The Night monkeys, Owl monkeys, or Douroucoulis are the members of the genus Aotus of New World monkeys (monotypic in family Nyctipithecidae). They are widely distributed in the forests of Central and South America, from Panama south to Paraguay and northern Argentina. The genus name means "earless"; they have ears, of course, but the external ears are tiny and hard to see. They are called Night monkeys because they are active at night and are in fact the only truly nocturnal monkeys.

Until 1983, all Night monkeys were placed into only a few species. Some authors still believe that there are only two or three true species, the remaining types being subspecies of these. The most widely agreed distinction is between a grey-necked group, including Aotus lemurinus, A. trivirgatus and A. vociferans, and a red-necked group, including A. miconax, A. nancymai, A. infulatus and A. azarae; authors recognising only two species refer to these as A. trivirgatus and A. azarae respectively.

Night monkeys make a notably wide variety of vocal sounds, 50-100 distinct calls having been identified. Unusually among the New World monkeys, they are monochromats, that is, they have no colour vision, presumably because it is of no advantage given their nocturnal habits.

All Night monkeys form pair bonds, and live in family groups of the mated pair with their immature offspring. Family groups defend territories by vocal calls and scent marking. Only one infant is born each year. The male is the primary caregiver, and the mother only carries the infant for the first week or so of its life.

Classification

• Family Nyctipithecidae
  • Gray-neck group
    • Gray-bellied Night Monkey, Aotus lemurinus
      • Aotus lemurinus lemurinus
      • Aotus lemurinus griseimembra
      • Aotus lemurinus zonalis
    • Hershkovitz's Night Monkey, Aotus hershkovitzi
    • Three-striped Night Monkey, Aotus trivirgatus
    • Spix's Night Monkey, Aotus vociferans
  • Red-neck group
    • Peruvian Night Monkey, Aotus miconax
    • Nancy Ma's Night Monkey, Aotus nancymae
    • Azara's Night Monkey, Aotus azarae
      • Aotus azarae azarae
      • Aotus azarae boliviensis
      • Aotus azarae infulatus

References

• Jacobs, G. H., Deegan, J. F., Neitz, J., Crognale, M. A., & Neitz, (1993). Photopigments and colour vision in the nocturnal monkey, Aotus. Vision Research, 33, 1773-1783.