Aotus trivirgatus
northern night monkey

Aotus trivirgatus cover most of tropical South America. From north to south they are found from Panama to northern Argentina. From east to west their range extends from the mouth of the Amazon to its headwaters in Peru and Ecuador. (Macdonald 1997)

Aotus trivirgatus can be found from sea level to 3200 feet elevation, in habitats ranging from rain forests and cloud forests to bordering savanna. They have a narrow range of temperature tolerance between 28 and 30 degrees C. They are arboreal creatures and are generally found traveling from one fruit tree to another throughout the season. Aotus trivirgatus is found to prefer large canopied fruit trees.

(Baer et al. 1994)

Both males and females of Aotus trivirgatus are similar in size with a body length of 24 to 47 cm. Tail length ranges from 22 to 42 cm. Coats range from grizzled brown, gray or reddish backs and off white to orange undersides. Coat color changes from one geographical location to another and for this reason, among others, A. trivirgatus is often separated into many different species or sub-species by different researchers. Aotus trivirgatus is the only nocturnal primate of the neotropics [See comments below]. They have the largest olfactory bulbs and accessory olfactory bulbs of all the New World monkeys presumably due to their reliance on smell during nocturnal activity. They also have large brown/orange eyes. The distinctive markings of the face include a triangular black patch between the eyes and black stripes on the sides, framing their otherwise white face.

(Macdonald 1997, Hershkovitz 1983, Wright 1994) (Hershkovitz, 1983; Macdonald, 1997)

Aotus trivirgatus are usually found in family groups where older siblings live with their parents well past infancy and help the mating pair to raise their younger offspring. It has been suggested that this too is a result of the high energy demands of infants. Also, there are limited opportunities for juveniles and subadults to encounter single owl monkeys of the opposite sex with whom to break off from their natal group and form a new pair.

Playing behavior in A. trivirgatus has been observed primarily between infants, juveniles, subadults and fathers. This generally occurs in the months that fruit is most abundant.

Aotus trivirgatus are territorial animals with a territory range of about 9 hectares. They defend these territories, and aggression will result when neighboring groups encounter each other at the borders of territories. Aggressive behaviors include loud whoop-like vocalizations, stiff legged jumping, chases and sometimes wrestling matches. Males and females participate in these territorial battles or standoffs. Conflicts rarely last more than 10 minutes and one group usually retreats.

(Wright 1994, Macdonald 1997)

Aotus trivirgatus eat primarily fruits, insects, nectar and leaves. They will also complement their diet with lizards, frogs and eggs for protein. During times when food is scarce, they seek out mostly nectar, figs and insects. At this time of year they seem to have the advantage over similar sized diurnal species that were chased away from these food sources by larger diurnal monkey.

(Baer et al. 1994)

Aotus trivirgatus have been used as a food source by many indigenous peoples of the neotropics. More recently they have proved invaluable as laboratory animals and have been used for various studies and experiments in testing human diseases and potential treatments. One example is the role that A. trivirgatus have had in testing antimalarial drugs, since they too can be carriers of the human malaria parasites. Commercially there is also a market for owl monkeys as pets. (Baer et al. 1994, Geiman and Meagher 1967)

Aotus trivirgatus are being threaten by extensive deforestation of the tropical rainforests of South America. They are sensitive to clear cutting as well as selective deforestation, because this limits the diversity of diets within each group's limited territory. Owl monkeys are also hunted for their meat, skins, skulls, and teeth. They are hunted primarily by subsistence hunters who have been forced to turn to these smaller monkeys for food because larger game is no longer available. Trade to the U.S. and other countries as lab animals and pets also diminished the populations in the 70's. Today government bans in most South American counties and the U.S. limit export and import, thus reducing the impact of trapping as a threat. Protected areas in many South American countries have also helped in the conservation of this species. Unfortunately, due to economic and political problems, bans on hunting, trapping and deforestation in many of these areas are not enforced. (Baer et al. 1994)

Aotus trivirgatus differ from most nocturnal animals by having color vision. This fact, along with the structure of the eye, suggests that the ancestors of the night monkeys were diurnal. Though they have evolved very large eyes for low light conditions their activity is dependent on moonlight and their activity is limited on very dark nights. (Macdonald, 1997)