Mary McDonald / Black striped capuchin (Sapajus libidinosus) using rocks to crack nuts, Piaui, Brazil

Mary McDonald / Black striped capuchin (Sapajus libidinosus) using rocks to crack nuts, Piaui, Brazil

Mary McDonald / Black striped capuchin (Sapajus libidinosus) using rocks to crack nuts, with young animal watching and learning, Piaui, Brazil

Mary McDonald / Black striped capuchin (Sapajus libidinosus) using rocks to crack nuts, Piaui, Brazil

Mary McDonald / Black striped capuchin (Sapajus libidinosus) using rock to crack nuts, Piaui, Brazil

Mary McDonald / Brown Capuchin (Cebus apella) using rocks to crack nuts, Piaui, Brazil

JIM CLARE / Large headed capuchin (Sapajus macrocephalus) monkey feeding on Maticia flowers, Manu NP, Peru.

David Tipling / Large headed capuchin (Sapajus macrocephalus). Cloud Forest, Manu NP, Peru, South America

Christophe Courteau / Brown capped capuchin (Cebus apella) looking menacing. Forest Is, Pantanal, Brazil.

Roy Mangersnes / Brown-capped Capuchin (Sapajus / Cebus apella) on vines. Madidi National Park, Bolivia.

Roy Mangersnes / Brown-capped Capuchin (Sapajus / Cebus apella) looking up through canopy. Madidi National Park, Bolivia.

Roy Mangersnes / Brown-capped Capuchin (Sapajus / Cebus apella) in tree. Madidi National Park, Bolivia.