Ben Cranke / Black-striped capuchin (Sapajus libidinosus) using rock as a tool to break open palm nut Parnaiba Headwaters National Park, Piaui, Brazil. July.

Ben Cranke / Black-striped capuchin (Sapajus libidinosus) using rock as a tool to break open palm nut, Parnaiba Headwaters National Park, Piaui, Brazil. July.

Ammonite / Male White-throated / White-faced capuchin (Cebus capucinus) climbing and jumping in canopy, showing use of prehensile tail, Santa Rosa National Park, Costa Rica.

Ammonite / White-throated capuchins (Cebus capucinus) alarm calling, Santa Rosa National Park, Costa Rica.

Ammonite / White-throated / White-faced capuchin (Cebus capucinus) climbing and playing with twig, showing use of prehensile tail, Santa Rosa National Park, Costa Rica.

Ammonite / Family of White-throated / White-faced capuchins (Cebus capucinus) resting and grooming each other, Santa Rosa National Park, Costa Rica.

Suzi Eszterhas / White-faced Capuchin (Cebus capucinus imitator) mother and baby. Osa Peninsula, Costa Rica

Cyril Ruoso / South American Squirrel Monkey (Saimiri sciureus) portrait, Peru

Mark Bowler / Common Squirrel Monkey (Saimiri sciureus ssp. macrodon) in tree, calling, Peru, captive

Thomas Marent / Cotton-top Tamarin (Saguinus oedipus) in tree, northern Colombia

Kevin Schafer / Golden Lion Tamarin (Leontopithecus rosalia) portrait, Poco das Antas Reserve, Atlantic Forest, southeast Brazil

Kevin Schafer / Golden Lion Tamarin (Leontopithecus rosalia) male with baby, Poco das Antas Reserve, Atlantic Forest, southeast Brazil