Brumback's night monkey (Aotus brumbacki)

Also known as: Brumback's owl monkey
Synonyms: Aotus lemurinus brumbacki
Spanish: Mico De Noche Llanero, Mono Nocturno
GenusAotus (1)
SizeMale head-body length: c. 34.6 cm (2)
Female head-body length: c. 34.1 cm (2)
Male weight: 0.8 - 1.3 kg (2)
Female weight: 0.5 - 1.2 kg (2)

Brumback’s night monkey is classified as Vulnerable (VU) on the IUCN Red List (1), and is listed on Appendix II of CITES (3).

The unusual Brumback’s night monkey (Aotus brumbacki), also known as Brumback's owl monkey, is a member of the genus Aotus, the only group of New World monkeys that are active solely at night (4). The species in this genus have brown eyes and specialised retinas that result in poor colour vision, but provide excellent vision in low light levels, an adaptation to their nocturnal lifestyle (5) (6).

Aotus monkeys range in colour from grey-tan to brown, with paler orange fur on their stomachs, and can be divided into two groups, grey-necked and red-necked (7). Brumback’s night monkey is a member of the grey-necked group, which have greyish or grizzled brown sides to the neck, and can be distinguished by a crest of fur between its shoulders (7). Both the male and female are of a similar size and weight (4).

Species in the genus Aotus typically move around on all fours in the tree canopy, and as the hindlimbs are longer than the forelimbs, these species are also skilled leapers (2).

Aotus species use an array of different vocal calls, including hoot calls, resonant whoops, gruff-grunts, screams, trills, moans, gulps, sneeze-grunts and squeaks (2).

Brumback’s night monkey is native to Colombia, where its range extends east from the Cordillera Oriental, between the Rio Arauca and Rio Guaviare. There have also been possible reports of this species from the Rio Orinoco (1).

Brumback’s night monkey is a tree-dwelling inhabitant of lowland primary and secondary rainforest, where the trees are evenly dispersed and there is a high level of plant species diversity (1) (2).

Brumback’s night monkey feeds mainly on fruit, supplementing its diet with flowers, nectar, leaves and even insects (4). The nightly distance Aotus species will travel is affected by both the availability of food and the level of light; records reveal that individuals travel twice as far when the moon is full, as opposed to on dark nights (8). A territorial species, it tends to live in small groups comprised of an adult breeding pair and their offspring (2).

Copulation tends to be brief, and Brumback's night monkey usually gives birth to just one infant, with inter-birth periods of one year (9). The male often carries the offspring, only handing it over to the female to suckle. Both sexes disperse once they are between 2.5 and 3.5 years of age (1).

Being predominantly nocturnal, Aotus species experience reduced competition with other primates for food (8). The most common predators of Aotus species include owls, snakes and carnivorous mammals such as big cats. Raptors may opportunistically take monkeys during the day if sleeping sites, usually tree holes or thickets of dense foliage, are exposed (4) (8).

These small, Neotropical primates are also unique in that they are naturally resistant to malaria-causing parasites (7) (10).

Brumback’s night monkey is one of the least studied species in Colombia, and its distribution is poorly understood (11). Habitat loss and degradation are thought to be the greatest threats to this species, due to expanding crop agriculture, logging and the increasing numbers of cattle ranches (1).

Although it is possible that Brumback’s night monkey occurs within national parks (1), in 7 out of 51 nationally protected areas in Colombia more than half the land has already been altered by human development (11). Ongoing civil unrest and armed conflict has also rendered some national parks dangerous to enter, thereby discouraging further scientific research (11).

Some Aotus monkeys are occasionally removed from the wild for use in malaria research due to their natural resistance, although this is thought to have little impact on population size (2).

Brumback’s night monkey is listed on Appendix II of the Convention on International Trade in Endangered Species (CITES), which means that trade in this species should be tightly controlled (3).

This little known species is thought to occur in some protected areas, including El Cocuy, Serranía de la Macarena, El Tuparro and Tinigua Natural National Parks (1).

The taxonomy of the genus Aotus is currently under debate and not yet fully understood, and the geographical distribution of Brumback’s night monkey needs to be clarified before a conservation status and action plan can be firmly decided (12).

More information on wildlife conservation in Colombia:

This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:

  1. IUCN Red List (November, 2011)
  2. Primate Info Net (November, 2011)
  3. CITES (November, 2011)
  4. Wright, P.C. (1994) The behavior and ecology of the owl monkey. In: Baer, J.F., Weller, R.E. and Kakoma, I. (Eds.) Aotus: The Owl Monkey. Academic Press, San Diego.
  5. Silveira, L.C.L., Yamada, E.S., Franco, E.C.S. and Finlay, B.L. (2001) The specialization of the owl monkey retina for night vision. Color Research and Application, 26: 118-122.
  6. Jacobs, G.H., Deegan, J.F., Neitz, J., Crognale, M.A. (1993) Photopigments and colour vision in the nocturnal monkey, Aotus. Vision Research, 33(13): 1773-1783.
  7. Hershkovitz, P. (1983) Two new species of night monkeys, genus Aotus (Cebidae, Platyrrhini): A preliminary report on Aotus taxonomy. American Journal of Primatology, 4: 209-243.
  8. Wright, P.C. (1989) The nocturnal primate niche in the new world. Journal of Human Evolution, 18(7): 635-658.
  9. Moynihan, M. (1964) Some behavior patterns of platyrrhine monkeys: I. The night monkeys (Aotus trivirgatus). Smithsonian Miscellaneous Collections, 146(5): 1-84.
  10. Ford, S.M. (1994) Taxonomy and distribution of the owl monkey. In: Baer, J.F., Weller, R.E. and Kakoma, I. (Eds.) Aotus: The Owl Monkey. Academic Press, San Diego.
  11. Stevenson, P.R., Guzman, D.C. and Defler, T.R. (2010) Conservation of Colombian primates: an analysis of published research. Tropical Conservation Science, 3(1): 45-62.
  12. Defler, T.R. and Bueno, M.L. (2007) Aotus diversity and the species problem. Primate Conservation, 22: 55-70.