Editing Megabat (section)

====Sight====
[[File:1977.05.03 Fijian Monkey-faced Bat ,Taveuni, Fiji 3443 ccccr.jpg|thumb|alt=A headshot of a bat with orangish-brown fur looking directly at the camera. Its eyes are piercingly orange.|The reddish-orange eyes of the [[Fijian monkey-faced bat]] (''Mirimiri acrodonta'')]]
With very few exceptions, megabats do not [[Animal echolocation|echolocate]], and therefore rely on sight and smell to navigate.<ref name="Muller"/> They have large eyes positioned at the front of their heads.<ref name="Graydon"/> These are larger than those of the common ancestor of all bats, with one study suggesting a trend of increasing eye size among pteropodids. A study that examined the eyes of 18 megabat species determined that the [[common blossom bat]] (''Syconycteris australis'') had the smallest eyes at a diameter of {{cvt|5.03|mm|in}}, while the largest eyes were those of [[large flying fox]] (''Pteropus vampyrus'') at {{cvt|12.34|mm|in}} in diameter.<ref>{{cite journal|doi=10.1038/s41467-017-02532-x|pmid=29311648|pmc=5758785|title=Auditory opportunity and visual constraint enabled the evolution of echolocation in bats|journal=Nature Communications|volume=9|issue=1|page=98|year=2018|last1=Thiagavel|first1=J.|last2=Cechetto|first2=C.|last3=Santana|first3=S. E.|last4=Jakobsen|first4=L.|last5=Warrant|first5=E. J.|last6=Ratcliffe|first6=J. M.|bibcode=2018NatCo...9...98T}}</ref> Megabat irises are usually brown, but they can be red or orange, as in ''[[Desmalopex]]'', ''[[Mirimiri]]'', ''[[Pteralopex]]'', and some ''Pteropus''.<ref>{{cite journal|doi=10.3161/150811008X331054|title=The systematic position of Pteropus leucopterus and its bearing on the monophyly and relationships of Pteropus (Chiroptera: Pteropodidae)|journal=Acta Chiropterologica|volume=10|pages=11–20|year=2008|last1=Giannini|first1=N. P.|last2=Almeida|first2=F. C.|last3=Simmons|first3=N. B.|last4=Helgen|first4=K. M.|hdl=11336/82001|s2cid=59028595|hdl-access=free}}</ref>

At high brightness levels, megabat [[visual acuity]] is poorer than that of humans; at low brightness it is superior.<ref name="Graydon">{{cite journal|journal=[[Journal of the Australian Mammal Society]]| pages=101–105| url=https://books.google.com/books?id=yENMUzuisWwC&pg=RA1-PA101| title=Vision in Flying-Foxes (Chiroptera:Pteropodidae)| volume=10| issue=2| year=1987| last1=Graydon| first1=M.| last2=Giorgi| first2=P.| last3=Pettigrew| first3=J.| doi=10.1071/AM87021| s2cid=254716342}}</ref> One study that examined the eyes of some ''Rousettus'', ''Epomophorus'', ''Eidolon'', and ''Pteropus'' species determined that the first three genera possess a ''[[tapetum lucidum]]'', a reflective structure in the eyes that improves vision at low light levels, while the ''Pteropus'' species do not.<ref name="Muller"/> All species examined had [[retina]]e with both [[rod cell]]s and [[cone cell]]s, but only the ''Pteropus'' species had S-cones, which detect the shortest wavelengths of light; because the spectral tuning of the [[opsin]]s was not discernible, it is unclear whether the S-cones of ''Pteropus'' species detect blue or ultraviolet light. ''Pteropus'' bats are [[Dichromacy|dichromatic]], possessing two kinds of cone cells. The other three genera, with their lack of S-cones, are [[Monochromacy|monochromatic]], unable to see color. All genera had very high densities of rod cells, resulting in high sensitivity to light, which corresponds with their nocturnal activity patterns. In ''Pteropus'' and ''Rousettus'', measured rod cell densities were 350,000–800,000 per square millimeter, equal to or exceeding other nocturnal or [[crepuscular]] animals such as the [[house mouse]], [[domestic cat]], and [[domestic rabbit]].<ref name="Muller">{{cite journal|doi=10.1159/000102971|pmid=17522478|title=Cone Photoreceptor Diversity in the Retinas of Fruit Bats (Megachiroptera)|journal=[[Brain, Behavior and Evolution]]|volume=70|issue=2|pages=90–104|year=2007|last1=Müller|first1=B.|last2=Goodman|first2=S. M.|last3=Peichl|first3=Leo|s2cid=29095435}}</ref>