Ernie Janes / Black howler (Alouatta caraya) male and female, captive, occurs in Brazil and Paraguay. With digitally added leaf pattern.

Ernie Janes / Black howler (Alouatta caraya) captive, occurs in South America.

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

Ernie Janes / Howler monkey (Alouatta caraya) resting in tree, Costa Rica.

Ernie Janes / Black howler (Alouatta caraya) male female pair. Captive, occurs in South America, with digitally added leaf pattern.

Bernard Castelein / Paraguyan howler monkey (Alouatta caraya) male and female, Pampas del Yacuma Protected Area, Bolivia

Bernard Castelein / Paraguyan howler (Alouatta caraya) female, Pampas del Yacuma Protected Area, Bolivia

Ernie Janes / Black howler (Alouatta caraya) captive, occurs in South America. Foliage digitally added.

Andy Rouse / Black Howler Monkey (Alouatta caraya) howling , Pantanal, Brazil

Hermann Brehm / Black Howler Monkey (Alouatta caraya) in tree, Pantanal, Brazil

Gabriel Rojo / Black howler monkey (Alouattacaraya) male and female in tree, Ibera Marshes, Corrientes Province, Argentina

Nick Garbutt / Black howler monkey (Alouatta caraya) resting in riverine forest canopy. Tributary of Cuiaba River, Mato Grosso, Pantanal, Brazil. September.

Gabriel Rojo / Black howler monkey (Alouatta¶Ã¿caraya) female, Ibera Marshes, Corrientes Province, Argentina

Luiz Claudio Marigo / Male Black Howler monkey (Alouatta caraya) at Encontro das aguas State Park, Pantanal, Mato Grosso State, Western Brazil.

Roland Seitre / Black howler monkey (Alouatta caraya) male, captive at Singapore Zoo, Singapore. Native to South America.

Roland Seitre / Black howler monkey (Alouatta caraya) female, captive at Singapore Zoo, Singapore. Native to South America.

LYNN M. STONE / Black howler monkey {Alouatta caraya} female, Captive

Nick Garbutt / Group of Black-and-gold howler monkeys (Alouatta caraya) females with infants, resting on tree branch, Cuiaba River, Northern Pantanal, Brazil.

Joel Sartore / Photo Ark / Black howler monkey (Alouatta caraya) male, head and shoulders portrait, John Ball Zoo. Captive, occurs in South America.

Joel Sartore / Photo Ark / Black howler monkey (Alouatta caraya) male, portrait, John Ball Zoo. Captive, occurs in South America.

Joel Sartore / Photo Ark / Black howler monkey (Alouatta caraya) male, head and shoulders portrait, John Ball Zoo. Captive, occurs in South America.

Joel Sartore / Photo Ark / Black howler monkey (Alouatta caraya) male, sitting, portrait, John Ball Zoo. Captive, occurs in South America.

Paul Williams / Black howler monkey (Alouatta caraya) looking out from tree foliage, Belize, Central America.

Paul Williams / Black howler monkey (Alouatta caraya) nibbling on leaves, Belize, Central America.

Paul Williams / Black howler monkey (Alouatta caraya) amongst tree foliage, Belize, Central America.

Ernie Janes / Black howler (Alouatta caraya) male and female, portrait, captive.