Editing Night monkey (section)

=== 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" />