project, Fragaszy/Ottoni/Izar Brazilian capuchin monkey field studies) — publishers independent, evidence may not be | kind=empirical eligibility=high (extractor: empirical/medium)]

Sources