Night monkeys typically occur in primary and secondary forest (including disturbed forest and selectively logged forest), seasonally flooded and terra firma, lowland forest, and submontane and montane (cloud forests) in Colombia and the Andes to 3,200 m above sea level (the specifically montane forms are Aotus lemurinus and Aotus miconax) (Hernández Camacho and Cooper 1976; Aquino and Encarnación 1994a; Defler 2004). 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 flower (seasonally important for the A. a. azarae in the Chaco), leaves, and small animals prey such as insects (Wright 1989; Fernandez-Duque 2007). Aotus azarae has been observed to include a significant portion of leaves in its diet (Ganzhorn and Wright 1994; Wright 1985; Arditi and Placci 1990; Giménez and Fernandez-Duque 2003), as has Aotus zonalis on Barro Colorado Island in an early study by Hladik and Hladik (1969).

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; Fernandez-Duque 2007). Solano (1995) estimated a home range of 17.5 ha for A. brumbacki on the Río Duda in Tinigua Natural National Park, Colombia. 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). A female A. azaraewas found to breed for the first time at 58 months of age (Fernandez-Duque et al. 2002). 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. In the Argentinean Chaco, A. azarae shows a peak of births between March and June (Fernandez-Duque 2007).

Size:
Hernández-Camacho and Defler (1985) recorded a weight of 875 g for one individual (sex unknown), and 455 g for a female, probably not fully grown.

Red List Category

Red List Criteria

Version

2008

Morales-Jiménez, A.L., Link, A. & Stevenson, P.

Mittermeier, R.A. & Rylands, A.B. (Primate Red List Authority)

This species is listed as Vulnerable as it is believed to have undergone a decline exceeding 30% over the past 3 generations (24 years) mainly as a result of ongoing habitat loss within its range. However, this species is less at risk than other Aotus species as there remain several strongholds in and around the PN Serrania de Macarena and PN Tinigua and they are able to persist in remaining forest fragments and gallery forests in the llanos.

No population information available. Aquino and Encarnación (1994b) reviewed population structure and densities for the genus.

Decreasing

Except for the region around Villavicencio, Meta, the distribution of this species remains poorly known. However, over much of the known range, their habitat is declining rapidly due to expanding illicit crops, armed conflict and expanding cattle ranching. The taxon may extend south to the Rio Guaviare, where there would be healthy populations protected by one or two large national parks.

Many Aotus have been released from captivity outside of their range and could be hybridizing, but very little is known of the effects of this practice.

This species is confirmed, or may occur, in the following protected areas:

El Cocuy Natural National Park (306,000 ha) (possibly in range, Defler 2003, 2004)
Serranía de la Macarena Natural National Park (630,000 ha) (in range, Defler 2003, 2004)
El Tuparro Natural National Park (548,000 ha) (possibly in range, Defler 2003, 2004)
Tinigua Natural National Park (201,875 ha) (Solano 1985, 1986).

This species is listed on Appendix II of CITES (as Aotus lemurinus brumbacki).