Owl monkey

The night monkeys, also known as the owl monkeys or douroucoulis, are the members of the genus Aotus of New World monkeys (monotypic in family Aotidae). The only nocturnal monkeys, they are native to Panama and much of tropical South America. Night monkeys constitute one of the few monkey species that are affected by the often deadly human malaria protozoan Plasmodium falciparum, making them useful as non-human primate experimental subjects in malaria research. Until 1983, all night monkeys were placed into only one (A. lemurimus) or two species (A. lemurinus and A. azarae). Chromosome variability showed that there was more than one species in the genus and Hershkovitz (1983) used morphological and karyological evidence to propose nine species, one of which is now recognised as a junior synonym. He split Aotus into two groups: a northern, gray-necked group (A. lemurinus, A. hershkovitzi, A. trivirgatus and A. vociferans) and a southern, red-necked group (A. miconax, A. nancymaae, A. nigriceps and A. azarae). Arguably, the taxa otherwise considered subspecies of A. lemurinus – brumbacki, griseimembra and zonalis – should be considered separate species, whereas A. hershkovitzi arguably is a junior synonym of A. lemurinus. A new species from the gray-necked group was recently described as A. jorgehernandezi. As is the case with some other splits in this genus, an essential part of the argument for recognizing this new species was differences in the chromosomes. Chromosome evidence has also been used as an argument for merging 'species', as was the case for considering infulatus a subspecies of A. azarae rather than a separate species. Fossil species have (correctly or incorrectly) been assigned to this genus, but only extant species are listed below. Family Aotidae Night monkeys have large brown eyes; the size improves their nocturnal vision increasing their ability to be active at night. They are sometimes said to lack a tapetum lucidum, the reflective layer behind the retina possessed by many nocturnal animals. Other sources say they have a tapetum lucidum composed of collagen fibrils. At any rate, night monkeys lack the tapetum lucidum composed of riboflavin crystals possessed by lemurs and other strepsirrhines, which is an indication that their nocturnalitiy is a secondary adaption evolved from ancestral diurnal primates. Their ears are rather difficult to see; this is why their genus name, Aotus (meaning 'earless') was chosen. There is little data on the weights of wild night monkeys. From the figures that have been collected, it appears that males and females are similar in weight; the heaviest species is Azara's night monkey at around 1,254 grams (2.765 lb), and the lightest is Brumback's night monkey, which weighs between 455 and 875 grams (1.003 and 1.929 lb). The male is slightly taller than the female, measuring 346 and 341 millimetres (13.6 and 13.4 in), respectively. Night monkeys can be found in Panama, Colombia, Ecuador, Peru, Brazil, Paraguay, Argentina, Bolivia, and Venezuela. The species that live at higher elevations tend to have thicker fur than the monkeys at sea level. Night monkeys can live in forests undisturbed by humans (primary forest) as well as in forests that are recovering from human logging efforts (secondary forest). A primary distinction between red-necked and gray-necked night monkeys is spatial distribution. Gray-necked night monkeys (Aotus lemurinus) are found north of the Amazon River, while the Red-necked group (Aotus azare) are localized south of the Amazon River. Red-necked night monkeys are found throughout various regions of the Amazon rainforest of South America, with some variation occurring between the four species of A. azare.  A. nancymaae occurs in both flooded and unflooded tropical rainforest regions of Peru, preferring moist swamp and mountainous areas. This species has been observed nesting in regions of the Andes and has recently been introduced to Colombia, likely as a result of post-research release into the community. A. nigriceps is also found mainly in the Peruvian amazon (central and upper amazon), however its range extends throughout Brazil and Bolivia to the base of the Andes mountain chain . Night monkeys such like A. nigriceps, generally inhabit cloud forests; areas with consistent presence of low clouds with a high mist and moisture content which allows for lush and rich vegetation to grow year round, providing excellent food ans lodging sources. A. miconax, like A. nancymaae, is endemic to the Peruvian Andes however it is found at a higher elevation, approximately 800 -2400 m above sea level and therefore exploits different niches of this habitat. The distribution of A. azare, extends further towards the Atlantic Ocean, spanning Argentina, Bolivia and the drier, south western regions of Paraguay (Fernandez- Duque et al, 2008), however unlike the other Red-necked night owl species, it is not endemic to brazil. During the daylight hours, Night monkeys rest in shaded tree areas. These species have been observed exploiting four different types of tree nests, monkeys will rest in; holes formed in the trunks of trees, in concave sections of branches surrounded by creepers and epiphytes, in dense areas of epiphyte, climber and vine growth and in areas of dense foliage. These sleeping sites provide protection from environmental stressors such as heavy rain, sunlight and heat. Sleeping sites are therefore carefully chosen based upon tree age, density of trees, availability of space for the group, ability of site to provide protection, ease of access to the site and availability of site with respect to daily routines. While Night monkeys are an arboreal species, nests have not been observed in higher strata of the rainforest ecosystem, rather a higher density of nests were recorded at low-mid vegetation levels. Night monkeys represent a territorial species, territories are defended by conspecifics through the use of threatening and agonistic behaviours. Ranges between Night monkey species often do overlap and result in interspecific aggressions such as vocalizing and chasing which may last up to an hour.