Night Monkey - Behavior and Intelligence

Behavior and Intelligence

The name “night monkey” comes from the fact that all species are active at night and are in fact the only truly nocturnal monkeys (an exception is the subspecies Aotus azarae azarae, which is cathemeral). Night monkeys make a notably wide variety of vocal sounds, with up to eight categories of distinct calls (gruff grunts, resonant grunts, screams, low trills, moans, gulps, sneeze grunts and hoots), and a frequency range of 190-1,950 Hz. Unusual among the New World monkeys, they are monochromats, that is, they have no colour vision, presumably because it is of no advantage given their nocturnal habits. They have a better spatial resolution at low light levels than other primates which contributes to their ability to capture insects and move at night.Night monkeys live in family groups of the mated pair with their immature offspring. Family groups defend territories by vocal calls and scent marking. The night monkey is socially monogamous, and all night monkeys form pair bonds. Only one infant is born each year. The male is the primary caregiver, and the mother only carries the infant for the first week or so of its life. This is believed to have developed because it increases the survival of the infant and reduces the metabolic costs on the female. It is not uncommon, however, for a female night monkey to “evict” a male night monkey and find another mate.