Night monkeys, also called owl monkeys, are the only nocturnal monkeys in the world. They are found in Argentina, Bolivia, Brazil, Colombia, Ecuador, Panama, Paraguay and Peru. Slight differences among the various gray- and red-necked species include thicker fur in night monkeys who live at higher elevations than their sea-level compatriots. Because it's very difficult to observe them, their total population and life span is unknown. Those in captivity live an average of 20 years.
Night monkeys inhabit primary, secondary and even remnant tropical forests. A forest is considered primary when it has remained undisturbed by nature or humankind for a long period of time that it reaches maturity. It is considered secondary when it has been disturbed -- by fires or timber harvest, for example -- and has regrown afterward, but not yet matured to the level of a primary forest. When a forest is cut up to make way for developments, fields or even pastures, the patches that remain are called remnant forests. Night monkeys prefer the dense foliage and vines afforded to them by primary forests. They can sleep or rest there and feed from the fruit, leaves, nectar and even insects in the trees. Deforestation has forced night monkeys to seek shelter in secondary and remnant forests.
Scrub and Wetlands
Night monkeys are also found in seasonally deciduous scrub forest, subtropical dry forest and gallery forest from Panama to Argentina and Paraguay. A forest is deciduous when the dominant species of its trees and other woody vegetation shed their leaves in winter and regrow them in spring. Subtropical dry forests are dry because of drought, common despite being located in warm climates with rainfall. Night monkeys seek out hollows in the trees of deciduous and subtropical forests to sleep and rest. Areas where there is not enough rainfall result in drier habitats, such as scrublands. They can use the entanglements as coverage for sleeping areas. Gallery forests are those that form corridors through wetlands and rivers, giving night monkeys access to the coverage and protection afforded by trees, as well as a water source.
Sea Level and Up High
Whether they remain at sea level or at high elevations, night monkeys prefer dense foliage so they tend to stick to dense canopy and areas that offer them a vast assortment of plant species. Some live at sea level and others at elevations as high as 10,498 feet. The thicker fur of night monkeys who live at higher elevations comes in handy, as temperatures can drop to as low as 41 F and even colder, depending on the region.
Andean and Colombian Night Monkeys
Andean night monkeys, found in Peru, prefer either lowland forests that flood seasonally or highland forests that never flood. In flooded forests, trees tend to have thickened trunks and branches that provide hollows, which make perfect sleeping quarters for night monkeys. Colombian night monkeys prefer primary forests where they can remain up high, though they can also be found in remnant and older secondary forests.