[9] At any rate, night monkeys lack the tapetum lucidum composed of riboflavin crystals possessed by lemurs and other strepsirrhines,[9] which is an indication that their nocturnality is a secondary adaption evolved from ancestrally diurnal primates.

[10] Night monkeys can be found in Panama, Colombia, Ecuador, Peru, Brazil, Paraguay, Argentina, Bolivia, and Venezuela.

[11] Red-necked night monkeys are found throughout various regions of the Amazon rainforest of South America, with some variation occurring between the four species.

Nancy Ma's night monkey occurs in both flooded and unflooded tropical rainforest regions of Peru, preferring moist swamp and mountainous areas.

[12] This species has been observed nesting in regions of the Andes[13] and has recently been introduced to Colombia, likely as a result of post-research release into the community.

[16] Night monkeys such like the black-headed night monkey, 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 and lodging sources.

[16] The distribution of A. azare, extends further towards the Atlantic Ocean, spanning Argentina, Bolivia and the drier, south western regions of Paraguay,[17] however unlike the other red-necked night monkey species, it is not endemic to Brazil.

[11] A study conducted by Wolovich et al., indicated that juveniles and females were much better at catching both crawling and flying insects than adult males.

[11] In night monkeys, mating occurs infrequently, however females are fertile year-round, with reproductive cycles range from 13 to 25 days.

Birthing season extends from September to March and is species-dependent, with one offspring being produced per year; however, in studies conducted in captivity, twins were observed.

They have a better spatial resolution at low light levels than other primates, which contributes to their ability to capture insects and move at night.

[27]  The presence of nocturnal behavior in Aotidae therefore exemplifies a derived trait; an evolutionary adaptation that conferred greater fitness advantages onto the night monkey.

As the ancestor of Aotidae was likely diurnal, selective and environmental pressures must have been exerted on the members of this family which subsequently resulted in the alteration of their circadian rhythm to adapt to fill empty niches.

Members of the family Aotidae, apply the predation avoidance theory, choosing very strategic covered nests sites in trees.

As they carefully construct their nests, night monkeys also benefit from the shade provided by the forest canopy which enables them to cool their bodies through the act of displacing themselves into a shady area.

[29] Additionally, finding food is energetically costly and completing this process during the day time usually involves the usage of energy in the form of calories and lipid reserves to cool the body down.

As night monkey territories generally have some edge overlap, there can be a large number of individuals coexisting in one area which may make it difficult for a male to defend many females at once due to high levels of interspecific competition for mates.

[35] Recent studies have proposed that night monkeys rely on olfaction and olfactory cues for foraging and communication significantly more than other diurnal primate species.

[21] This trend is reflected in the species physiology; members of Aotidae possess larger scent perception organs than their diurnal counterparts.

[36] It is therefore likely that increased olfaction capacities improved the fitness of these nocturnal primate species; they produced more offspring and passed on these survival enhancing traits.

When foraging at night, members of the family Aotidae will smell fruits and leaves before ingesting to determine the quality and safety of the food source.

As they are highly frugivorous and cannot perceive colour well, smell becomes the primary determinant of the ripeness of fruits and is therefore an important component in the optimal foraging methods of these primates.

[36] Night monkeys possess several scent glands covered by greasy hair patches, which secrete pheromones that can be transferred onto vegetation or other conspecifics.

[21] This is especially important in night monkeys as they cannot rely on visual cues, such as the presence of a tumescence, to determine female reproductive state.

[37] There is a preference for scents of a particular type; those which indicate reproductive receptivity, which increases species fitness by facilitating the production of offspring.

Most night monkey species are threatened by varying levels of habitat loss throughout their range, caused by agricultural expansion, cattle ranching, logging, armed conflict, and mining operations.

Species such as Nancy Ma's night monkey, like human beings, are susceptible to infection by the Plasmodium falciparum parasite responsible for malaria.

[39] This trait caused them to be recommended by the World Health Organization as test subjects in the development of malaria vaccines.

[41] Increased research and knowledge of night monkey ecology is an invaluable tool in determining conservation strategies for these species and raising awareness for consequences of the anthropogenic threats facing these primates.

[42] Radio collaring not only allows for the identification of individuals within a species, increased sample size, more detailed dispersal and range patterns, but also facilitates educational programs which raise awareness for the current biodiversity crisis.