Gray-bellied Night Monkey

Gray-bellied Night Monkey
Conservation status: Vulnerable
Gray-bellied Night Monkey
Scientific classification
Species:A. lemurinus
Binomial name
Aotus lemurinus
I. Geoffroy Saint-Hilaire, 1843

The Gray-bellied Night Monkey (Aotus lemurinus), also called the Lemurine Owl Monkey or Night Monkey, is a small New World monkey of the family Aotidae. Native to tropical and subtropical forests of South and Central America, Gray-bellied Night Monkeys face a significant threat from hunting, harvesting for use in pharmaceutical research and habitat destruction.


Physical description

Like other members of their genus, these monkeys are nocturnal; their small, round heads are striped with black and are dominated by two large, brown eyes. The overall effect is not unlike an owl; the monkeys' eyes shine a reddish orange by reflected light. Their white eyebrows are bushy, with a patch of darker fur between them. Their grey fur is described as dense and woolly, with the animals' undersides yellow to orange in colour. Their brownish black to orange tail is not prehensile and invariably tipped with black.

Gray-bellied Night Monkeys have slender limbs with long, delicate fingers; their fingertip pads are wide. Adults may attain a weight of 1.3 kilograms; there is no sexual dimorphism observed.

Habitat and diet

Found in both dry and moist areas, Gray-bellied Night Monkeys occupy all levels of the forest canopy; however, they are seldom found on the ground. They prefer dense vegetation with tangles of vines where the trees are evenly dispersed. Lemurine Owl Monkeys range from Colombia and north-eastern Argentina to Ecuador and Panama; they are also found in the tropical Andes.

By day the monkeys slumber in the cavities of trees or in dense thickets; by night, they search the canopy for a variety of food items. Primarily frugivores (fruit-eating), these monkeys also eat vegetation, insects, nectar, and even other small mammals and birds when fruit is scarce.

Behaviour and reproduction

Most active during twilight hours and periods of bright moonlight, the Gray-bellied Night Monkey troop consists of a mated pair and their offspring, up to five individuals in total. These monkeys are noted for their monogamy; parental duties are shared between the lead pair and the juveniles. However, it is the male who assumes the bulk of care giving and rearing responsibilities; the female serves only to nurse the infants. Remarkably, even if the male dies the female will refuse to take over from him.

Characteristically vociferous, the monkeys produce a range of calls: from soft clicks and low-pitched guttural rumblings to owl-like hoots and high-pitched shrieks when threatened. When not feeding, the monkeys are typically inactive. Like other members of their genus, Gray-bellied Night Monkeys claim a relatively small territory of about 0.1 km². Scent is central to these monkeys' intraspecies communication; territories are marked with brown, oily secretions from the base of the tail.

Birthing peaks at the end of the dry season and in the midst of the wet season. Gestation averages 133 days, usually resulting in a single infant; twins are a rarity. There is only one litter per year. Sexual maturity is reached at 2.5 to 3.5 years of age, at which point the offspring disperse; that is, they leave the troop in search of an unattached mate.


There are three subspecies of the Gray-bellied Night Monkey:

  • Aotus lemurinus lemurinus
  • Aotus lemurinus griseimembra
  • Aotus lemurinus zonalis

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