Editing Night monkey (section)

==Behavior==
The name "night monkey" comes from the fact that all species are active at night and are, in fact, the only truly [[nocturnal]] monkeys (an exception is the subspecies of [[Azara's night monkey]], ''Aotus azarae azarae'', which is [[cathemeral]]).<ref name=Lang/> Night monkeys make a notably wide variety of vocal sounds, with up to eight categories of distinct calls (gruff grunts, resonant grunts, sneeze grunts, screams, low trills, moans, gulps, and hoots), and a frequency range of 190–1,950&nbsp;Hz.<ref>{{cite journal | author = Moynihan, M. | title = Some behavior patterns of platyrrhine monkeys. I. The night monkey (''Aotus trivirgatus'') | journal = Smithsonian Miscellaneous Collections | year = 1964 | volume = 146 | issue = 5 | pages = 1–84}}</ref> Unusual among the New World monkeys, they are [[monochromat]]s, that is, they have no colour vision, presumably because it is of no advantage given their nocturnal habits. 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.<ref>{{cite journal | author = Jacobs, G. H. | author2 = Deegan, J. F. | author3 = Neitz, J. | author4 = Crognale, M. A. | year = 1993 | title = Photopigments and colour vision in the nocturnal monkey, ''Aotus'' | journal = Vision Research | volume = 33 | pages = 1773–1783 | doi = 10.1016/0042-6989(93)90168-V | pmid = 8266633 | issue = 13| citeseerx = 10.1.1.568.1560 | s2cid = 3745725 }}</ref> Night monkeys live in family groups consisting of a mated pair and their immature offspring. Family groups defend [[territory (animal)|territories]] by vocal calls and [[scent marking]].

The night monkey is socially monogamous, and all night monkeys form [[pair bond]]s.<ref>{{Cite web |last=Cummings |first=Mike |date=November 13, 2023 |title=Good partners and great dads: insights into the world of owl monkeys |url=https://news.yale.edu/2023/11/13/good-partners-and-great-dads-insights-world-owl-monkeys |access-date=August 8, 2024 |website=Yale News}}</ref> Only one infant is born each year. The male is the primary caregiver, and the mother carries the infant for only the first week or so of its life. This is believed to have developed because it increases the survival of the infant and reduces the metabolic costs on the female. Adults will occasionally be evicted from the group by same-sex individuals, either kin or outsiders.<ref name="Fernandez-Duque2008">{{Cite journal | last1 = Fernandez-Duque | first1 = E. | title = Natal dispersal in monogamous owl monkeys (''Aotus azarai'') of the Argentinean Chaco | doi = 10.1163/156853908X397925 | journal = Behaviour | volume = 146 | issue = 4 | pages = 583–606 | year = 2009 | hdl = 11336/104367 | url = http://www.sas.upenn.edu/~eduardof/Publications/Fernandez-Duque%202009%20Natal%20Dispersal.pdf| citeseerx = 10.1.1.533.3310 }}</ref>

=== Nocturnality ===
The family ''Aotidae'' is the only family of nocturnal species within the suborder [[Simian|Anthropoidea]]. Whereas other divisions of primates, including [[Strepsirrhini]] and [[Tarsier|Tarsiidae]], include many nocturnal and cathemeral species, the anthropoids possess very few nocturnal species and therefore it is highly likely that the ancestors of the family ''Aotidae'' did not exhibit nocturnality and were rather diurnal species.<ref name="Ankel-Simons-2008">{{Cite journal|last1=Ankel-Simons|first1=F.|last2=Rasmussen|first2=D.T.|date=2008|title=Diurnality, nocturnality, and the evolution of primate visual systems|journal=American Journal of Physical Anthropology|volume=137|issue=S47|pages=100–117|doi=10.1002/ajpa.20957|pmid=19003895|issn=0002-9483|doi-access=free}}</ref> &nbsp;The presence of nocturnal behavior in ''Aotidae'' therefore exemplifies a derived trait; an evolutionary adaptation that conferred greater fitness advantages onto the night monkey.<ref name="Ankel-Simons-2008" /> &nbsp;Night monkey share some similarities with nocturnal prosimians including low basal metabolic rate, small body size and good ability to detect visual cues at low light levels.<ref name="Wright-1989">{{Cite journal|last=Wright|first=Patricia C.|date=November 1989|title=The nocturnal primate niche in the New World|journal=Journal of Human Evolution|volume=18|issue=7|pages=635–658|doi=10.1016/0047-2484(89)90098-5|bibcode=1989JHumE..18..635W |issn=0047-2484}}</ref> Their responses to olfactory stimulus are intermediate between those of the prosimians and diurnal primate species, however the ability to use auditory cues remains more similar to diurnal primate species than to nocturnal primate species.<ref name="Wright-1989" /> This provides further evidence to support the hypothesis that nocturnality is a derived trait in the family ''Aotidae''.

