Nick Hawkins / White-faced capuchin monkey (Cebus capucinus) in Tenorio Volcano National Park, Costa Rica

Bernard Castelein / Guianan brown capuchin (Sapajus apella) chewing on branch, Pampas del Yacuma Protected Area, Bolivia

Alex Hyde / Brown / Tufted Capuchin (Cebus apella) family group in cloud forest, Manu Biosphere Reserve, Peru.

Mark Bowler / Black capuchin, (Sapajus nigritus) female standing on hind legs, Rio de Janeiro, Brazil.

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

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.

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

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

Luciano Candisani / Golden Lion Tamarin (Leontopithecus rosalia) portrait, Atlantic Forest, Brazil

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

Thomas Marent / Cotton-top Tamarin (Saguinus oedipus) with red pollen after feeding on flower nectar, Tayrona National Natural Park, Colombia

Thomas Marent / Saddle-back Tamarin (Saguinus fuscicollis) mother with young, Tambopata-Candamo Nature Reserve, Peru

Thomas Marent / Emperor Tamarin (Saguinus imperator), Manu National Park, Peru

Thomas Marent / Black-faced Lion Tamarin (Leontopithecus caissara), Superagui National Park, Atlantic Forest, Brazil

Cyril Ruoso / Bare-eared Squirrel Monkey (Saimiri ustus) in tree, Peru

Michael & Patricia Fogden / Black-crowned Central American Squirrel Monkey (Saimiri oerstedii) male in rainforest, Costa Rica

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

Claus Meyer / Cotton-top Tamarin (Saguinus oedipus), Colombia

Claus Meyer / Golden-headed Lion Tamarin (Leontopithecus chrysomelas) portrait, Atlantic Forest ecosystem, Brazil

Claus Meyer / Pygmy Marmoset (Cebuella pygmaea) endangered, pair, world's smallest primate, Amazon, Brazil

Claus Meyer / Emperor Tamarin (Saguinus imperator) portrait, Amazon ecosystem, Brazil

Claus Meyer / Emperor Tamarin (Saguinus imperator) calling, Amazon, Brazil

Claus Meyer / Golden-headed Lion Tamarin (Leontopithecus chrysomelas), Atlantic Forest, Brazil

Claus Meyer / Emperor Tamarin (Saguinus imperator), Amazon, Brazil

Pete Oxford / Brown Capuchin (Cebus apella) using a rock to crack open a Piassava Palm (Attalea funifera) nut, Cerrado habitat, Piaui State, Brazil

Pete Oxford / Brown Capuchin (Cebus apella) using a rock to crack open a Piassava Palm (Attalea funifera) nut, Cerrado habitat, Piaui State, Brazil

Pete Oxford / Brown Capuchin (Cebus apella) in tree drinking from Piassava Palm (Attalea funifera) nut, monkeys use rocks and anvils to crack open nuts, Cerrado habitat, Piaui State, Brazil

Pete Oxford / Brown Capuchin (Cebus apella) stabilizes itself with its prehensile tail while using a heavy rock hammer to crack open palm nuts placed in small pits in the anvil rock surface, Cerrado habitat, Brazil

Pete Oxford / Brown Capuchin (Cebus apella) stabilizes itself with its prehensile tail while using a heavy rock hammer to crack open palm nuts placed in small pits in the anvil rock surface, Cerrado habitat, Brazil

Gerry Ellis / South American Squirrel Monkey (Saimiri sciureus), Monkey Island, Amazon Basin, Brazil

Gerry Ellis / White-faced Capuchin (Cebus capucinus) monkey calling, Corcovado National Park, Costa Rica

Gerry Ellis / White-faced Capuchin (Cebus capucinus) monkey, Corcovado National Park, Costa Rica

Norbert Wu / White-faced Capuchin (Cebus capucinus) monkey resting in rainforest, Costa Rica

Suzi Eszterhas / Brown capuchin monkey (Sapajus apella). Pantanal, Brazil.

Konrad Wothe / Young Spix's white-fronted capuchin monkey (Cebus unicolor) rainforest, Amazon, Brazil.

David Pattyn / White-faced Capuchin (Cebus capucinus imitator) Carara National Park, Costa Rica

David Pattyn / White-faced Capuchin (Cebus capucinus imitator) Manuel Antonio National Park, Quepos, Costa Rica

David Pattyn / Black-crowned Central American squirrel monkey (Saimiri oerstedii) pair playing with each other. Close-up Manuel Antonio National Park, Quepos, Costa Rica

David Pattyn / Black-crowned Central American squirrel monkey (Saimiri oerstedii) pair playing with each other, on with hand over mouth of other, Manuel Antonio National Park, Quepos, Costa Rica

David Pattyn / Black-crowned Central American squirrel monkey (Saimiri oerstedii) pair playing with each other Manuel Antonio National Park, Quepos, Costa Rica

David Pattyn / Black-crowned Central American squirrel monkey (Saimiri oerstedii) pair playing with each other Manuel Antonio National Park, Quepos, Costa Rica

David Pattyn / Black-crowned Central American squirrel monkey (Saimiri oerstedii) pair playing with each other, one with hand over eyes of other, Manuel Antonio National Park, Quepos, Costa Rica