Alouatta caraya is found in deciduous, seasonally deciduous, mixed evergreen, gallery, and xeric forests, as well as in forest patches in savanna habitats. Today, it occupies forest patches throughout a large part of the Cerrado of central Brazil, and the Pantanal of Mato Grosso. It occupies deciduous forest (caatinga alta) in some areas in southern Piaui, western Bahia and north-western Minas Gerais. In Rio Grande do Sul occurs in mixed evergreen forest (Araucaria), forest patches in savanna, seasonal deciduous forest (Codenotti et al. 2002; Codenotti and Silva 2004) and gallery forest. In Argentina, it specializes in semi-dry deciduous forests and gallery forests as well as the typical island forests of the Chaco (Arditi and Placci 1990; Brown and Zunino 1994). In Bolivia, it is found in the Chaco and Chiquitano forests, and gallery forest and forest islands in the Beni. In Paraguay, Stallings (1985; Stallings et al. 1989) reported that A. caraya occurs throughout the eastern forests and gallery forests of the southern and western Chaco along the ríos Paraguai and Pilcomayo, and the numerous small rivers that drain the Chacoan plain. It can also be found in sporadic xeric forests, continuous with gallery forests.

Mean adult male weight ranges from 6.42 kg (n=58, Rumiz 1990) to 7.77 kg (n=9, Svoboda et al. 2006), while mean adult female weight ranges from 4.33 kg (n=117, Rumiz 1990) to 5.13 kg (n=12, Svoboda et al. 2006). Like the spider monkeys, they are prehensile-tailed, with a naked patch of skin on the under surface at the tip. Their most characteristic feature is the deep jaw that surrounds the hyoid apparatus, a resonating chamber, and enlarged larynx that produces their howls (grunts, roars and barks) (Kitchen et al. 2015). Howling sessions, usually involving the entire group, can be heard particularly in the early morning and are audible at distances of 1-2 km (Drubbel and Gautier 1993; Cunha and Byrne 2006).

Howler monkeys have a folivorous-frugivorous diet (Crockett and Eisenberg 1987). The molar teeth are particularly adapted for their chewing leaves through shearing. Although they regularly include mature leaves in their diet, softer, less fibrous, young leaves are preferred when they are available. Howlers spend up to 70% of their day lying and sitting in the canopy, while their enlarged caeca ferment the leaves. Their folivory and ability to eat mature leaves is undoubtedly one of the keys to their wide distribution and the wide variety of vegetation types they inhabit. Mature fruit is the other important food item, especially wild figs (Ficus) in many regions, but they also eat leaf petioles, buds, flowers (sometimes seasonally very important), seeds, moss, stems, twigs and bark. A few groups inhabiting orchards near human habitations were reported to eat bird eggs (Bicca-Marques et al. 2009).

Behavioral and ecological field studies have been carried out mostly in Argentina and Brazil (see reviews by Bicca-Marques 2003, Oklander et al. 2011, Arroyo-Rodríguez et al. 2015, Cristóbal-Azkarate et al. 2015, Dias and Rangel-Negrín 2015, Fortes et al. 2015, Martínez-Mota et al. 2015).

This is a wide-ranging species occurring throughout most of central-western Brazil (with range expanses to the north, northeast and south; Ludwig et al. in press), eastern Bolivia (Wallace et al. 2013), eastern Paraguay (Stallings 1985), northeastern Argentina (Brown and Zunino 1994) and potentially reaching northwestern Uruguay (Villalba et al. 1995). It inhabits moist semi-deciduous, deciduous or higher altitude habitats within the Cerrado, Caatinga, Chaco, Pantanal, Pampa and Atlantic Forest biomes, mostly in gallery or floodplain forests and marginally in more humid forests of the Amazon.

The range of Alouatta caraya partly overlaps that of other howler species. It occurs in sympatry with A. guariba clamitans in the states of Paraná and Rio Grande do Sul in south Brazil (Aguiar et al. 2007, 2014; Bicca-Marques et al. 2008) and the Province of Misiones in Argentina (Agostini et al. 2008). Hybridization is suspected in these contact zones. In the state of Rondônia, Brazil, the species occurs in sympatry with A. puruensis (Alves 2006, 2013). Alencar and Melo (2013) report a potential contact zone with A. belzebul in the state of Tocantins, Brazil. In Beni and Santa Cruz departments of Bolivia, the species is found in sympatry with A. sara (Buntge and Pyritz 2007, Wallace and Rumiz 2010).