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.<ref name="Ankel-Simons-2008" /> Being active in the night rather than during the day time, gave ''Aotus'' access to better food sources, provided protection from predators, reduced interspecific competition and provided an escape from the harsh environmental conditions of their habitat.<ref name="Fernández-Duque-2010">{{Cite journal|last1=Fernández-Duque|first1=Eduardo|last2=de la Iglesia|first2=Horacio|last3=Erkert|first3=Hans G.|date=2010-09-03|title=Moonstruck Primates: Owl Monkeys (''Aotus'') Need Moonlight for Nocturnal Activity in Their Natural Environment|journal=PLOS ONE|volume=5|issue=9|pages=e12572|doi=10.1371/journal.pone.0012572|pmid=20838447|pmc=2933241|issn=1932-6203|bibcode=2010PLoSO...512572F|doi-access=free}}</ref> To begin, resting during the day allows for decreased interaction with diurnal predators. Members of the family ''Aotidae,'' apply the predation avoidance theory, choosing very strategic covered nests sites in trees.<ref name="Savagian-2017">{{Cite journal|last1=Savagian|first1=Amanda|last2=Fernandez-Duque|first2=Eduardo|date=2017-01-04|title=Do Predators and Thermoregulation Influence Choice of Sleeping Sites and Sleeping Behavior in Azara's Owl Monkeys (''Aotus azarae azarae'') in Northern Argentina?|journal=International Journal of Primatology|volume=38|issue=1|pages=80–99|doi=10.1007/s10764-016-9946-5|s2cid=9881118|issn=0164-0291}}</ref> These primates carefully choose areas with sufficient foliage and vines to provide cover from the sun and camouflage from predators, but which simultaneously allow for visibility of ground predators and permit effective routes of escape should a predator approach too quickly.<ref name="Fernández-Duque-2010" /><ref name="Aquino-1986" /> Activity at night also permits night monkeys to avoid aggressive interactions with other species such as competing for food and territorial disputes; as they are active when most other species are inactive and resting.<ref name="Fernández-Duque-2010" />

Night monkeys also benefit from a nocturnal life style as activity in the night provides a degree of protection from the heat of the day and the thermoregulation difficulties associated.<ref name="Savagian-2017" /> Although night monkey, like all primates are endothermic, meaning they are able to produce their own heat, night monkeys undergo behavioural thermoregulation in order to minimize energy expenditure.<ref name="Savagian-2017" /> During the hottest points of the day, night monkeys are resting and therefore expending less energy in the form of heat. 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.<ref name="Savagian-2017" /> 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. Foraging during the night when it is cooler, and when there is less competition, supports the optimal foraging theory; maximize energy input while minimizing energy output.<ref name="Savagian-2017" />

