Night monkeys typically occur in primary and secondary forests (including fragmented forest and selectively logged forest), seasonally flooded and terra firme forests, and in lowland and sub-montane forests (Hernández-Camacho and Cooper 1976; Aquino and Encarnación 1994a; Defler 2004; Tirira 2007; Maldonado and Peck 2014). In Ecuador, this species occurs in humid tropical forests between 200 and 900 m asl, and in subtropical forests up to 1,550 m (Tirira 2007).

Night monkeys are nocturnal and they are most active at dawn and dusk. During the day A. vociferans groups rest within holes in trees and old palms, mainly at heights of between 10-20 m. These nests are occasionally shared with other mammals (Puertas et al. 1995; Tirira 2007). Their diet includes fruit, nectar and flowers, leaves, and small animal prey such as insects (Wright 1989; Fernandez-Duque 2007).

As other Aotus species, A. vociferans are socially monogamous and live in small groups of between 3 and 5 individuals, composed of an adult pair and offspring of different ages, with an average group size of 3.3 individuals (Fernandez-Duque et al. 2008; Defler 2010). Males carry infants (Rotundo et al. 2002, 2005). Both sexes disperse. Night monkeys are territorial—groups occupy overlapping territories of 5-18 ha (depending on the species and location) (Wright 1978, 1981; Fernandez-Duque 2007). Fernandez-Duque et al. (2008) estimated a home range size of 6.3 ha for A. vociferans in Yasuní National Park, and observed groups ranging over their territories only at night, and more actively under a full moon.

The average weight of adult A. vociferans individuals is of 707.5 g for males and 698 g for females (Defler 2010). Captive male A. lemurinus reach sexual maturity at 2 years of age, and captive female A. vociferans and A. nancymaae first breed at 3-4 years. Single offspring are the rule (Fernandez-Duque 2007).

Aotus vociferans occurs almost exclusively to the north of the Amazon River, extending to Brazil, Colombia, Ecuador and Peru. A small enclave population is found on the right bank of the Solimões River, near the lower Purus River. However, Vidal et al. (2013) reported a group 220 miles west of this enclave, suggesting a possible extension of the species distribution to the south of the Amazon River.

To the north of the Amazon River its distribution is limited by geographical barriers: to the north by the Guaviare river in Colombia, to the west by the Andean Ridge, and to the east probably by the Rio Negro in Brazil (Aquino and Encarnación 1988, 1994; Defler 2010; Groves 2005; Hernandez-Camacho and Cooper 1976).  

The species is listed on Appendix II of CITES.

The species is classified as Near Threatened (NT) in the Red Book of Mammals of Ecuador (De La Torre et al. 2011).

The species is confirmed, or may occur, in a number of protected areas:

Colombia
Amacayacu Natural National Park (293,000 ha) ( Defler 2004, Maldonado and Peck, 2014)
Cahuinari Natural National Park (575,500 ha) (in range, Defler 2004)
Serrania de Chiribiquete Natural National Park (1,280,000 ha) (in range, Defler 2004)
Cordillera de los Picachos Natural National Park (286,600 ha) (in range, Defler 2004)
La Paya Natural National Park (442,000 ha) (Polanco-Ochoa et al. 1999)
Nukak Natural National Reserve (855,000 ha) (in range, Defler 2004)
Puinawai Natural National Reserve (1,092,500 ha) (in range, Defler 2004)

Ecuador
Yasuní National Park (982,000 ha) (Tirira 2007)
Sumaco-Napo Galeras National Park (205,249 ha) (Tirira 2007)
Cayambe-Coca Ecological Reserve (403,000 ha) (in range) (Tirira 2007)
Limoncocha Biological Reserve (4,613 ha) (in range) (Tirira 2007)
Cuyabeno Faunistic Reserve (603,380 ha) (in range) (Tirira 2007)
Cóndor National Park (2,440 ha) (Tirira 2007)

Brazil
Jaú National Park (2,378,410 ha)
Juamí-Japurá Ecological Station (832,078 ha)
Mamirauá State Sustainable Development Reserve (1,124,000 ha)
Amanã State Sustainable Development Reserve (2,350,000 ha)

Peru
Reserva Nacional Pucacuro (637,954 ha)

Parque Nacional Güeppí-Sekime (203,628 ha)

Given the increasing threats faced by A. vociferans and the lack of information on the present status of its populations, it is recommended that:

• Population density estimations are undertaken in protected areas and areas where the species is most vulnerable (see Threats).

• The effects of long-term extraction and post-experimental release of individuals on local populations are evaluated (see Threats).

• The subspecies’ resilience to human impact, deforestation and hunting pressure is evaluated.

• Suitable practices of landscape management are developed that contribute to the sustainable use of resources, minimizing the impact on primate populations and habitat.

• National campaigns to prevent illegal trade are instigated.