Cyril Ruoso / Common woolly monkeys (Lagothrix lagotricha) climbing over keeper in Ikamaperou Sanctuary, Amazon, Peru. October 2006.

Cyril Ruoso / Keeper feeding Common woolly monkeys (Lagothrix lagotricha) in Ikamaperou Sanctuary, Amazon, Peru. October 2006.

Cyril Ruoso / Common woolly monkey (Lagothrix lagotricha) reaching forward, Ikamaperou Sanctuary, Amazon, Peru.

Cyril Ruoso / Humboldt's Woolly Monkey (Lagothrix lagotricha), Pacaya Samiria National Park, Peru

Kevin Schafer / Guatemalan Black Howler Monkey (Alouatta pigra) calling, Community Baboon Sanctuary, Belize, Central America. Endangered species.

Kevin Schafer / Guatemalan Black Howler Monkey (Alouatta pigra) climbing, Community Baboon Sanctuary, Belize, Central America. Endangered species.

Suzi Eszterhas / Black-handed spider monkey (Ateles geoffroyi), Osa Peninsula, Costa Rica.

Ammonite / Black-handed / Geoffroy's spider monkey (Ateles geoffroyi) feeding on figs, Santa Rosa National Park, Costa Rica.

Ammonite / Juvenile Mantled howler monkey (Alouatta palliata) climbing through canopy, showing use of prehensile tail, Santa Rosa National Park, Costa Rica.

Ammonite / Mantled howler monkey (Alouatta palliata) climbing through canopy, showing use of prehensile tail, Santa Rosa National Park, Costa Rica.

Juan Carlos Munoz / Black howler monkeys (Alouatta caraya) male and two females calling from tree, captive, Apenheul Park, Netherlands.

Cyril Ruoso / Black Howler Monkey (Alouatta caraya) female resting in tree, native to South America