Night monkeys typically occur in primary and secondary forest (including disturbed forest and selectively logged forest), seasonally flooded and terra firma, lowland forest, submontane forest (Hernández-Camacho and Cooper 1976; Aquino and Encarnación 1994a; Defler 2003, 2004; Tirira 2007). In Ecuador, this species occurs in humid tropical forest between 200 and 900 m above sea level, and in the Cordillera del Condor, in subtropical forest up to 1,550 m (Tirira 2007). Aquino and Encarnación (1994b) reviewed the habitat and forest preferences of the genus.

Night monkeys are nocturnal: they are most active at dawn and dusk. The only exception is Aotus azarae azarae of the Chaco of southern Bolivia, Paraguay and Argentina, which is cathemeral (active during night and day). They are frugivorous; their diet includes fruit, nectar and flowers, leaves, and small animals prey such as insects (Wright 1989; Fernandez-Duque 2007).

They are socially monogamous, living in small groups of an adult pair and offspring of different ages (infant, one or two juveniles and sometimes a subadult. In A. a. azarae, a significant number of adults range alone. They may be subadults that have left their natal groups or older adults which have been evicted from their groups by competitors (Fernandez-Duque and Huntington 2002; Fernandez-Duque 2004). Both sexes disperse. Males care for the infants (carry them) (Rotundo et al. 2002, 2005). Lone adults were observed by Villavicencio Galindo (2003) in northern Colombia. Night monkeys are territorial—groups occupy overlapping territories of 5-18 ha (depending on the species and location) (Wright 1978, 1981; Fernandez-Duque 2007). Wright (1994) and Fernandez-Duque (2007) review the behaviour and ecology of the genus.

Captive male A. lemurinus reach sexual maturity when 2 years old, and captive female A. vociferans and A. nancymaae first breed when 3-4 years old (Dixson 1983; Fernandez-Duque 2007). In the wild, male A. azarae reach adult weight only when about 4 years old, and age at first reproduction is about 5 years of age (Juárez et al. 2003; Fernandez-Duque 2004). Single offspring are the rule. Wright (1985) recorded births between August and February for A. nigriceps in Peru (Manu National Park), and Aquino et al. (1990) indicated a birth season between December and March for A. nancymaae in north-eastern Peru.

Size:
Adult male weight average 0.697±.024 kg (n=4, range 0.568-8.0 kg) (Hernández-Camacho and Defler 1985).

Red List Category

Red List Criteria

Year Assessed

Assessor/s

Reviewer/s

Contributor/s

Aquino and Encarnación (1988) estimated a density of 33.0 individuals/km², and Heltne (1977) 7.9 individuals/km² in north-eastern Peru. Aquino and Encarnación (1994b) reviewed population structure and densities for the genus.

Decreasing

There are no known major threats at present. The species was reported as common and widespread in Ecuador and Peru (Aquino and Encarnación 1994a; Tirira 2007).

Large numbers are used in medical research, sometimes illegally, which should be monitored to understand the effect on populations.

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

Colombia
Amacayacu Natural National Park (293,000 ha) (in range, Defler 2003, 2004)
Cahuinari Natural National Park (575,500 ha) (in range, Defler 2003, 2004)
Serrania de Chiribiquete Natural National Park (1,280,000 ha) (in range, Defler 2003, 2004)
Cordillera de los Picachos Natural National Park (286,600 ha) (in range, Defler 2003, 2004)
Cueva de los Guacharos Natural National Park (9,000 ha) (in range, Defler 2003, 2004)
La Paya Natural National Park (442,000 ha) (Polanco-Ochoa et al. 1999)
Nukak Natural National Reserve (855,000 ha) (in range, Defler 2003, 2004)
Puinawai Natural National Reserve (1,092,500 ha) (in range, Defler 2003, 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)

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

Peru
None.

It is listed on Appendix II of CITES.