Kevin Schafer / Guatemalan black howler monkey (Alouatta pigra) sitting in tree howling, Community Baboon Sanctuary, Belize. Endangered species.

Mark Bowler / Red howler monkey (Alouatta seniculus) howling, captive

Mark Bowler / Red howler monkey (Alouatta seniculus) portrait, captive

Mark Bowler / Red howler monkey (Alouatta seniculus) howling, captive, digitally modified

Juan Carlos Munoz / Black howler monkey (Alouatta caraya) female howling, Pantanal NP, Mato Grosso, Brazil Not available for ringtone/wallpaper use.

Juan Carlos Munoz / Black howler monkey (Alouatta caraya) baby being carried by mother, Pantanal NP, Mato Grosso, Brazil

Thomas Marent / Red Howler Monkey (Alouatta seniculus) calling, Peru

Edwin Giesbers / Young Black howler monkey (Alouatta caraya) looking down from tree, Costa Rica

Claus Meyer / Brown Howler Monkey (Alouatta fusca) baby clinging to branch, Amazon ecosystem, Brazil

Gabriel Rojo / Black howler monkey female in tree {Alouatta caraya} Ibera, Argentina

Pete Oxford / Red howler monkey in canopy {Alouatta seniculus} rainforest Madre de Dios, Peru

Anup Shah / Black howler monkey portrait, native to South America