Suzi Eszterhas / Colombian red howler monkey (Alouatta seniculus) mother and baby in tree. Northern Colombia.

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

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

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

Lucas Bustamante / Two Red howler monkeys (Alouatta seniculus) fighting, Tambopata, Madre de Dios, Peru.

Lucas Bustamante / Two Red howler monkeys (Alouatta seniculus) lying on ground, Tambopata, Madre de Dios, Peru.

Lucas Bustamante / Red howler monkey (Alouatta seniculus) sitting in tree, Tambopata, Madre de Dios, Peru.

Thomas Marent / Red Howler Monkey (Alouatta seniculus) calling, Magdalena Valley, Colombia

Juergen & Christine Sohns / Red Howler Monkey (Alouatta seniculus), native to South America

Steve Gettle / Red Howler Monkey (Alouatta seniculus), Tambopata National Reserve, Peru