While protection from predators, interspecific interactions, and the harsh environment propose ultimate causes for nocturnal behavior as they increase the species fitness, the proximate causes of nocturnality are linked to the environmental effects on circadian rhythm.<ref name="Fernandez-Duque-2003">{{Cite journal|last=Fernandez-Duque|first=Eduardo|date=2003-09-01|title=Influences of moonlight, ambient temperature, and food availability on the diurnal and nocturnal activity of owl monkeys (''Aotus azarai'')|journal=Behavioral Ecology and Sociobiology|volume=54|issue=5|pages=431–440|doi=10.1007/s00265-003-0637-9|bibcode=2003BEcoS..54..431F |s2cid=32421271|issn=0340-5443|hdl=11336/50695|hdl-access=free}}</ref> While diurnal species are stimulated by the appearance of the sun, in nocturnal species, activity is highly impacted by the degree of moon light available. The presence of a new moon has correlated with inhibition of activity in night monkeys who exhibit lower levels of activity with decreasing levels of moon light.<ref name="Fernandez-Duque-2003" /> Therefore, the lunar cycle has a significant influence on the foraging and a nocturnal behaviors of night monkey species.<ref name="Fernandez-Duque-2003" />

=== Pair-bonded social animals (social monogamy) ===
Night monkeys are socially monogamous—they form a bond and mate with one partner. They live in small groups consisting of a pair of reproductive adults, one infant and one to two juveniles.<ref name="Fernandez-Duque-2012">{{Cite journal|last=Fernandez-Duque|first=E.|date=January 2012|title=Owl monkeys ''Aotus'' spp in the wild and in captivity|journal=International Zoo Yearbook|volume=46|issue=1|pages=80–94|doi=10.1111/j.1748-1090.2011.00156.x|issn=0074-9664|hdl=11336/101658|hdl-access=free}}</ref> These species exhibit mate guarding, a practice in which the male individual will protect the female he is bonded to and prevent other conspecifics from attempting to mate with her.<ref name="Wartmann-2014">{{Cite journal|last1=Wartmann|first1=Flurina M.|last2=Juárez|first2=Cecilia P.|last3=Fernandez-Duque|first3=Eduardo|date=2014-07-04|title=Erratum to: Size, Site Fidelity, and Overlap of Home Ranges and Core Areas in the Socially Monogamous Owl Monkey (''Aotus azarae'') of Northern Argentina|journal=International Journal of Primatology|volume=35|issue=5|pages=940|doi=10.1007/s10764-014-9787-z|issn=0164-0291|doi-access=free}}</ref>&nbsp; Mate guarding likely evolved as a means of reducing energy expenditure when mating. 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.<ref>{{Cite journal|last=Fernandez-Duque|first=Eduardo|date=March 2016|title=Social monogamy in wild owl monkeys ( Aotus azarae ) of Argentina: the potential influences of resource distribution and ranging patterns: Monogamy in Owl Monkeys|journal=American Journal of Primatology|language=en|volume=78|issue=3|pages=355–371|doi=10.1002/ajp.22397|pmc=5398412|pmid=25931263}}</ref> Night monkeys form bonded pairs and the energy expenditure of protecting a mate is reduced.<ref name="Wartmann-2014" /> Pair bonding may also be exhibited as a result of food distribution. In the forest, pockets of food can be dense or very patchy and scarce. Females, as they need energy stores to support reproduction are generally distributed to areas with sufficient food sources.<ref name="Fernandez-Duque-2015">{{Cite journal|last=Fernandez- Duque|first=E|date=2015|title=Love in the time of Monkeys|journal=Natural History|volume=122|jstor=}}</ref> Males will therefore also have to distribute themselves to be within proximity to females, this form of food distribution lends itself to social monogamy as finding females may become difficult if males have to constantly search for females which may be widely distributed depending on food availability that year.<ref name="Fernandez-Duque-2015" />

However, while this does explain social monogamy, it does not explain the high degree of paternal care which is exhibited by these primates. After the birth of an infant, males are the primary carrier of the infant, carrying offspring up to 90% of the time.<ref name="Fernandez-Duque-2012" /> In addition to aiding in child care, males will support females during lactation through sharing their foraged food with lactating females.<ref name="Wolovich-2008">{{Cite journal|last1=Wolovich|first1=Christy K.|last2=Evans|first2=Sian|last3=French|first3=Jeffrey A.|date=March 2008|title=Dads do not pay for sex but do buy the milk: food sharing and reproduction in owl monkeys (''Aotus'' spp.)|journal=Animal Behaviour|volume=75|issue=3|pages=1155–1163|doi=10.1016/j.anbehav.2007.09.023|s2cid=36121485|issn=0003-3472}}</ref> Generally, food sharing is not observed in nature as the search for food requires a great degree of energy expenditure, but in the case of night monkey males, food sharing confers offspring survival advantages. As lactating females may be too weak to forage themselves, they may lose the ability to nurse their child, food sharing therefore ensures that offspring will be well feed.<ref name="Wolovich-2008" /> The act of food sharing is only observed among species where there is a high degree of fidelity in paternity. Giving up valuable food sources would not confer an evolutionary advance unless it increased an individual's fitness; in this case, paternal care ensures success of offspring and therefore increases the father's fitness.<ref name="Wolovich-2008" />

