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.

Sources