Alouatta caraya occurs in numerous protected areas:

Argentina

• Iguazú National Park (55,000 ha) (Brown and Zunino 1994)
• Pilcomayo National Park (60,000 ha) (Brown and Zunino 1994)
• Chaco National Park (14,000 ha) (Brown and Zunino 1994)

Bolivia

• Kaa-Iya Gran Chaco National Park (3,441,115 ha)
• Otuquis Pantanal National Park (903,350 ha)
• Otuquis Natural Area of Integrated Management (102,600 ha)
• San Matías Natural Area of Integrated Management (2,918,500 ha)
• Noel Kempff Mercado National Park (1,500,000 ha) (Wallace et al. 1998)
• Ríos Blanco y Negro National Reserve (1,423,900 ha) (Wallace et al. 2000)

Brazil

• Araguaia National Park (555,517 ha)
• Brasília National Park (40,398 ha) (Santini 1986)
• Gama Cabeça-de-Veado Environmental Protection Area (25,000 ha) (Alves 2006)
• Águas Emendadas Ecological Station (10,547 ha) (cited in Holzmann 2012).
• Chapada dos Veadeiros National Park (65.514 ha)
• Emas National Park (132,642 ha)
• Vagafogo Private Reserve of Natural Heritage/Vagafogo Wildlife Sanctuary (17 ha)
• Silvânia National Forest (486 ha)
• Meandros do Rio Araguaia Environmental Protection Area (359,190 ha)
• Serra da Capivara National Park (91,848 ha) (Moura 2007)
• Grande Sertão Veredas National Park (230,853 ha)
• Chapada Diamantina National Park (152,141 ha)
• Pantanal Matogrossense National Park (135,606 ha)
• Serra da Bodoquena National Park (77,021 ha)
• Taiamã Ecological Station (11,554 ha)
• Mario Viana Municipal Biological Reserve (470 ha) (cited in Holzmann 2012)
• Serra da Bodoquena National Park(77,021 ha)
• Prosa State Park (133 ha)
• Matas do Segredo State Park (177 ha)
• Serra do Cipó National Park (31,639 ha) (Oliveira et al. 2003)
• Serra da Canastra National Park (197,809 ha)
• Cavernas do Peruaçu National Park (56,448 ha)
• Serra das Araras State Park (11,137 ha)
• Rio Pandeiros Environmental Protection Area (393,060 ha)
• Serra do Sabonetal Private Reserve of Natural Heritage (82,500 ha)
• Veredas do Peruaçu Park (30,702 ha)
• Lajedão Environmental Protection Area (12,000 ha)
• Jaíba Biological Reserve (6,358 ha)
• Grão Mogol State Park (28,404 ha) (IEF 2011)
• Taiamá Ecological Station (914,300 ha)
• Jataí State Ecological Station (9,010 ha) (Paese et al. 2007)
• Paulo de Faria Ecological Station (433 ha)
• Aguapeí State Park (9,050 ha)
• Rio do Peixe State Park (7,712 ha)
• Ibirapuitã State Biological Reserve (308 ha) (Marques 2003)
• Ibirapuitã Environmental Protection Area (316,882 ha) (Marques 2003)
• Banhado São Donato Biological Reserve (4,392 ha) (Slomp et al. 2011)
• Uruguaiana Municipal Natural Park (Slomp et al. 2011)
• Ilha dos Milanos Ecological Reserve (Slomp et al. 2011)
• Santa Isabel do Butuí Private Reserve of Natural Heritage (135 ha)
• Ilha Grande National Park (76.033 ha) (Aguiar et al. 2007)
• Ilhas e Várzeas do Rio Paraná Environmental Protection Area (1,005,180 ha) (Aguiar et al. 2007; Passos et al. 2007)
• Nova Querência Private Reserve of Natural Heritage  (50 ha) (Godoy et al. 2004; Odalia-Rímoli et al. 2008)
• Guaporé Biological Reserve (615,771 ha) (Alves 2006)

Paraguay

• Cerro Cora National Park (5,500 ha) (probably extinct, Stallings 1985)
• Ybicui National Park (5,000 ha) (Stallings 1985)
• Tinfunque National Park (280,000 ha) (the most important protected area in Paraguay for this species; Stallings 1985)
• Defensores del Chaco National Park (780,000 ha) (Stallings 1985)
• Caaguazu National Park (6,000 ha) (Stallings 1985)
• Kuri y National Reserve (2,000 ha) (Stallings 1985)
• Yakui Protected Forest (1,000 ha) (Stallings 1985)
• Nacunday Protected Forest (1,000 ha) (Stallings 1985).

It is listed on Appendix II of CITES.