=== Olfactory communication and foraging ===
Recent studies have proposed that night monkeys rely on olfaction and olfactory cues for foraging and communication significantly more than other diurnal primate species.<ref name="Wolovich-2007" /> This trend is reflected in the species physiology; members of Aotidae possess larger scent perception organs than their diurnal counterparts. The olfactory bulb, accessory olfactory bulb and volume of lateral olfactory tract are all larger in ''Aotus'' than in any of the other new world monkey species.<ref name="Bolen-1997">{{Cite journal|last1=Bolen|first1=Rosina H.|last2=Green|first2=Steven M.|date=1997|title=Use of olfactory cues in foraging by owl monkeys (''Aotus nancymai'') and capuchin monkeys (Cebus apella).|journal=Journal of Comparative Psychology|volume=111|issue=2|pages=152–158|doi=10.1037/0735-7036.111.2.152|pmid=9170280|issn=1939-2087}}</ref> 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.<ref name="Bolen-1997" /> The benefits of increased olfaction in night monkeys are twofold; increased ability to use scent cues has facilitated night time foraging and is also an important factor in mate selection and sexual attractivity.<ref name="Wolovich-2007" />

As a substantial portion of the night monkey's activities occurring during the dark hours of the night, there is a much lower reliance of visual and tactile cues. 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.<ref name="Bolen-1997" /> Upon finding a rich food source, night monkeys have been observed scent marking not only the food source, but the route from their sleeping site to the food source as well. Scent can therefore be used as an effective method of navigation and reduce energy expenditure during subsequent foraging expeditions.<ref name="Bolen-1997" /> Night monkeys possess several scent glands covered by greasy hair patches, which secrete pheromones that can be transferred onto vegetation or other conspecifics. Scent glands are often located subcaudal, but also occur near the muzzle and the sternum.<ref name="Wolovich-2007" /> The process of scent marking is accomplished through the rubbing of the hairs covering scent glands onto the desired "marked item".

[[Olfactory cues]] are also of significant importance in the process of mating and mate guarding. Male night monkeys will rub subcaudal glands onto their female partner in a process called "partner marking" in order to relay the signal to coexisting males that the female is not available for mating.<ref name="Wolovich-2007" /> Night monkeys also send chemical signals through urine to communicate reproductive receptivity. In many cases, male night monkeys have been observed drinking the urine of their female mate; it is proposed that the pheromones in the urine can indicate the reproductive state of a female and indicate ovulation.<ref name="Wolovich-2007" /> 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.<ref name="Wolovich-2007" /> Therefore, night monkey olfactory communication, as a sexually dimorphic trait conferring increased reproductive success, is a result of [[sexual selection]]. This trait demonstrates sexual dimorphism, as males have larger subcaudal scent glands compared to female counterparts and sex differences have been recorded in the glandular secretions of each sex.<ref name="Spence-Aizenberg-2018">{{Cite journal|last1=Spence-Aizenberg|first1=Andrea|last2=Williams|first2=Lawrence E.|last3=Fernandez-Duque|first3=Eduardo|date=2018-05-02|title=Are olfactory traits in a pair-bonded primate under sexual selection? An evaluation of sexual dimorphism in ''Aotus nancymaae''|journal=American Journal of Physical Anthropology|volume=166|issue=4|pages=884–894|doi=10.1002/ajpa.23487|pmid=29719049|issn=0002-9483|doi-access=free}}</ref> 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.<ref name="Spence-Aizenberg-2018" />