The owl monkey has a heavily furred body and tail and is characterized by its large eyes and round head. It is usually grayish in colour, with dark markings on the head, and has an inflatable sac under the chin that amplifies its calls. A nocturnal monkey, it can see very well at night and moves with agility in the trees, leaping and jumping with ease. It rarely descends to the ground.
Fruit, leaves, insects and spiders are its main foods, but it also takes some small mammals and birds. The owl monkeys usually live in pairs, accompanied by their offspring. Several families may group together during the day to sleep in a hollow tree or in a nest among foliage. The female gives birth to a single young, which clings to its mother for the first few weeks of life before it starts to climb alone.
Range: Panama to Paraguay (patchy distribution).
Size: Body: 9 1/2 - 14 1/2 in (24 - 37 cm). Tail: 12 1/4 - 15 3/4 in (31 - 40 cm).
Southern night monkey
Night monkeys, which are also known as douroucoulis or owl monkeys, are the only nocturnal monkeys in the world. These rare monkeys live in most types of forest, except those close to water. Biologists used to think there was a single species, but it is now known that there are several living across South America.
The large eyes of these monkeys collect enough light for them to see in the gloom. Owl monkeys can only see in monochrome (black and white), but this still allows them to run and jump through the trees even on the darkest nights. By day, they rest in nests made from dry leaves and twigs.
Owl monkeys have large eyes which give them good night vision. Their thick, woolly fur gives them a rounded appearance, and their tails, which are not prehensile, are thickened and furry at their tips.
Owl monkeys live in family groups, with one adult pair and two or three of their young. Family members warn each other of approaching danger, such as tree snakes or birds of prey, with long "wook" alarm calls. The monkeys have loose sacs of skin under their chins, which they inflate to amplify these calls. At night the owl monkeys rely on scent as well as calls to communicate with other monkeys and with nearby groups. The scent comes from their urine, and also from glands on their chests, which the monkeys rub against branches.
Distribution: Central and South America from Panama southward to Brazil, but patchily distributed.
Food: Fruit, nuts, leaves, bark, flowers, gums, insects and small vertebrates.
Size: 24 - 37cm (9.5 - 14.5 in); 0.6 - 1 kg (1.25- 2.2 lb).
Maturity: 2 years.
Breeding: Single young born throughout the year.
Life span: 18 years.
Northern night monkey
Size: 24 - 47 cm (9.5 - 18.5 in); 0.8 - 1.3 kg (1.75-2.75 lb).
Northern night monkeys have a brown or grey back and a pale red underside. Like their close relatives, the southern night monkeys, they are nocturnal. (The niche of feeding at night is taken by lemurs, bushbabies and other non-monkey primates in Africa and Asia.) Northern night monkeys range from southern Panama to northern Argentina, and from the Andes to the Atlantic coast. They live in lowland rainforests and mountain cloud forests, moving slowly from tree to tree as they feed on fruit and insects. They have the best-developed sense of smell of all the New World monkeys. Individuals hoot into the darkness to attract mates. Owl monkeys form monogamous pairs. A single young or twins are born in January. The males do more than the females to raise the young. The young stay with their parents for several months after weaning, forming a small family group.
Nancy Ma’s Night Monkey
Until 1983, there was thought to be only one species of owl monkey, but genetic tests have shown that eight separate species actually exist.
These primates represent the only nocturnal group of monkeys, emerging from their sleeping dens shortly after nightfall, and returning before dawn. They forage in groups, seeking out fruiting trees, and have remarkable reflexes that allow them to catch night-flying insects such as moths in flight. They can also jump distances of up to 4 m (13 ft) safely. Owl monkeys spend their time in the upper part of the forest canopy, and face few predators, other than birds of prey.
Distribution: Found in South America, south of the Amazon, restricted to the border area between Peru and Brazil, from Maranon in the north, extending south to the Juru.
Weight: Around 780 g (28 oz)
Length: 72 cm (28.5 in); up to 35 cm (14 in) tall
Maturity: From 2 years
Gestation Period: 133 days
Breeding: 1; weaning occurs at 6 - 8 months
Diet: Omnivorous, feeding on fruit, vegetation, invertebrates, plus eggs and small birds
Lifespan: Up to 20 years in captivity.
Enhanced nighttime vision
This is made possible by large eyes, with a relatively spherical lens and more rod cells on the retina where tire image forms.
Owl monkey has a flattened face, with owl-like disc markings of white fur around the eyes.
Hands and feet
This species is very agile, and can grasp branches securely.
A bird can be plucked off its nest more easily in the darkness than would be possible during the day.
Owl monkeys are quadrupeds, moving along the branches on all four feet, and this helps them to maintain their balance.