Aotus azaraeAzara's night monkey(Also: feline night monkey)

Geographic Range

Aotus azarae is found only in South America. It inhabits the area south from the Rio Madre de Dios and Rio Guapore in Bolivia into Paraguay and northern Argentina. In Argentina, the southern night owl ranges south of the Rio Bermejo and east from the Rio Paraguai to the Andes. This species is divided into two subspecies, Aotus azarae boliviensis and Aotus azarae azarae, by an area extending roughly from Lago Uberaba on the east to Sucre, Bolivia, on the west. Aotus a. boliviensis is the northern subspecies; A. a. azarae, the southern one. Baer (1994), Nowak (1991)


Aotus azarae live in the trees of Bolivia, Paraguay, and northern Argentina. They sleep there during the day and rarely come down to the ground. They use lianas to move from tree to tree in the dense forest. They feed and work at night making them less apt to deal with predation. Grzimek (1990)

Physical Description

Azara's night monkeys are one of the smaller cebid species. Its head and body length ranges from about 240-370 mm, with a tail length of approximately 316-400 mm. The tail is not prehensile and its the posterior third is black. In a species this small, there is no need for a prehensile tail because it is so lightweight. There is also no sexual dimorphism in size or in any other aspect of the morphology of this species other than the genitalia. The head is relatively round and the eyes are very large with well-developed eyelids. The retina contains rods only. The ears are rather small and cannot be seen because of the short, dense, semiwooly, and soft fur. The fur has a grayish/agouti dorsum with a slightly more reddish stripe down the side. The area around the central face is brown with a white border, and there are large white patches over the eyes. There are also three black stripes that extend into the forehead red fur on the sides of the neck. Azara's night monkeys also have a throat sac under the chin that allows them to create resonant vocalizations.

The tooth formula is I2/2, C1/1, P3/3, M3/3, and it equals 36 teeth. The upper molars have four cusps, and the lower molars have four or sometimes five. This family is set apart from other primates by their platyrrhine nose (a wide form of the septum that separates the nostrils). The long and thin digits bear flattened or curved nails. It's great toe is well-developed and widely opposable to the other toes. There is no baculum.

Macdonald (1984), Nowak (1991)

  • Sexual Dimorphism
  • sexes alike
  • Range mass
    0.6 to 1 kg
    1.32 to 2.20 lb
  • Range length
    240 to 370 mm
    9.45 to 14.57 in


The father takes an active role in raising the young and the relationship among the mother and father is monogamous. This permanent pairing is based on the intolerance of males and females for other individuals of their own sex.

The gestational period ranges from 126-133 days and usually only 1 baby is born, rarely 2. The weight at birth ranges from 3.2-3.7 ounces. Young are weaned anywhere from five to twelve months, and they reach sexual maturity at two years of age.

Macdonald (1984), Nowak (1990)

  • Range number of offspring
    1 to 2
  • Range gestation period
    126 to 133 days
  • Range weaning age
    5 to 12 months
  • Average age at sexual or reproductive maturity (female)
    2 years
  • Average age at sexual or reproductive maturity (male)
    2 years

In the first week of life, the newborn night monkey nestles in his or her mother's groin. Once the second week comes, the father assists in carrying the baby at his groin. And by the third week, the father carries the baby there full-time. Beginning with the second month, the baby is carried in a jockey-like posture on the father's back, which is where the monkey will stay until the age of four to five months. During the final half of that first year, the young night monkey increases it's play with it's siblings. It is also during this time that the young night monkey relates more to the mother than to the father.

  • Parental Investment
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • male
      • female
  • pre-independence
    • provisioning
      • female
    • protecting
      • male
      • female
  • extended period of juvenile learning


Azara's night monkeys live as small family groups, usually consisting of the parents and 2-4 young. Their huge eyes adapt them for nocturnal life. They sleep through the day huddled together in hollow trees or dense foliage. They become active at the beginning of twilight, by hunting and foraging through the tropical forests of South America. When they awaken, all family members stretch elaborately, urinate, and defecate. Eventually one parent leaves the sleeping tree and makes its way to the first feeding tree by way of lianas. The rest of the family followed in order, first parents then children. Night monkeys are most active when there is a full moon. When there is total darkness, they tend to shift some of their activity into the later and earlier hours of daylight. Grzimek (1990), Nowak (1991)

Communication and Perception

Food Habits

Azara's night monkeys are omnivorous, feeding on insects, fruits, leaves, seeds, bark, flowers, gums, bird eggs, and small vertebrates. Night monkeys feed in trees, foraging at night as a small family. They tend to feed in the same fruit trees on successive nights. (Macdonald, 1984; Nowak, 1991)

  • Animal Foods
  • birds
  • mammals
  • amphibians
  • reptiles
  • eggs
  • insects
  • terrestrial non-insect arthropods
  • Plant Foods
  • leaves
  • wood, bark, or stems
  • seeds, grains, and nuts
  • fruit
  • flowers
  • sap or other plant fluids

Economic Importance for Humans: Positive

Aotus azarae is of great importance to humans in that it provides a nonhuman primate for biomedical research. It has played an indispensable role in many research studies such as the study of malaria and other natural infections, viral oncogenesis, ophthalmology research, neocortical organization and function, and memory-related functions. (Baer, 1994)

  • Positive Impacts
  • research and education

Economic Importance for Humans: Negative

There are no adverse affects of Aotus azarae on humans.

Conservation Status

This species is not yet endangered. They are very successful due to their nocturnal behavior. Despite destruction of their habitat, Aotus azarae have persisted because of their ability to adapt to new environmental situations. These monkeys are killed for their fur and meat. They are also used extensively in biomedical research. Intensive deforestation has decreased food sources. (Grzimek, 1990; Nowak, 1991; Baer, 1994)

Other Comments

Their wild population has increased due to an embargo that was imposed by source contries in the 1970's. Between 1968 and 1972, the United States imported 20,869 owl monkeys (including other species of the genus Aotus), primarily from Columbia and Bolivia. Between 1976 and 1980, the number was drastically reduced to 3300 individuals. (Baer, 1994)


Candace T. Smith (author), University of Michigan-Ann Arbor.



living in the southern part of the New World. In other words, Central and South America.

World Map


Referring to an animal that lives in trees; tree-climbing.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.


uses smells or other chemicals to communicate


animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.


offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).


Having one mate at a time.


having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.


active during the night


an animal that mainly eats all kinds of things, including plants and animals


remains in the same area


reproduction that includes combining the genetic contribution of two individuals, a male and a female


associates with others of its species; forms social groups.


uses touch to communicate


reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.


Baer, J.F., I. Kakoma, R.E. Weller. 1994. Aotus: The Owl Monkey. Academic Press, San Diego.

Britannica. Britannica Search.

Grzimek, B. 1990. Encyclopedia of Mammals. McGraw-Hill Publishing, Co. Vol. 2. pp. 120-173

Macdonald, D.W. 1984. Encyclopedia of Mammals. Equinox (Oxford) Ltd. pp. 352-352

Nowak, R. M. 1991. Walker's Mammals of the World. Fifth Edition. Johns Hopkins University Press, Baltimore. pp. 445-448

Primate Gallery.

Smithsonian Institute. Mammals Species of the World.