Night Monkeys: Aotidae

Physical characteristics: The three-striped night monkey has a woolly, dense fur that varies in coloration from grizzled gray to brown to reddish. Its undersides are orange or yellowish. The ears are small and rounded. Very large eyes are forward-facing and are brown or orange. Large white patches surround the eyes and the mouth, giving the appearance of alertness even when sleeping. Three dark stripes extend from the top of the nose and on each side of the head. The distinctive facial markings may prove helpful for communications among family members, especially on moonless nights. The legs, which are longer than the arms, are used for jumping. An inflatable

Three-striped night monkeys live in family groups, which typically consist of the parents and their infant and juvenile offspring. (© Kevin Schafer/Corbis. Reproduced by permission.)

sac under the chin is used to produce loud vocalizations. The orange, bushy tail, which is tipped in black, is non-prehensile. It is used for maintaining balance when leaping on branches and moving on hands and feet through the different levels of the forest. Males weigh about 1.8 pounds (0.8 kilograms). Females are slightly smaller. The monkeys measure 9.5 to 18.5 inches (24 to 47 centimeters) with a tail length of 8.7 to 16.5 inches (22 to 42 centimeters).

Geographic range: Three-striped night monkeys are found in Brazil, Colombia, and Venezuela.

Habitat: Three-striped night monkeys inhabit different types of forests, including evergreen forests, wet and dry forests, and forests along rivers. They prefer forests with thick, tangled vines and thickets for cover during sleep or rest. They also thrive near human developments.

Diet: Three-striped night monkeys feed mainly on fruits, supplementing them with insects, tree frogs, nectar, and leaves.

Behavior and reproduction: Three-striped night monkeys live in family groups in forest trees. A typical family consists of the parents and their infant and juvenile offspring. The family forages at night, staying up longer on moonlit nights. They travel through the same areas of the trees, which is especially helpful in finding their way in the dark. They usually move on all fours, but can jump from tree to tree. During the day, they share a sleeping site among tangled vines, dense vegetation, or in a tree hollow.

Mothers give birth to a single infant annually, although they may have twins, but very rarely. Fathers are the principal caregivers, carrying the infant starting from birth. They play with the infant and older offspring, guard them against predators, and also teach them. The infant is given to the mother only during nursing. The mother does not participate in play and gives the infant back to the father immediately after it is fed. The infant is weaned by eight months of age. Older offspring help the father care for the newborn. The young stay with the family for up to three years, leaving peacefully on their own.

Three-striped night monkeys are territorial, advertising their ownership with secretions from scent glands in the chest and the tail base. They also use urine for scent marking. They soak their fur and the soles of their feet with urine, which gets transferred to leaves, branches, and trunks. They are loud creatures, announcing their presence with different types of sounds. They use an owl-like hoot when ready to mate or when separated while foraging in the dark. They whoop and grunt to threaten intruders, and trill when greeting each other. Hostile physical communications include back-arching, furraising, defecating, and urinating.

Three-striped night monkeys and people: Three-striped night monkeys are hunted for food by native people. They are also trapped and sold as pets. These monkeys have been found to be carriers of the human malaria parasites. They are especially valued for research in the development of drugs used for treatment and prevention of malaria.

Conservation status: The three-striped night monkey is not a threatened species. ∎