Owing to a paucity of species-specific studies, very little is known about the biology of the Andean night monkey. However, night monkeys are typically arboreal nocturnal forest dwellers that are most active on moonlit nights, and sleep under tangles of vines or in tree hollows during the day. By foraging at night these monkeys are able to avoid competition with diurnal monkeys for food and predation from birds of prey. A small, agile monkey, the Andean night monkey is adept at running on branches and, despite its comparatively small size, is capable of spectacular leaps of several metres (5). It is a largely frugivorous species, but will also eat leaves, bark, flowers and will catch large insects out of the air (4).
The basic group of the Andean night monkey is a breeding pair and their offspring, which defend a small territory (4). Night monkeys produce a remarkable variety of calls, inflating a sac under the chin to create a resonance in the voice, and use a number of trills and screams to communicate (5). Olfactory communication is also extremely important, with mature monkeys attracting mates by urinating on the hands and rubbing them on branches (2). Pairs are monogamous and will mate annually, producing a single young after a gestation period of some 133 to 141 days. Although the mother suckles the infant, the father is largely responsible for its upbringing, defending, playing with and instructing the young. The juveniles stay with the parents for two to four years, after which time they become temporarily nomadic as they search for a mate (5).