Owl or Night Monkey
Owl monkeys (Aotus), also called night monkeys or douroucoulis, are the only nocturnal monkeys in the New World. Their large eyes give them excellent night vision. Their fur is woolly and their ears are hardly visible beneath their dense fur.
Their habitats range from Panama to Argentina. They are the most widely distributed of the New World monkeys. Despite this fact, their survival is threatened by habitat loss, hunting for food, and capture for use in pharmaceutical research.
These are very small monkeys, averaging 14 inches in length, with a 16-inch tail. They weight about 2 pounds. They live about 20 years.
Unlike most primates, owl monkeys pair for life and become very stressed if separated from their partners. They live in small family groups comprised of the adult pair, one infant, and one or two juveniles. Both female and male children leave the family group at the age of three years to find a mate and form new family groups.
Dad owl monkeys are instrumental to early care of the young. Dads begin carrying their young the day they are born and continue to do so up to 80% of the time for the first five months. Dad only hands the baby over to Mom to suckle every few hours. Because of the Dads’ involvement, Moms are freed to be pregnant or nursing most of the time.
The family group communicates with each other through a range of shrieks, squeaks, grunts, gulps, sneezes, hisses and clicks. Sometimes they also produce an owl-like hoot. They call over distances using their throat sacs to amplify their voices.
They live in trees, spending daylight hours hidden in hollows or in vine tangles. At sundown, they move about easily on all fours on branches and vines in the forests. They can leap across gaps up to 16-feet; a great distance for their tiny size.
Owl monkeys are most active one hour after dusk and one hour before dawn. In regions where there are fewer daytime predators, owl monkey are more active during the day. Strictly nocturnal owl monkeys are more than twice as active during a full moon.
They eat fruit, insects, leaves, and nectar. Because of their nighttime activity, there is less competition with daytime fruit eaters, plus they gain the advantage of meals of larger nocturnal insects. They are particularly adept at grabbing flying insect out of the air or snatching them off of a branch.
Since 65-70% of their diet is fruit, owl monkeys are important seed dispersal agents; seeds pass through their gut unharmed. Their foraging behaviors facilitate insect control and replant the forest through reseeding. Thus, in the grand scheme, these tiny primates have very important jobs.
Conservation status: Least concern, but, as with all monkeys, they are threatened by habitat loss and hunting.*
~ From our Autumn 2006 Staying Connected newsletter
Conservation status update May 2016
View video of wild Northern night monkeys courtesy of ARKive.org
The Only Nocturnal New World Monkey
The arboreal Owl Monkeys (genus Aotus) are divided into two groups based on color variations, geographic distribution and karyotypes. These two groups are commonly known as:
Owl Monkeys are not sexually dimorphic in size, with weights ranging from one to three pounds depending on subspecies. Characteristics of these cute wide-eyed primates include light yellow fur on their undersides (stomach, inner legs, under arms) and crown-like stripes on their heads (between and on sides of eyes). Fur thickness in Owl Monkeys is dependent on their geographical location, with monkeys occurring at higher elevations having thicker coats to keep them warm compared to those living closer to sea-level with thinner hair. Probably the most obvious of the Owl Monkeys' physical appearance, are their huge beautiful brown eyes that are adapted to suit their visual needs in the dark.
The range of Night Monkeys is large and species are distributed through southern Central America and northern South America (countries with Aotus species include: Argentina, Bolivia, Brazil, Columbia, Ecuador, Paraguay, Peru, and Venezuela). Owl Monkeys can be found in a variety of habitats including: tropical forests, scrub forests, gallery forests, and primary and secondary forests.
Interesting ecology: Although Owl Monkeys are known to be nocturnal in behavior, Azara’s Night Monkey (Aotus azarae) has been found to also demonstrate cathemeral activity patterns. This means that they can be active both in daytime and nighttime (Fernandez-Duque, 2003). This adaptation of a cathemeral lifestyle may be an adaptation to the climate of Argentina and Paraguay and to avoid having to be active during the cold moonless nights.
Night Monkeys are monogamous primates with families comprising of a mating pair and their offspring. Only one baby is born each year. Unlike most primates, after the first few weeks of life the primary caregiver is the male. A night in the life of an Owl Monkey begins right before sunset, where family groups (of a mating pair and their offspring) leave their nesting sites in search of food.
Their diet is mainly made up of fruit while other food items including insects, foliage and flowers supplement their diets. After feeding for quite some time the monkeys will take rest breaks, socialize with their conspecifics and get back to foraging and feeding. After an evening full of the before-mentioned activities the monkeys head back to their nesting sites, which are located in thickets or tree holes, and occasionally occupied with other nocturnal animals like bats.
Video of the Grey-legged NIght Monkey (Aotus griseimembra) courtesy of ARKive.org
Written by Kaitlyn-Elizabeth Foley as part of her November 2011 Letters from the Field blog series.